May 16, 2018, by Tim Radford
One affected species: A female pied flycatcher. Image: Courtesy of Tom Wallis
Climate change means warmer and earlier springs. And that may be of no help to those bird species that get the timing wrong.
LONDON, 16 May, 2018 – Insectivorous birds could find that earlier springs leave them late at the supper table. Global warming and the advance of spring could mean that the caterpillars have already peaked by the time the blue tits and flycatchers have hatched their hungry broods.
Scientists from six British universities report in the journal Nature Ecology and Evolution that the hatching of forest birds could become increasingly out of step with the maximum supply of the grubs that feed their hungry young.
And, they believe, this may be a change with no winners. A study of blue tits, great tits and pied flycatchers found that geography made no significant difference: the prediction that birds in the warmer south of England may suffer most from this avian mistiming could not be confirmed.
“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,” said Malcolm Burgess, of the University of Exeter in the UK, and the Royal Society for the Protection of Birds.
“Our work suggests that as springs warm in the future, less food is likely to be available for the chicks of insectivorous woodland birds”
“With spring coming earlier due to climate change, leaves and caterpillars emerge earlier and birds need to breed earlier to avoid being mismatched. We found that the earlier the spring, the less able birds are to do this.”
Amateur and professional ornithologists have been observing bird populations for more than a century and have huge bodies of data to work with.
In any changing situation, some species respond to evolution’s challenges, and some – at least for a while – falter.
Researchers have recorded examples of what they call “phenotypic plasticity” in the great tit Parus major. Five years ago they confirmed that the little birds were laying eggs two weeks earlier than 50 years ago. Swiss scientists have evidence that alpine species are moving uphill as temperatures edge ever higher.
But as human populations have swollen, and natural habitat has been lost, bird counts have been falling. Climate change amplifies the hazard.
Arriving too late
And one seeming victim is the pied flycatcher, which migrates to the UK for the breeding season and isn’t in British forests in time to respond to ever-earlier springs.
To establish their findings, researchers collected evidence of oak leafing dates, the droppings from caterpillars that exploit oak trees, and records of egg laying within the three species.
“Our work suggests that as springs warm in the future, less food is likely to be available for the chicks of insectivorous woodland birds, unless evolution changes the timing of their breeding,” said Karl Evans, of the University of Sheffield, one of the authors. – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.