Climate change

No need to head south: climate change could end bird migrations


DURHAM, England – There is perhaps no better way to say winter is really on its way than to see the annual journey to warmer climates for birds around the world. But could the wonderful event become a thing of the past? Climate change could lift the curtain on spectacular bird migrations, new research suggests.

Bird migrations are among nature’s most exciting sites. Herds can number in the millions, resembling a tornado. Many common varieties, including nightingales and willow warblers, already spend up to two more months in the winter breeding grounds.

They could possibly stick around for good, scientists say. “If trends continue, some birds will not spend time in sub-Saharan Africa at all – and instead spend the whole year in Europe,” says lead author Kieran Lawrence, a doctoral student in the Biosciences Department of Durham University. , in a report.

The best-known birds are long-distance migrants, such as swallows, which breed in Europe and overwinter in Africa. At least 4,000 species are regular migrants, or about 40% of the global total.

In remote areas of the north, such as Canada or Scandinavia, most birds move south to escape the winter. In temperate regions like the UK, around half of the species migrate, including cuckoos, swifts and other insectivores that don’t find enough food during the cold months. On the other hand, blackbirds that are typically found in gardens in January are often winter visitors from Eastern Europe.

“The changes in migratory patterns that we are already seeing could result in longer breeding seasons for these species, as well as spillover effects on other species, both here in the UK and in traditional destinations of winter migration. 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, ”says Lawrence. “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. “

The study shows that trans-Saharan migratory birds spend up to 50 to 60 days less per year in their non-breeding areas in Africa. It is based on over 50 years of birding data from traditional retreats in the African country, The Gambia and Gibraltar on the southern coast of Spain. The significant reduction suggests that they are able to survive longer in Europe than before.

Migratory treks involve round trips of at least 10,000 miles. Some may stop making them for good, say the authors. It was previously believed that birds were able to time them based on changes in the length of the day. But the results suggest they are making more nuanced decisions – in response to global warming and available vegetation.

The study found that the birds now arrive at their winter destinations later in the fall than before. They also left the sites earlier in the spring, reducing the overall time in the non-breeding areas.

“Next, we aim to apply a new model, which we are developing in Durham, to simulate these complex migrations, and which we can then apply to future scenarios to understand how the patterns we have identified in trans-Saharan birds in recent years. decades can continue or change, ”said project leader Professor Stephen Willis.

The data was collected by ornithologists in The Gambia and Gibraltar between 1964 and 2019 and 1991 and 2018, respectively. They allowed researchers to explore changes in arrival and departure and relate them to environmental factors.

“It is very satisfying to see the constructive way in which records of Gambian migratory birds, collected by dedicated birders over 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, ”added co-author Clive Barlow, who has lived in The Gambia since 1985, where he tends birds. . watch safaris.

In tropical regions, such as the Amazon rainforest, fewer species migrate because the weather and food supply are more reliable there year-round.

The study is published in the journal Biology of global change.

South West News Service writer Mark Waghorn contributed to this report.


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