Study warns climate change could bring curtain down on spectacular bird migrations

By Mark Waghorn via SWNS

Climate change could bring the curtain down on spectacular bird migrations, according to new research.

They are among the most thrilling sights in nature. Flocks can number in their millions - resembling a tornado.

Many common varieties, including Nightingales and Willow Warblers, are now spending up to two months longer in winter breeding grounds. They may eventually remain for good.

Study lead author Kieran Lawrence said: "If the trends continue, in time some birds will spend no time at all in sub-Saharan Africa - and instead the full year within Europe."

The most famous are long distance migrants, such as swallows, which breed in Europe and spend the winter in Africa.

At least 4,000 species are regular migrants - about 40 percent of the world's total.

In far northern regions, such as Canada or Scandinavia, most birds move south to escape winter.

In temperate areas like the UK about half the species migrate including cuckoos, swifts and other insect-eaters that can't find enough food.

On the other hand, blackbirds in your garden in January are often winter visitors from Eastern Europe.

Lawrence, a PhD biosciences student at Durham University, said: "The changes in migratory habits we are already seeing could lead to longer breeding seasons for these species, as well as knock-on effects on other species, both here in the UK and in the traditional winter migration destinations.

"In Europe, the longer presence of traditionally migratory birds could lead to increased competition for autumn/winter food and resources for resident bird species that do not migrate.

"Meanwhile, in the traditional migration destinations of sub-Saharan Africa a reduction in the time migratory birds spend there could have implications for ecosystem services such as insect consumption, seed dispersal and pollination."

The study shows trans-Saharan migratory birds are spending as many as 50 to 60 fewer days a year in their non-breeding grounds in Africa.

It's based on over 50 years of bird-sighting data from traditional retreats in The Gambia and Gibraltar.

The significant reduction suggests they are able to survive longer in Europe than before.

Marathon treks involve round trips of at least 10,000 miles. Some may stop making them for good, say the British team.

It was previously thought birds were able to time them through changes in day length.

But the findings suggest they are making more nuanced decisions - responding to global warming and available vegetation.

The study, published in the journal Global Change Biology, found birds were now arriving at their winter destinations later into the autumn than before.

They were also departing the locations earlier in the spring - slashing the overall period in non-breeding grounds.

Project leader Professor Stephen Willis said: "Next, we aim to apply a new model, which we are developing at 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 over recent decades may continue or change."

Records were gathered by ornithologists in The Gambia and Gibraltar between 1964 and 2019 and 1991 and 2018, respectively.

They enabled the researchers to explore changes in arrival and departure and relate them to environmental factors.

Co-author Clive Barlow, who has lived in The Gambia since 1985 where he runs birdwatching safaris, added "It is very satisfying to see the constructive way the Gambian migrant bird records, collected by dedicated ornithologists over many decades, are now being used to highlight the changing migratory patterns of these species.

"Until the current research, no-one had realised the extent to which migrant birds are spending less of the year in sub-Saharan Africa."

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