132949369
Nonbreeder birds at colonies display qualitatively similar seasonal mass change patterns as breeders
Abstract The difficulty in studying nonbreeding birds means that little is known about them or their resource requirements, despite forming a large and significant component of a population. One way to assess food requirements is to examine changes in body mass, because it indicates the amount of food acquired. In terms of body mass changes, our expectation is that nonbreeders will either (a) be in poorer condition than the breeders which potentially explains why they do not breed or (b) remain at a stable higher mass as they are unconstrained by the physiological costs associated with rearing chicks. Here, we interrogate body mass datasets of breeding and nonbreeding birds of two penguin species to assess these predictions and determine whether differences in mass exist between these two groups throughout the breeding season. The first dataset is from a wild Adélie penguin population, where bird mass was recorded automatically and breeding status determined from a resighting program. A second population of captive gentoo penguins were weighed regularly each breeding season. We demonstrate that although there were times in each year when breeders were heavier than their nonbreeding counterparts for both populations, the mass changes showed qualitatively similar patterns throughout the breeding season irrespective of breeding status. Heavier breeders at times during the breeding season are not unexpected but the overall similar pattern of mass change irrespective of breeding status is in contrast to expectations. It appears that breeding status per se and the constraints that breeding places on birds are not the only driver of changes in mass throughout the breeding season and, although not explicitly studied here, the role of hormones in driving changes in appetite could be key to explain these results. These results present a significant step toward understanding food requirements of nonbreeders in avian populations.
87708004
Modelling Annual Changes in Numbers of Breeding Fulmars, Fulmarus glacialis, at a Colony in Orkney
(1) During a long-term study of breeding fulmars in Orkney, the number of birds breeding each year has increased on average, but with some considerable variations between years. (2) In a species with deferred maturity, low fidelity to natal colony and which is faithful to both mate and nest site, the factors causing changes in breeding numbers are likely to be annual survival of established breeders and annual recruitment of new breeders. (3) Recruitment could not be measured directly, but an index was determined, based upon the number of unringed breeding birds. However, in the observed data there were some occasions in which not all of the unringed birds breeding in one year necessarily bred the following year. There is some evidence to suggest that this may be due to intermittent breeding and/or emigration, probably involving inexperienced breeders. (4) A new index of 'recruitment', which could be negative, was calculated from the observed data. A model was developed to simulate breeding population size over a series of years, using observed annual values of survival and 'recruitment' as input parameters. (5) Simulations from the model were realistic in terms of variation between years and correlations between variables. (6) The model was therefore run using particular observed values for both 'recruitment' and survival. It was found that 'recruitment' had a much greater effect upon the population size than did survival of breeding adults. (7) The model was then used to predict the size of the breeding population one year in advance, with reasonable accuracy. (8) The simulations highlight the need for further information about the behaviour and movements of potential breeding recruits.
73607888
ON COLONY SIZE , BREEDING SUCCESS , RECRUITMENT AND INTER-COLONY DISPERSAL IN A TASMANIAN COLONY OF SHORT-TAILED SHEARWATERS PUFFINUS TENUIROSTRIS OVER A 30-YEAR PERIOD
SERVENTY, D.L. and P.J. CURRY 1984. Observations on colony size, breeding success, recruitment and intercolony dispersal in a Tasmanian colony of Short-tailed Shearwaters Puffinus tenurrostrrs over a 30-year period. Emu 84: 71-79. A programme to mark a small colony of Short-tailed Shearwaters, by means of monel leg-bands, was begun on Fisher Island during 1947-50 as part of a comprehensive study. Banding of all adults and their young has colitinued every year since (to 1980). The numbsrf breeding bu r rowsoc_cup ied~~h year declined steadily during the first 25 years of the study, at the end of which numbers had been reduced by 71%. More recently, numbers have begun to increase again. No change has occurred in the relative sizes of three sub-colonies existing within the island. Annual rates of breeding success were usually lower than those reported from other less-studiedcolcGn?es and have tenTeZT03eeZher relatilvilyhigh (> 55%) or else poor (< 40%). Some chicks were raised every year; on average, the smallest sub-colony was as successful as the largest. Nearly all breeding failures occurred before the chick-rearing stage and few successfully hatched chicks failed to fledge. No banded young were recaptured at the colony before age two and most not until three years and upwards. Age at first breeding for both sexes ranged from five to at least ten years. Forty-one per cent of chicks banded over 20 consecutive seasons were subsequently recovered alive on their natal island but only 35% of these were recruited as breeders. Losses of immatures and young adults through emigration were offset by an annual recruitment of unbanded immigrants, most of which could not have been bred on the island. After 30 years, the proportion of Fisherbred breeders in the colony was stable at 41-46%. Band recoveries confirmed inter-colony dispersal by young adults. Fisher-bred birds found in nearby colonies were encountered mainly in the nearest breeding area on the closest neighbouring island. Repeated disturbance of the colony during the course of the study is thought to have contributed to the decline of the colony, due to increased burrow desertion, decreased breeding success and decreased recruitment of young adults.
1037122
Long-term population studies of seabirds.
Long-term studies of seabirds, some now 30-40 years old, have begun to reveal significant age-related changes in the survival and reproduction o f these long-lived animals. Evidence for density-dependent regulation of seabird numbers, however, remains sparse whereas unpredictable, disastrous breeding years may be an important influence. Critical evaluation will require better data on (1) the extent of movements of seabirds between colonies, (2) the characteristics of those individuals that contribute disproportionately to the next generation, and (3) the importance of year and/or cohort effects on population processes.
86570386
Age and the timing of breeding in a long‐lived bird: a role for stress hormones?
Summary 
1. Young birds often reproduce later in the season than older ones, with poorer breeding success, but the proximate mechanisms involved in such a pattern remain poorly studied, especially in long-lived species. One possible mechanism is the endocrine stress response which is accompanied by the release of corticosterone. Elevated corticosterone levels can trigger physiological and behavioural responses that may delay or even suppress reproduction. 
 
2. We tested the hypothesis that the delayed timing of breeding of young birds may be related to a greater susceptibility to stress compared with older ones during the pre-laying period of the breeding season. For this purpose, known-age (7–44 years old) pre-laying snow petrels, Pagodroma nivea, were monitored for baseline and acute stress-induced corticosterone levels. We examined whether baseline and stress-induced corticosterone levels were related to age, and whether they could influence the decision to breed and egg-laying date. 
 
3. Young snow petrels were more likely to skip the breeding season and to breed later than middle-aged birds. In addition, the oldest birds bred later than middle-aged ones, suggesting a possible senescence on laying dates. Baseline corticosterone levels were independent of age but young and very old birds were more sensitive to stress than middle-aged ones. However, there was no effect of stress-induced corticosterone levels on breeding decision and egg-laying date. Elevated baseline corticosterone levels during the pre-laying period were associated with a higher probability of skipping breeding in females and a delayed timing of egg-laying in both sexes. 
 
4. These results suggest that the greater susceptibility of young breeders to stress was not the functional mechanism explaining their delayed timing of breeding. Baseline corticosterone levels, although independent of age, appear to be a more likely mediator of breeding decision and egg-laying date. In long-lived birds, the relationship between age and timing of breeding may be rather indirect, as other age-related factors such as breeding experience or foraging skills may have a deeper impact on baseline corticosterone than age per se.
88013377
Reproductive endocrinology and mechanisms of breeding inhibition in cooperatively breeding Florida Scrub Jays Aphelocoma C. coerulescens)
Although the ecological and evolutionary bases of cooperative breeding have received close scrutiny, few studies have explored the physiological mechanisms responsible for delayed breeding by helpers. We chose the Florida Scrub Jay, Aphelocoma c. coerulescens, to determine whether breeders and nonbreeders have different hormone profiles during the reproductive season. We found that male nonbreeders had significantly lower testosterone levels and higher progesterone levels than did male breeders. Nonbreeder and breeder males had similar plasma levels of corticosterone. Elevated plasma levels of progesterone in nonbreeder males may interfere with the reproductive activity at the behavioral or physiological level. Alternatively, progesterone may enable these nonbreeding males to express parental behavior in the absence of a parent/offspring relationship, but the occurrence of the highest levels of progesterone during nest building and egg laying supports the former interpretation. In females, we found that nonbreeders had significantly lower levels of estradiol and corticosterone than breeders. The low levels of primary sex steroid hormones in male and female nonbreeders may physiologically and behaviorally inhibit reproductive activity and suggest hat these individuals are reproductively incompetent. The absence of high levels of corticosterone in nonbreeders suggests that this reproductive inhibition is not due to glucocorticoid-mediated stress imposed by dominant breeders.
86551100
Intermittent Breeding of the Fulmar (Fulmarus glacialis (L.)), with some General Observations on Non‐Breeding in Sea‐Birds
Summary. 
 
1 
 There is a large non-breeding population of Fulmars and other Pro-cellariiform birds, which suggests that they do not breed annually. 
 
2 
 In non-breeding Fulmars obtained in northern Labrador in July it was found that the length of the middle claws varied from 16.0 to 10.6 mm., due to wear. As pelagic birds can only wear down their claws when breeding, this observation strongly suggests a non-breeding population of mixed age-groups. 
 
3 
 Ovaries from four representative non-breeding females were sectioned, and histological confirmation obtained of the relation of claw-length to age. Resorbed remnants of ovulated follicles prove that all these birds had bred in one or many previous years, and thus that their reproduction is intermittent. 
 
4 
 A case of follicular atresia accompanied by the extrusion of yolk into the stroma is figured. 
 
5 
 When breeding is inhibited in the Fulmar and certain other birds the annual (post-nuptial) moult occurs prematurely. A short discussion is given of other effects of inhibited breeding in marine birds.
87588505
Non-breeders as a buffer against environmental stress : declines in numbers of great skuas on Foula, Shetland, and prediction of future recruitment
1. The number of breeding great skuas Catharacta skua on Foula, Shetland, was determined by counting apparently occupied territories (AOTs) during the 1988 and 1990 breeding seasons (2400 and 2340 AOTs, respectively, representing 20% of the northern hemisphere population). 2. A decrease in the availability of the preferred food, sandeels Ammodytes marines, has been accompanied by a slight fall in AOTs, a considerable increase in foraging effort of breeding adults and a 75% fall in breeding success, indicating that food shortage has put the population under stress. 3. Two methods are presented which allow the number of non-breeding great skuas frequenting Foula to be estimated, based on studies of individually colourringed birds. Totals of 3303 (SE = 243) and 4013 (SE = 479) non-breeding great skuas were estimated to frequent Foula in the 1989 and 1990 breeding seasons, respectively. These totals are far greater than indicated by individual counts, due to each bird staying in the colony an average of only 16-21 days. 4. Both the number of breeders and the peak number of non-breeders have declined since 1977, although the peak number of non-breeders decreased much more (non-breeders by 80%, breeders by 21.5%). The rapid decrease in numbers of non-breeders appears to be due to increased recruitment as a consequence of a reduction in adult survival rate, since age at first breeding and breeding success did not change before 1987. 5. Because breeding success since 1987 has been only 25% of the previous average, we predict that the dramatic reduction in the number of non-breeders at Foula since the mid-1970s will soon be followed by a rapid reduction in recruitment, and a further and much faster drop in breeding numbers, over the next few years. 6. This study supports the suggestion of Porter & Coulson (1987) that numbers of non-breeders at seabird colonies may provide an early and sensitive indication of environmental changes having adverse effects on the population, since non-breeders act as a buffer to such stress.
53629328
Large-scale population assessment informs conservation management for seabirds in Antarctica and the Southern Ocean: A case study of Adélie penguins
Abstract Antarctica and the Southern Ocean are increasingly affected by fisheries, climate change and human presence. Antarctic seabirds are vulnerable to all these threats because they depend on terrestrial and marine environments to breed and forage. We assess the current distribution and total abundance of Adelie penguins in East Antarctica and find there are 3.5 (95% CI 2.9–4.2) million individuals of breeding age along the East Antarctic coastline and 5.9 (4.2–7.7) million individuals foraging in the adjacent ocean after the breeding season. One third of the breeding population numbering over 1 million individuals breed within 10 km of research stations, highlighting the potential for human activities to impact Adelie penguin populations despite their current high abundance. The 16 Antarctic Specially Protected Areas currently designated in East Antarctica offer protection to breeding populations close to stations in four of six regional populations. The East Antarctic breeding population consumes an average of 193 500 tonnes of krill and 18 800 tonnes of fish during a breeding season, with consumption peaking at the end of the breeding season. These findings can inform future conservation management decisions in the terrestrial environment under the Protocol on Environmental Protection to develop a systematic network of protected areas, and in the marine environment under the Convention for the Conservation of Antarctic Marine Living Resources to allow the consumption needs of Adelie penguins to be taken into account when setting fishery catch limits. Extending this work to other penguin, flying seabird, seal and whale species is a priority for conservation management in Antarctica and the Southern Ocean.
205318019
Recruitment and survival of immature seabirds in relation to oil spills and climate variability.
1. In long-lived animals with delayed maturity, the non-breeding component of the population may play an important role in buffering the effects of stochastic mortality. Populations of colonial seabirds often consist of more than 50% non-breeders, yet because they spend much of their early life at sea, we understand little about their impact on the demographic process. 2. Using multistate capture-mark-recapture techniques, we analyse a long-term data set of individually identifiable common guillemots, Uria aalge Pont., to assess factors influencing their immature survival and two-stage recruitment process. 3. Analysis of the distribution of ringed common guillemots during the non-breeding season, separated by age classes, revealed that all age classes were potentially at risk from four major oil spills. However, the youngest age class (0-3 years) were far more widely spread than birds 4-6 years old, which were more widely spread than birds aged 6 and over. Therefore the chance of encountering an oil spill was age-dependent. 4. A 2-year compound survival estimate for juvenile guillemots was weakly negatively correlated with winter sea-surface temperature, but was not influenced by oil spills. Non-breeder survival did not vary significantly over time. 5. In years following four oil spills, juvenile recruitment was almost double the value in non-oil-spill years. Recent work from Skomer Island showed a doubling of adult mortality associated with major oil spills, which probably reduced competition at the breeding colony, allowing increased immature recruitment to compensate for these losses. We discuss the implications of compensatory recruitment for assessing the impact of oil pollution incidents.
46821668
Energyscapes and prey fields shape a North Atlantic seabird wintering hotspot under climate change
There is an urgent need for a better understanding of animal migratory ecology under the influence of climate change. Most current analyses require long-term monitoring of populations on the move, and shorter-term approaches are needed. Here, we analysed the ecological drivers of seabird migration within the framework of the energyscape concept, which we defined as the variations in the energy requirements of an organism across geographical space as a function of environmental conditions. We compared the winter location of seabirds with their modelled energy requirements and prey fields throughout the North Atlantic. Across six winters, we tracked the migration of 94 little auks (Alle alle), a key sentinel Arctic species, between their East Greenland breeding site and wintering areas off Newfoundland. Winter energyscapes were modelled with Niche Mapper™, a mechanistic tool which takes into account local climate and bird ecophysiology. Subsequently, we used a resource selection function to explain seabird distributions through modelled energyscapes and winter surface distribution of one of their main prey, Calanus finmarchicus. Finally, future energyscapes were calculated according to IPCC climate change scenarios. We found that little auks targeted areas with high prey densities and moderately elevated energyscapes. Predicted energyscapes for 2050 and 2095 showed a decrease in winter energy requirements under the high emission scenario, which may be beneficial if prey availability is maintained. Overall, our study demonstrates the great potential of the energyscape concept for the study of animal spatial ecology, in particular in the context of global change.
54923494
Modelling population dynamics of seabirds: importance of the effects of climate fluctuations on breeding proportions
Environmental factors and their interactions are likely to have shaped specific breeding and survival strategies in top predators. Understanding how climatic factors affect populations requires detailed investigation of the demographic parameters and population modelling. Here, we focus on the modelling of a southern fulmar population over a 39 year period in Terre Adelie, Antarctica, using Leslie matrix models to understand from a prospective and retrospective point of view, how vital rates and their variations, affect the cyclic population dynamics. The elasticity of population growth rate to adult survival was very high (0.95), as predicted by a slow–fast continuum in avian life histories. However, adult survival varied little between years (mean±SD: 0.92±0.07), and could not explain the strong fluctuations observed in the number of breeders and chicks. The high temporal fluctuations of the proportion of breeders (0.57±0.22) and breeding success (0.70±0.14) had the strongest impact on population dynamics, despite their weak elasticities (0.05). Before the 1980s, population fluctuations were mainly explained by a direct impact of sea-ice extent (SIE) anomalies during summer (by a threshold effect) on the proportion of breeders. After 1980s, 3 years periodic population fluctuations were best predicted by 3 years cyclic variations in the proportion of breeders. SIE showed a marked change of periodicity during the 1980s, and SIE during winter fluctuated with a 3 years periodicity during 1980–1995. The marked change in population dynamics, through a change of the variations of the proportion of breeders, may be explained in the light of a regime shift that probably occurred around the 1980s, and which affected the sea ice environment, the availability of prey, and thus the demographic parameters and population dynamics of southern fulmars.
84923897
Colony attendance and censusing of Black Guillemots Cepphus grylle in Shetland
The diurnal rhythm of colony attendance by Black Guillemots varied seasonally. No tidal effects were detected but in April attendance was lower when winds exceeded force 4. Numbers were most stable during 05.00–08.00 GMT in the pre-breeding period. Counts at this time and in winds of force 4 or less provide the best estimate of adult populations. Between late March and mid-May, counts of adults associated with breeding habitat account for most birds occupying suitable nest sites and censuses in northern Britain should be conducted in this period. As the proportion of non-breeding adults varies between colonies, no universal correction factor can be used to estimate the number of breeding attempts from counts of birds. Counts aimed at detecting maximum attendance provide greater accuracy than single counts made by flushing all birds on to the sea but take longer. Monitoring units should be stretches o-f coastline that include a number of colonies of different sizes.
127779324
Adélie and Chinstrap Penguins: Their Potential as Monitors of the Southern Ocean Marine Ecosystem
Analysis of annual variability in the parameters recommended by CCAMLR for ecosystem monitoring revealed considerable variation among the parameters for which we have sufficient data to make an assessment. Interpretation of the observed variability was greatly enhanced when several parameters were considered simultaneously. In concert, the parameters should be useful for assessing perturbations in the Antarctic ecosystem. The choice of Adelie and chinstrap penguins as key indicator species seems an excellent one, given their very different responses to the highly variable conditions in the Antarctic Peninsula region, their species-specific breeding patterns, and the asynchrony between their respective breeding seasons. If a time series of data becomes available, it may be possible to differentiate between fishery-induced and natural perturbations in the ecosystem.
16178456
Thermodynamic modelling predicts energetic bottleneck for seabirds wintering in the northwest Atlantic
SUMMARY Studying the energetics of marine top predators such as seabirds is essential to understand processes underlying adult winter survival and its impact on population dynamics. Winter survival is believed to be the single most important life-history trait in long-lived species but its determinants are largely unknown. Seabirds are inaccessible during this season, so conventional metabolic studies are extremely challenging and new approaches are needed. This paper describes and uses a state-of-the-art mechanistic model, Niche Mapper™, to predict energy expenditure and food requirements of the two main seabird species wintering in the northwest Atlantic. We found that energy demand increased throughout the winter phase in both species. Across this period, mean estimated daily energy requirements were 1306 kJ day–1 for Brünnich's guillemots (Uria lomvia) and 430 kJ day–1 for little auks (Alle alle) wintering off Greenland and Newfoundland. Mean estimated daily food requirements were 547 g wet food day–1 for Brünnich's guillemots, and 289 g wet food day–1 for little auks. For both species and both wintering sites, our model predicts a sharp increase in energy expenditure between November and December, primarily driven by climatic factors such as air temperature and wind speed. These findings strongly suggest the existence of an energetic bottleneck for North Atlantic seabirds towards the end of the year, a challenging energetic phase which might explain recurrent events of winter mass-mortality, so called `seabird winter wrecks'. Our study therefore emphasizes the relevance of thermodynamics/biophysical modelling for investigating the energy balance of wintering marine top predators and its interplay with survival and population dynamics in the context of global change.
84331250
FIELD METABOLIC RATE AND FOOD REQUIREMENT SCALING IN MAMMALS AND BIRDS
Field metabolic rates (FMRs or HF), all measured using doubly labeled water, of 23 species of eutherian mammals, 13 species of marsupial mammals, and 25 species of birds were summarized and analyzed allometrically (log10-1og10 regressions). FMR is strong- ly correlated with body mass in each of these groups. FMR scales differently than does basal or standard metabolic rate in eutherians (FMR slope = 0.81) and marsupials (FMR slope = 0.58), but not in birds (FMR slope = 0.64 overall, but 0.75 in passerines and 0.75 in all other birds). Medium-sized (240-5 50 g) eutherians, marsupials, and birds have similar FMRs, and these are - 17 times as high as FMRs of like-sized ectothermic vertebrates such as iguanid lizards. For endothermic vertebrates, the energy cost of surviving in nature is enormous compared with that for ectotherms. Within the eutherians, marsupials, or birds, FMR scales differently for the following subgroups: rodents, passerine birds, her- bivorous eutherians, herbivorous marsupials, desert eutherians, desert birds, and seabirds. Equations are given for use in predicting daily and annual FMR and food requirement of a species of terrestrial vertebrate, given its body mass.
88192227
Daily body-mass loss and nitrogen excretion during molting fast of Macaroni Penguins
SHORT, L. L. 1972. Hybridization, taxonomy and avian evolution. Ann. Mo. Bot. Gard. 59:447-453. TAYLOR, A. L., AND E. D. FORSMAN. 1976. Recent range extensions of the Barred Owl in western North America, including the first records for Oregon. Condor 78:560-561. U.S. FISH AND WILDLIFE SERVICE. 1990. Determination of threatened status for the Northern Spotted Owl, Final rule. U.S. Federal Register 55(123): 26114-26194. Voous, K. H. 1989. Owls of the Northern Hemisphere. MIT Press, Cambridge, Massachusetts.
5623588
Refeeding signal in fasting-incubating king penguins: changes in behavior and egg temperature.
This study is directed toward understanding the process of feeding stimulation ("refeeding signal") that has been suggested to operate below a body mass threshold or critical metabolic status in spontaneously fasting birds. Behavior and egg temperature (T(egg)) were continuously monitored by video monitoring and biotelemetry, respectively, in fasting-incubating king penguins kept in a pen to prevent relief by the partner until spontaneous egg abandonment. Penned birds fasted 10 days more and lost 1.2 kg more than birds relieved normally by their partner, abandoning the egg about 1 wk after reaching a critical body mass. Definitive egg abandonment was preceded by transitory abandonments of progressively increasing duration during which time the birds went further and further away from their egg. There were marked interindividual differences but on average transitory abandonments began 36 +/- 5 h before the definitive abandonment and were paralleled by resumption of display songs signaling the readiness of the bird to depart for feeding. T(egg) was maintained at around 35.7 degrees C during normal incubation but significantly decreased the last 2 days before egg abandonment. These changes are interpreted as reflecting a stimulation to refeed at a threshold body mass corresponding to a critical fat store depletion. Thus the fasting-incubating king penguin appears to be an interesting animal model for understanding the long-term metabolic control of feeding behavior in relation to energy status.
4381796
Behavioral changes in fasting emperor penguins: evidence for a "refeeding signal" linked to a metabolic shift.
This study examines the relationships between metabolic status and behavior in spontaneously fasting birds in the context of long-term regulation of body mass and feeding. Locomotor activity, escape behavior, display songs, body mass, and metabolic and endocrine status of captive male emperor penguins were recorded during a breeding fast. We also examined whether body mass at the end of the fast affected further survival. The major part of the fast ( phase II) was characterized by the maintenance of a very low level of locomotor activity, with almost no attempt to escape, by an almost constant rate of body mass loss, and by steady plasma levels of uric acid, β-hydroxybutyrate, and corticosterone. This indicates behavioral and metabolic adjustments directed toward sparing energy and body protein. Below a body mass of ∼24 kg ( phase III), spontaneous locomotor activity and attempts to escape increased by up to 8- and 15-fold, respectively, and display songs were resumed. This probably reflected an increase in the drive to refeed. Simultaneously, daily body mass loss and plasma levels of uric acid and corticosterone increased, whereas plasma levels of β-hydroxybutyrate decreased. Some experimental birds were seen again in following years. These findings suggest that at a threshold of body mass, a metabolic and endocrine shift, possibly related to a limited availability of fat stores, acts as a "refeeding signal" that improves the survival of penguins to fasting.
4426019
Thermal strategies of king penguins during prolonged fasting in water
ABSTRACT Most animals experience periods of unfavourable conditions, challenging their daily energy balance. During breeding, king penguins fast voluntarily for up to 1.5 months in the colony, after which they replenish their energy stores at sea. However, at sea, birds might encounter periods of low foraging profitability, forcing them to draw from previously stored energy (e.g. subcutaneous fat). Accessing peripheral fat stores requires perfusion, increasing heat loss and thermoregulatory costs. Hence, how these birds balance the conflicting demands of nutritional needs and thermoregulation is unclear. We investigated the physiological responses of king penguins to fasting in cold water by: (1) monitoring tissue temperatures, as a proxy of tissue perfusion, at four distinct sites (deep and peripheral); and (2) recording their oxygen consumption rate while birds floated inside a water tank. Despite frequent oscillations, temperatures of all tissues often reached near-normothermic levels, indicating that birds maintained perfusion to peripheral tissues throughout their fasting period in water. The oxygen consumption rate of birds increased with fasting duration in water, while it was also higher when the flank tissue was warmer, indicating greater perfusion. Hence, fasting king penguins in water maintained peripheral perfusion, despite the associated greater heat loss and, therefore, thermoregulatory costs, probably to access subcutaneous fat stores. Hence, the observed normothermia in peripheral tissues of king penguins at sea, upon completion of a foraging bout, is likely explained by their nutritional needs: depositing free fatty acids (FFA) in subcutaneous tissues after profitable foraging or mobilizing FFA to fuel metabolism when foraging success was insufficient. Summary: Maintenance of near-normothermic temperatures in peripheral tissues of king penguins when fasting in cold water suggests maintained perfusion, presumably to mobilize free fatty acids from subcutaneous adipose tissue.
54764932
Environmental conditions and life history constraints determine foraging range in breeding Adélie penguins
Foraging movements of Adelie penguins are constrained both by environmental con- ditions (e.g. sea ice cover) and life history factors (e.g. regular offspring provisioning). We describe within season changes in foraging range, trip duration and body condition of Adelie penguins nest- ing at Bechervaise Island, East Antarctica, in the context of these constraints. Penguins were satellite tracked over multiple seasons during the incubation, guard, creche and pre-moult phases of their annual cycle. They ranged farthest during incubation when sea ice was extensive and shortest dur- ing the guard stage when chicks were small and sea ice limited in extent. Prior to their annual moult the birds foraged hundreds of kilometres to the west and east of their breeding sites. A recurrent polynya facilitated access to the sea early in the season when ice cover was extensive. Kernel analy- ses showed that penguins foraged most intensively close to the colony, along submarine canyons and at the continental shelf break. Increases in foraging range, as the chick rearing period progressed, were consistent with changing energy requirements of adults and chicks and likely intraspecific competition. Whilst provisioning their offspring, penguins adopted a variable combination of time minimising and food maximising foraging behaviour in which choice of foraging rule was determined largely by adult body condition.
83593073
Measurements and seasonal changes in weight of guillemots Uria aalge at a breeding colony
We caught, weighed and measured Guillemots at a colony before and during the breeding season, and when they returned to the colony in October following the main moult of the year. Their sex and breeding status were assessed by detailed observations. Males were heaviest in the prelaying period and lightest when they had young. Lost weight was regained by the autumn. Females showed a similar pattern but the changes were less marked. Adults showed a significant decline in weight with increasing age of the chick. Nonbreeding birds had similar wing lengths to adults but were lighter in weight. We could detect no effect of weight in the prebreeding period on whether or not birds bred, when the egg was laid or breeding success.
15750878
Physiological Condition and Reproductive Consequences in Adélie Penguins1
Abstract Animals must make “decisions” (e.g., when or whether to breed, the effort to put into a breeding episode) by integrating physiological, environmental and social inputs. This integration can be studied only in a field context. In Adélie penguins (Pygoscelis adeliae) reproduction is constrained by foraging ecology, mode of transport, and the extreme latitude at which they live. The decision whether to breed in a given year is influenced by body conditions. Adélie penguins must fast for several weeks during the early reproductive stages and use stored fat for metabolic energy. Females that return to the colony, but do not breed, are 10–12% lighter than females that do breed. Birds that are relatively low in body mass tend to have lower reproductive success than heavier birds, and an individual's reproductive success is positively correlated with the body fat stores it had on arrival. After eggs are laid, parents alternate in attending the nest. Nest failure occurs if one parent does not make a timely return and its fasting partner must eventually leave. During normal-length fasts plasma corticosterone and glucose levels do not change. Blood β-hydroxybutyrate levels gradually increase during the fast while uric acid levels remain low, but in birds with the longest fasts (>∼50 days), ketone levels may fall and uric acid levels increase, indicative of a switch from using fat to using body proteins for metabolism. In incubating males, hematocrit and hemoglobin concentrations also increase, suggesting dehydration can accompany energy stress during the breeding fast.
411545
To breed or not to breed: a seabird's response to extreme climatic events
Intermittent breeding is an important life-history strategy that has rarely been quantified in the wild and for which drivers remain unclear. It may be the result of a trade-off between survival and reproduction, with individuals skipping breeding when breeding conditions are below a certain threshold. Heterogeneity in individual quality can also lead to heterogeneity in intermittent breeding. We modelled survival, recruitment and breeding probability of the red-footed booby (Sula sula), using a 19 year mark–recapture dataset involving more than 11 000 birds. We showed that skipping breeding was more likely in El-Niño years, correlated with an increase in the local sea surface temperature, supporting the hypothesis that it may be partly an adaptive strategy of birds to face the trade-off between survival and reproduction owing to environmental constraints. We also showed that the age-specific probability of first breeding attempt was synchronized among different age-classes and higher in El-Niño years. This result suggested that pre-breeders may benefit from lowered competition with experienced breeders in years of high skipping probabilities.
42916254
How partnerships end in guillemots Uria aalge: chance events, adaptive change, or forced divorce?
Divorce in socially monogamous species can result from different mechanisms, for example, chance events, active desertion of the partner, or the intrusion of a third individual ousting the partner. We compared the predictions associated with such mechanisms with data from common guillemots (Uria aalge) breeding on the Isle of May, Scotland. The data cover the years 1982--2005 and show a yearly divorce rate of 10.2%. In most divorces (86%), one of the original partners moved to another breeding site, whereas the other bird stayed and bred with a new partner. On average, movers had a significantly lower breeding success after divorce, stayers were largely unaffected, whereas the incoming birds benefited significantly from the change. This pattern fits best the predictions of the "forced-divorce" hypothesis, suggesting that many divorces were caused by incoming birds rather than the original partners or chance events. Although we are unable to document the precise behavioral sequence that led to divorces, our interpretation is supported by observations of frequent fights over breeding-site ownership. Our data also indicate within-population diversity of divorce mechanisms: some divorces were apparently accidental, others desertion of partners and sites if the latter were of low quality. Our study finally illustrates that a negative correlation between breeding success and probability of divorce (which our data show) need not indicate the adaptiveness of divorce for the original partners. Because such a connection has often been made, adaptive divorce may in general be less common than usually assumed. Copyright 2007, Oxford University Press.
21934158
Working less to gain more: when breeding quality relates to foraging efficiency.
In animal populations, a minority of individuals consistently achieves the highest breeding success and therefore contributes the most recruits to future generations. On average, foraging performance is important in determining breeding success at the population level, but evidence is scarce to show that more successful breeders (better breeders) forage differently than less successful ones (poorer breeders). To test this hypothesis, we used a 10-year, three-colony, individual-based longitudinal data set on breeding success and foraging parameters of a long-lived bird, the Adélie Penguin, Pygoscelis adeliae. Better breeders foraged more efficiently than poorer breeders under harsh environmental conditions and when offspring needs were higher, therefore gaining higher net energy profit to be allocated to reproduction and survival. These results imply that adverse "extrinsic" conditions might select breeding individuals on the basis of their foraging ability. Adélie Penguins show sufficient phenotypic plasticity that at least a portion of the population is capable of surviving and successfully reproducing despite extreme variability in their physical and biological environment, variability that is likely to be associated with climate change and, ultimately, with the species' evolution. This study is the first to demonstrate the importance of "extrinsic" conditions (in terms of environmental conditions and offspring needs) on the relationship between foraging behavior and individual quality.
83755661
THE TIMING OF BIRDS‘ BREEDING SEASONS
Summary 
Examination of survival rdtes of nestlings and fledglings of some species show that there is a strong tendency for those young which are hatched earliest in the season to have the greatest chance of surviving to breed. Since natural selection so strongly favours parents who leave many surviving young, the question arises as to why other birds breed later than the date at which they could most successfully raise their young. 
 
It is suggested that the food supply for the breeding females immediately prior to the breeding season may limit their ability to form eggs and the females may thus not be able to lay at the time which would result in young being in the nest at the best time for raising them, but as soon after this time as the female is able to produce her eggs. Not all species are likely to be prevented, by food shortage, from breeding at the best time for raising young and the groups of birds most likely to be affected are discussed.
19490597
Effects of age and reproductive status on individual foraging site fidelity in a long-lived marine predator
Individual foraging specializations, where individuals use a small component of the population niche width, are widespread in nature with important ecological and evolutionary implications. In long-lived animals, foraging ability develops with age, but we know little about the ontogeny of individuality in foraging. Here we use precision global positioning system (GPS) loggers to examine how individual foraging site fidelity (IFSF), a common component of foraging specialization, varies between breeders, failed breeders and immatures in a long-lived marine predator—the northern gannet Morus bassanus. Breeders (aged 5+) showed strong IFSF: they had similar routes and were faithful to distal points during successive trips. However, centrally placed immatures (aged 2–3) were far more exploratory and lacked route or foraging site fidelity. Failed breeders were intermediate: some with strong fidelity, others being more exploratory. Individual foraging specializations were previously thought to arise as a function of heritable phenotypic differences or via social transmission. Our results instead suggest a third alternative—in long-lived species foraging sites are learned during exploratory behaviours early in life, which become canalized with age and experience, and refined where possible—the exploration-refinement foraging hypothesis. We speculate similar patterns may be present in other long-lived species and moreover that long periods of immaturity may be a consequence of such memory-based individual foraging strategies.
35461302
The biochemistry of natural fasting at its limits
There are several groups of animals that are adapted for extremely long duration fasting as part of their reproductive cycle. Penguins, bears and seals routinely fast without food or water for months at time. However, they do not ‘starve’, as the biochemical implications of starving are very different from those of successful fasting. There are distinct biochemical adaptations in lipid, carbohydrate and especially protein metabolism that allow these animals to survive. It appears, at least for penguins and seals, that the duration of the fast may be limited by changes that occur in biochemical regulation near the end of the fast. In all of these species, the biochemistry of fasting and the ecological and behavioral demands of their breeding cycles are closely interrelated.
89125347
How to molt while fasting in the cold: the metabolic and hormonal adaptations of Emperor and King penguins
Like other penguin species, molting Emperor Aptenodytes forsteri and King A. patagonica penguins remain ashore and fast for several weeks during which their entire plumage is simultaneously renewed. Molt therefore involves the use of endogenous lipid reserves and body protein to meet the nutrient requirements not only for new feather synthesis, but also for the increase in energy expenditure associated with the decrease in thermal insulation. This energetic and metabolic stress results in a 45% decrease in body mass and in a 50% loss of body protein. There is no evidence that metabolic hormones such as glucagon, insulin and corticosterone play a major role in the control of metabolic events specifically related to molt. In contrast, the marked increase in circulating thyroxine at the onset of new feather synthesis in adult Emperor and King penguins, and in Emperor Penguin chicks, suggests that this hormone triggers molt by stimulating the development of the new plumage. On the other hand, triiodothyronine could intervene in the control of energy metabolism in situations of acute cold exposure, as during the loss of old feathers in the antarctic adult Emperor Penguins.
92183093
Fit is fat: winter body mass of Atlantic Puffins Fratercula arctica
ABSTRACT Capsule: Atlantic Puffins Fratercula arctica from Scottish and Norwegian populations were significantly heavier in winter than when rearing chicks. Aims: To compare body masses of Atlantic Puffins on their wintering grounds off the Faroe Islands with those of birds rearing chicks at colonies in Scotland and Norway. Methods: We took standardized measurements of wing length and body mass of Atlantic Puffins during the summer chick-rearing period and on the wintering grounds near the Faroe Islands. These measurements were used to estimate seasonal changes in body mass for the two breeding populations. In three cases data were available for individuals weighed both at the colony and on the wintering grounds. Results: On average, Atlantic Puffins breeding in Scotland and Norway increased their body mass by 20–30% between the chick-rearing period and winter. The very limited individual level data accorded well with the population level estimates. Conclusions: Our results provide the first estimates of the order of magnitude in mass change between two key life history stages in this species. They indicate that gains in body mass between chick-rearing and winter are at least double the decline in mass previously recorded between incubation and chick-rearing. Given the Atlantic Puffin’s deteriorating conservation status, improved information on seasonal changes in body condition should help determine the underlying causes of die-offs in major wreck incidents such as those reported in recent years.
86544244
Fat or lean: adjustment of endogenous energy stores to predictable and unpredictable changes in allostatic load
Summary
The ability to store energy endogenously is an important ecological mechanism that allows animals to buffer predictable and unpredictable variation in allostatic load. The secretion of glucocorticoids, which reflects changes in allostatic load, is suggested to play a major role in the adjustment of endogenous stores to these varying conditions.
Although crucially important, the relationship between allostatic load and energy stores remains largely unexplored. Two contrasting hypotheses describe how stores may be adjusted: animals may use low allostatic loads to increase stores to a maximum possible (‘fat and fit’), or they can attain a lean physique due to fitness advantages of a low body mass (‘lean and fit’).
We compiled observational and experimental data available for a long-lived seabird to examine the relationship between glucocorticoids and stored energy at two life history stages (incubation and chick-rearing). Data were collected across multiple years and colonies in the North Pacific, thereby reflecting the wide range of environmental conditions birds' encounter in the marine environment. During experimental manipulations, allostatic load was minimized by supplementing food to free-living birds.
We found that the relationship between allostatic load and energy stores was clearly curvilinear at both life history stages. Observational data suggested that energy stores remained relatively stable under low allostatic load and decreased under high loads. Experimental data showed that birds did not maximize energy stores under favourable conditions but maintained energy stores below a physiologically attainable level.
Energy stores remained consistently lower during chick-rearing compared to incubation across the wide range of variations in allostatic load suggesting that stage-specific trade-offs limit the accumulation of energy during favourable environmental conditions. Secretion of glucocorticoids did not appear to mediate this shift in energy stores between the life history stages.
Overall, results of this study support the ‘lean and fit’ hypothesis. We conclude that increased energy stores may not necessarily reflect better environmental conditions experienced by individuals or predict their higher fitness. A major advantage of adopting a lean physique when environmental conditions allow may be the avoidance of additional energetic costs for moving a heavy body. In breeding seabirds, this advantage may be more important during chick-rearing. In the focal species, the secretion of glucocorticoids might be involved in regulation of energy stores within a life history stage but does not appear to mediate an adaptive shift in energy stores between the incubating and chick-rearing stages of reproduction.
55621332
GEOGRAPHIC STRUCTURE OF ADÉLIE PENGUIN POPULATIONS: OVERLAP IN COLONY-SPECIFIC FORAGING AREAS
In an investigation of the factors leading to geographic structuring among Adelie Penguin (Pygoscelis adeliae) populations, we studied the size and overlap of colony- specific foraging areas within an isolated cluster of colonies. The study area, in the south- western Ross Sea, included one large and three smaller colonies, ranging in size from 3900 to 135 000 nesting pairs, clustered on Ross and Beaufort Islands. We used triangulation of radio signals from transmitters attached to breeding penguins to determine foraging loca- tions and to define colony-specific foraging areas during the chick-provisioning period of four breeding seasons, 1997-2000. Colony populations (nesting pairs) were determined using aerial photography just after egg-laying; reproductive success was estimated by com- paring ground counts of chicks fledged to the number of breeding pairs apparent in aerial photos. Foraging-trip duration, meal size, and adult body mass were estimated using RFID (radio frequency identification) tags and an automated reader and weighbridge. Chick growth was assessed by weekly weighing. We related the following variables to colony size: foraging distance, area, and duration; reproductive success; chick meal size and growth rate; and seasonal variation in adult body mass. We found that penguins foraged closest to their respective colonies, particularly at the smaller colonies. However, as the season pro- gressed, foraging distance, duration, and area increased noticeably, especially at the largest colony. The foraging areas of the smaller colonies overlapped broadly, but very little foraging area overlap existed between the large colony and the smaller colonies, even though the foraging area of the large colony was well within range of the smaller colonies. Instead, the foraging areas of the smaller colonies shifted as that of the large colony grew. Colony size was not related to chick meal size, chick growth, or parental body mass. This differed from the year previous to the study, when foraging trips of the large colony were very long, parents lost mass, and chick meals were smaller. In light of existing data on prey abundance in neritic waters in Antarctica suggesting that krill are relatively evenly distributed and in high abundance in the Southern Ross Sea, we conclude that penguins depleted or changed the availability of their prey, that the degree of alteration was a function of colony size, and that the large colony affected the location (and perhaps ultimately the size) of foraging areas for the smaller colonies. It appears, therefore, that foraging dynamics play a role in the geographic structuring of colonies in this species.
83696479
Ashmole's halo : direct evidence for prey depletion by a seabird
Fish population densities were measured at various instances from 2 large colonies of double-crested cormorants Phalacrocorax auritus to test the hypothesis that seabirds deplete prey close to their colonies. Fish densities were significantly lower in bays used by cormorants for feeding than in those outside their foraging range. Our findings provide direct evidence for prey depletion, and support Ashmole's (1963)hypothesis that seabird populations are limited by food supplies during the breeding 
season. 
).
86903696
Reproductive consequences of environment-driven variation in Adélie penguin breeding phenology
Adelie penguins Pygoscelis adeliae exhibit phenological variability across their geo- graphic range due to fixed and variable forcing factors acting differentially on populations. Shifts in breeding phenology can be indicative of environmental change when cues for breeding ini - tiation are tightly linked with environmental conditions. Adelie penguins on opposite sides of Antarctica display contrasting trends in clutch initiation dates, with different explanations of underlying causes. To make comparisons possible with a third significant Adelie penguin popula- tion region, we examined temporal trends and driving factors of breeding phenology at Becher- vaise Island in East Antarctica. We have extended existing knowledge by examining how pheno- logical dates are related throughout a breeding season, as well as the reproductive consequences of phenological variation. In contrast to other sites, we saw no evidence at this site of shifts towards early or delayed arrival or clutch initiation. Arrival, clutch initiation dates and the length of the incubation period had different environmental forcing factors, which explained up to 36% of the temporal variability. Penguins had a reduced courtship and egg-lay period when their arrival was delayed, and this led to later clutch initiation, later parent departure for foraging trips and later chick hatch. The phenological variations recorded here were not detrimental to chick-rearing. In particular, a delay in the start of breeding activities did not result in poor reproductive success. This indicates the importance of other factors for chick survival. Inter-annual pheno logical vari- ability at this location is compared with that at other locations to further develop the colony latitude-breeding phenology relationship for Adelie penguins.
43908349
Statistical Computing: An Introduction to Data Analysis Using S-PLUS
First, a clari cation: This book is not about traditional statistical computing topics, such as random number generation, approximation of probability distribution functions, least squares computations, and so forth. The book’s subtitle reveals what it is about: “An Introduction to Data Analysis using S-PLUS.” Crawley’s intention, as stated in the Preface, is to provide “both an introduction to and a reference manual for statistics and computing.” (The commercial package S-PLUS appears in the subtitle, but the Preface notes the availability of the freeware R system, which can be obtained at www.r-project.org. The author states that all the examples in the book will also work in R. Based on my experience with the two packages, some code tweaking may be required when using R, but you cannot beat the price.) My  rst reaction when I began to peruse this book was “wow”: More than 750 pages, covering a vast range of topics in statistical modeling. Roughly speaking, the  rst third of the book covers material suitable for a  rst course in statistics, the middle third covers basic applied linear models (regression and analysis of variance), and the  nal third covers a number of advanced statistical modeling methods, including generalized linear models, tree-based models, nonparametric smoothing, survival analysis, time series, mixed-effects models, and spatial statistics. There is a certain logic to the sequencing of topics in the text, but Crawley has made some nonstandard (one might even say quirky) decisions. For instance, power calculations are discussed three chapters before the classical hypothesis testing procedures are introduced. The early chapter on basic graphical techniques includes displays of tree-based models but excludes probability plotting. The formal introduction of probability distributions is quite thorough, but does not appear until Chapter 26, two-thirds of the way through the book. A number of examples involve the use of procedures that are not formally introduced until much later in the book. (Including more cross-referencing when this happens would make the book more effective as a self-study guide.) On balance, I can recommend this book for the intended audience, as long as they understand what they are in for. It contains a wealth of sage advice about the process of designing studies, analyzing data, and  tting statistical models and could become a treasured reference. However, the style is fairly terse and fast-paced, and neophytes may  nd it somewhat overwhelming. In the Preface, Crawley says “Learning S-PLUS will not be easy, but you won’t regret making the effort.” The same can be said for reading this book.
61891765
Least-Squares Means: The R Package lsmeans
Least-squares means are predictions from a linear model, or averages thereof. They are useful in the analysis of experimental data for summarizing the effects of factors, and for testing linear contrasts among predictions. The lsmeans package (Lenth 2016) provides a simple way of obtaining least-squares means and contrasts thereof. It supports many models fitted by R (R Core Team 2015) core packages (as well as a few key contributed ones) that fit linear or mixed models, and provides a simple way of extending it to cover more model classes.
3912443
Energetic Physiology Mediates Individual Optimization of Breeding Phenology in a Migratory Arctic Seabird
The influence of variation in individual state on key reproductive decisions impacting fitness is well appreciated in evolutionary ecology. Rowe et al. (1994) developed a condition-dependent individual optimization model predicting that three key factors impact the ability of migratory female birds to individually optimize breeding phenology to maximize fitness in seasonal environments: arrival condition, arrival date, and ability to gain in condition on the breeding grounds. While empirical studies have confirmed that greater arrival body mass and earlier arrival dates result in earlier laying, no study has assessed whether individual variation in energetic management of condition gain effects this key fitness-related decision. Using an 8-year data set from over 350 prebreeding female Arctic common eiders (Somateria mollissima), we tested this component of the model by examining whether individual variation in two physiological traits influencing energetic management (plasma triglycerides: physiological fattening rate; baseline corticosterone: energetic demand) predicted individual variation in breeding phenology after controlling for arrival date and body mass. As predicted by the optimization model, individuals with higher fattening rates and lower energetic demand had the earliest breeding phenology (shortest delays between arrival and laying; earliest laying dates). Our results are the first to empirically determine that individual flexibility in prebreeding energetic management influences key fitness-related reproductive decisions, suggesting that individuals have the capacity to optimally manage reproductive investment.
205777525
Corticosterone and foraging behavior in a diving seabird: the Adélie penguin, Pygoscelis adeliae.
Because hormones mediate physiological or behavioral responses to intrinsic or extrinsic stimuli, they can help us understand how animals adapt their foraging decisions to energetic demands of reproduction. Thus, the hormone corticosterone deserves specific attention because of its influence on metabolism, food intake and locomotor activities. We examined the relationships between baseline corticosterone levels and foraging behavior or mass gain at sea in a diving seabird, the Adélie penguin, Pygoscelis adeliae. Data were obtained from free-ranging penguins during the brooding period (Adélie Land, Antarctica) by using satellite transmitters and time-depth-recorders. The birds were weighed and blood sampled before and after a foraging trip (pre-trip and post-trip corticosterone levels, respectively). Penguins with elevated pre-trip corticosterone levels spent less time at sea and stayed closer to the colony than penguins with low pre-trip corticosterone levels. These short trips were associated with a higher foraging effort in terms of diving activity and a lower mass gain at sea than long trips. According to previous studies conducted on seabird species, these results suggest that penguins with elevated pre-trip corticosterone levels might maximize the rate of energy delivery to the chicks at the expense of their body reserves. Moreover, in all birds, corticosterone levels were lower post-foraging than pre-foraging. This decrease could result from either the restoration of body reserves during the foraging trip or from a break in activity at the end of the foraging trip. This study demonstrates for the first time in a diving predator the close relationships linking foraging behavior and baseline corticosterone levels. We suggest that slight elevations in pre-trip corticosterone levels could play a major role in breeding effort by facilitating foraging activity in breeding seabirds.
4783719
Ghrelin affects stopover decisions and food intake in a long-distance migrant
Significance Twice a year, billions of birds migrate across continents. Along their route, most species spend considerable time at stopover sites to replenish their fuel stores. What physiological signals tell them when they are ready to continue their journey? Ghrelin is a recently discovered hormone involved in appetite regulation. We found that ghrelin concentrations correlated positively with fat stores of wild garden warblers. Further, birds injected with ghrelin decreased their food intake and increased their drive to continue migration. Hence, our study shows that hormones regulating food intake and energy stores control migratory behavior. This is a previously unknown role for a hormonal system shared by birds and mammals, whose disruption causes eating disorders and obesity. Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird’s brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers (Sylvia borin) captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.
17849861
Exogenous corticosterone mimics a late fasting stage in captive Adelie penguins (Pygoscelis adeliae).
Fasting is part of penguin's breeding constraints. During prolonged fasting, three metabolic phases occur successively. Below a threshold in body reserves, birds enter phase III (PIII), which is characterized by hormonal and metabolic shifts. These changes are concomitant with egg abandonment in the wild and increased locomotor activity in captivity. Because corticosterone (CORT) enhances foraging activity, we investigated the variations of endogenous CORT, and the effects of exogenous CORT on the behavioral, hormonal, and metabolic responses of failed breeder Adélie penguins. Untreated and treated captive male birds were regularly weighed and sampled for blood while fasting, and locomotor activity was recorded daily. Treated birds were implanted with various doses of CORT during phase II. Untreated penguins entering PIII had increased CORT (3.5-fold) and uric acid (4-fold; reflecting protein catabolism) levels, concomitantly with a rise in locomotor activity (2-fold), while prolactin (involved in parental care in birds) levels declined by 33%. In CORT-treated birds, an inverted-U relationship was obtained between CORT levels and locomotor activity. The greatest increase in locomotor activity was observed in birds implanted with a high dose of CORT (C100), locomotor activity showing a 2.5-fold increase, 4 days after implantation to a level similar to that of birds in PIII. Moreover, uric acid levels increased three-fold in C100-birds, while prolactin levels declined by 30%. The experimentally induced rise in CORT levels mimicked metabolic, hormonal, and behavioral changes, characterizing late fasting, thus supporting a role for this hormone in the enhanced drive for refeeding occurring in long-term fasting birds.
2038560
Elevated corticosterone levels decrease reproductive output of chick-rearing Adélie penguins but do not affect chick mass at fledging
Stress hormones allow animals to adjust their physiology and behaviour to predictable and unpredictable changes in the environment. We investigated the effects of an increase in stress hormone levels on the breeding effort and the reproductive ouput of chick-rearing male Adélie penguins.
30576212
Sea ice cover and its influence on Adélie Penguin reproductive performance.
The relationship between Adélie Penguins (Pygoscelis adeliae) and ice is well established, with sea ice influencing penguin populations through a variety of processes operating at different spatial and temporal scales. To further explain the relationship between sea ice and Adélie Penguin reproductive performance, we investigated the relative importance of various measures of sea ice cover on breeding success at Béchervaise Island, East Antarctica. Our results show a clear distinction in the response of penguins to different types of ice, as well as to the timing of the presence of sea ice. Nearshore sea ice, which is composed primarily of fast ice during the guard stage of the breeding season, had an overwhelmingly strong and negative impact on penguin reproductive performance. The influence of winter and offshore guard-stage ice was only evident in conjunction with nearshore ice. Predicting Adélie Penguin population growth in relation to changes in the sea ice environment may be complicated because penguin-ice interactions vary according to the type of sea ice present, the season in which it is present, and the processes contributing to population growth that are influenced by sea ice.
7584865
Climate change and Southern Ocean ecosystems I: how changes in physical habitats directly affect marine biota.
Antarctic and Southern Ocean (ASO) marine ecosystems have been changing for at least the last 30 years, including in response to increasing ocean temperatures and changes in the extent and seasonality of sea ice; the magnitude and direction of these changes differ between regions around Antarctica that could see populations of the same species changing differently in different regions. This article reviews current and expected changes in ASO physical habitats in response to climate change. It then reviews how these changes may impact the autecology of marine biota of this polar region: microbes, zooplankton, salps, Antarctic krill, fish, cephalopods, marine mammals, seabirds, and benthos. The general prognosis for ASO marine habitats is for an overall warming and freshening, strengthening of westerly winds, with a potential pole-ward movement of those winds and the frontal systems, and an increase in ocean eddy activity. Many habitat parameters will have regionally specific changes, particularly relating to sea ice characteristics and seasonal dynamics. Lower trophic levels are expected to move south as the ocean conditions in which they are currently found move pole-ward. For Antarctic krill and finfish, the latitudinal breadth of their range will depend on their tolerance of warming oceans and changes to productivity. Ocean acidification is a concern not only for calcifying organisms but also for crustaceans such as Antarctic krill; it is also likely to be the most important change in benthic habitats over the coming century. For marine mammals and birds, the expected changes primarily relate to their flexibility in moving to alternative locations for food and the energetic cost of longer or more complex foraging trips for those that are bound to breeding colonies. Few species are sufficiently well studied to make comprehensive species-specific vulnerability assessments possible. Priorities for future work are discussed.