Project

Breeding Ecology of Arctic Raptors Under Global Climate Change

Goal: Understand behaviors and ecology of Gyrfalcons that reflect resiliency or vulnerability to global climate change.

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Project log

David L Anderson
added 3 research items
The peregrine falcon (Falco peregrinus) and the gyrfalcon (Falco rusticolus) are top avian predators of Arctic ecosystems. Although existing monitoring efforts are well established for both species, collaboration of activities among Arctic scientists actively involved in research of large falcons in the Nearctic and Palearctic has been poorly coordinated. Here we provide the first overview of Arctic falcon monitoring sites, present trends for long-term occupancy and productivity, and summarize information describing abundance, distribution, phenology, and health of the two species. We summarize data for 24 falcon monitoring sites across the Arctic, and identify gaps in coverage for eastern Russia, the Arctic Archipelago of Canada, and East Greenland. Our results indicate that peregrine falcon and gyrfalcon populations are generally stable, and assuming that these patterns hold beyond the temporal and spatial extents of the monitoring sites, it is reasonable to suggest that breeding populations at broader scales are similarly stable. We have highlighted several challenges that preclude direct comparisons of Focal Ecosystem Components (FEC) attributes among monitoring sites, and we acknowledge that methodological problems cannot be corrected retrospectively, but could be accounted for in future monitoring. Despite these drawbacks, ample opportunity exists to establish a coordinated monitoring program for Arctic-nesting raptor species that supports CBMP goals.
While collating contributions and comments from 36 researchers, the coordinating authors accidentally omitted Dr. Suzanne Carrière from the list of contributing co-authors. Dr. Carrière's data are described in Tables 1 and 3, Figure 2 and several places in the narrative.The new author list is thus updated in this article.
We know little regarding how specific aspects of habitat influence spatial variation in site occupancy by Arctic wildlife, yet this information is fundamental to effective conservation. To address this information gap, we assessed occupancy of 84 Gyrfalcon (Falco rusticolus Linnaeus, 1758) breeding territories observed annually between 2004 and 2013 in western Alaska. In line with the theory of population regulation by site dependence, we asked whether Gyrfalcons exhibited a nonrandom pattern of site selection and if heterogeneous landscape attributes correlated with observed occupancy patterns. We characterized high- and low-occupancy breeding territories as those occupied more or less often than expected by chance, and we evaluated land cover at 1 and 15 km circles centered around nesting territories to identify habitat variables associated with observed occupancy patterns. We tested 15 competing models to rank hypotheses reflecting prey and habitat variables important to nesting Gyrfalcons. We confirmed a nonrandom pattern of site selection but found only weak evidence that the distribution of prey habitat was responsible for this pattern. We reason that preferential habitat use by nesting Gyrfalcons may be determined by spatial scales other than those we measured or may be driven by landscape-level attributes at time periods other than during the brood rearing period.
Bryce W Robinson
added a research item
Climate and landscape change are expected to affect species' distributions and interactions, with potentially harmful consequences for specialist predators. Availability of optimal prey can affect reproductive success in raptors, especially in the Arctic, where dramatic differences in prey availability occur both within and between years. However, behavioral responses of dietary specialist, resident predators such as Gyrfalcons (Falco rusticolus) to changes in prey availability remain poorly understood. To improve understanding of how climate-driven changes in prey availability may affect diet of avian predators in the Arctic, we characterized Gyrfalcon diet on the Seward Peninsula, Alaska, in 2014 and 2015 from images representing 2008 prey items obtained by motion-activated cameras at 20 nests. We documented two important dietary shifts: the proportion of ptarmigan (Willow Ptarmigan [Lagopus lagopus] and Rock Ptarmigan [L. muta]) in the diet declined throughout the brood-rearing period in both years, and also differed between years. In both cases, ptarmigan were replaced by Arctic ground squirrels (Urocitellus parryii) in the diet. Despite shifts in prey composition, dietary breadth did not change, which revealed a facultative shift in prey use in which Gyrfalcons relied on prey of large size rather than prey of a particular taxon. We describe previously undocumented prey-use patterns during Gyrfalcon breeding, specifically an interchange between two prey species that are keystones in tundra ecology. These results are important for informing predictive models of climate change and adaptive species management plans. Further study of the interchange between prey types described in this study can strengthen insight into key ecosystem processes, and the cause and effect of potential decoupling of predator-prey interactions.
David L Anderson
added an update
We just published a book with research methods for raptors. Based on experience studying Gyrfalcons, the book is written so that the methods can be applied to raptors around the world. Each chapter is designed to present possible research questions on a topic (e.g., nestling growth), then gives R code and a sample data set so that the reader can test the methods, design their own questions, and get started.
 
David L Anderson
added an update
The field crew of Mike Henderson, Devin Johnson, and Adam Eichenwald made it to the field last week. In the first week of work they installed cameras in two nests, started ptarmigan surveys, and completed aerial surveys for raptor occupancy. It's been stellar!
 
David L Anderson
added a research item
Nest collapse has been documented in many bird species, with little discussion of adult behavior following collapse. We present evidence of a partial collapse of a Gyrfalcon (Falco rusticolus) nest during the nestling period and the subsequent adult response. A nest camera captured the nest collapse and showed one adult Gyrfalcon holding a live nestling in its beak before leaving the nest. Later, we found the surviving nestling alive in an alternate nest 5 m from the original nest, presumably transported there by the adult. We believe this is the first report of an adult Gyrfalcon moving a nestling to a new location following nest disturbance. We place this observation into a context of Gyrfalcon nesting behavior described in published sources. The continued use of nest cameras may provide additional documentation and insight into this behavior and its prevalence in birds.
David L Anderson
added an update
New publication on nest relocation in Gyrfalcons out in Wilson Journal of Ornithology.
 
David L Anderson
added a research item
We report Crested Auklet Aethia cristatella as a prey item of a Gyrfalcon Falco rusticolus nesting in inland western Alaska. This represents the first documented case as a Gyrfalcon prey item during the breeding season in North America, and the fourth documented case of inland movements of Crested Auklet. The presence of the auklet in the Gyrfalcon nest is notable due to the distance (105 km) to the nearest coastline. Weather likely caused the inland movement of the auklet. Because of the connection between weather events and inland movements of alcids, and the predicted increase and severity of weather due to climate change, continued reporting of inland movements may serve as a measure of change and its impacts on seabirds. Continued use of nest cameras to monitor raptor diet during nesting may also serve as a sampling tool for capturing similar instances of inland movements, and complement the use of eBird for sightings of live birds in understudied areas to gain a better understanding of the frequency of inland movements in the family Alcidae.
David L Anderson
added a project goal
Understand behaviors and ecology of Gyrfalcons that reflect resiliency or vulnerability to global climate change.