10455233
The early birds and the rest: do first nesters represent the entire colony?
Climate change studies have detected earlier spring arrival of breeding birds. However, first nest dates (date first nests were found), which commonly provide the metric for earlier arrival, can be biased by population size or sampling effort. Our aims were to determine if: 1) first nest dates and median nest date (date when at least 50 % of all females have nested) were equivalent predictors for the spring arrival and 2) first nest date or median nest date were related to nest numbers. We recorded first and median nest dates and nest numbers at the common eider (Somateria mollissima) colony at Rif, Iceland, during 1992–2013. First nest date was advanced by 11 days during the study, but median nest date was advanced by only 4 days. First nest date and median nest date were correlated, but this relationship was only a small improvement over the null model (Nagelkerke R2 = 30 %). We found a relationship with nest count for both first and median nest dates once the analysis had accounted for inter-annual variability. First nest date may not represent the colony as a whole but rather the physically fittest or the most determined individuals, which may be more prone to nest early than the general population. Nesting birds must decide how much to advance breeding based on nest numbers and other non-temporal cues which necessitate earlier breeding. We argue that nest numbers affect the birds in a biological sense and that the advancement was not explained solely by increased nest numbers.
16265663
Selection on laying date is connected to breeding density in the pied flycatcher
Timing of reproduction and clutch size are important determinants of breeding success, especially in seasonal environments. Several recent bird population studies have shown changes in breeding time and in natural selection on it. These changes have often been linked with climate change, but few studies have investigated how the traits or natural selection are actually connected with climatic factors. Furthermore, the effect of population density on selection has been rarely considered, despite the potential importance of density in demographic processes. We studied variation in natural selection on laying date and on clutch size in relation to measures of spring phenology and population density in a long-term study of pied flycatchers in SW Finland. The phenological stage of the environment at mean egg-laying did not affect the direction of selection on either laying date or on clutch size. There was, however, stronger selection for earlier laying date when the breeding density of the population was high, suggesting that early breeding is not necessarily beneficial as such, but that its importance is emphasized when high population density increases competition. In addition, early breeding was favoured when the pre-breeding period was cool, which may indicate an increased advantage for the fittest individuals in harsher conditions. In the middle of the twentieth century, there was selection for large clutch size, which subsequently ceased, along with an overall decrease in recruit production. Our results indicate that attention should be paid to demographic factors such as breeding density when studying natural selection and temporal changes in it.
83735675
Early springs and breeding performance in two sympatric duck species with different migration strategies
The capacity of migratory species to adapt to climate change may depend on their migratory and reproductive strategies. For example, reproductive output is likely to be influenced by how well migra ...
87983508
Clutch-Size Determination in Precocial Birds: A Study of the Common Eider
-Clutch-size determination in the Common Eider (Somateria mollissima) was evaluated in a colony in northern Norway. Females in good body condition (determined from mass at hatching) produced large clutches and had a shorter incubation period than females with small body reserves. Females in good body condition cared for young (including adoption of the young of other females), while females in poor body condition abandoned their young soon after hatching. Repeatability (an upper limit to heritability) of clutch size, which for individual females varies from three to six eggs, does not differ significantly from zero. A hypothesis is proposed, suggesting that there is a trade-off involved in allocating body reserves to eggs, incubation, and care of chicks and that females use a particular clutch-size strategy related to their body condition and ability to care for young. Received 8 May 1992, accepted 12 May 1993. LACK (1947, 1948) SUGGESTED that clutch size in altrical birds was ultimately limited by the ability of the parents to rear young. Although Lack's hypothesis has been somewhat modified (see Williams 1966, Charnov and Krebs 1974, H0gstedt 1980), the idea of brood-size limitation has been supported by many studies (for reviews, see Klomp 1970, Dijkstra et al. 1990). The adaptive significance of clutch size in birds with self-feeding precocial young is an enigma (Arnold and Rohwer 1991). Clearly, Lack's hypothesis for clutch-size determination in altricial birds cannot apply to precocial birds. A number of other hypotheses have been proposed (see Winkler and Walters 1983). The one most often applied is the egg-production hypothesis (Winkler and Walters 1983, Arnold and Rohwer 1991). This hypothesis was proposed by Lack (1967, 1968), who suggested that clutch size ultimately is limited by the hen's ability to allocate nutrient reserves to egg laying. However, except for studies on arctic-nesting geese (Ankney and MacInnes 1978), evidence corroborating the hypothesis is scarce. A number of studies have shown that female waterfowl use body reserves for egg production (Ankney et al. 1991). However, use of body reserves for egg production has uncritically been used as evidence that available body reserves determine the optimal clutch size (Arnold and Rohwer 1991). Even if nutrient reserves influence number of eggs produced, there may be a trade-off between the use of body reserves for egg production and for later use during incubation (Erikstad 1986, Gloutney and Clark 1991) and care of chicks (Lessells 1986, Bustnes and Erikstad 1991). In this study we examine some of the hypotheses that have been put forth as possible explanations for within-season variation in clutch size. We outline a new hypothesis that combines several earlier ideas to show that clutch-size determination could be affected by an interaction of female body condition, egg predation, and parental care. MATERIALS AND METHODS The study was carried out in a Common Eider (Somateria mollissima) breeding colony near Troms0 in northern Norway (69?49'N, 18?15'E) in 1986-1989. The colony was on a 0.65-km2 island (Grind0ya) and contained 400 breeding pairs. Searches were begun in early May when first nests were initiated. Nests were visited at oneor two-day intervals to determine laying dates and clutch sizes. A clutch was assumed to be complete and incubation to have begun when no new eggs were recorded during a period of three days. We determined intraspecific nest parasitism by detecting multiple eggs laid in a nest within 24 h. The frequency was very low (less than 1%; unpubl. data). All parasitic clutches were excluded from the analysis. Incubation was assumed to begin on the day that the final egg was laid and was completed when one chick had hatched. Females were caught on the nest with a net at hatching and weighed using a spring balance (? 10 g). For a few females caught three to five days before hatching, we estimated hatching mass by using a daily mass
86127328
Seasonal declines in reproductive success of the common tern Sterna hirundo: timing or parental quality?
Reproductive success declines over the course of the breeding season in many bird species. Two categories of hypothesis have been evoked to explain this decline. The “timing” hypothesis suggests that seasonal declines in breeding success are attributable to the date of laying. The “parental quality” hypothesis suggests that seasonal declines result from the fact that young, inexperienced, or low quality birds breed later in the season. To evaluate the relative importance of timing and parental quality, egg exchanges and removals were used to manipulate hatching dates of common terns Sterna hirundo. Indices of quality, attendance, provisioning rates, and reproductive success of birds in three experimental groups (delayed hatch pairs, advanced hatch pairs, and pairs induced to relay) were compared to those of date-matched controls. Pairs that hatched chicks early raised more chicks than pairs hatching chicks late in the season, regardless of initial laying date. This suggests that hatching chicks early is advantageous in itself. Our results, however, also support the parental quality hypothesis. There was a significant negative relationship between natural laying date and fledging success, independent of hatching date. Differences in chick growth and survival suggest that higher quality adults may be able to compensate for the disadvantages of late hatching dates and achieve similar reproductive success to that of pairs hatching chicks early. We found that pairs hatching chicks late in the season were subject to more incidents of kleptoparasitism than those hatching chicks early. This may be a proximate factor contributing to seasonal declines in reproductive success for common terns, although such a mechanism would not be likely in non-colonial species. Failure to control for egg quality may have biased the results of some prior egg exchange experiments. Additionally, altered cost of incubation may be an unavoidable confounding factor in studies designed to manipulate timing of breeding.
32672297
Individual variation in timing of migration: causes and reproductive consequences in greater snow geese (Anser caerulescens atlanticus)
Decisions made by birds during migration to breeding grounds can strongly affect the fitness of individuals. We investigated possible causes and reproductive consequences of inter-individual variation in the migratory behavior of an arctic-nesting species, the greater snow goose (Anser caerulescens atlanticus), by radio-tracking females at their staging area and on their breeding grounds. Females showed relatively high repeatability in the duration of migration (ri=0.37) and arrival date on the breeding grounds (ri=0.42) suggesting that these traits are characteristics of individuals. Conversely, no individual consistency in departure date from the staging area was detected (ri=−0.02) indicating that environmental factors may have a large influence. Females paired with dominant males departed slightly earlier from the staging area than females accompanied by subordinate males. However, neither social status on the staging area (i.e. paired vs unpaired) nor dominance scores were associated with arrival time of individuals. Finally, the probability of breeding was positively related to arrival date indicating a reproductive cost of arriving too early on the breeding grounds. The combination of breeding probability and seasonal decline in breeding success nonetheless suggests that females arriving a few days earlier than the median arrival date attained highest reproductive success. Our results show that assessing the fitness consequences of early arrival by focusing solely on breeding females would lead to an overestimation of the genuine benefits. This study also indicates possible genetically based differences among individuals in migration duration and arrival time on the breeding grounds.
27888971
Age-specific nest-site preference and success in eiders
Variation in nest concealment is puzzling given the expected strong selection for safe nest sites. Selecting a concealed nest may decrease the risk of clutch predation but hinder parents from escaping predators, providing a possible solution to this paradox. Because the relative value of current versus future reproduction may vary with breeder age or state, nest concealment may also vary as a function of these attributes. We tested four predictions of the female and clutch safety trade-off hypothesis in eiders (Somateria mollissima): (1) nest concealment is negatively related to escape possibilities, (2) our capture rate of females is higher in covered nests, (3) egg predation is higher in open nests, and (4) overall nest success is unrelated to nest habitat. We also analysed nest microhabitat preferences and nest success relative to breeder age and body condition, controlling for nest spatial centrality. As expected, nest concealment and potential escape angle were negatively related, and capture by us, indicating female predation vulnerability, increased with nest cover. Clutch size was smaller in open nests, suggesting higher partial clutch predation, while it was larger among experienced and good-condition breeders. The probability of successful hatching was unrelated to nest habitat, positively associated with breeder experience, and negatively associated with hatching date. Experienced females selected more concealed and centrally located nests without sacrificing potential escape angles. The age-specific spatial distribution of nests on islands was unrelated to nest initiation dates, indicating no apparent competition. The age-specific preference of eiders for concealed nests may reflect declining reproductive value with age or confidence in surviving despite selecting a concealed nest. The apparently positive relationship between female age and survival and fecundity in eiders refutes the former alternative. Individual improvement in choosing safe nest sites, coupled with differential survival of individuals performing well, most likely explains age-specific nest-site preference and success.
17862052
Spring phenology and timing of breeding in short-distance migrant birds: phenotypic responses and offspring recruitment patterns in common goldeneyes
Understanding how organisms adjust breeding dates to exploit resources that aff ect fi tness can provide insights into impacts of climate change on avian demography. For instance, mismatches have been reported in long-distance migrant bird species when environmental cues experienced during spring migration are decoupled from conditions on breeding grounds. Short-distance migrant bird species that store reproductive nutrients prior to breeding may avoid or buff er adverse phenological eff ects. Furthermore, reduced short-term reproductive success could be off set by higher future recruitment of surviving off spring. We evaluated whether recruitment of locally-hatched female off spring was related to hatching date alone or strength of mismatched breeding date for 405 individually-marked adult female common goldeneyes Bucephala clangula (a short-distance migrant) and their ducklings from a site in central Finland where ice-out date has advanced by ∼ 2 weeks over 24 yr. Path analyses revealed that older, early-nesting females with good body condition and larger broods recruited the most female off spring. Off spring recruitment decreased strongly among females that bred late relative to other females in the population each year; the extent of mismatched breeding date, i.e. hatching date scaled to annual ice-out date, was less infl uential. Overall, most females advanced breeding dates when ice-out occurred earlier in spring, but some females exhibited greater fl exibility in response to ice-out conditions than did others. In general, directional selection favoured early breeding over a wide range of ice-out dates. Our results seem most consistent with a hypothesis that some short-distance migrant species like goldeneyes have the capacity to track and respond appropriately to changing environmental conditions prior to onset of breeding.
16180986
Multiple aspects of plasticity in clutch size vary among populations of a globally distributed songbird.
Plasticity in life-history characteristics can influence many ecological and evolutionary phenomena, including how invading organisms cope with novel conditions in new locations or how environmental change affects organisms in native locations. Variation in reaction norm attributes is a critical element to understanding plasticity in life history, yet we know relatively little about the ways in which reaction norms vary within and among populations. We amassed data on clutch size from marked females in eight populations of house sparrows (Passer domesticus) from North America and Europe. We exploited repeated measures of clutch size to assess both the extent of within-individual phenotypic plasticity and among-individual variation and to test alternative hypotheses about the underlying causes of reaction norm shape, particularly the decline in clutch size with date. Across all populations, females of this multibrooded species altered their clutch size with respect to date, attempt order, and the interaction of date and order, producing a reaction norm in multidimensional environmental space. The reaction norm fits that predicted by a model in which optimal clutch size is driven by a decline with date hatched in the ability of offspring to recruit. Our results do not fit those predicted for other proposed causes of a seasonal decline in clutch size. We also found significant differences between populations in response to date and the date by attempt order interaction. We tested the prediction that the relationship with date should be increasingly negative as breeding season becomes shorter but found steeper declines in clutch size with date in populations with longer seasons, contrary to the prediction. Populations also differed in the level of among-individual variation in reaction norm intercept, but we found no evidence of among-individual variation in reaction norm slope. We show that complex reaction norms in life-history characters exhibit within- and among-population variance. The nature of this variance is only partially consistent with current life-history theory and stimulates expansions of such theory to accommodate complexities in adaptive life history.
83607774
Reproductive consequences of egg‐laying decisions in snow geese
Summary 
 
 
1. Even though feeding conditions typically improve over time during the laying period, clutch size decreases over the course of the nesting period in most bird species. We examined whether seasonal decrease in offspring value could explain the seasonal decline in clutch size in arctic-nesting greater snow geese (Anser caerulescens atlanticus L.). 
 
 
 
2. Nesting was synchronized within a year, with more than 90% of the nests being initiated within about 8 days. Despite this high synchrony, there was a steep seasonal decline in clutch size in each of the 7 years of the study, from about five eggs in early clutches to three in late ones (−0·20 egg day−1). 
 
 
 
3. Late parents performed more poorly than early parents in most components of reproductive success. The relationship between laying date and nesting success was curvilinear, early and late nests having a higher failure rate than those initiated near the median. Prefledging survival decreased by about 50% over the season, although the earliest hatched goslings also tended to have a reduced survival. The postfledging survival showed the strongest seasonal decline, as survival probability of late-hatched birds was about five times lower than in early-hatched ones. 
 
 
 
4. Overall reproductive success showed a very steep seasonal decline as the number of young surviving to the first winter was about eight times lower in late-nesting birds than in early-nesting ones. Reproductive success declined slightly in the earliest-nesting birds, suggesting a cost to nesting too early. 
 
 
 
5. The observed clutch size generally matched the clutch size that yielded the highest reproductive success for each laying date, except in earliest-nesting birds which should have done better by slightly delaying nesting. Our data suggest that trading off additional eggs for earlier nesting to increase reproductive success is an option in geese. Consequently, the seasonal decline in clutch size may be an adaptive response to seasonally declining survival prospects of offspring.
130802377
Rapid Advance of Spring Arrival Dates in Long-Distance Migratory Birds
Several bird species have advanced the timing of their spring migration in response to recent climate change. European short-distance migrants, wintering in temperate areas, have been assumed to be more affected by change in the European climate than long-distance migrants wintering in the tropics. However, we show that long-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants. By analyzing a long-term data set from southern Italy, we show that long-distance migrants also pass through the Mediterranean region earlier. We argue that this may reflect a climate-driven evolutionary change in the timing of spring migration.
11528282
Bird migration times, climate change, and changing population sizes
Past studies of bird migration times have shown great variation in migratory responses to climate change. We used 33 years of bird capture data (1970–2002) from Manomet, Massachusetts to examine variation in spring migration times for 32 species of North American passerines. We found that changes in first arrival dates – the unit of observation used in most studies of bird migration times – often differ dramatically from changes in the mean arrival date of the migration cohort as a whole. In our study, the earliest recorded springtime arrival date for each species occurred 0.20 days later each decade. In contrast, the mean arrival dates for birds of each species occurred 0.78 days earlier each decade. The difference in the two trends was largely explained by declining migration cohort sizes, a factor not examined in many previous studies. We found that changes in migration cohort or population sizes may account for a substantial amount of the variation in previously documented changes in migration times. After controlling for changes in migration cohort size, we found that climate variables, migration distance, and date of migration explained portions of the variation in migratory changes over time. In particular, short-distance migrants appeared to respond to changes in temperature, while mid-distance migrants responded particularly strongly to changes in the Southern Oscillation Index. The migration times of long-distance migrants tended not to change over time. Our findings suggest that previously reported changes in migration times may need to be reinterpreted to incorporate changes in migration cohort sizes.
13841318
Climate change and phenological responses of two seabird species breeding in the high-Arctic
The timing of breeding is a life-history trait that can greatly affect fitness, because suc- cessful reproduction depends on the match between the food requirements for raising young and the seasonal peak in food availability. We analysed phenology (hatch dates) in relation to climate change for 2 seabird species breeding in the high-Arctic, little auks Alle alle and black-legged kittiwakes Rissa tridactyla, for the periods 1963-2008 and 1970-2008, respectively. We show that spring climate has changed during the study period, with a strong increase in both air temperature (TEMP) and sea surface temperature (SST) and a decrease in sea ice concentration. Little auks showed a trend for ear- lier breeding over the study period, while kittiwakes showed a non-significant trend for later breed- ing, demonstrating different phenological responses in these 2 species. Little auks and kittiwakes adjusted their timing of breeding to different environmental signals. Spring TEMP was the best pre- dictor of little auk phenology, with a significant negative effect. Spring SST was the strongest predic- tor of kittiwake phenology, with a non-significant negative effect. Spring sea ice concentration and the North Atlantic Oscillation (NAO) winter index had a low relative variable importance. Furthermore, in kittiwakes, years with late breeding were associated with low clutch size and mean annual breeding success, indicating poor investment and food availability. This study identifies some spring environ- mental factors important for regulating the timing of breeding in the high-Arctic, most likely through effects on snow cover limiting access to nest sites and the development of the polar marine food web. It remains to be investigated whether environmental factors are reliable predictors of marine prey phenology, and whether the decision to start breeding is constrained by food availability.
14751853
Reproductive timing and investment in relation to spring warming and advancing agricultural schedules
AbstractAdvances in mowing schedules have led to early and rapid declines in the seasonal food availability for, and survival rates of, chicks of grassland-breeding waders. Concurrently, increased levels of soil fertilization may have improved food abundance for adults. These developments are assumed to have resulted in an advancement of laying during 1930–1976 in several meadowbird species, including Black-tailed Godwits. Despite an apparent selective advantage of early breeding, after 1976 Godwits stopped advancing their laying dates. We have analyzed the timing of breeding and reproductive investment in Dutch Black-tailed Godwits relative to recent changes in agricultural practices and climate during 1976–2007. Early and late spring temperatures and precipitation in March were used as indicators for the timing of fertilizer application and mowing, and also as qualitative measures of relative food availability for adults and chicks. When precipitation was higher in March, Black-tailed Godwits laid earlier. Following warmer winters, the earliest females laid larger eggs, which hatched heavier chicks with a higher survival probability. We suggest that the positive effect of an increasing March precipitation on invertebrate abundance may be constrained by the current policy of rigid control of the water table. This policy prevents Godwits from further advancing laying dates, which would increase their chick’s survival prospects under increasingly early mowing schedules. Policy-makers should, next to delaying mowing schedules, also consider reduced draining in early spring as a tool to help stop the population decline of the Black-tailed Godwit.ZusammenfassungBrutzeitpunkt und Reproduktion von Uferschnepfen in Bezug auf Veränderungen landschaftlicher Aktivitäten und Klimaerwärmung
 Immer frühere Mahdzeitpunkte führen zu einer immer früheren und schnellen Verringerung der saisonalen Nahrungsverfügbarkeit, und damit auch einer starken Abnahme der Überlebenschancen von Wiesenvogelküken. Im Gegensatz dazu hat die zeitgleiche zunehmende Düngung von Grasland sehr wahrscheinlich die Nahrungsgrundlage für adulte Wiesenvögel verbessert. Dies hatte zur Folge dass gleich mehrere Arten von Wiesevögeln einschließlich der Uferschnepfe zwischen 1930 und 1976 ihre Eiablage immer früher tätigten. Überraschenderweise, und obwohl eine früherer Eiablagezeitpunkt anscheinend einen Selektionsvorteil verschafft, stellten Uferschnepfen das Verfrühen der Eiablage nach 1976 ein. Hier präsentieren wir eine Analyse des Zeitpunktes der Eiablage und der Investition in die Reproduktion von niederländischen Uferschnepfen vor dem Hintergrund der rezenten Veränderungen landwirtschaftlicher Aktivitäten und des Klimas im Zeitraum von 1976–2007. Wir verwenden die mittleren Temperaturen während des frühen und späten Frühjahres sowie die Niederschlagssumme im März als Indikatoren für respektive den Zeitpunkt der Düngung, der Mahd und als qualitatives Maß des relativen Nahrungsangebot für adulte Uferschnepfen und Jungtiere. In Jahren mit feuchterem März legten Uferschnepfen ihre Eier früher. Nach wärmeren Wintern legten frühe Weibchen größere Eier, aus welchen Kücken in besserer Kondition schlüpften, welche eine bessere Überlebenswahrscheinlichkeit hatten. Unsere Resultate suggerieren, dass der positive Effekt, den die Klimaänderung auf den Niederschlag im Frühjahr, und damit auch auf die Nahrungsverfügbarkeit für adulte Uferschnepfen hat, durch die starke Kontrolle des Grundwasserspiegels zunichte gemacht wird. Dies verhindert, dass Uferschnepfen früher legen können, was die Überlebenschancen der Kücken unter immer früheren Mahdterminen deutlich verringert.
4414217
Climate change and population declines in a long-distance migratory bird
Phenological responses to climate change differ across trophic levels, which may lead to birds failing to breed at the time of maximal food abundance. Here we investigate the population consequences of such mistiming in the migratory pied flycatcher, Ficedula hypoleuca. In a comparison of nine Dutch populations, we find that populations have declined by about 90% over the past two decades in areas where the food for provisioning nestlings peaks early in the season and the birds are currently mistimed. In areas with a late food peak, early-breeding birds still breed at the right time, and there is, at most, a weak population decline. If food phenology advances further, we also predict population declines in areas with a late food peak, as in these areas adjustment to an advanced food peak is insufficient. Mistiming as a result of climate change is probably a widespread phenomenon, and here we provide evidence that it can lead to population declines.
7974435
Climate change effects on migration phenology may mismatch brood parasitic cuckoos and their hosts
Phenological responses to climate change vary among taxa and across trophic levels. This can lead to a mismatch between the life cycles of ecologically interrelated populations (e.g. predators and prey), with negative consequences for population dynamics of some of the interacting species. Here we provide, to our knowledge, the first evidence that climate change might disrupt the association between the life cycles of the common cuckoo (Cuculus canorus), a migratory brood parasitic bird, and its hosts. We investigated changes in timing of spring arrival of the cuckoo and its hosts throughout Europe over six decades, and found that short-distance, but not long-distance, migratory hosts have advanced their arrival more than the cuckoo. Hence, cuckoos may keep track of phenological changes of long-distance, but not short-distance migrant hosts, with potential consequences for breeding of both cuckoo and hosts. The mismatch to some of the important hosts may contribute to the decline of cuckoo populations and explain some of the observed local changes in parasitism rates of migratory hosts.
86553506
Climate-forced seasonal mismatch between the hatching of rhinoceros auklets and the availability of anchovy
Predator-prey relationships are key to understanding complex marine ecosystem dynamics. The match-mismatch hypothesis posits that predators time energy-intensive activities, such as reproduction, to periods of high food availability. However, predators may be constrained by various ecological or physiological processes, leading to mistimed activities relative to prey availabil- ity. We investigated inter-annual variation in the timing of breeding for a piscivorous seabird (rhinoc- eros auklet Cerorhinca monocerata) in relation to availability of a preferred prey item, Japanese anchovy Engraulis japonicus, using data collected over 18 yr between 1984 and 2006 at Teuri Island in the northern Japan Sea. Our primary goals were (1) to identify the climatic factors that affect the seabirds' timing of breeding, proxied by hatching date, and anchovy seasonal availability, and (2) to quantify the fitness effects of predator-prey matches and mismatches relative to climate variability. Hatching date was later in years with lower spring air temperatures. Auklets switched their feeding from sandlance and juvenile greenling to anchovy when it was transported into the birds' foraging range with the seasonal northern expansion of 13°C warm water from the south. The mismatch between hatching date and the period of high anchovy availability was most pronounced when spring air temperatures were warm, and there was a weak Tsushima (warm) Current. Spring air tem- perature was influenced by spring atmospheric pressure gradients in the Arctic and northern Eur- asia, which drive the east Asian winter monsoon, whereas timing of the Tsushima warm water expan- sion was influenced by winter surface pressures over the western North Pacific. Chick growth rates, mass at fledging, and overall fledging success (fitness) were lower during mismatch years when the auklets fed less on anchovy. The auklets were constrained to adjust hatching date because the sea- sonal mismatch appeared to be driven by independent and unpredictable surface pressure patterns.
10948732
Population and geographic range dynamics: implications for conservation planning
Continuing downward trends in the population sizes of many species, in the conservation status of threatened species, and in the quality, extent and connectedness of habitats are of increasing concern. Identifying the attributes of declining populations will help predict how biodiversity will be impacted and guide conservation actions. However, the drivers of biodiversity declines have changed over time and average trends in abundance or distributional change hide significant variation among species. While some populations are declining rapidly, the majority remain relatively stable and others are increasing. Here we dissect out some of the changing drivers of population and geographic range change, and identify biological and geographical correlates of winners and losers in two large datasets covering local population sizes of vertebrates since 1970 and the distributions of Galliform birds over the last two centuries. We find weak evidence for ecological and biological traits being predictors of local decline in range or abundance, but stronger evidence for the role of local anthropogenic threats and environmental change. An improved understanding of the dynamics of threat processes and how they may affect different species will help to guide better conservation planning in a continuously changing world.
8196971
Divergence in timing of parental care and migration in barnacle geese
In migratory geese, the extended association of parents and offspring is thought to play a crucial role in culturally transmitting the migration strategy to the next generation. Goslings migrate with their parents and associate closely with them almost until the next breeding season. Families do not break up until spring migration, when the parent--offspring conflict intensifies during preparation for the next generation of offspring. Recently, the commencement of spring migration of the Russian population of the barnacle goose has been delayed by about 1 month. Here, we investigated whether the duration of parental care behavior changed with this alteration in migratory behavior. In contrast to our expectation, we found that parental care terminated well before the commencement of spring migration and that parent--offspring associations were nearly absent during spring migration. We argue that the mechanisms for determining the duration of parental care is different from that determining the commencement of spring migration; hence, we conclude that a divergence in timing has developed between both behaviors. A consequence of this divergence could be that the cultural transmission of migratory behavior is disrupted, possibly playing a role in the recent establishment of new populations of Barnacle geese across the Russian flyway. Copyright 2011, Oxford University Press.
129048354
Effects of sea ice on breeding numbers and clutch size of a high arctic population of the common eider Somateria mollissima
Abstract The breeding performance of high-arctic bird populations shows large inter-annual variation that may be attributed to environmental variability, such as the timing of snow melt and break-up of the landfast sea ice that surrounds breeding colonies on islands and along coasts. In the Kongsfjorden area (79°N) on Svalbard, the number of breeding pairs and the average egg clutch size vary considerably among years. In this study, data on breeding performance are presented from 15 years in the period 1981–2000. The results showed that early break-up of sea ice in Kongsfjorden resulted in larger numbers of nests and larger average clutch sizes than late break-up. Also, individual islands with early break-up of sea ice in a particular year had more nests and larger clutch sizes compared to other islands surrounded by sea ice during a longer period in spring. Thus, the inter-annual variation in the break-up of sea ice in the fjord has considerable implications for the inter-annual variability of recruitment to the population. The results indicate that the effects of global warming on changes in the sea ice melting regime in coastal regions are important for the reproductive output of island-nesting eiders.
86820905
Nesting success of common eiders Somateria mollissima as influenced by nest-site and female characteristics in the Gulf of the St. Lawrence
Abstract In the common eider Somateria mollissima as well as in many other bird species, nesting success has been associated with female reproductive characteristics and predator accessibility to the nest site. In this study, we tested the following predictions on nesting common eiders: 1) female and nest-site characteristics are correlated within a colony, where those with the highest ranked reproductive traits nest where the environment provides best protection, 2) females nesting on forested islands generally exhibit better reproductive traits than females nesting on open islets (hereafter habitats) because the former provide the best nest protection, and consequently, 3) colonies located on forested islands have higher nesting success than those on open islets. During the summers of 1995 and 1996, we recorded nesting success at 270 eider nests on two forested islands and four open islets. Simultaneously, we measured several variables describing nest (nest concealment, vegetation height, distance to shore and density of associated nesting gulls) and female (laying date and clutch size) characteristics. Using factor analysis to relate nest-site and female characteristics, we found a correlation between factor scores within four of the six colonies monitored. This correlation indicated that females with largest clutch size and early laying were associated with nest sites of low concealment that were close to shore. However, female score did not differ with habitat. Nesting success did not differ between habitats when controlled for female and nest scores, but was related to female score, and marginally to nest-site score. Because nesting success was principally related to female characteristics rather than to nest-site characteristics, we suggest that eiders rely on nest attendance rather than on nest concealment to protect their nests. Nesting close to shore may shorten incubation recesses and improve hatchling survival when leaving the nest.
22854968
Habitat-specific clutch size and cost of incubation in eiders reconsidered
The energetic incubation constraint hypothesis (EICH) for clutch size states that birds breeding in poor habitat may free up resources for future reproduction by laying a smaller clutch. The eider (Somateria mollissima) is considered a candidate for supporting this hypothesis. Clutch size is smaller in exposed nests, presumably because of faster heat loss and higher incubation cost, and, hence, smaller optimal clutch size. However, an alternative explanation is partial predation: the first egg(s) are left unattended and vulnerable to predation, which may disproportionately affect exposed nests, so clutch size may be underestimated. We experimentally investigated whether predation on first-laid eggs in eiders depends on nest cover. We then re-evaluated how nesting habitat affects clutch size and incubation costs based on long-term data, accounting for confounding effects between habitat and individual quality. We also experimentally assessed adult survival costs of nesting in sheltered nests. The risk of egg predation in experimental nests decreased with cover. Confounding between individual and habitat quality is unlikely, as clutch size was also smaller in open nests within individuals, and early and late breeders had similar nest cover characteristics. A trade-off between clutch and female safety may explain nest cover variation, as the risk of female capture by us, mimicking predation on adults, increased with nest cover. Nest habitat had no effect on female hatching weight or weight loss, while lower temperature during incubation had an unanticipated positive relationship with hatching weight. There were no indications of elevated costs of incubating larger clutches, while clutch size and colony size were positively correlated, a pattern not predicted by the ‘energetic incubation constraint’ hypothesis. Differential partial clutch predation thus offers the more parsimonious explanation for clutch size variation among habitats in eiders, highlighting the need for caution when analysing fecundity and associated life-history parameters when habitat-specific rates of clutch predation occur.
12812748
Do purely capital layers exist among flying birds? Evidence of exogenous contribution to arctic-nesting common eider eggs
The strategy of relying extensively on stored resources for reproduction has been termed capital breeding and is in contrast to income breeding, where needs of reproduction are satisfied by exogenous (dietary) resources. Most species likely fall somewhere between these two extremes, and the position of an organism along this gradient can influence several key life-history traits. Common eiders (Somateria mollissima) are the only flying birds that are still typically considered pure capital breeders, suggesting that they depend exclusively on endogenous reserves to form their eggs and incubate. We investigated the annual and seasonal variation in contributions of endogenous and exogenous resources to egg formation in eiders breeding at the East Bay colony in the Canadian Arctic. We collected prey items along with females and their eggs during various stages of breeding and used two complementary analytical approaches: body reserve dynamics and stable isotope [δ13C, δ15N] mixing models. Indices of protein reserves remained stable from pre-laying to post-laying stages, while lipid reserves declined significantly during laying. Similarly, stable isotope analyses indicated that (1) exogenous nutrients derived from marine invertebrates strongly contributed to the formation of lipid-free egg constituents, and (2) yolk lipids were constituted mostly from endogenous lipids. We also found evidence of seasonal variation in the use of body reserves, with early breeders using proportionally more exogenous proteins to form each egg than late breeders. Based on these results, we reject the hypothesis that eiders are pure capital layers. In these flying birds, the fitness costs of a strict capital breeding strategy, such as temporary loss of flight capability and limitation of clutch and egg size, may outweigh benefits such as a reduction in egg predation rate.
84358977
Factors affecting nest site selection and nesting success in the Common Eider Somateria mollissima
Nesting site selection and nesting success in Common Eiders Somateria mollissima were studied over a 3-year period (1991–1993) in the Mast River delta (58o24'N, 94o24'W), 40 km east of Churchill, Manitoba, Canada. Eiders preferentially nested on islands that had incubating Lesser Snow Geese Anser caerulescens caerulescens on them; this effect was also seen between years on the same islands. Eiders which nested on islands with geese had a reduced chance of having eggs taken by predators during egg-laying and had a greater chance of hatching once incubation had begun, independent of the number of other eiders nesting on the island. The distance to a goose nest was less in nests which did not lose eggs prior to incubation than in those which did, but there was no difference in the distance to a goose nest in eider clutches which did or did not hatch. Artificial eider eggs placed closer to goose nests had a lower probability of being predated than those placed farther away. Nests on islands farther up the river and farther from the mainland had higher nesting success, presumably because these nesting islands were inaccessible to Arctic Foxes Alopex lagopus.
84464169
Detecting population heterogeneity in effects of North Atlantic Oscillations on seabird body condition: get into the rhythm
Climatic influences on animal populations, mediated by changes in condition-dependent survival or reproduction, have long intrigued ecologists. We analyzed links between winter North Atlantic Oscillations (NAO), a large scale climatic phenomenon affecting weather conditions over the North Atlantic and the Arctic, and average pre-laying body mass in common eiders. Body mass is a good proxy for condition-dependent reproductive output in this species. Time series links were assessed for two eider populations breeding at high latitudes, over a 10- and a 21-year time series. Winter NAO affected body mass in both populations and these effects were easier to detect when changes in the series rhythm were assessed using a novel method based on data discretization and information theory, rather than detection based on changes in amplitude, assessed using traditional linear models. Winter conditions affected body condition of eiders in both populations. Different mechanisms, however, are likely to be involved in the two populations, one being presumably affected by direct effects of climate and the other by effects through the food chain. Therefore, the same species can respond along different pathways to the same large scale climatic pattern, an important consideration when seeking to understand or manage the response of species to present and future climate change.
21289902
Pre-laying climatic cues can time reproduction to optimally match offspring hatching and ice conditions in an Arctic marine bird
Individuals breeding in seasonal environments are under strong selection to time reproduction to match offspring demand and the quality of the post-natal environment. Timing requires both the ability to accurately interpret the appropriate environmental cues, and the flexibility to respond to inter-annual variation in these cues. Determining which cues are linked to reproductive timing, what these cues are predicting and understanding the fitness consequences of variation in timing, is therefore of paramount interest to evolutionary and applied ecologists, especially in the face of global climate change. We investigated inter-annual relationships between climatic variation and the timing of reproduction in Canada’s largest breeding population of Arctic common eiders (Somateria mollissima) in East Bay, Nunavut. Warmer spring temperatures predicted both earlier mean annual laying dates and the earlier ice-free conditions required by ducklings for post-natal growth. Warmer springs had higher variation in this temperature cue, and the population laying distribution became increasingly positively-skewed in warmer summers, potentially indicating that more low-quality females had the opportunity to commence laying in warmer years. Females that timed laying to match duckling hatching just prior to fully ice-free conditions obtained the highest duckling survival probability. Inter-annual data on repeated breeding attempts revealed that the individuals examined show a similar degree of laying flexibility in response to climatic variation; however, there was significant individual variation in the absolute timing of laying within an average year. This work sheds light on how reproductive timing is related to and influenced by variation in local climate and provides vital information on how climate-related variation in reproductive timing influence a fitness measure in an Arctic species. Results are especially relevant to future work in polar environments given that global climatic changes are predicted to be most intense at high latitudes.
86227149
Interactions between lay date, clutch size, and postlaying energetic needs in a capital breeder
The condition-dependent model of optimal clutch size assumes body reserves required to initiate egg production include those for subsequent breeding phases. The threshold is expected to be similar among individuals, and hence postlaying condition should be independent of clutch size and lay date. Alternatively, the cost of incubation hypothesis predicts that females laying larger clutches should secure extra resources for incubation, and the expected fitness hypothesis suggests females adjust their condition according to the anticipated fitness benefits of the clutch. In these 2 cases, postlaying condition is predicted to be positively related to clutch size. We tested these predictions in common eider (Somateria mollissima), a precocial bird that produce eggs mostly from stored lipids and partly from endogenous proteins and rely extensively on reserves to incubate. We collected females at incubation onset and measured body condition indicators. Clutch size (number of eggs laid or number found in the nest at incubation onset) was not related to postlaying fat stores but females that laid fewer eggs maintained extra protein reserves. Timing of breeding was not related to postlaying body mass or protein reserves, whereas lay date's relationship with fat stores varied annually. Our results are generally consistent with the condition-dependent model and indicate variation in postlaying condition is mostly driven by factors other than clutch size and lay date. These data are inconsistent with the cost of incubation and the expected fitness hypotheses and suggest body store differences at incubation onset are mostly caused by environmental conditions encountered by laying females. Copyright 2011, Oxford University Press.
130920816
A choice between two adjacent islands: is switching nest sites related to weather or nest density in the Common Eider (Somateria mollissima)?
Birds change nest sites between years in response to breeding success in previous years,activitiesof other breeders,or weather conditions.Sixteen yearsof banding dataand nestcountsoftheCommonEiderinRif,westernIceland,wereusedtoevaluateprobabilityofswitching nest islands. The two man-made islands studied had different substrates (grassvs. rock) and in someyears, differentnest-initiation dates. Nestnumberswerenotrelatedtoweather.Theapparentsurvivalwasnotrelatedtoannualvariation,weatherornestden-sity. Conversely, theprobabilityof switching islands(movementprobability) was plausi-blyaffected bythreecovariates:(1)winterswith higher precipitation decreased theprob-abilityofswitchingfromthegrassytotherockyisland;(2)aswintersbecamemilderfrom1993 to 2008, the probability of switching islands decreased; and (3) as the nest numbersincreased from 155 to 606 during 1993–2008, the probability of switching islands de-creased. Winter weather may have affected nest switching primarily via precipitation,which partly determined water levels in the colony. An inverse relationship between nestdensity and the probability of switching islands is consistent with conspecific facilitationin colonially-nesting bird species.
12570953
Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics
Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species–habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate change on seabirds.
17010978
Long-Term Changes in Nutrients and Mussel Stocks Are Related to Numbers of Breeding Eiders Somateria mollissima at a Large Baltic Colony
Background The Baltic/Wadden Sea eider Somateria mollissima flyway population is decreasing, and this trend is also reflected in the large eider colony at Christiansø situated in the Baltic Sea. This colony showed a 15-fold increase from 1925 until the mid-1990's, followed by a rapid decline in recent years, although the causes of this trend remain unknown. Most birds from the colony winter in the Wadden Sea, from which environmental data and information on the size of the main diet, the mussel Mytilus edulis stock exists. We hypothesised that changes in nutrients and water temperature in the Wadden Sea had an effect on the ecosystem affecting the size of mussel stocks, the principal food item for eiders, thereby influencing the number of breeding eider in the Christiansø colony. Methodology/Principal Finding A positive relationship between the amount of fertilizer used by farmers and the concentration of phosphorus in the Wadden Sea (with a time lag of one year) allowed analysis of the predictions concerning effects of nutrients for the period 1925–2010. There was (1) increasing amounts of fertilizer used in agriculture and this increased the amount of nutrients in the marine environment thereby increasing the mussel stocks in the Wadden Sea. (2) The number of eiders at Christiansø increased when the amount of fertilizer increased. Finally (3) the number of eiders in the colony at Christiansø increased with the amount of mussel stocks in the Wadden Sea. Conclusions/Significance The trend in the number of eiders at Christiansø is representative for the entire flyway population, and since nutrient reduction in the marine environment occurs in most parts of Northwest Europe, we hypothesize that this environmental candidate parameter is involved in the overall regulation of the Baltic/Wadden Sea eider population during recent decades.
3447380
State dependent effects of elevated hormone: nest site quality, corticosterone levels and reproductive performance in the common eider.
Nest shelter in incubating birds is of major importance in providing protection against unfavourable conditions such as harshness of the environment and exposure to predators. We examined the link between nest shelter, baseline corticosterone (CORT) levels and hatching success in common eiders (Somateria mollissima) incubating at nest sites with different levels of shelter. Since more sheltered nest sites could be occupied by better-quality females, we also used an experimental manipulation of nest shelter to separate the effects of the physical attributes of the nest site from those of individual quality. We compared birds with naturally sheltered nests, exposed nests and exposed nests provided with artificial nest shelters and measured clutch size, body condition, CORT levels at the end of incubation and hatching success. If nest shelter reduces CORT levels, we predicted that CORT levels would be highest at the least sheltered sites, and that the provision of artificial shelter would reduce CORT levels. We found that nest shelter was not related to CORT levels in incubating eiders. Nest shelter, however, affected body condition, with females at exposed sites losing more body mass during incubation than females at naturally and artificially sheltered nests. Interestingly however, in those birds nesting at the exposed sites, with and without artificial shelter, those with the highest CORT levels had the lowest hatching success. This relationship was not evident in females nesting at naturally sheltered sites. These results suggest that the level of nest shelter does not directly affect CORT levels in females. Instead, we suggest that the relationship between CORT levels and hatching success is state-dependent. Exposed sites are occupied by individuals that laid smaller clutches, and hence are likely to be of lower quality, and the negative effects of elevated CORT on hatching success are more pronounced in these females.
24417556
Effects of down collection on incubation temperature, nesting behaviour and hatching success of common eiders (Somateria mollissima) in west Iceland
Incubating common eiders (Somateria mollissima) insulate their nests with down to maintain desirable heat and humidity for their eggs. Eiderdown has been collected by Icelandic farmers for centuries, and down is replaced by hay during collection. This study determined whether down collecting affected the female eiders or their hatching success. We compared the following variables between down and hay nests: incubation temperature in the nest, incubation constancy, recess frequency, recess duration, egg rotation and hatching success of the clutch. Temperature data loggers recorded nest temperatures from 3 June to 9 July 2006 in nests insulated with down (n = 12) and hay (n = 12). The mean incubation temperatures, 31.5 and 30.7°C, in down and hay nests, or the maximum and minimum temperatures, did not differ between nest types where hatching succeeded. Cooling rates in down, on average 0.34°C/min and hay nests 0.44°C/min, were similar during incubation recesses. Females left their nests 0–4 times every 24 h regardless of nest type, for a mean duration of 45 and 47.5 min in down and hay nests, respectively. The mean frequency of egg rotation, 13.9 and 15.3 times every 24 h, was similar between down and hay nests, respectively. Hatching success adjusted for clutch size was similar, 0.60 and 0.67 in down and hay nests. These findings indicate that nest down is not a critical factor for the incubating eider. Because of high effect sizes for cooling rate and hatching success, we hesitate to conclude that absolutely no effects exist. However, we conclude that delaying down collection until just before eggs hatch will minimize any possible effect of down collection on females.
87096654
Variation in nest composition and abundances of ectoparasites between nests in colonially breeding Common Eiders Somateria mollissima
ABSTRACT Capsule: The occurrence of high numbers of ectoparasites in nests of Common Eiders may be related to nest densities and nesting behaviour. Aims: To estimate abundances of ectoparasites and occurrence of blood-covered eggs, and relate those to nest bowl ages, nest bottom material and the incubation stages of eggs, in nests at two different Common Eider colonies. Methods: Nests were collected at Hvallátur and Rif, two sites at Breiðafjörður, West Iceland, in June and July 2012. The nest bottom material was classified to vegetation species and invertebrates were identified to species when possible. Results: The flea Ceratophyllus garei was the dominant ectoparasite at both sites, with median abundances higher at Hvallátur than at Rif in June. In July, the mean abundance of fleas was higher than observed in June at Rif. There were positive relationships between the flea abundances and the incubation stages of the nests, the blood cover of the eggs and the type of nesting material. No relationship was observed between the age of nesting bowls and adult flea abundances. Conclusion: Disadvantages of large parasite loads on the later nesters (second clutch in each nest) at Rif may be compensated by shared nest attendance and the concurrent added time for preening for females while other females attend their nests.
26971330
Indeterminate laying and flexible clutch size in a capital breeder, the common eider
Clutch size control in capital breeders such as large waterfowl has been much debated. Some studies have concluded that clutch size in ducks is determined before the start of laying and does not change in response to egg additions or removals. The response, however, may depend on the timing of tests, and experiments may have been too late for females to alter the number of eggs. We here study clutch size responses to predation of first and second eggs in the common eider, using protein fingerprinting of egg albumen to verify that the same female continues laying in the nest after predation. Sixty of 79 females with early egg predation (one or both of the two first eggs) deserted the nest. Among the 19 females that stayed and continued laying, the mean number of eggs produced was 4.4, significantly higher than the 3.7 in non-predated nests. The staying females had similar egg size and clutch initiation date as females that deserted, and their body mass and clutch initiation date was similar to that of females whose clutches were not predated. Even capital-breeding common eiders may therefore be indeterminate layers, as many females in which early eggs are removed lay more eggs than others. A previous study has shown that they can reduce their laying if eggs are added. Our results add to increasing evidence that ducks have more flexible egg production than previously thought.
128144438
Estimating Trends for Antarctic Birds in Relation to Climate Change
The earth’s climate is changing rapidly and these changes are expected to affect the structure and functioning of ecosystems. It is now clearly established that recent climate changes have impacted on living organisms. Several studies have demonstrated changes in population abundance, geographic distribution, and even microevolutionary changes in relation to climatic fluctuations (Parmesan, 2006).
117866366
Extending the Linear Model With R: Generalized Linear, Mixed Effects and Nonparametric Regression Models
cover point processes in the modern sense of random measures. This chapter also is more technical than the subsequent two on Markov processes. Chapter 4 (on discrete-time countable state Markov processes) is extremely short. At only 32 pages, it is shorter than all those covering a specific type of process, except for Chapter 6 (martingales). I wonder how much the typical student will benefit from the minimal, and delayed, presentation of this topic. In my experience, most students need this material early on, to fully appreciate just what stochastic processes are and what the relevant issues are, before moving on to the more technical processes. The fifth chapter (on continuous-time countable state Markov processes) is the best-developed chapter and contains many more examples than do the other chapters. Birth–death processes and queuing models get substantial coverage, and there is plenty of material here that an instructor may choose to incorporate into a course. I personally believe that an undergraduate text also should devote more space to discussion of covariance structure, especially in the context of Gaussian processes, to reinforce the notions of dependence. Examples with Kalman filters, time series, and control theory are certainly within the range of applications appropriate for a text such as this one. The opening chapter is quite long, covering a wide range of basic probability concepts, such as classification of distributions according to hazard rate behavior (e.g., IFR), partial ordering of distributions, Wald’s identity, general limit theorems, and even advanced inequalities, such as Hölder’s and Minkowski’s. The concise treatment makes these results easy to refer to, but again few if any examples are given for each topic and no context in which the student might appreciate their value is provided. On the other hand, these presentations can be skipped and then returned to later as needed. Although the title claims finance as an applied area, I could find only one financial application (options pricing in the chapter on Brownian motion), unless a few applications to actuarial science are included. The bottom line is that I would not use this book as a text for either an undergraduate or a graduate course. However, I will likely put it on the reference list for my course.
10040306
Generalized linear mixed models: a practical guide for ecology and evolution.
How should ecologists and evolutionary biologists analyze nonnormal data that involve random effects? Nonnormal data such as counts or proportions often defy classical statistical procedures. Generalized linear mixed models (GLMMs) provide a more flexible approach for analyzing nonnormal data when random effects are present. The explosion of research on GLMMs in the last decade has generated considerable uncertainty for practitioners in ecology and evolution. Despite the availability of accurate techniques for estimating GLMM parameters in simple cases, complex GLMMs are challenging to fit and statistical inference such as hypothesis testing remains difficult. We review the use (and misuse) of GLMMs in ecology and evolution, discuss estimation and inference and summarize 'best-practice' data analysis procedures for scientists facing this challenge.
86596952
CONSPECIFIC REPRODUCTIVE SUCCESS AND BREEDING HABITAT SELECTION: IMPLICATIONS FOR THE STUDY OF COLONIALITY
Habitat selection is a crucial process in the life cycle of animals because it can affect most components of fitness. It has been proposed that some animals cue on the reproductive success of conspecifics to select breeding habitats. We tested this hypothesis with demographic and behavioral data from a 17-yr study of the Black-legged Kittiwake (Rissa tridactyla), a cliff-nesting seabird. As the hypothesis assumes, the Black-legged Kittiwake nesting environment was patchy, and the relative quality of the different patches (i.e., breeding cliffs) varied in time. The average reproductive success of the breeders of a given cliff was predictable from one year to the next, but this predictability faded after several years. The dynamic nature of cliff quality in the long term is partly explained by the autocorrelation of the prevalence of an ectoparasite that influences reproductive success. As predicted by the performance-based conspecific attraction hypothesis, the reproductive success of current breeders on a given cliff was predictive of the reproductive success of new recruits on the cliff in the following year. Breeders tended to recruit to the previous year’s most productive cliffs and to emigrate from the least productive ones. Consequently, the dynamics of breeder numbers on the cliffs were explained by local reproductive success on a year-to-year basis. Because, on average, young Black-legged Kittiwakes first breed when 4 yr old, such a relationship probably results from individual choices based on the assessment of previous-year local quality. When breeders changed breeding cliffs between years, they selected cliffs of per capita higher reproductive success. Furthermore, after accounting for the potential effects of age and sex as well as between-year variations, the effect of individual breeding performance on breeding dispersal was strongly influenced by the average reproductive success of other breeders on the same cliff. Individual breeding performance did not appear to influence the probability of dispersing for birds breeding on cliffs with high local reproductive success, whereas individual breeding performance did have a strong effect on dispersal for birds that bred on cliffs with lower local reproductive success. This suggests that the reproductive success of locally breeding conspecifics may be sufficient to override an individual’s own breeding experience when deciding whether to emigrate. These results, which are supported by behavioral observations of the role of prospecting in recruitment, suggest that both first breeders and adults rely on the reproductive success of conspecifics as “public information” to assess their own chances of breeding successfully in a given patch and to make settling decisions. A corollary prediction is that individuals should attempt to breed near successful conspecifics (a form of social attraction) in order to benefit from the same favorable local environmental conditions. Such a performance-based conspecific attraction mechanism can thus lead to an aggregative distribution of nests and may have played a role in the evolution of coloniality.
84752745
A long‐term study of the population dynamics of Common Eiders Somateria mollissima: why do several parameters fluctuate markedly?
Capsule The population dynamics of an Eider population has been studied from1958 to 2006 to evaluate the causes of changes in abundance and breeding potential. Aims To evaluate the changes in clutch size, survival rate of adult ducks, the extent of non‐breeding, and recruitment to the breeding population of Common Eiders nesting on Coquet Island, Northumberland. Methods Survival rates, recruitment and size of the population have been determined by an annual mark-recapture study, while the numbers of nests and clutch size have been directly recorded each year. Results There was marked annual variation in the number of ducks alive, their mortality rates, extent of non‐breeding, clutch size and recruitment of adult ducks. Overall, the annual survival rate and clutch size decreased, and numbers of adult ducks, and presumably the population, peaked on two occasions. Conclusions No density‐dependent effects were identified and the size of the population was mainly determined by changes in the adult survival rates. Because of non‐breeding, nest counts were an unreliable measure of the population size. It is suggested that food shortage is the main factor that has produced the long‐term changes in the population and there is an indication that adverse conditions for Eiders have extended over much of northern Europe in recent years. Identification of why the duckling survival rates were so low and whether these can be increased offers the most likely means of active conservation of this species and would involve management of feeding sites rather than breeding areas.
14181477
Aggressive neighbors and dense nesting: nest site choice and success in high-Arctic common eiders
Minimizing the risk of nest predation has led some bird species to exploit the nest defense behavior of other species. At Nasaruvaalik Island, Nunavut, Canada, some common eiders (Somateria mollissima borealis) nest within the boundaries of Arctic tern (Sterna paradisaea) colonies, while others nest elsewhere on the island, away from the terns. We tested the effects of location (within vs. outside the tern colonies), density of common eider nests, and annual variation on the nesting parameters of common eiders. Our results suggest that nesting in association with Arctic terns does not confer an obvious benefit to eiders. Such associative nesting of eiders and terns may be the result of overlapping habitat preferences between the two species, or a general scarcity of suitable nesting habitat for ground-nesting species in the high Arctic. However, eiders nesting in higher densities with other eiders had greater nest success and lower total clutch predation, indicating a positive correlation between nest density and success.
53169598
Stress responsiveness, age and body condition interactively affect flight initiation distance in breeding female eiders
Predation may drive differential selection among personality types, but the mechanism linking personality with predation risk is poorly understood. One such mechanism may be provided by stress hormones (corticosterone in birds), which are linked to boldness towards predators. However, because of feedbacks between boldness and future fitness expectations, the relationship between boldness and stress physiology may be modulated by individual quality. We investigated flight initiation distances (FIDs) of incubating eider, Somateria mollissima, females in relation to handling-induced corticosterone concentrations and individual quality (female breeding experience, body condition). We investigated whether FIDs were repeatable, and whether stress responsiveness and individual quality attributes, either independently or interactively, affected FIDs. We also analysed whether incubation duration, a period of peak predation pressure on females, would depend on female boldness towards predators (FID), controlling for individual quality. FIDs were repeatable within and between seasons, and females with higher handling-induced corticosterone concentrations generally had longer FIDs. However, this relationship was modulated by interactions between stress responsiveness and individual quality. High stress responsiveness was associated with longer FIDs in younger females, while the opposite was found for the oldest females. Furthermore, the FIDs of females in good body condition increased less strongly with increasing stress-induced circulating corticosterone. Shy females (long FIDs) and those in poor body condition had shorter incubation periods. Boldness is thus linked to stress responsiveness, helping to explain why stress responses may be correlated with survival. However, physiological stress effects on boldness cannot be understood in isolation from effects of individual quality.
86502458
Boldness and Stress Responsiveness as Drivers of Nest‐Site Selection in a Ground‐Nesting Bird
Nest-site selection involves trade-offs between the probability of nest discovery by egg predators, danger to the incubating parent from predators and provision of an appropriate microclimate for incubation, and all three components are potentially influenced by nest concealment and distance to habitat edge. Personality traits also affect habitat choice, and the trade-off hypothesis suggests that variable stress-coping strategies may evolve because individuals prioritize either productivity (proactive coping) or survival (reactive coping), both of which cannot be simultaneously maximized. Applying this hypothesis to understand nest-site selection by female eider ducks (Somateria mollissima), we predicted that bold individuals with attenuated stress responsiveness should select concealed nests further away from the shore, thereby promoting clutch survival at the potential expense of reduced escape opportunities for themselves. In testing this prediction, we controlled for individual quality (female body condition and breeding experience) and verified that individual stress responses and nest-site preferences were consistent by analysing their repeatability. Finally, we analysed how the viable proportion of the clutch was related to nest-site and female characteristics. Our prediction was supported: bold females [short flight initiation distance (FID)] and those with lower handling-induced body temperature were found in concealed nests, and bold females and those with lower handling-induced corticosterone concentrations occupied nests farther from the shore. The viable proportion of the clutch peaked at intermediate proportional nest-cover and increased linearly with increasing nest distance from the shore. Stress coping styles may thus be related to nest-site selection, but their fitness consequences may be manifested indirectly through the nest-site characteristics.
84968589
Brood Parasitism and Nest Takeover in Common Eiders
Conspecific brood parasitism (CBP) is an alternative breeding tactic that occurs in many brood-tending animals and can have important fitness effects for both host and parasite. We use protein fingerprinting of egg albumen to distinguish the eggs from different females and to estimate the frequency, pattern and tactics of CBP and other forms of mixed maternity in a Hudson Bay population of common eiders (Somateria mollissima sedentaria). Mixed clutches, containing eggs from more than one female, occurred in 31% of the 86 nests studied that progressed to clutch completion. Other females than the host laid 8% of the eggs. In 11 (41%) of the mixed clutches another female laid before the host started laying, corroborating the hypothesis that takeover of nests started by other females accounts for many of the mixed clutches in this population. Our results also indicate that traditional non-molecular methods of identifying foreign eggs may considerably underestimate the frequency of mixed clutches.
17133853
Does spring ice cover influence nest initiation date and clutch size in common eiders?
Understanding how environmental factors affect ecological parameters is important to understanding and predicting impacts of environmental change. Given evidence and anticipated impacts of climate variability, this is especially true with respect to sea ice and its role in animal life history in northern regions. We examined relationships between the extent of consolidated spring ice cover (pack and landfast), nest initiation and clutch size in common eiders (Somateria mollissima) in northern Labrador, a sub-Arctic region on the east coast of Canada. Our initial prediction was that eiders would delay nesting and have smaller clutches in years with more extensive spring ice cover. Between 1998 and 2003, we surveyed coastal islands for breeding eiders and collected information on nest age and clutch size. For those years, we estimated ice cover based on Radarsat-1 images supplied by the Canadian Ice Service during the spring period (approximately June 7–12). We found that spring ice cover was a significant positive predictor of nest initiation date, and the regression equation indicated that if the average extent of ice cover around nesting islands increased by 18 ha, average nesting date was delayed by approximately 1 day. Nest initiation date was a significant negative predictor of clutch size, and the regression equation indicated that a 20 day delay in nesting reduced average clutch size by approximately 1 egg. However, ice cover itself was not a significant predictor of clutch size. Our findings suggest that eiders breed when ice is present, but ice extent may negatively influence aspects of their breeding ecology.
87211336
Patterns of Nutrient and Energy Expenditure in Female Common Eiders Nesting in the High Arctic
-In 1982 we studied weight loss, changes in body composition, and energy expenditure in breeding female Common Eiders (Somateria mollissima borealis) in Svalbard, Norway. Feeding ceased during laying and incubation. From prelaying to hatching, total weight declined by 46.4%, lipid by 81.4%, and protein by 36.8%. Daily energy expenditure during laying was 2,528 kJ, 5.2 times greater than during incubation. Rate of lipid expenditure during laying was 3.3 times greater than during incubation, and rate of protein expenditure was 8.8 times greater. Of the birds' total prelaying energy, 33.8% was expended during laying, 34.6% during incubation, and 31.6% remained at hatching. An estimated 31.6% of the energy expended during laying was invested in eggs. Sixteenand 18-carbon fatty acids dominated in lipid of the fattest and leanest birds. The major nutrient and energy donors during breeding were 16:0 and 18:1 fatty acids. Svalbard eider eggs weighed ca. 17.5% less and were incubated ca. 1.5 days shorter than eggs from the species' most southerly range limit. This apparent adaptation to arctic existence gave an estimated energy savings of 6.5% during breeding. Received 27 September 1989, accepted 4 April 1990. DURING reproduction, female waterfowl require substantial nutrients, mainly lipids and protein, both for egg synthesis and as an energy source during laying and incubation. The pattern of nutrient acquisition for and allocation to reproduction differs among various waterfowl species. Some, like the Ruddy Duck (Oxyura jamaicensis), depend almost exclusively on dietary intake throughout breeding (Tome 1984). Ring-necked Ducks (Aythya collaris; Hohman 1986) and Mallards (Anas platyrhynchos; Krapu 1981) obtain most of the protein required for egg production from the diet, while endogenous lipid reserves supply much of the fat needed for egg production and the energy for incubation. Most Arctic-nesting geese, however, feed sparsely during laying and incubation, and draw heavily on endogenous reserves stored before arrival on the breeding grounds (Ryder 1970, Ankney 1977, Ankney and MacInnes 1978, Raveling 1979). Female Common Eiders (Somateria mollissima borealis) (hereafter, Eiders) feed heavily near nesting islands during the 4-6 weeks before laying, and increase body weight by approximately 20% above winter levels (Gorman and 3Present address: Sofiesgt. 74,0454 Oslo 4, Norway. Milne 1971). They then fast completely during incubation (Cooch 1965: 30, Gorman and Milne 1971, Milne 1976, Korschgen 1977) and apparently during laying as well (Korschgen 1977); the nutrients and energy required for both producing and incubating a clutch of eggs are drawn entirely from endogenous reserves. The Eider represents an extreme case of seasonal negative energy and nutrient balance in breeding birds. Milne (1976) and Korschgen (1977) investigated changes in the body weight and composition of Eiders throughout the year, and Korschgen (1977) studied weight changes in selected organs and muscles mainly during incubation. Neither study presented detailed data on the changes in weight and body composition that occur in laying when the rate of energy and nutrient expenditure is substantial. Our aim was to investigate the extent and pattern of endogenous nutrient and energy expenditure during laying and incubation in female Eiders breeding in the high Arctic. We also provide comparative data from a population breeding near the species' northern range limit. STUDY AREA AND METHODS The study was conducted at Ny-Alesund in the Kongsfjord region of West Spitsbergen (78?55'N, 660 The Auk 107: 660-668. October 1990 This content downloaded from 157.55.39.104 on Sun, 19 Jun 2016 05:47:30 UTC All use subject to http://about.jstor.org/terms October 1990] Arctic Breeding in Female Eiders 661 12000'E) in the Svalbard (Norway) archipelago during 1982. Eiders returned to the Kongsfjord region around mid-April after wintering farther south. Birds concentrated in patches of open water near the mouth of the fjord to forage before nesting. Pairs began flights to the inner fjord in late May, apparently to investigate ice conditions near breeding islands there. Eiders usually concentrate breeding efforts on five major islands in the inner Kongsfjord, as well as near the research station at Ny-Alesund. Laying often begins at different times on adjacent islands because of local variation in ice conditions (Parker and Mehlum in press). Consequently, all birds collected for body composition analysis were collected at the Ny-Alesund colony. Females were collected at four precisely known stages of the reproductive cycle designated as (1) two-three weeks before laying: females collected shortly after pairs began to arrive near the Ny-Alesund colony (i.e. 2-3 weeks before laying began [n = 4]); (2) prelaying: females with large follicles collected just before laying and within 3 days of commencement of laying in the colony (n = 7); (3) postlaying: females collected after 2-3 days of incubation (mean = 2.1), each checked regularly during laying to minimize the possibility of dump nesting or loss of eggs to predators (n = 7); and (4) hatching: females collected on the nest with hatched or hatching young (n = 8). An additional 14 females at this stage were captured and weighed to increase the sample size of bird weights at hatching. Immediately after collection, birds were weighed (total carcass weight) on a Salter spring scale to the nearest 10 g. They were then completely hand-plucked and singed. The intestines (emptied), gizzard (emptied), liver, both pectoral muscles, and the ovary with oviduct were excised, and wet weights were recorded to the nearest 0.1 g. The featherless carcass (including excised muscles and organs) was weighed (featherless carcass weight) and frozen at 20?C in double plastic bags. In preparation for the body composition analysis, the frozen material was sawed on a band saw into pieces and homogenized in a food grinder. The water content of each carcass was determined by drying duplicate 15-g samples to constant weight in a vacuum oven for 2 days at room temperature and ca. 1 day at 30?C. The remaining material was burned at 600?C to constant weight (for approx. 4 h) to obtain ash values. Total lipid was determined with a modified Folch extraction (chloroform-methanol), and total protein by the macro-Kjeldahl method with protein expressed as the product of nitrogen times 6.25. Both lipid and protein determinations were based on 6-10 g samples, usually in triplicate (Holm et al. 1973). Calculation of energy content in lipid is based on a conversion factor of 38.53 kilojoules per gram (kJ g-1), as direct calorimetry of fat samples (n = 9) from both fat and lean birds gave this same value. The energy content of protein was derived using a standard conversion factor of 19.67 kJ.g-l (Pullar and Webster 1977). The energy in subsamples of total homogenate from nine different carcasses, including individuals from each of the four classes of breeding birds, was determined by direct calorimetry. These direct values were compared with total energy values of the same birds derived by calculation as a check for accuracy. Energy values throughout are expressed in kilojoules (4.184 kJ = 1 kcal). Samples of homogenate from the fattest bird collected 2-3 weeks before laying and the leanest bird collected at hatching were analyzed for fatty-acid composition using standard gas chromatography methods. All analyses were done at the Institute for Nutrition Research, School of Medicine, University of Oslo, Oslo, Norway. Statistical comparisons of carcass, organ, muscle, lipid, protein, water, and ash weight were made using one-way analysis of variance with significance level set at P < 0.05.