Dr. Scott Petrie, Long Point Waterfowl Executive Director
Dr. Jack Millar, University of Western Ontario
Dr. Michael Schummer, Long Point Waterfowl Scientist
Sandhill Cranes (Grus canadensis) are the most numerous species of crane in the world. Migratory populations have broad breeding, migratory, and wintering ranges throughout North America that extend into Siberia, Russia (FIG. 1). There are six migratory populations of Sandhill Crane, including: the Pacific Flyway Population (Lesser subspecies [G. c. canadensis]), the Central Valley Population (Greater subspecies [G. c. tabida]), the Lower Colorado River Valley Population (Greater subspecies; Central Valley Population), the Rocky Mountain Population (Greater subspecies), the Eastern Population (Greater subspecies), and the Mid-Continent Population (Lesser, Greater and Canadian subspecies [G. c. rowanii]; Mid-Continent Population).
Figure 1. From Case & Sanders 2009: Approximate nesting, wintering, and primary migration and staging areas of the six migratory Sandhill Crane populations (compiled from information in Lewis 1977, Drewien and Lewis 1987, Sharp et al. 2000, Tacha et al. 1994, and data from radio-telemetered birds provided by G. Krapu, Northern Prairie Wildlife Research Center, Jamestown, ND).
The Eastern Population traditionally breeds primarily throughout the Great Lakes region (including Wisconsin, Michigan, and Ontario) and winters in Florida and parts of southern Georgia. During both spring and autumn migration, Eastern Population cranes stage throughout the east-central United States including Illinois, Indiana, Ohio, Kentucky, Tennessee, and Alabama, and, to the north, along the North Shore of Lake Huron, Ontario, including Manitoulin and St. Joseph Islands. The Eastern Population has been expanding in population size and breeding range; however, researchers are still seeking a precise estimate of the current extent of the Eastern Population throughout the annual cycle.
At present, the Eastern Population’s population status is monitored by the Fall Sandhill Crane Survey coordinated by the United States Fish and Wildlife Service. The fall survey is a long-term annual survey, first initiated in 1979. The survey is conducted by volunteers and state/federal agency officials from the Atlantic and Mississippi Flyways (Wisconsin, Michigan, Indiana, Tennessee, Georgia, and Florida). The primary objective of the survey is to count Eastern Population cranes that concentrate (staging and migrating) in Indiana, Michigan, and Wisconsin. Results from 2009 suggest that the population index is approaching 60,000 cranes with a five-year average (2005-2009) of approximately 40,000 ± 4968.4 cranes (See graph on right - Fall Sandhill Crane Survey numbers from 1979 to 2009).
Researchers and biologists are working to adapt survey methodology to provide more statistically robust data by reducing within and between year variation resulting from surveyor bias. To assist in this effort, researchers from Long Point Waterfowl partnered with the Canadian Wildlife Service and the Ontario Ministry of Natural Resources to collect the first minimum provincial population estimate.
Figure 3. Sandhill Crane being released immediately after being outfitted with a solar-powered GPS transmitter mounted on a PVC leg-band after being captured in early August 2010 on Manitoulin Island, Ontario.
With additional assistance from countless volunteers from the public, observers followed crane numbers at more than 20 roost sites from Sault Ste. Marie, ON. to Espanola, ON. along the north shore including Manitoulin and St. Joseph Islands to the south and counted nearly 9,000 cranes over two days in autumn 2009.
As an integral component of Long Point Waterfowl student Everett Hanna’s M.Sc. thesis at the University of Western Ontario, a team of researchers from Long Point Waterfowl headed back into the field on Manitoulin Island to collect additional information relating to EP migratory ecology during summer and autumn, 2010. During July and August, cranes were captured (n = 17) using rocket nets at baited sites throughout central Manitoulin Island. Select cranes (n = 9) were outfitted with solar-powered GPS tracking units mounted on leg-bands (FIG. 3). Tracking units are programmed to acquire GPS fixes every six hours for 3-5 years.
The primary application of these data is to compare migration chronology between local (cranes that likely breed and spend the summer on Manitoulin) and migrant (cranes that likely breed and spend the summer elsewhere and migrate to Manitoulin from the mainland during late summer or early autumn). Cranes that were captured and banded in 2010 were assumed to be local because of timing of capture (i.e., during summer before staging and migration commence). Population surveys (roost counts) were conducted throughout autumn migration in 2010 to investigate migration chronology of non-marked cranes whereas remotely collected tracking data were used to calculate departure of marked cranes. Seven of nine marked cranes departed the study area prior to recording peak numbers at the study site (FIG. 4).
Figure 4. Location of first stopovers made by Sandhill Cranes marked on Manitoulin Island, Ontario during autumn migration 2010. Dates of first GPS fix are displayed in white. Red arrows denote cranes that departed the study are before peak number of autumn migrants was recorded.
These findings suggest that local cranes depart the study site before migrants. This behaviour is likely a result of earlier nest initiation dates at lower latitudes and proximity to high quality food sources (i.e., agricultural grain fields). These factors have disparate implications for adult and juvenile age groups (e.g., juveniles continue structural growth during migration whereas adults are no longer growing). Therefore, migration may be linked to age-specific factors, particularly because cranes remain in tightly-knit family groups during autumn migration. To investigate family group migration, a new research programme was developed and proposed to transfer the project from the Master’s to Doctoral program at UWO. The proposed programme is entitled “Physiology, behaviour, and habitat use of Sandhill Crane family groups during autumn migration”. Thus, the proposed study is an evaluation of nutrient reserves and migratory chronology of family groups of EP cranes a key staging area in Ontario using data relating to lipid reserves, foraging behaviour, and food density that will be collected during autumn migration 2011 and 2012.
During autumn, Eastern Population cranes acquire lipids to fuel migration by eating agricultural grains at staging areas along their migratory route to wintering areas in southeastern North America. In Ontario, cranes primarily eat barley and corn during staging and migration. Although estimates of food availability and depletion exist for some staging areas for the Mid-Continent Population, no data have been collected at Eastern Population staging areas. Density of food resources at staging areas may influence lipid acquisition rates and subsequent timing of migratory departure during autumn. Therefore, timing of migratory departure in cranes could depend on lipid levels in adults, juveniles, or some combination of these or other physiological (e.g., structural growth) or environmental (e.g., weather patterns) factors. Migration
chronology has been studied in birds with substantial parental investment (e.g., post-fledging care), but no studies have compared within-family physiological condition of adults or juveniles to determine which most influences migratory chronology/timing. Understanding factors that prompt or inhibit autumn migration in Sandhill Crane family groups represents original scientific information that has not been studied in other species. This study will evaluate various physiological and environmental factors known to influence autumn migration in avian species that migrate as family groups. This research will also enable managers to identify habitat needs for use in landscape-level conservation efforts.
The central hypothesis to be addressed is that the relationship between nutrient (lipid and protein) levels of parents and their offspring within family groups is related to proximity to peak departure. Specifically, we predict that, if family group emigration is limited by juveniles, then adult crane lipid levels will reach an asymptote prior to peak departure but juvenile lipid levels will continue to increase until departure (i.e., show no asymptote). Family groups remaining after peak departure will show the greatest disparity in within-family lipid levels (i.e., greatest spread between juveniles and adults) because they missed the optimal migratory period (i.e., peak migration). To provide further support to this central question, concurrent field observations will be made to measure foraging behaviour to estimate rates of energy expenditure using metabolic cost coefficients. In addition, agricultural grain density will be estimated at regular intervals from harvest through peak departure from the study area to estimate change in available energy. By estimating food density, this research will be able to offer a more comprehensive explanation of patterns in behaviour and lipid levels within family groups.
Sandhill Cranes: Movement Maps
Past Movement Maps
Spring migration routes of Sandhill Cranes (n = 9) marked on Manitoulin Island, Ontario, Canada during July and August 2010. Eight of the nine marked cranes wintered in southern Georgia or Florida, USA; the remaining crane wintered in northwestern Tennessee, USA. All marked cranes returned to Manitoulin Island during April and May 2011.
Summer locations (June – August) of Sandhill Cranes (n = 9) marked on Manitoulin Island, Ontario, Canada during July and August 2010. One of nine transmitters failed (and subsequently went offline) in early June 2011. The remaining eight marked cranes followed traditional habitat use patterns targeting pastures and hay fields until the grain harvest started in mid-August. Traditional roost sites were also used throughout the summer months.
Fall migration routes of Sandhill Cranes (n = 8 ) marked on Manitoulin Island, Ontario, Canada during July and August 2010. Six of the remaining eight marked cranes departed Manitoulin Island between October 01 – 04, 2011. The final two cranes departed on October 22 and 26, 2011. Marked cranes followed traditional migratory pathways northwest along Manitoulin Island and south through upper Michigan, USA, subsequently stopping at staging areas in central Michigan and northwestern Indiana, USA where they remain at present.
Project Sponsors and Partners
Canadian Wildlife Service
Long Point Waterfowl
Ontario Ministry of Natural Resources
Ontario Federation of Anglers and Hunters
The University of Western Ontario
Wildlife Habitat Canada
Webless Migratory Game Bird Fund