Indirect effects of climate change are often mediated by trophic interactions and consequences for individual species depend on how they are tied into the local food web. Here we show how the response of demographic rates of an arctic bird of prey to fluctuations in small rodent abundance changed when small rodent community composition and dynamics changed, possibly under the effect of climate warming. We observed the breeding biology of rough‐legged buzzards (Buteo lagopus) at the Erkuta Tundra Monitoring Site in southern Yamal, low arctic Russia, for 19 years (1999–2017). At the same time, data on small rodent abundance were collected and information on buzzard diet was obtained from pellet dissection. The small rodent community experienced a shift from high‐amplitude cycles to dampened fluctuations paralleled with a change in species composition toward less lemmings and more voles. Buzzards clearly preferred lemmings as prey. Breeding density of buzzards was positively related to small rodent abundance, but the shift in small rodent community lead to lower numbers relative to small rodent abundance. At the same time, after the change in small rodent community, the average number of fledglings was higher relative to small rodent abundance than earlier. These results suggest that the buzzard population adapted to a certain degree to the changes in the major resource, although at the same time density declined. The documented flexibility in the short‐term response of demographic rates to changes in structure and dynamics of key food web components make it difficult to predict how complex food webs will be transformed in a warmer Arctic. The degree of plasticity of functional responses is indeed likely to vary between species and between regions, depending also on the local food web context.

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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.

Many birds nest in association with aggressive birds of other species to benefit from their protection against predators. We hypothesized that the protective effect also could extend to foraging resources, whereby the resultant resource-enriched habitats near a nest of aggressive raptors could be an alternative cause of associations between nesting bird species with non-overlapping foraging niches. In the Arctic, the Rough-legged Hawk (Buteo lagopus) and the Peregrine Falcon (Falco peregrinus) are 2 raptor species with non-overlapping food resources that have been reported to nest sometimes in close proximity. Since nesting Peregrine Falcons are very aggressive, they may protect the small rodent prey near their nests from predation, and Rough-legged Hawks could use these hot spots as a nesting territory. In 2 regions in low Arctic Russia we found that (1) the nesting territories of Peregrine Falcons were indeed enriched with small rodents as compared to control areas, (2) the probability of nest association between the 2 raptors increased when rodent abundance was generally low in the region where hawks did not use alternative prey, and (3) hawk reproductive success increased when nesting close to Peregrine Falcons. These results suggest that implications of aggressive nest site defense in birds in certain cases may involve more mechanisms than previously explored. A key ecological process in tundra, rodent population cycles, may explain the occurrence and adaptive significance of a specific behavior pattern, the nesting association between 2 raptor species.

Migratory species have a limited time for habitat selection upon arrival at the breeding grounds. This is especially evident in arctic migrants, which are restricted by a narrow window of opportunity when environmental conditions are favorable for breeding. This general time constraint is amplified in rough-legged buzzards (Buteo lagopus) who, as many other arctic predators, rely on rodent (lemming) cycles during the breeding season, a 3–5 year period of waxing and waning local food abundance. It remains unclear how arctic predators, especially migrants, can find nesting areas where rodents are numerous when their selection time is so limited. We hypothesized that rough-legged buzzards select nesting areas during the previous breeding season. We tracked 43 rough-legged buzzards using GPS telemetry and assessed their movements post-breeding prospecting behavior to test our hypothesis. Here we show that rough-legged buzzards search for a nesting location during the previous breeding season in a post-breeding period. In the following year, individuals return to and attempt to breed in the area they inspected the year before. Rough-legged buzzards, regardless of breeding success, remained in the Arctic all breeding season until the end of September. Failed breeders prospected more than successful ones. At the same time, buzzards that bred in the rodent-free ecosystem prospected less and showed a high level of philopatry. Therefore, as rodent cycles have been predicted to collapse in the warming Arctic, we can expect arctic predators to change their movement patterns in the future with serious potential consequences for their conservation. We anticipate our study provides a step forward toward understanding movement and settlement decisions in animals experiencing high inter-annual environmental variation.