The premature start of spring in Europe is threatening the life cycle of long distance migratory birds, a study published in Proceedings of the Royal Society B suggests. Analyzing records spanning 50 years of 117 bird species that annually relocate from Africa or southern Europe to breeding grounds in northern Europe, researchers found that certain birds’ arrival is being knocked out of sync with the optimal time for mating and raising their chicks.
Birds flying shorter distance seem less affected by the earlier season. Long distance migrators that have not rescheduled their arrival times are confronted with “ecological mismatch” and are facing diminishing numbers.
“Peaks in food abundance, such as insects, are very narrow in northern latitudes; so if you arrive too late and miss the peak, then you miss the best opportunity to raise your offspring,” co-author Professor Saino told the BBC News.
Saino notes that the fate of these birds, most of which spend the other half of the year in sub-Saharan regions, also depends on winter conditions. They may not be able to shift their winter sites northward, while if they shift these sites southward they will have to fly further to reach European breeding grounds.
Image: Hirundo rustica [barn swallow] in flight. Taken by Thermos, wikimedia commons.