Pied flycatchers (Ficedula hypoleuca) and great tits (Parus major) interact a lot. Both rely on the sudden appearance of caterpillars to raise their young, and both compete for the same nesting resources. In recent years, researchers in the Netherlands began to notice something new was happening. Flycatchers were arriving to their nesting sites to find great tits were already occupying them, and the great tits were killing them when they showed up. The dynamic was a consequence of climate change, biologists concluded. As European winters warm, pied flycatchers migrating from Africa reach their breeding grounds and find great tits have already claimed their nesting sites. Because the great tits are residents, researchers found, they’re able to adapt to the changing climate in a way the migrating flycatchers can’t.
Watch a video on the birds’ deadly nest box competition below. The full study appears in Current Biology.