Migratory birds, including the willow warbler, garden warbler and nightingale, could eventually stop flying south for the winter, as they spend more time in their European breeding grounds.
Analysis of more than 50 years of bird records in The Gambia and Gibraltar has revealed that some migratory species crossing the Sahara spend between 50 and 60 days less on average in Africa each winter.
The study, published in the journal Global Change Biology, looked at changes in arrival and departure dates in The Gambia and Gibraltar as well as changes in climate and vegetation.
While birds were previously thought to time their seasonal migration based on daylight hours, analysis suggests that birds are making more nuanced decisions based on available vegetation and climate change.
Records from 1964 to 2019 analyzed by scientists at Durham University found that the species arrived at their winter destinations later in the fall than in the past and also left these places earlier in the spring, reducing the weather. spent in their winter homes.
Over a 27-year period, migratory birds, including Reed Warblers, Northern Wheatear and White Gorges, increased their time in Europe by an average of 16 days.
Lead author Kieran Lawrence in Durham said: âIf the trends we have seen in this study continue, we might see that over time some birds will not spend any time in sub-Saharan Africa at all and instead will spend time in sub-Saharan Africa. whole year in Europe. . “
Many of these small migratory birds are suffering from a significant decline in their UK populations, with nightingales in danger of extinction and breeding warblers in England down 45% in the past 24 years. But populations of chicks, a short-distance migrant that winters mainly in Europe or North Africa, increased 114% over the same period.
While a reduction in migration could help some species survive, Lawrence said there were wider potential implications in Europe and Africa. “In Europe, the longer presence of traditionally migratory birds could lead to increased competition for food and fall / winter resources for resident bird species that do not migrate,” he said.
“Meanwhile, in traditional migration destinations of sub-Saharan Africa, a reduction in the time migrating birds spend there could have implications for ecosystem services such as insect consumption, seed dispersal and pollination. “
Global warming has already altered some patterns of short-haul migration to Britain, with many other blackcaps now wintering in the country rather than moving to mainland Europe. In Europe, the white stork has reduced its migration to Africa, with many birds wintering in the Iberian Peninsula rather than moving further south.
Co-author Clive Barlow, a bird expert from The Gambia, said: ‘It is very satisfying to see the constructive way in which records of Gambian migratory birds, collected by dedicated birders for many decades, are now being used. to highlight the changing migratory patterns of these species. Until current research, no one had realized how much less migratory birds spend the year in sub-Saharan Africa.