Bird brains might pay the ultimate price for climate change, science says.
Pied flycatchers make an annual road trip from sub-Saharan Africa to northern Europe to chow on caterpillars, build nests — and mate. They typically return to Africa a few months later with their new vacation babies. But over the past decade, flycatchers are arriving for mating season to find their nesting sites already occupied by great tits.
But these territorial tits don’t just get their feathers ruffled. See, great tits are locals, and these townies don’t tolerate tourists. A turf war ensues, one in which they peck flycatchers to death — and eat their brains, according to a new study published in Current Biology.
This rise in brutal bird-on-bird violence is due to a shift in migration and nesting timelines, researchers say. Tits traditionally mated two weeks before pied flycatchers, but since the 1980s, flycatcher breeding season has increasingly inched up earlier in the month of April.
Warmer spring temperatures caused caterpillars to flourish sooner in the month, so flycatchers adapted to arrive earlier, as well. Today, their breeding periods occasionally overlap with tit time due to “climate change-related factors,” the study says.
Deep in the heart of the Dwingelderveld and Drents-Friese Wold forests in the Netherlands, researchers tracked a total of 88 flycatcher victims (86 males and two females) during nest checks, 86 of which were killed by great tits and two by blue tits. The dead flycatchers were all found in active tit nests and had severe head wounds — and often their brains were, uh, missing.
“Great tits are superior competitors when it comes down to a brawl,” lead study author Jelmer Samplonius, a climate change ecologist at the University of Edinburgh, tells Popular Science. “They have really strong claws, and they hold onto [the flycatchers] and peck the back of their skulls, always in the same spot.”
According to data taken from 950 nests and nearly 3,000 birds between 2007 and 2016, the authors found that great tits killed nearly one in 10 flycatchers.
Sara Keen, a behavioral ecologist at Cornell University who wasn’t involved with the new study, tells Popular Science she’s struck by how behavioral responses to climate change appear to be putting bird brains at risk.
“Understanding different responses to changing environments will be a crucial part of species vulnerability assessments in coming years,” she says.