Factors influencing incubation behavior and nesting success of Yellow-billed Loons in Arctic Alaska

Reductions in nest attendance can increase predation risk and, therefore, reduce nesting success of ground-nesting birds. We recorded the incubation behavior, nest predators, and nesting success of Yellow-billedLoons (Gavia adamsii) at 2 adjacent study areas with differing amounts of industrial activity on the Arctic Coastal Plain of Alaska, USA, during 2008–2015 and 2019. Successful pairs had higher incubation constancies (97.3 ± 1.7% [SE], n = 96 nests) than failed pairs (91.6 ± 3.1%, n = 79 nests) and took fewer and shorter recesses than failed pairs. The intrusion of conspecifics into territories significantly lowered the daily incubation constancy of nesting pairs. Daily incubation constancy also declined as the daily maximum temperature increased, especially during periods with little wind. Both conditions contributed to nest failure. Predation was the primary cause of nest failure, with Glaucous Gulls (Larus hyperboreus) and Parasitic Jaegers (Stercorarius parasiticus) accounting for 41% of the nest failures. These avian predators took advantage of unattended nests, underscoring the consequence of disrupting incubation behavior. In both study areas, nest survival decreased as recess frequency increased. In the Colville Delta study area, loons with territories composed of separate nesting and brood-rearing lakes had lower nest survival than loons that used 1 lake for both activities. In the National Petroleum Reserve-Alaska study area (NPR-A), loons nesting on shorelines and peninsulas had lower nest survival than those nesting on islands and nest survival decreased as the proportion of days with intruders increased. The overall probability of a nest hatching ≥1 egg in the Colville Delta study area was 0.40 (95% CI = 0.26–0.54) and was 0.68 (95% CI = 0.40–0.91) in the NPR-A study area. Our results demonstrate the importance of nest attendance by Yellow-billed Loons in warding off nest predators on the Arctic Coastal Plain of Alaska and provide a mechanism that shows how a warming Arctic climate could negatively affect Yellow-billed Loons.