Extended Data Fig. 4. Alternative thermoregulatory scenarios.

Energetic expenditures on thermoregulation over time across migrant and resident blackbirds. To quantify the sensitivity of our findings to alternative T_a timeseries, we considered alternatives for both overwintering residents as well as migrants. For migrants we considered T_a timeseries comprised of the mean T_a across the winter range (top middle, primary result in main text) but also considered 25% and 75% temperature quantiles from across the range on each day. On the breeding grounds, the ambient temperature is better estimated but does not include the potential for buffering via the disproportionate use of warmer micro-climates. Thus, we considered two extreme alternative scenarios wherein we inflated the T_a for wintering residents (but not for migrants) by one and two degrees (rows). Blue shaded area denotes the core winter period.