Tue, Aug 16, 2022: 8:30 AM-8:45 AM
513E
Background/Question/MethodsAnnual molts are energy and resource demanding periods in the lives of birds that have important fitness consequences. Despite this, little is known on how climate impacts the timing of molt in wild birds and how this has and will continue to be modified by climate change. To address this gap, we examined over three decades of constant-effort bird banding data from the Coyote Creek Field Station, CA, which included detailed documentation of molt for four passerine species: Bushtits, Chestnut-backed Chickadees, Song Sparrows, and Common Yellowthroats. We hypothesized the adult pre-basic molt advanced in years with higher mean breeding season temperatures and lower growing season precipitation to better match periods of resource availability. To test this, we built binomial models in a Bayesian framework to estimate the probability a captured bird was actively molting as a function of Julian day, climate variables, and the interaction between climate and day.
Results/ConclusionsWe found significant effects of climate variation on the timing of molt for two species: Song Sparrows and Common Yellowthroats. For every 100mm increase in growing season precipitation there was a 6.5- and 5.1-day delay in the day of maximum molting probability for Song Sparrows and Common Yellowthroats, respectively. For every 1°C increase in mean breeding season temperature there was 7.0-day advancement in the day of maximum molting probability for Song Sparrows. Our results suggest Song Sparrows and Common Yellowthroats have significant plasticity of molt phenology and are likely responding to local climate conditions, though the exact mechanisms by which this might occur are unknown. The predicted warming and drying over the next century from climate change at our study site may drive long-term delays in molting for Common Yellowthroats, though the impact on Song Sparrows is less clear as temperature and precipitation have opposite effects.
Results/ConclusionsWe found significant effects of climate variation on the timing of molt for two species: Song Sparrows and Common Yellowthroats. For every 100mm increase in growing season precipitation there was a 6.5- and 5.1-day delay in the day of maximum molting probability for Song Sparrows and Common Yellowthroats, respectively. For every 1°C increase in mean breeding season temperature there was 7.0-day advancement in the day of maximum molting probability for Song Sparrows. Our results suggest Song Sparrows and Common Yellowthroats have significant plasticity of molt phenology and are likely responding to local climate conditions, though the exact mechanisms by which this might occur are unknown. The predicted warming and drying over the next century from climate change at our study site may drive long-term delays in molting for Common Yellowthroats, though the impact on Song Sparrows is less clear as temperature and precipitation have opposite effects.