Pacific Barrow’s Goldeneye refine migratory phenology in response to overwintering temperatures and annual snowmelt

Authors: Jesse Kemp, W. Sean Boyd, Tesia M. Forstner, Daniel Esler, Timothy D. Bowman, David C. Douglas, Danica Hogan, Malcolm McAdie, Jonathan E. Thompson, Megan Willie, and David J. Green

Year: 2023

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Keywords: annual cycle, Barrow’s Goldeneye, Bucephala islandica, climate, migration, phenology, sea duck, tagging effects, Garrot d’Islande

Abstract: Timing of seasonal bird migrations is broadly determined by internal biological clocks, which are synchronized by photoperiod, but individuals
often refine their migratory timing decisions in response to external factors. Using 11 years of satellite telemetry data, we show that Pacific
Barrow’s Goldeneye (Bucephala islandica) at higher latitudes initiated spring and molt migrations later and fall migration earlier than individuals
at lower latitudes. We further show that individuals refined migratory timing in response to interannual variation in environmental conditions.
Individual Barrow’s Goldeneye initiated spring migration earlier in years with warmer springs at their overwintering locations and concluded
spring migration earlier in years with earlier annual snowmelt on their breeding grounds. Because individuals respond to conditions both where
they initiate and where they conclude spring migration, our results suggest that Barrow’s Goldeneye update their migratory decisions en route.
For all 3 migrations in their annual cycle, birds delayed initiating migration if they had been captured and tagged prior to that migration. Birds
that initiated migration late for their latitude were less likely to include a stopover and completed that migration faster, partially compensating
for delayed departures. Our results are consistent with the hypothesis that Barrow’s Goldeneye uses a combination of endogenous cues and
environmental cues in migratory decision making. Sensitivity to environmental cues suggests that Barrow’s Goldeneye may have behavioral
plasticity that is adaptive when faced with ongoing climate change.

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