Climate change is disrupting the timing of bird migration relative to food availability, creating phenological mismatches that reduce survival and reproductive success.
Individual birds arriving at breeding grounds after peak food abundance have reduced chick-rearing success and elevated adult mortality from energy deficit. The welfare consequence of phenological mismatch is both reproductive failure - chicks that starve before fledging - and adult exhaustion from attempting to raise chicks in suboptimal food conditions. Climate adaptation in migratory birds is constrained by fixed photoperiod cues for migration departure, creating a biological trap as warming advances food availability without advancing migration timing.