Snow Goose Population Research Articles

Long-term study of the tundra food web at a hotspot of Arctic biodiversity, the Bylot Island Field Station

We present the history of research activities at the Bylot Island Field Station of the Centre d’études nordiques, a hotspot of biodiversity in the Canadian Arctic. Intensive wildlife studies started at the station in the late 1980s, initially focussing on greater snow goose ecology and its impacts on the tundra vegetation. Since then, studies have expanded to encompass the whole vertebrate food web and have become one of the most comprehensive ecological monitoring programs in the Canadian Arctic. The main vertebrate species monitored include snow geese, lemmings, shorebirds, avian predators, buntings, and Arctic foxes. Over time, we recorded 66 bird and 10 mammal species, including 51 confirmed breeders. Contributions of the program to the field of ecology are numerous, but our demonstration of the dominant role played by predator–prey interactions in the Arctic food web is especially significant for the understanding of direct and indirect trophic interactions. Our studies provided essential information for management decisions taken to control the overabundant greater snow goose population and supported international efforts to assess the state of Arctic biodiversity. Future directions will reflect the need to deepen our understanding of trophic interactions and the effects of climate change using innovative advanced technologies.

Morphological differences and migration patterns of greater and lesser snow geese in New York State

AbstractLesser (Chen caerulescens caerulescens, LSGO) and greater snow goose (Chen caerulescens atlantica, GSGO) populations have increased substantially in the past 50 years. The light goose conservation order established in 1998 (Canada) and 1999 (U.S.) aimed to increase snow goose harvest and stabilize populations because breeding ground abundance was thought to negatively impact arctic ecosystems. In the Atlantic flyway, where LSGO and GSGO are both available for harvest, techniques to differentiate sub‐species in the field using morphology may be helpful for harvest management because mid‐continent LSGO are ~16 times more abundant than GSGO (n < 1,000,000). We investigated percentages and spatial distribution of LSGO and GSGO in the spring harvest in NY as this information could be useful for snow goose population and harvest management decisions. We developed a discriminant function analysis (DFA) using heads from snow geese harvested during spring 2016 to 2018 and were able to differentiate between LSGO and GSGO with 95.5% accuracy. Based on the DFA results, we estimated that spring harvest in New York state was 80% GSGO and 20% LSGO. Using band recoveries from autumn and spring harvests, we also identified that GSGO harvest occurred farther west during spring than autumn and in the 2010s than prior two decades. Our results indicate that GSGO comprise most snow goose harvest in New York state and provide evidence for a shift in spring migration patterns of GSGO since the 1990s.

Local population collapse of Ross's and lesser snow geese driven by failing recruitment and diminished philopatry

Dynamics of free‐ranging animal populations can result from complex interplays of survival, recruitment and movement. Yet incomplete understanding of demography impedes conservation strategies intended to modify population dynamics of focal species. We estimated survival and per capita production of young, as well as emigration and immigration, from 1997 to 2017 in Ross's goose Anser rossii and lesser snow goose Anser caerulescens caerulescens, which are sympatric species of migratory birds that nest in the central Canadian Arctic at one of the largest breeding colonies in North America. We formed age‐structured integrated population models (IPMs) for each species that jointly analyzed live and dead encounter data as well as breeding adult population size and fecundity data to understand drivers of population dynamics. We compared the demography between species because both species increased during the 1990s and early 2000s yet thereafter snow geese declined, while Ross's geese continued to increase, then stabilized and similarly declined. Declines in Ross's and snow goose populations were caused by reduced per capita production of young, and juvenile survival, as well as increased adult and juvenile emigration. Stronger declines in juvenile survival in snow geese explain their earlier population decline compared to Ross's geese. Despite the divergence in population trends in Ross's and snow geese, we found strong synchrony in demographic rates which suggested substantial emigration from this colony and similar responses to environmental conditions. Direct estimation of demographic patterns in the IPM framework permitted hypothesis testing and inference about the role of immigration, even though immigrant sources were unsampled. We provide a novel m‐array implementation specific to a multi‐state Burnham model which greatly improved computational efficiency and convergence of posterior estimates. Our findings are an important reminder of the role that permanent movements can play in animal demography and metapopulation structure.

Liberalized harvest regulations have not affected overabundant Snow Geese in Northern Manitoba

Abstract Large amounts of money are spent each year to control overabundant species that imperil biodiversity and ecosystem functioning across the globe. Lesser Snow Geese (Anser caerulescens caerulescens) are emblematic of this issue, as their overabundance has affected a whole suite of plant, insect, and bird communities via a trophic cascade that managers have attempted to stop before it spreads further across the North American (sub)Arctic. To achieve this goal, liberalized harvest measures designed to decrease Lesser Snow Goose survival and abundance were implemented almost 2 decades ago. Our previous quantitative assessment of management effectiveness indicated that the growing Lesser Snow Goose population quickly overwhelmed a satiated hunter population despite liberalized harvest regulations, eventually reducing the fraction of Lesser Snow Geese being harvested each year. Consistent with the philosophy of adaptive resource management, we apply improved methods to additional years of monitoring data to evaluate the ongoing impact of harvest conservation efforts on Lesser Snow Goose harvest rates. Our previous results suggested little effect of liberalized harvest regulations on harvest rates, but our new findings suggest even less of an impact. Harvest rates have recently stabilized at ~3%, the lowest levels observed over the last 48 yr of our study. Barring adverse effects of environmental change on natural mortality or reproductive success, additional measures will need to be taken to reduce Lesser Snow Goose overabundance and their ecosystem damage.

Impacts of Climate Change and Intensive Lesser Snow Goose (Chen caerulescens caerulescens) Activity on Surface Water in High Arctic Pond Complexes

Rapid increases in air temperature in Arctic and subarctic regions are driving significant changes to surface waters. These changes and their impacts are not well understood in sensitive high-Arctic ecosystems. This study explores changes in surface water in the high Arctic pond complexes of western Banks Island, Northwest Territories. Landsat imagery (1985–2015) was used to detect sub-pixel trends in surface water. Comparison of higher resolution aerial photographs (1958) and satellite imagery (2014) quantified changes in the size and distribution of waterbodies. Field sampling investigated factors contributing to the observed changes. The impact of expanding lesser snow goose populations and other biotic or abiotic factors on observed changes in surface water were also investigated using an information theoretic model selection approach. Our analyses show that the pond complexes of western Banks Island lost 7.9% of the surface water that existed in 1985. Drying disproportionately impacted smaller sized waterbodies, indicating that climate is the main driver. Model selection showed that intensive occupation by lesser snow geese was associated with more extensive drying and draining of waterbodies and suggests this intensive habitat use may reduce the resilience of pond complexes to climate warming. Changes in surface water are likely altering permafrost, vegetation, and the utility of these areas for animals and local land-users, and should be investigated further.

Outfitter use as a constraint negotiation mechanism in snow goose hunting

Beginning in the 1970s, mid-continent snow goose (Chen caerulescens caerulescens and C. rossii) populations have grown rapidly, resulting in extensive damage to tundra breeding habitats (Batt, 1997...

A race against time: habitat alteration by snow geese prunes the seasonal sequence of mosquito emergence in a subarctic brackish landscape

Species compositions in highly seasonal habitats often exhibit predictable patterns through time. However, the roles that ecological interactions play in shaping the sequence of species phenologies through a season are largely unexplored. Across the tundra on the Hudson Bay Lowlands, extensive foraging by lesser snow goose populations has been driving alterations to the landscape. Here, I show that this widespread and dramatic disturbance increases evaporation rates of ephemeral ponds and consequently constricts the temporal availability of seasonal aquatic habitats for larval mosquitoes. I also show that this constriction decreases the temporal diversity of closely related univoltine mosquito species that have varying emergence schedules. Three species of mosquitoes emerged through the season from four sampled ephemeral ponds associated with no goose grubbing; only one species emerged, early in the season, from the four ponds that experienced heavy grubbing. This study demonstrates a mechanism for temporal composition change in a ubiquitous and abundant group of arthropods on the tundra. It does not show life history evolution of emergence time of mosquitoes; however, it highlights the rather unexplored role of ecological interactions in altering the diversity of phenologies across seasonal time.

Antibodies to Influenza A Viruses in Wintering Snow Geese (Chen caerulescens) in Texas.

Wild waterfowl in the order Anseriformes are recognized reservoirs for influenza A viruses (IAVs); however, prevalence of infection can vary greatly by species. Few isolates of IAVs have been reported from snow geese (Chen caerulescens), and generally they have not been regarded as an important component of this reservoir. In February 2013, 151 combined cloacal and oropharangeal swabs and 147 serum samples were collected from snow geese wintering on the Gulf coast of Texas. None of the swab samples tested positive by virus isolation, but antibodies to IAVs were detected in 87 (59%) birds tested by competitive blocking ELISA (bELISA). To further characterize these detected antibodies, positive samples were tested by virus microneutralization (MN) for antibodies to viruses representing 14 hemagglutinin subtypes (HA1-HA12, H14, and H15). By MN, antibodies to H1 (n = 41; 47%), H5 (n = 32; 37%), H6 (n = 49; 56%), H9 (n = 50; 57%), and H12 (n = 24; 28%) were detected. Snow goose populations have increased in North America since the 1960s, and their association with agricultural lands provides a potential indirect source of IAV infection for domestic poultry. This potential, as well as the detection of antibodies to HA subtypes H5, H9, and H12 that are not well represented in other waterfowl species, suggests that further snow geese surveillance is indicated.

Are Wintering Areas Shifting North? Learning from Lesser Snow Geese Banded in Southwest Louisiana

Several avian species have shifted their wintering or staging areas north in response to advancing onset of spring. Our objectives were to determine whether (1) the latitudinal distribution of recoveries changed for Chen caerulescens caerulescens (Lesser Snow Goose; hereafter Snow Goose) banded in southwest Louisiana, and (2) annual propor- tions of recoveries within Louisiana relative to other locations in the midcontinent flyways were related to local weather or Snow Goose population estimates for southwest Louisiana. We collated and analyzed population indices from the annual midwinter waterfowl survey for the period 2002-2013 with band recovery and local weather data. Latitudes of recovery shifted north during the period, and the increases were independent of season (fall, midwin- ter, and late winter/spring migration). Annual proportions of recoveries within Louisiana (all from southwest Louisiana), were lower during wet winters when the largest numbers of Snow Geese were counted in southwest Louisiana. We concluded that Snow Geese banded in our study area have shifted their wintering range northwards. Furthermore, the prob- ability of recovery in Louisiana was somewhat dependent on Snow Goose numbers present, apparently because hunters shoot proportionally fewer banded birds during years with more Snow Geese, which in turn were related to high amounts of precipitation in the area.

Limnological regime shifts caused by climate warming and Lesser Snow Goose population expansion in the western Hudson Bay Lowlands (Manitoba, Canada).

Shallow lakes are dominant features in subarctic and Arctic landscapes and are responsive to multiple stressors, which can lead to rapid changes in limnological regimes with consequences for aquatic resources. We address this theme in the coastal tundra region of Wapusk National Park, western Hudson Bay Lowlands (Canada), where climate has warmed during the past century and the Lesser Snow Goose (LSG; Chen caerulescens caerulescens) population has grown rapidly during the past ∽40 years. Integration of limnological and paleolimnological analyses documents profound responses of productivity, nutrient cycling, and aquatic habitat to warming at three ponds (“WAP 12”, “WAP 20”, and “WAP 21″), and to LSG disturbance at the two ponds located in an active nesting area (WAP 20, WAP 21). Based on multiparameter analysis of 210Pb-dated sediment records from all three ponds, a regime shift occurred between 1875 and 1900 CE marked by a transition from low productivity, turbid, and nutrient-poor conditions of the Little Ice Age to conditions of higher productivity, lower nitrogen availability, and the development of benthic biofilm habitat as a result of climate warming. Beginning in the mid-1970s, sediment records from WAP 20 and WAP 21 reveal a second regime shift characterized by accelerated productivity and increased nitrogen availability. Coupled with 3 years of limnological data, results suggest that increased productivity at WAP 20 and WAP 21 led to atmospheric CO2 invasion to meet algal photosynthetic demand. This limnological regime shift is attributed to an increase in the supply of catchment-derived nutrients from the arrival of LSG and their subsequent disturbance to the landscape. Collectively, findings discriminate the consequences of warming and LSG disturbance on tundra ponds from which we identify a suite of sensitive limnological and paleolimnological measures that can be utilized to inform aquatic ecosystem monitoring.

Avian-Driven Modification of Seasonal Carbon Cycling at a Tundra Pond in the Hudson Bay Lowlands (Northern Manitoba, Canada)

The past ∼40 years have seen a geometric increase (5–7% per year) in the size of the lesser snow goose (LSG; Chen caerulescens caerulescens) population and marked spatial expansion of the area they inhabit within the coastal fen ecotype of Wapusk National Park (Hudson Bay Lowlands, northern Canada), raising concerns and uncertainty about the environmental effects of their activities (grubbing of vegetation, soil disturbance, deposition of feces) on the abundant shallow tundra ponds. In this study, we use conventional limnological measurements as well as water and carbon (C) isotope tracers to explore similarities and differences in seasonal patterns of hydrological, limnological, and biogeochemical conditions of 15 shallow coastal fen ponds that currently have minimal (if any) disturbance from the LSG population with one pond (WAP 20) that is subject to substantial LSG activity. Carbon isotope measurements reveal that C cycling at WAP 20 (LSG-disturbed site) is markedly different compared to the other ponds, whereas only small differences were observed in hydrological conditions and concentrations of major nutrients and chlorophyll a of pond water. A mid-summer decrease in C isotope composition of dissolved inorganic carbon (DIC) occurred at WAP 20, likely as a consequence of high pond-water pH and intense C demand by aquatic productivity. These conditions appear to have promoted “chemically enhanced CO2 invasion,” which causes strong kinetic C isotope fractionation. High C demand at WAP 20 is also suggested by mid-summer 13C enrichment in particulate organic matter. In contrast, the ponds with little to no LSG activity exhibited expected seasonal C isotope behavior (i.e., 13C enrichment of DIC) under conditions of increasing productivity when C is in relatively low demand. Small differences in nutrient concentrations may be due to rapid uptake by the benthic mat at WAP 20. Data from the low disturbance ponds also provide baseline information for future studies assessing potential effects of LSG.

Climate change, phenology, and habitat degradation: drivers of gosling body condition and juvenile survival in lesser snow geese

Nesting migratory geese are among the dominant herbivores in (sub) arctic environments, which have undergone unprecedented increases in temperatures and plant growing days over the last three decades. Within these regions, the Hudson Bay Lowlands are home to an overabundant breeding population of lesser snow geese that has dramatically damaged the ecosystem, with cascading effects at multiple trophic levels. In some areas the overabundance of geese has led to a drastic reduction in available forage. In addition, warming of this region has widened the gap between goose migration timing and plant green-up, and this 'mismatch' between goose and plant phenologies could in turn affect gosling development. The dual effects of climate change and habitat quality on gosling body condition and juvenile survival are not known, but are critical for predicting population growth and related degradation of (sub) arctic ecosystems. To address these issues, we used information on female goslings marked and measured between 1978 and 2005 (4125 individuals). Goslings that developed within and near the traditional center of the breeding colony experienced the effects of long-term habitat degradation: body condition and juvenile survival declined over time. In newly colonized areas, however, we observed the opposite pattern (increase in body condition and juvenile survival). In addition, warmer than average winters and summers resulted in lower gosling body condition and first-year survival. Too few plant 'growing days' in the spring relative to hatch led to similar results. Our assessment indicates that geese are recovering from habitat degradation by moving to newly colonized locales. However, a warmer climate could negatively affect snow goose populations in the long-run, but it will depend on which seasons warm the fastest. These antagonistic mechanisms will require further study to help predict snow goose population dynamics and manage the trophic cascade they induce.

Comparative survival and recovery of Ross's and lesser snow geese from Canada's central arctic

AbstractLarge increases in several populations of North American arctic geese have resulted in ecosystem‐level effects from associated herbivory. Consequently, some breeding populations have shown density dependence in recruitment through declines in food availability. Differences in population trajectories of lesser snow geese (Chen caerulescens caerulescens; hereafter snow geese) and Ross's geese (C. rossii) breeding in mixed‐species colonies south of Queen Maud Gulf (QMG), in Canada's central arctic, suggest that density dependence may be limiting snow goose populations. Specifically, long‐term declines in age ratios (immature:adult) of harvested snow geese may have resulted from declines in juvenile survival. Thus, we focused on juvenile (first‐year) survival of snow and Ross's geese in relation to timing of reproduction (annual mean nest initiation date) and late summer weather. We banded Ross's and snow geese from 1991 to 2008 in the QMG Migratory Bird Sanctuary. We used age‐structured mark‐recapture models to estimate annual survival rates for adults and juveniles from recoveries of dead birds. Consistent with life history differences, juvenile snow geese survived at rates higher than juvenile Ross's geese. Juvenile survival of both species also was lower in late seasons, but was unrelated to arctic weather measured during a 17‐day period after banding. We found no evidence of density dependence (i.e., a decline in juvenile survival over time) in either species. We also found no interspecific differences in age‐specific hunting vulnerability, though juveniles were more vulnerable than adults in both species, as expected. Thus, interspecific differences in survival were unrelated to harvest. Lower survival of juvenile Ross's geese may result from natural migration mortality related to smaller body size (e.g., greater susceptibility to inclement weather or predation) compared to juvenile snow geese. Despite lower first‐year survival, recruitment by Ross's geese may still be greater than that by snow geese because of earlier sexual maturity, greater breeding propensity, and higher nest success by Ross's geese. © 2012 The Wildlife Society.

Spring snow goose hunting influences body composition of waterfowl staging in Nebraska

AbstractA spring hunt was instituted in North America to reduce abundance of snow geese (Chen caerulescens) by increasing mortality of adults directly, yet disturbance from hunting activities can indirectly influence body condition and ultimately, reproductive success. We estimated effects of hunting disturbance by comparing body composition of snow geese and non‐target species, greater white‐fronted geese (Anser albifrons) and northern pintails (Anas acuta) collected in portions of south‐central Nebraska that were open (eastern Rainwater Basin, ERB) and closed (western Rainwater Basin, WRB; and central Platte River Valley, CPRV) to snow goose hunting during springs 1998 and 1999. Lipid content of 170 snow geese was 25% (57 g) less in areas open to hunting compared to areas closed during hunting season but similar in all areas after hunting was concluded in the ERB. Protein content of snow geese was 3% (14 g) less in the region open to hunting. Greater white‐fronted geese had 24% (76 g; n = 129) less lipids in the hunted portion of the study area during hunting season, and this difference persisted after conclusion of hunting season. We found little difference in lipid or protein content of northern pintails in relation to spring hunting. Indirect effects of spring hunting may be considered a collateral benefit regarding efforts to reduce overabundant snow goose populations. Disrupted nutrient storage observed in greater white‐fronted geese represents an unintended consequence of spring hunting that has potential to adversely affect reproduction for this and other species of waterbirds staging in the region. © 2012 The Wildlife Society.

Impact of Geese on the Limnology of Lakes and Ponds from Bylot Island (Nunavut, Canada)

AbstractArctic freshwater ecosystems are important habitats for northern wildlife. Arctic climate impact studies suggest that global change could result in major modifications and perturbations of lakes, ponds and wildlife. Most studies focus either on freshwater ecosystems or on animal populations, but few have investigated the links that exist between them. Animal populations have the potential to alter the nutrient inputs in lakes and ponds via faeces. The present study is the first to reveal the impact of an expanding Greater Snow Goose (Chen caerulescens atlantica) population on the limnology of arctic lakes and ponds. A survey of 27 freshwater ecosystems was performed on Bylot Island (Nunavut, Canada) in order to identify patterns in limnological conditions. Using a multivariate statistical approach, our study shows that the presence of birds in the catchment of lakes and ponds has an impact on their nutrient status. Concentrations of major ions that were related to the distance from the sea were the main environmental variable explaining the limnological differences observed among lakes and ponds. Nutrient variables that were mostly related to the presence of Snow Geese played a secondary but significant role. N and P concentrations were different among impacted and non‐impacted sites, underlining the impact of animal populations on northern freshwater ecosystems. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Early Learning and its Effect on Population Structure. Studies of a Wild Population of Snow Geese

Assortative mating has been described in the dimorphic Lesser Snow Goose. Evidence is provided which shows that most birds select a mate of a colour similar to that of the family in which they were raised. The pre-pairing experience influences mate choice and thus influences the genetic structure of the population. These results provide the first evidence to our knowledge that mate selection based on familial appearance operates intraspecifically in the wild. It was found that approximately 10 % of the birds choose mates opposite to the familial colour. These exceptions account for the frequency of mixed matings in the population. Several theories to explain the exceptions are considered.

POPULATION TRENDS OF TUNDRA-NESTING BIRDS AT CAPE CHURCHILL, MANITOBA, IN RELATION TO INCREASING GOOSE POPULATIONS

To assess potential changes in tundra-nesting bird populations relative to increased herbivory by growing Lesser Snow Goose (Chen caerulescens caerulescens) and Ross's Goose (C. rossii) populations, we estimated avian population densities in coastal tundra near Cape Churchill, Manitoba, Canada in June 1984, 1999, and 2000. We also compared bird abundance in altered and intact freshwater sedge (Carex spp.) meadows to assess bird response at a smaller spatial scale, the habitat patch. At the landscape scale, Herring Gull (Larus argentatus) densities were significantly greater in both 1999 and 2000 than 1984, and Semipalmated Sandpiper (Calidris pusilla) and Savannah Sparrow (Passerculus sandwichensis) densities were greater in 2000 than 1984. As a group, tundra-nesting passerine densities were significantly greater in 1999 than 1984. Dunlin (Calidris alpina) densities were significantly lower in 1999 than 1984, and many larger, ground-nesting birds declined in abundance and occurrence along transects in later years. At the smaller spatial scale, passerines and shorebirds were less abundant in altered than intact freshwater sedge meadows. Our results indicate that most abundant breeding birds on the study area did not exhibit lower densities in later years despite increased effects of goose herbivory on vegetation. At the habitat patch scale, the same groups of species had lower abundances in altered versus largely intact habitats. Although goose herbivory can alter tundra vegetation and lead to lower abundance of several bird species, habitat alteration may have to be widespread and severe to elicit population declines over a large area.

Winter Fidelity and Apparent Survival of Lesser Snow Goose Populations in the Pacific Flyway

Abstract The Beringia region of the Arctic contains 2 colonies of lesser snow geese (Chen caerulescens caerulescens) breeding on Wrangel Island, Russia, and Banks Island, Canada, and wintering in North America. The Wrangel Island population is composed of 2 subpopulations from a sympatric breeding colony but separate wintering areas, whereas the Banks Island population shares a sympatric wintering area in California, USA, with one of the Wrangel Island subpopulations. The Wrangel Island colony represents the last major snow goose population in Russia and has fluctuated considerably since 1970, whereas the Banks Island population has more than doubled. The reasons for these changes are unclear, but hypotheses include independent population demographics (survival and recruitment) and immigration and emigration among breeding or wintering populations. These demographic and movement patterns have important ecological and management implications for understanding goose population structure, harvest of admixed populations, and gene flow among populations with separate breeding or wintering areas. From 1993 to 1996, we neckbanded molting birds at their breeding colonies and resighted birds on the wintering grounds. We used multistate mark‐recapture models to evaluate apparent survival rates, resighting rates, winter fidelity, and potential exchange among these populations. We also compared the utility of face stain in Wrangel Island breeding geese as a predictor of their wintering area. Our results showed similar apparent survival rates between subpopulations of Wrangel Island snow geese and lower apparent survival, but higher emigration, for the Banks Island birds. Males had lower apparent survival than females, most likely due to differences in neckband loss. Transition between wintering areas was low (<3%), with equal movement between northern and southern wintering areas for Wrangel Island birds and little evidence of exchange between the Banks and northern Wrangel Island populations. Face staining was an unreliable indicator of wintering area. Our findings suggest that northern and southern Wrangel Island subpopulations should be considered a metapopulation in better understanding and managing Pacific Flyway lesser snow geese. Yet the absence of a strong population connection between Banks Island and Wrangel Island geese suggests that these breeding colonies can be managed as separate but overlapping populations. Additionally, winter population fidelity may be more important in lesser snow geese than in other species, and both breeding and wintering areas are important components of population management for sympatric wintering populations.

Lesser Snow Geese, <em>Chen caerulescens caerulescens</em>, and Ross's Geese, <em>Chen rossii</em>, of Jenny Lind Island, Nunavut

We surveyed the Lesser Snow (Chen caerulescens caerulescens) and Ross’s geese (Chen rossii) of Jenny Lind Island, Nunavut, using aerial photography in June 1988, 1998, and 2006, and a visual helicopter transect survey in July 1990. The estimated number of nesting geese was 39 154 ± SE 2238 in 1988, 19 253 ± 2323 in 1998, and 21 572 ± 1898 in 2006. In 1988 an estimated 2.7% of the nesting geese were Ross’s. The July 1990 population of adult-plumaged birds was 25 020 ± 3114. The estimated percentage blue morph among Snow and Ross’s geese was 19.0% in 1988, 25.1% in 1989, 23.0% in 1990 and 21.1% in 2006. Estimated pre-fledged Snow Goose productivity was 47% young in 1989 and 46% in 1990. Combined numbers of Snow and Ross’s geese on Jenny Lind Island grew over 250 fold, from 210 adults in 1962-1966 to 54 100 adults in 1985. Numbers subsequently declined, to 42 200 in 1988, 25 000 in 1990, 20 300 in 1998, and 26 400 in 2006. Population decline between 1985 and 1990 was consistent with anecdotal reports by others that die-offs of Snow Geese occurred in 1984, 1985 and 1989, and with our August 1989 fieldwork which found evidence of habitat degradation and malnourishment of young geese. In spite of limited food resources on Jenny Lind Island, the colony continued to exist in 2006 at near its 1990 and 1998 levels. Further studies there could provide insights for management of the overabundant mid-continent Snow Goose population and its arctic habitats.

Changes in abundance and spatial distribution of geese molting near Teshekpuk Lake, Alaska: interspecific competition or ecological change?

Goose populations molting in the Teshekpuk Lake Special Area of the National Petroleum Reserve—Alaska have changed in size and distribution over the past 30 years. Black brant (Branta bernicla nigricans) are relatively stable in numbers but are shifting from large, inland lakes to salt marshes. Concurrently, populations of greater white-fronted geese (Anser albifrons frontalis) have increased seven fold. Populations of Canada geese (Branta canadensis and/or B. hutchinsii) are stable with little indication of distributional shifts. The lesser snow goose (Anser caerulescens caerulescens) population is proportionally small, but increasing rapidly. Coastline erosion of the Beaufort Sea has altered tundra habitats by allowing saltwater intrusion, which has resulted in shifts in composition of forage plant species. We propose two alternative hypotheses for the observed shift in black brant distribution. Ecological change may have altered optimal foraging habitats for molting birds, or alternatively, interspecific competition between black brant and greater white-fronted geese may be excluding black brant from preferred habitats. Regardless of the causative mechanism, the observed shifts in species distributions are an important consideration for future resource planning.