James O. Leafloor

Influence of body size and condition on harvest and survival of juvenile Canada geese

Direct recoveries for Canada goose (Branta canadensis interior) goslings from the portion of the Southern James Bay Population (SJBP) on Akimiski Island, Nunavut, Canada, have declined markedly since 1987. We suspected that poor gosling nutrition, due to limited food resources on brood-rearing areas, was causing low survival. Consequently, we measured body size and condition of 2,893 unfledged goslings during late July and early August, 1994-1996. Based on 128 recoveries of dead birds during hunting seasons and 69 recaptures during summer on Akimiski Island, we estimated the separate influences of gosling size and condition on subsequent probabilities of recovery by hunters and survival. Estimated survival probabilities were 0.025, 0.051, and 0.147, and reporting probabilities were 0.0026, 0.0051, and 0.0142 for 1994-1996, respectively. Annual variation in both probabilities was related to size and condition of goslings, which were largest and in the best condition in 1996, followed by 1995, and then 1994. Estimates of slopes suggested that relatively small increases in both body size and condition resulted in increased survival and reporting probabilities. Unlike previous waterfowl research, our results showed that the largest goslings, and those in the best condition, were the most likely to be shot. We suggest that goslings in poor condition died on Akimiski Island before they fledged. We conclude that food availability was limiting recruitment, and predict that harvest restrictions on SJBP Canada geese will not result in an increase in the segment of the population that nests on Akimiski Island.

Molt migrant Canada geese in Northern Ontario and Western James Bay

We undertook migration monitoring surveys and analysis of long-term banding data to determine if there was a significant premolt movement of Canada geese (Branta canadensis) from restored and reintro duced populations in southern Canada and midcontinent United States into northern Ontario and western James Bay. We examined migration chronology, origins, and demographic characteristics of molt migration of Canada geese in northern Ontario and on Akimiski Island, Northwest Territories. From 1985 to 1989, a conspicuous northward migration of large Canada geese was documented throughout northern Ontario from midMay to the end of June, well after the April migration of the subarctic nesting subspecies of Canada geese (B. c. interior); most nesting interior Canada geese in the Hudson Bay and James Bay lowlands were incubating eggs at this time. Summer-banded Canada geese originating from populations in 26 states and 6 Canadian provinces were captured in coastal areas of James Bay and Hudson Bay between the borders of Quebec and Manitoba. Morphometric discrimination indicated the presence of molting giant Canada geese (B. c. maxima) Most foreign, summer-banded birds were yearlings (53%) and 2-year-olds (17%), but birds up to 15 years old were captured. Approximately 58% of 2-15-year-old females had brood patches, which indicated a nesting attempt in the year of recapture. We suggest that increasing populations of giant Canada geese and declining habitat availability on northern brood-rearing areas will result in increasing levels of competition between populations of Canada geese. Presence of molt migrants on northern breeding areas will also complicate management of some Arctic and subaretic nesting populations of Canada geese.

Lincoln estimates of mallard (Anas platyrhynchos) abundance in North America

Estimates of range-wide abundance, harvest, and harvest rate are fundamental for sound inferences about the role of exploitation in the dynamics of free-ranging wildlife populations, but reliability of existing survey methods for abundance estimation is rarely assessed using alternative approaches. North American mallard populations have been surveyed each spring since 1955 using internationally coordinated aerial surveys, but population size can also be estimated with Lincolns method using banding and harvest data. We estimated late summer population size of adult and juvenile male and female mallards in western, midcontinent, and eastern North America using Lincolns method of dividing (i) total estimated harvest, , by estimated harvest rate, , calculated as (ii) direct band recovery rate, , divided by the (iii) band reporting rate, . Our goal was to compare estimates based on Lincolns method with traditional estimates based on aerial surveys. Lincoln estimates of adult males and females alive in the period June–September were 4.0 (range: 2.5–5.9), 1.8 (range: 0.6–3.0), and 1.8 (range: 1.3–2.7) times larger than respective aerial survey estimates for the western, midcontinent, and eastern mallard populations, and the two population estimates were only modestly correlated with each other (western: r = 0.70, 1993–2011; midcontinent: r = 0.54, 1961–2011; eastern: r = 0.50, 1993–2011). Higher Lincoln estimates are predictable given that the geographic scope of inference from Lincoln estimates is the entire population range, whereas sampling frames for aerial surveys are incomplete. Although each estimation method has a number of important potential biases, our review suggests that underestimation of total population size by aerial surveys is the most likely explanation. In addition to providing measures of total abundance, Lincolns method provides estimates of fecundity and population sex ratio and could be used in integrated population models to provide greater insights about population dynamics and management of North American mallards and most other harvested species.

Genetic methods for determining racial composition of Canada goose harvests

We used molecular genetic markers and established statistical methods to estimate proportional contributions of subspecies and breeding populations to admixed wintering and migratory Canada goose (Branta canadensis) harvests. We compared harvest estimates across spatially and temporally explicit sampling intervals. We characterized 997 individuals from breeding populations in Canada representing interior Canada geese (B. c. interior; n = 4) and in Michigan representing giant Canada geese (B. c. maxima; n = 5) for 5 microsatellite loci. We determined that microsatellite loci coupled with maximum-likelihood methods provided accurate and precise proportional contribution estimates of samples from each subspecies and population. We first conducted simulation analyses and derived harvest estimates for unknown individuals representing a range of plausible harvest mixture scenarios using blind tests. Based on harvested individuals collected over a 4-year period (1993-1996), we found that the racial composition of Canada goose harvests varied significantly among years and across early, regular, and late seasons within a year. Harvest composition varied spatially between management areas in different regions and between managed and private lands in close (<40 km) geographic proximity. Higher proportions of resident giant Canada geese were harvested during early hunting seasons and on private lands relative to migratory interior Canada geese. Harvest estimates suggest that individuals from different subspecies and populations are differentially abundant or susceptible to harvest at different times of the fall season, during different years, and populations across different geographic locations. Given that baseline genetics data are available for subspecies of management interest, genetic methods can provide harvest composition estimates at many spatial and temporal scales, including enumeration of statistical confidence.

Clinal Size Variation in Canada Geese Affects Morphometric Discrimination Techniques

We evaluated morphometric discrimination models designed to use skull length to differentiate between giant Canada geese (Branta canadensis maxima) and interior Canada geese (B. c. interior). We found significant differences in mean skull lengths of interior Canada geese from 3 areas in James Bay (Duncans multiple range test, P < 0.05). Geese decreased in size with increasing latitude, but those from Akimiski Island did not fit this pattern, and were smaller than those from the adjacent mainland. Morphometric discrimination techniques appeared to work adequately in northwest James Bay and on Akimiski Island, but were less reliable in southern James Bay, where the largest interior Canada geese were found. Molt migrant giant Canada geese were apparent in all areas, but most were distinguishable by morphometric methods from interiors at all sites except southern James Bay. Detailed knowledge of geographic variation in body size will improve the usefulness of morphometric discrimination techniques for Canada goose research and management. We recommend the skull length models developed by Moser and Rolley (1990) for use in differentiating giant from interior Canada geese in much of the Mississippi Flyway, except where southern James Bay mainland geese occur. J. WILDL. MANAGE. 61(1):183-190

GROWTH AND DEVELOPMENT OF PREFLEDGING CANADA GEESE AND LESSER SNOW GEESE: ECOLOGICAL ADAPTATION OR PHYSIOLOGICAL CONSTRAINT?

Abstract Neonate, gosling, and adult Canada Geese (Branta canadensis interior) and Lesser Snow Geese (Chen caerulescens caerulescens) were collected to evaluate if growth rates and developmental patterns differed interspecifically and to determine if such differences were better explained by physiology of the growth process or by ecological conditions historically experienced by those two species. Patterns of growth and development of Canada and Lesser Snow goose goslings were similar to those reported for other Arctic geese, but differences in relative growth rates and developmental patterns of external structures, digestive organs, and skeletal muscles were observed between these two species. As compared to Canada Geese, body parts associated with locomotion and acquisition or processing of food generally increased at relatively faster rates and were more developed relative to adult size in Lesser Snow Geese. Relative rates of increase for carcass protein and body mass in these two species did not support a physiological constraint on growth. Rates and patterns of growth and development were better explained as adaptations to ecological factors, such as growing season and nesting or brood rearing conditions, historically experienced by these two species.

A Hybrid Zone between Canada Geese (Branta canadensis) and Cackling Geese (B. Hutchinsii)

ABSTRACT. We studied patterns of geographic variation in structural size and genetic characteristics of white-cheeked geese inhabiting coastal areas of Hudson Bay, Canada, from northern Manitoba to southern Nunavut to determine the degree of morphological and spatial overlap, if any, between Cackling Geese (Branta hutchinsii) and Canada Geese (B. canadensis) in this region. Most Canada Geese occurred in sub-Arctic habitats south of 59°N latitude, and most Cackling Geese occurred in Arctic habitats north of 60°N, but the two species overlapped in a narrow zone between 59°N and 60°N latitude that coincided with the ecotone between sub-Arctic and Arctic ecozones. Mismatches between morphological and genetic characteristics of some individual females suggested that introgression had occurred in this area, and contrasting patterns in the nuclear and mitochondrial DNA (mtDNA) were consistent with female natal philopatry and male-biased dispersal. Evidence of introgression in the nuclear genome was geographically more widespread than evidence of introgression in the mtDNA genome. We suggest that the persistence of Canada Goose mtDNA in phenotypic Cackling Geese is a result of historical hybridization events that occurred when the Arctic—sub-Arctic ecotone was located farther north during a warmer climatic period. Despite evidence of introgression, most birds that we sampled appeared to belong to one or the other parental species, on the basis of their consistent identification using morphological, mtDNA, and nuclear DNA characteristics. We suggest that the area of overlap represents a tension zone between Canada Geese and Cackling Geese that is maintained by behavioral and ecological factors that limit effective dispersal.

COMPOSITION OF EGGS AND NEONATES OF CANADA GEESE AND LESSER SNOW GEESE

Abstract We collected eggs, neonates, and adults of Canada Geese (Branta canadensis interior) and Lesser Snow Geese (Chen caerulescens caerulescens) from Akimiski Island, Nunavut, during the 1996 breeding season. This was done to assess interspecific differences in egg composition, egg-nutrient catabolism, developmental maturity, tissue maturity, and body reserves, and to relate observed differences in those variables to ecological conditions historically experienced by Canada Geese and Lesser Snow Geese. Eggs of both species had identical proportional compositions, but Canada Goose embryos catabolized 13% more of their egg protein, whereas Lesser Snow Goose embryos catabolized 9% more of their egg lipid. Neonate Canada Geese and Lesser Snow Geese had similar protein reserves, relative to body size, but Lesser Snow Geese had relatively smaller lipid reserves than did Canada Geese. Relative to conspecific adults, Lesser Snow Goose goslings generally were structurally larger at hatch than were Canada Goose goslings. Neonate Lesser Snow Geese had more developmentally mature keels, wings, and breast muscles, and larger gizzards and caeca for their body size, than did neonate Canada Geese. Despite hatching from smaller eggs and having a shorter period of embryonic growth, skeletal muscles and gizzard tissues of Lesser Snow Geese were more functionally mature than those of Canada Geese. Increased lipid use during embryonic development could account for how Lesser Snow Geese hatched in a more developmentally and functionally mature state. In turn, differences in developmental and functional maturity of Lesser Snow Geese, as compared to Canada Geese, likely are adaptations that offset metabolic costs associated with their small body size, or to selection pressures associated with high arctic environmental conditions and colonial nesting and brood rearing.

Nest survival aNd deNsity of CaCkliNg geese (Branta HutcHinsii) iNside aNd outside a ross's goose (cHen rossii) ColoNy

ABSTRACT. The influence of heterospecifics on successful avian reproduction remains poorly understood, despite the role that such relationships may play in the evolution of reproductive strategies. We estimated nest survival of Cackling Geese (Branta hutchinsii) near McConnell River, Nunavut, in 2004 and 2005 in relation to (1) nest initiation date; (2) nest age; (3) nesting habitat; (4) presence in or absence from a colony composed mainly of Rosss Geese (Chen rossii); and (5) density of neighboring Lesser Snow Geese (C. caerulescens caerulescens) and Rosss Geese. We also assessed whether there was any consistent pattern in nest densities of Cackling Geese inside and outside the colony, using distance sampling methods that account for imperfect detection. Nest survival declined both with later nesting and with increased densities of surrounding Lesser Snow Geese and Rosss Geese, independently of whether or not Cackling Geese nested in the Rosss Goose colony. However, despite these negative interspecific effects at the neighborhood scale, nests had higher survival probabilities inside the colony than outside it when we controlled for nest initiation date and density of neighboring Lesser Snow Goose and Rosss Goose nests. There was no consistent difference in nest densities of Cackling Geese nesting inside and outside the colony. We conclude that Cackling Geese coincidentally establish nest sites inside the colony; the best nest locations are in low-density areas of the colony, but the location of these areas is unpredictable among years because Rosss Geese usually initiate nests later than Cackling Geese.

Hunting Vulnerability of Local and Migrant Canada Geese: A Comment

Lindberg and Malecki (1994) estimated the vulnerability of large local Canada geese (mainly Branta canadensis maxima) and smaller migrants (mainly B. c. interior) to fall hunting in northwestern Pennsylvania, 1988-89. They reported that local Canada geese were harvested proportionately more than their availability in the fall population, and migrants proportionately less than their availability, in 9 of 10 2-week periods. We evaluated several of the assumptions inherent in Lindberg and Maleckis (1994) calculations. We then reanalysed their data using modified assumptions and found that vulnerabilities were not consistently different among local geese and migrants. Vulnerability estimates were sensitive to relatively small changes in population sizes of local and migrant geese. We suggest that the apparently high vulnerability of local Canada geese was caused by underestimation of their numbers in the fall population, and overestimation of their numbers in the harvest.