Gyrfalcon (Falco rusticolus) Breeding Performance Across Natural and Infrastructure-Associated Nesting Sites on the Yamal Peninsula, Russia: A Comparison of Two Breeding Seasons

Spring conditions may influence reproduction in the Gyrfalcon, Falco rusticolus, but their effects are difficult to separate from prey variation. We compared 66 nesting territories in 2024 and 69 in 2025 across natural tree nests, artificial nests mounted in trees, rock nests, and raven-built bridge nests on the Yamal Peninsula, Russia. Occupancy did not differ between years (35/66 vs. 40/69; Fisher’s exact test, p = 0.606). The proportion of occupied territories with a confirmed nesting attempt was higher in 2025 but not statistically significant (18/35 vs. 30/40; p = 0.053). Hatching success was higher in 2025 (7/15 vs. 26/29; p = 0.003), as was apparent nesting success among attempts with known outcomes (3/11 vs. 19/24; p = 0.007). Exact paired comparisons of permanent quadrats detected no interannual difference in ptarmigan pellet occurrence. The reproductive contrast coincided with earlier warming and snowmelt in 2025. Direct observations of eggs laid in snow or ice accumulated within raven-built bridge nests illustrated a nest-scale pathway to early failure. Although this two-year comparison documents an association between spring conditions and breeding performance rather than demonstrating causality, the results show why spring conditions, prey, and functional nest-site availability should be evaluated together in Gyrfalcon monitoring and conservation.