April 23 (UPI) -- Spring is getting warmer and arriving earlier as a result of global warming. And according to new research, the shifting season is throwing off the timing of predators and their prey, specifically birds and their preferred insects.
Researchers at the universities of Edinburgh and Exeter studied the nesting and feeding patters of three bird species, blue tits, great tits and pied flycatchers. All three time their mating and nesting patterns so their offspring are hungriest when caterpillars are most abundant.
But as the new research showed, warmer, earlier springs are pushing the abundance of oak leaves and the caterpillars that feed on them earlier in the year. As a result, chicks are hatching too late to benefit from the nutritious glut of caterpillars.
"Forests have a short peak in caterpillar abundance, and some forest birds time their breeding so this coincides with the time when their chicks are hungriest," Exeter researcher Malcolm Burgess said in a news release. "With spring coming earlier due to climate change, leaves and caterpillars emerge earlier and birds need to breed earlier to avoid being mismatched."
Scientists found pied flycatchers had the greatest difficulty adjusting their nesting timing to match seasonal shifts. Pied flycatchers are migratory, spending their winters outside the United Kingdom. Thus, they're less able to respond to signs of an early spring.
Researchers have previously suggested northern birds will be less affected by the seasonal shifts, but the latest study, published Monday in the journal Nature Ecology and Evolution, showed northern and southern populations were equally impacted by changes in seasonal patterns.
"We found no evidence of north-south variation in caterpillar-bird mismatch for any of the bird species," said Edinburgh researcher Ally Phillimore. "Therefore, population declines of insectivorous birds in southern Britain do not appear to be caused by greater mismatch in the south than the north."
It's possible evolution will inspire a shift in the timing of bird mating and nesting patterns. If not, hatchlings will continue to go hungry as climate change yields earlier, warmer springs.