Climate change is causing phenological mismatches between bird breeding timing and the peak of food sources — creating welfare crises for chicks hatching when caterpillar and insect peaks have already passed.
Bird chicks that hatch after the caterpillar peak face a welfare crisis: parents making intense foraging trips return with inadequate food, chicks that cannot grow to fledgling weight die from starvation or are too weak to survive early independence. The welfare harm is experienced by millions of chicks annually, in species ranging from blue tits to pied flycatchers. The mechanism is climate change — a human-caused shift in seasonal timing that birds evolved responses to navigate but cannot adjust quickly enough to track.