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

Ornithology, 2023, 140, 1–13 https://doi.org/10.1093/ornithology/ukad024 Advance access publication 12 May 2023 Research Article Pacific Barrow’s Goldeneye refine migratory phenology in response to overwintering temperatures and annual snowmelt Centre for Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada Environment and Climate Change Canada, Science and Technology Branch, Pacific Wildlife Research Centre, Delta, British Columbia, Canada 3 U.S. Geological Survey, Alaska Science Center, Anchorage, Alaska, USA 4 U.S. Fish and Wildlife Service, Anchorage, Alaska, USA 5 Environment and Climate Change Canada, Canadian Wildlife Service, Yellowknife, Northwest Territories, Canada 6 Marmot Recovery Foundation, Nanaimo, British Columbia, Canada 7 Office of the Chief Scientist, Alberta Environment and Parks, Edmonton, Alberta, Canada 8 Canadian Wildlife Service, Environment and Climate Change Canada, Delta, British Columbia, Canada 1 2 *Corresponding author: 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. Keywords: annual cycle, Barrow’s Goldeneye, Bucephala islandica, climate, migration, phenology, sea duck, tagging effects, Garrot d’Islande How to Cite Kemp, J., W. S. Boyd, T. M. Forstner, D. Esler, T. D. Bowman, D. C. Douglas, D. Hogan, M. McAdie, J. E. Thompson, M. Willie, and D. J. Green (2023). Pacific Barrow’s Goldeneye refine migratory phenology in response to overwintering temperatures and annual snowmelt. Ornithology 140:ukad024. LAY SUMMARY • Migratory birds time their annual migrations to take advantage of temporal and spatial variation in resources, disease, and predation. • Timing of these migrations is broadly determined by an internal biological clock set by day length, but individuals may refine when and how they migrate in response to environmental conditions. • We used 11 years of satellite tracking data to investigate migratory cues in Barrow’s Goldeneye, a species of sea duck. • We found that birds used weather conditions as migratory cues, leaving their wintering grounds earlier in warmer springs and arriving on their breeding grounds earlier when the snow melted earlier in the year. • Because individuals respond to conditions both where they start and where they end spring migration, our results suggest that Barrow’s Goldeneye update their migratory decisions during migration. • Barrow’s Goldeneye’s ability to respond to environmental cues suggests that they may be able to adapt to ongoing climate change. Submission Date: September 26, 2022. Editorial Acceptance Date: May 1, 2023 © American Ornithological Society 2023. Published by Oxford University Press for the American Ornithological Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License ((https://creativecommons.org/ licenses/by/4.0/)), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact Downloaded from https://academic.oup.com/auk/article/140/3/ukad024/7160511 by Withers user on 17 September 2023 Jesse Kemp,1,* W. Sean Boyd,2 Tesia M. Forstner,1 Daniel Esler,3 Timothy D. Bowman,4 David C. Douglas,3 Danica Hogan,5 Malcolm McAdie,6 Jonathan E. Thompson,7 Megan Willie,8 and David J. Green1 2 Pacific Barrow’s Goldeneye migration phenology J. Kemp et al. Bucephala islandica de la population de l’Ouest affine sa phénologie migratoire en réponse aux températures d’hivernage et à la fonte des neiges annuelle RÉSUMÉ Mots-clés: cycle annuel, Bucephala islandica, climat, migration, phénologie, canard de mer, effets du marquage INTRODUCTION Timing of annual migrations, during which birds may move thousands of kilometers, result from a complex interaction between endogenous biological clocks and exogenous environmental conditions. Endogenous biological clocks generate circannual rhythms, which are synchronized primarily by photoperiod (Gwinner 1996, Åkesson et al. 2017), and are responsible for the broad seasonal timing of migrations (Berthold 1984, Gwinner 1996). Intraspecific variation in migratory timing often varies with latitude due to its relationship with photoperiod (Gow et al. 2018, Smith et al. 2020), and these latitudinal effects can carry over to affect the timing of subsequent events in the annual cycle (Gow et al. 2018, Forstner et al. 2022). Individuals also have flexibility to refine their timing decisions in response to external environmental factors, such as seasonal variation in weather conditions (Haest et al. 2020) or food availability (van der Graaf et al. 2006). For example, temperature can affect timing of spring migration (Haest et al. 2020) as well as departure from intermediate staging sites (Shariati-Najafabadi et al. 2016). Wind conditions can also affect migratory departures as well as flight duration and arrival timing (Gill et al. 2009, Drake et al. 2014, Haest et al. 2020). Additionally, seasonal variation in weather-mediated food conditions along the migration route can drive the timing of migration. For example, on northward spring migrations, some herbivorous geese are known to follow a green wave of progressively available forage along their spring migration route (van der Graaf et al. 2006, van Wijk et al. 2012). Similarly, on northward migra (...truncated)