Arctic-nesting Birds Research Articles

Linking geomorphological processes and wildlife microhabitat selection: nesting birds select refuges generated by permafrost degradation in the Arctic

Abstract. To gain better insight into the cascading impact of warming-induced changes in the physical landscape on biodiversity, it is crucial to better understand links between abiotic and ecological processes governing species distribution. Abiotic processes shaping the physical characteristics of the environment could significantly influence predator movements in the landscape and ultimately affect biodiversity through interspecific interactions. In the Arctic tundra, the main terrestrial predator (Arctic fox) avoids patches of wetlands composed of ponds with islets that can act as refuges for prey. Little is known about the geomorphological processes generating islets selected by prey species. Our study aimed to identify (i) the physical characteristics of islets selected by Arctic-nesting birds and (ii) the geomorphological processes generating islets available in the landscape. Over two breeding seasons, we determined the occurrence of nesting birds (cackling goose, glaucous gull, and red-throated loon) on islets (N=396) found over a 165 km2 area on Bylot Island (Nunavut, Canada). Occupied islets were located further away from the shore (10.6 m ± 7.3 SD vs. 7.4 m ± 6.8 SD) and surrounded by deeper water (33.6 cm ± 10.6 SD vs. 28.1 cm ± 11.5 SD) than unoccupied islets. As expected, all three bird species selected islets less accessible to Arctic foxes, with nesting occurrence increasing with distance to shore and water depth around islets. Based on high-resolution satellite imagery and field observations, we found that ice-wedge polygon degradation generated the majority of islets (71 %) found in the landscape. Those islets were on average farther from the shore and surrounded by deeper water than those generated by other processes. As polygon degradation is projected to accelerate in response to warming, new refuges will likely emerge in the Arctic landscape, but current refuges could also disappear. Changes in the rate of polygon degradation may thus affect Arctic tundra biodiversity by altering predator–prey interactions.

Additional data confirms the impact of the COVID19 lockdown on the behavior and fattening of migratory snow geese

The COVID19 lockdown provided a unique opportunity to study the impact of human activities and conservation measures on wildlife. However, most lockdown studies were opportunistic and based on limited data, because this ‘natural experiment’ was unexpected and short-lasting. Replication of scientific results is the cornerstone of the scientific method and ensures that conclusions from such short-term studies are robust. Here, we test predictions arising from a previous study where we showed the impact of the lockdown-induced reduction in hunting disturbance on the body condition and behavior of greater snow geese (Anser caerulescens a.), a species whose management is crucial for the conservation of northern ecosystems. The analysis of two additional years of data confirmed our predictions. The return to a high hunting pressure in springs 2021–2022 (post-lockdown) reduced overall goose body condition compared to the lockdown year. Goose fattening in post-lockdown springs was very similar to pre-lockdown years, differing from 2020 when a high body condition was reached earlier in spring than in any other year. Radio-tracked birds spent more time in profitable but risky agricultural lands in 2021 compared to 2020, as was the case in the pre-lockdown year. Our study provides robust evidence confirming the impacts of spring hunting on greater snow goose physiology. It demonstrates the long-lasting efficiency of the spring conservation hunt established two decades ago to limit the size of the population with the aim of preserving Arctic ecosystems from overgrazing and associated negative impacts on other arctic-nesting birds.

Do Arctic-nesting birds respond to earlier snowmelt? A multi-species study in north Yukon, Canada

Climate change has altered the timing of many ecological processes, especially in the Arctic. The initiation of nesting is a key signal of phenological changes in Arctic-nesting birds, and is possibly connected to the circumpolar trend of earlier snowmelt. We collected data on lay dates of 7 bird species, representing shorebirds, passerines, a bird of prey, and seabirds, nesting on Herschel Island, Yukon, Canada, in the years 1984–1986 and 2007–2009. Snowmelt was significantly earlier in the 2007–2009 period. Shorebirds and passerines showed trends to earlier lay dates in conjunction with earlier snowmelt; the other species did not. The strength of response in lay date was correlated with the general categories of foods known to be used by study species. However, six species showed a longer time interval between snowmelt and egg-laying in early compared to late springs, suggesting the need for further monitoring of how robust their responses to snowmelt are in the future.

Arctic-nesting birds find physiological relief in the face of trophic constraints

A climate-induced phenological mismatch between the timing of reproduction and the timing of food resource peaks is one of the key hypothesized effects of climate change on wildlife. Though supported as a mechanism of population decline in birds, few studies have investigated whether the same temperature increases that drive this mismatch have the potential to decrease energetic costs of growth and compensate for the potential negative effects of reduced food availability. We generated independent indices of climate and resource availability and quantified their effects on growth of Dunlin (Calidris alpina) chicks, in the sub-arctic tundra of Churchill, Manitoba during the summers of 2010–2011 and found that when resource availability was below average, above average growth could be maintained in the presence of increasing temperatures. These results provide evidence that chicks may find physiological relief from the trophic constraints hypothesized by climate change studies.

The marine side of a terrestrial carnivore: intra-population variation in use of allochthonous resources by arctic foxes.

Inter-individual variation in diet within generalist animal populations is thought to be a widespread phenomenon but its potential causes are poorly known. Inter-individual variation can be amplified by the availability and use of allochthonous resources, i.e., resources coming from spatially distinct ecosystems. Using a wild population of arctic fox as a study model, we tested hypotheses that could explain variation in both population and individual isotopic niches, used here as proxy for the trophic niche. The arctic fox is an opportunistic forager, dwelling in terrestrial and marine environments characterized by strong spatial (arctic-nesting birds) and temporal (cyclic lemmings) fluctuations in resource abundance. First, we tested the hypothesis that generalist foraging habits, in association with temporal variation in prey accessibility, should induce temporal changes in isotopic niche width and diet. Second, we investigated whether within-population variation in the isotopic niche could be explained by individual characteristics (sex and breeding status) and environmental factors (spatiotemporal variation in prey availability). We addressed these questions using isotopic analysis and Bayesian mixing models in conjunction with linear mixed-effects models. We found that: i) arctic fox populations can simultaneously undergo short-term (i.e., within a few months) reduction in both isotopic niche width and inter-individual variability in isotopic ratios, ii) individual isotopic ratios were higher and more representative of a marine-based diet for non-breeding than breeding foxes early in spring, and iii) lemming population cycles did not appear to directly influence the diet of individual foxes after taking their breeding status into account. However, lemming abundance was correlated to proportion of breeding foxes, and could thus indirectly affect the diet at the population scale.

Timing of breeding, peak food availability, and effects of mismatch on chick growth in birds nesting in the High Arctic

In seasonal environments, breeding events must be synchronized with resource peaks to ensure production and growth of offspring. As changes in climate may affect trophic levels differentially, we hypothesized that a lack of synchrony between chick hatch and resource peaks could decrease growth rates in chicks of shorebirds nesting in the High Arctic. To test this hypothesis, we compared growth curves of chicks hatching in synchrony with peak periods of food abundance to those hatching outside of these peak periods. We also tested for changes in lay dates of shorebirds in the Canadian Arctic using recent and historical data. Mean daily temperatures during the laying period increased since the 1950s by up to 1.5 °C, and changes in lay dates were apparent for three shorebird species, yet differences in median lay dates between 1954 and 2005–2008 were only significant for White-rumped Sandpiper ( Calidris fuscicollis (Viellot, 1819)). During 2005–2008, there was only 1 year of relatively high synchrony between hatch and resource peaks. Asynchrony between hatch and peaks in Tipulidae biomass reduced growth rates in chicks of Baird’s Sandpiper (Calidris bairdii (Coues, 1861)). As anticipated changes in climate may decouple phenological events, the effects of asynchrony on growth rates of arctic-nesting birds warrant further investigation.

Lower Predation Risk for Migratory Birds at High Latitudes

Quantifying the costs and benefits of migration distance is critical to understanding the evolution of long-distance migration. In migratory birds, life history theory predicts that the potential survival costs of migrating longer distances should be balanced by benefits to lifetime reproductive success, yet quantification of these reproductive benefits in a controlled manner along a large geographical gradient is challenging. We measured a controlled effect of predation risk along a 3350-kilometer south-north gradient in the Arctic and found that nest predation risk declined more than twofold along the latitudinal gradient. These results provide evidence that birds migrating farther north may acquire reproductive benefits in the form of lower nest predation risk.

Predator behaviour and predation risk in the heterogeneous Arctic environment

1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3.5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic lemming populations indirectly alter the spatial distribution of productive nests due to a complex interaction between habitat structure, prey-switching and foraging success of foxes.

Population genetic structure in migratory sandhill cranes and the role of Pleistocene glaciations

Previous studies of migratory sandhill cranes (Grus canadensis) have made significant progress explaining evolution of this group at the species scale, but have been unsuccessful in explaining the geographically partitioned variation in morphology seen on the population scale. The objectives of this study were to assess the population structure and gene flow patterns among migratory sandhill cranes using microsatellite DNA genotypes and mitochondrial DNA haplotypes of a large sample of individuals across three populations. In particular, we were interested in evaluating the roles of Pleistocene glaciation events and postglaciation gene flow in shaping the present-day population structure. Our results indicate substantial gene flow across regions of the Midcontinental population that are geographically adjacent, suggesting that gene flow for most of the region follows an isolation-by-distance model. Male-mediated gene flow and strong female philopatry may explain the differing patterns of nuclear and mitochondrial variation. Taken in context with precise geographical information on breeding locations, the morphologic and microsatellite DNA variation shows a gradation from the Arctic-nesting subspecies G. c. canadensis to the nonArctic subspecies G. c. tabida. Analogous to other Arctic-nesting birds, it is probable that the population structure seen in Midcontinental sandhill cranes reflects the result of postglacial secondary contact. Our data suggest that subspecies of migratory sandhills experience significant gene flow and therefore do not represent distinct and independent genetic entities.

Effects of spring conditions on breeding propensity of Greater Snow Goose females

Breeding propensity, defined as the probability that a sexually mature adult will breed in a given year, is an important determinant of annual productivity. It is also one of the least known demographic parameters in vertebrates. We studied the relationship between breeding propensity and conditions on spring staging areas (a spring conservation hunt) and the breeding grounds (spring snow cover) in Greater Snow Geese (Chen caerulescens atlantica), a long distance migrant that breeds in the High Arctic. We combined information from mark–recapture, telemetry, and nest survey data to estimate breeding propensity over a 7–year period. True temporal variation in breeding propensity was considerable (mean: 0.574 [95 % CI considering only process variation: 0.13 to 1.0]). Spring snow cover was negatively related to breeding propensity (bsnow=-2.05 ± 0.96 SE) and tended to be reduced in years with a spring hunt (b = -0.78 ± 0.35). Nest densities on the breeding colony and fall ratios of young:adults were good indices of annual variation in breeding propensity, with nest densities being slightly more precise. These results suggest that conditions encountered during the pre-breeding period can have a significant impact on productivity of Arctic-nesting birds

Foraging Behaviours and Population Dynamics of Arctic Foxes

... The main objectives of my work are to examine (1) how arctic foxes use seasonally abundant foods and (2) how seasonal and annual fluctuations in food abundance affect foraging behaviours and population dynamics of arctic foxes. I am especially interested in how arctic foxes use geese and their eggs (i.e., seasonally abundant foods) and how this varies with fluctuations in small mammal abundance (i.e., foods that fluctuate annually). ... My work is done at Karrak Lake (67°14'N, 100°16'W) and surrounding areas in the Queen Maud Gulf Bird Sanctuary in Nunavut, Canada. ... Fieldwork for my project was done in the spring and summers of 2000-04, and data analyses are currently underway. I monitor population dynamics of arctic foxes in two goose nesting areas at Karrak Lake and two areas outside the influence of nesting geese, whereas I monitor foraging behaviours of arctic foxes in one section of the goose colony at Karrak Lake. ... I examine foraging behaviours of arctic foxes by observing individually marked foxes with spotting scopes .... Avoiding cache loss to competitors is a critical component for the evolution of caching .... I examine how nesting distribution of geese and dispersal of geese away from the colony affect cache loss by evaluating the survival rate of experimentally deployed caches .... I examine arctic fox diets by comparing isotope ratios (delta 13C and delta 15N) of fox tissues ... with those of food items collected in the field .... Fur is metabolically inactive, whereas blood is metabolized continuously ..., so by examining spring blood and winter fur I obtain information on both spring and fall diets. Geese are not present at Karrak Lake in either spring or fall, so goose signatures in this study represent foods cached in summer. I monitor population dynamics of arctic foxes ... through line-transect surveys, mark-recapture studies, and den inventories. ... Goose eggs (from both nests and existing caches) made up 91% of all foods taken by arctic foxes during goose-nesting at Karrak Lake. Foxes cached 96% of these eggs (i.e., most eggs from existing caches were moved to new locations) whereas other foods (i.e., small mammals, geese, and passerine eggs) were either consumed immediately or brought back to den sites. ... Age of cache sites and dispersal by geese away from the colony after hatch (when ca. 1 million geese and their offspring leave the colony in about 10 days) affected loss of experimental caches. These results suggest that both food abundance and strategies to prevent ageing of cache sites (e.g., cache site selection and moving of caches in poor condition) were important in affecting the arrangement of caches at our study site. Cached eggs constituted 30% to 40% of the arctic foxes' diet in autumn and 0% to 30% in spring. ... The abundance of arctic foxes was predominantly affected by abundance of geese ... whereas the density of breeding foxes and litter size were predominantly affected by small mammal abundance. ... This study will provide information on how seasonal and annual fluctuations in food abundance influence use of stored foods and population dynamics of arctic foxes. ... This study will also provide information on predator-prey interactions, which can be used for management and conservation of both arctic foxes and Arctic-nesting birds. ...

Foraging Patterns of Arctic Foxes at a Large Arctic Goose Colony

Arctic foxes ( Alopex lagopus ) are the main predators of many arctic-nesting birds, and such predation can have a large impact on the nesting performance of geese in some years and in some parts of the Arctic. We examined foraging patterns of arctic foxes at a large lesser snow goose ( Chen caerulescens caerulescens ) colony on Banks Island, Canada, from 1996 to 1998 and were especially interested in the proportion of food that was cached for later use and the impact that fox predation had on goose productivity. Arctic foxes took mostly eggs when foraging among geese, and most of these eggs (97%) were cached for later use. Adult geese and lemmings were taken in low numbers, and most of these foods (83% of geese and 75% of lemmings) were eaten immediately. In years with high fox abundance, the foxes spent considerable effort moving eggs from old caches. This behaviour may have resulted from high rates of cache pilfering, or foxes may have been moving caches to deter cache pilfering. The impact of fox predation was low in all years, and foxes took only about 4-8% of all eggs available at the colony during incubation each year. However, caching and use of cached eggs may influence the survival of arctic foxes by forming significant parts of their winter diet or by supplementing the diets of growing young: during nesting each year, foxes took on average 900-1570 eggs per fox.

A Tropical Volcano, High Predation Pressure, and Breeding Biology of Arctic Waterbirds: A Circumpolar Review of Breeding Failure in the Summer of 1992

Although periodic breeding failures of Arctic-nesting birds on a regional scale are common, a breeding failure encompassing almost the entire Arctic in the same year is exceptional. In the spring and summer of 1992, however, the aerosol cloud resulting from the 1991 eruption of Mount Pinatubo (Philippines) had reached the high northern latitudes and caused significant cooling in most of the Arctic, with widespread negative consequences for Arctic-breeding birds. At the same time, low abundance of small rodents and high abundance of predators presented additional problems for breeding birds in parts of the Palearctic. We compiled data on breeding biology of Arctic waterfowl and waders from more than 30 field studies to illuminate in what ways the circumpolar bad weather and predation influenced the breeding season of Arctic birds in 1992. Most projects reported a higher proportion of nonbreeders and a delayed onset of nest initiation compared to other years. Hatching and fledging success of the low number of late breeders was reduced. In addition, some projects reported lower clutch sizes and increased adult mortality. Detailed data from field studies are complemented by data on overall reproductive success of waterfowl and wader populations collected from staging and wintering grounds. In total, there was an almost complete reproductive failure for waders and waterfowl throughout the Arctic in 1992, suggesting a short-term effect on global waterbird populations. This is an example of climatic fluctuations influencing reproductive biology of a group of species on a circumpolar scale.

Nest-Site Distribution and Overland Brood Movements of Northern Pintails in Alberta

Distribution of nests of northern pintails (Anas acuta) was examined around shallow waterbodies on grazed, mixed prairie in southern Alberta. Pintails were the most common ducks nesting on the mainland prairie but not on the more densely vegetated artificial islands. Nest density on the islands for pintails (10.4/ ha) and all duck species combined (80.0/ha) was much greater than that on the mainland (pintails = 0.160.17/ha and all = 0.26-0.31/ha). Hatching sucess of pintail nests on the prairie appeared to be relatively high, probably a result of nests being widely dispersed over large areas of suitable habitat. Pintail nests on the prairie were most commonly situated 1-2 km from water. A hypothesis that pintails nest far from water to avoid male-chasing was repudiated in favor of one that such behavior reduces nest predation. Substantial overland travel by pintail broods is common, necessitated by the distance that hens nest from water. Simulated 3-km nest-to-water movements of pintail ducklings did not deplete their lipid reserves or impair growth. J. WILDL. MANAGE. 51(4):716-723 The importance of prairie breeding habitat to the overall productivity of northern pintails is evidenced by the low apparent reproductive output of arctic-nesting birds (Calverley and Boag 1977, Derksen and Eldridge 1980) and the positive correlation between continental recruitment and the relative proportion of birds inhabiting the prairies (Smith 1970). Within the prairies, the grasslands of southern Alberta support higher densities of breeding pintails than any other region (Vermeer 1972, Bellrose 1979). Much of this area is rangeland, and consequently, many of the birds breeding there nest on grazed prairie. Most information on the location of nest sites of pintails has come from Manitoba and North Dakota where pintails frequently nest, often unsuccessfully, in cultivated fields (Sowls 1955:66, Milonski 1958, Higgins 1977, Krapu 1977). Pintails reportedly nest farther from water than other ducks (Keith 1961, Bellrose 1980: 271), but no systematic searches have been conducted to determine the distribution of their nests relative to water. Nests placed far from water are often thought to result in reduced duckling survival because of the extended overland travel required to get to water; e.g., Sayler 1962, Dzubin and Gollop 1972. In areas where artificial islands have been created, the distribution of nests on the mainland can be compared to that on islands to evaluate the efficacy of the islands in increasing waterfowl production. This study examined the location of pintail nests around a number of shallow basins in grazed prairie near Brooks, Alberta. Pintail use of artificial islands for nesting sites was compared to that of the mainland and contrasted with that of other duck species. The distance of pintail nests from water was determined, and the hypothesis that male pursuit flights cause hens to nest far from water was considered. The consequences of nesting far from water were examined, particularly the effect of overland movement on the condition of ducklings. Financial support of this study was provided by grants to D. A. Boag from the Nat. Sci. and Eng. Res. Counc., and Can. Natl. Sportmen's Fund. Ducks Unlimited Can. and the Brooks Wildl. Cent. of the Gov. Alberta provided invaluable logistic support. Thanks to T. S. Coleman, R. Cotter, G. G. Gregoire, A. J. Murphy, and T. D. Sorochan for their assistance in the field. Special thanks to D. A. Boag for his comments on the manuscript and also to C. D. Ankney, S. J. Hannon, V. Lewin, A. R. Palmer, A. Shires, W. D. Wishart, and P. M. Woodard. The Bamfield Mar. Stn. provided the facilities and personal support for revision of this paper. STUDY AREA AND METHODS The study was conducted in an area of grazed prairie about 35 km southeast of Brooks, Alberta, from 1981 to 1984. The study area included 4 impoundments that are managed for waterfowl production by Ducks Unlimited, Canada. These impoundments (Tilley O, Tilley P, Kininvie F, and Kininvie S) were described by Giroux (1981). At high water levels, the areas Present address: Bamfield Marine Station, Box 99, Bamfield, British Columbia VOR 1BO, Canada.