Off to a flying start
■ Spring is arriving earlier in Europe than it did just a few decades ago – the result of human-caused climate change – and migratory birds are struggling to adapt. As the warmer months encourage caterpillars to hatch, grow and pupate early, the bird species that feed on them in their larval stage are arriving too late, leaving them and their chicks with a limited food supply. But researchers in Sweden and the Netherlands have discovered that migratory birds can be taught to adapt to the changing climate.
As pied flycatchers began to return to the Netherlands after overwintering in Africa, Dutch biologists caught them and drove them further north to Vombs Fure, an area of pine forest near Skåne in southern Sweden – a distance of about 600 kilometres, which a pied flycatcher could cover in just two nights – where they were released. Here, caterpillars hatch roughly two weeks later than in the Netherlands. ‘The birds that were given a lift from the Netherlands to Skåne synchronised very well with the food peak,’ says Jan-Åke Nilsson, a biologist at Lund University in Sweden.
The following year, the chicks of the Dutch pied flycatchers didn’t stop in the Netherlands during their migration, returning instead to the pine forest where they were born. ‘The number of small birds, particularly migratory birds, has decreased drastically throughout Europe,’ says Nilsson. ‘By flying a little further north, these birds, at least in principle, could synchronise with their food resources and there is hope that robust populations of small birds can be maintained, even though springs are arriving ever-earlier.’