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

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 snow melt 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 three 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 use a combination of endogenous cues and environmental cues in migratory decision making. Sensitivity to environmental cues suggests that Barrow’s Goldeneye may have behavioural plasticity that is adaptive when faced with ongoing climate change.

Dispersal of juvenile Barrow’s goldeneyes (Bucephala islandica) mirrors that of breeding adults

“…For example, because juveniles spend more time on nonbreeding areas, they have higher risk of exposure to marine-based contamination (e.g., oil spills) than adults. Also, adult Barrow’s goldeneyes have been shown to adjust their spring migration to accommodate variation in weather and snow conditions [ 58 ], which juveniles likely do not need to do given their later departure. Recognition of age-specific movement and habitat use may be important when considering environmental or anthropogenic effects on wildlife populations (Additional file 1 ).…”

Application of lidar to assess the habitat selection of an endangered small mammal in an estuarine wetland environment

“…The use of these variables may dominate the results of models seeking to explain more subtle elements of habitat selection including habitat structure. To look more closely at the selection for specific elements of habitat structure, we followed the methods described in Žydelis et al (2006) and forced the four standard variables into all our multivariate models grouped as a single "BASE" covariate (Kemp et al, 2023;Morin et al, 2020). By condensing these four covariates into a single group, we reduced the number of possible candidate models and allowed for a focused assessment of the relative importance of lidar-derived structure covariates (Morin et al, 2020).…”