Shrinking bird pays the bill for warming

Foraging red knots in MauritaniaImage copyright
© Jan van de Kam – Netherlands

Image caption

Red knots (Calidris canutus) are wading birds that use their long bills to probe the mud for invertebrate food

A migratory bird has shrunk in stature as temperatures warm at its Arctic breeding ground, according to research.

As a consequence of climate change, the red knot may have a lower survival chance on a different continent, say scientists.

The shore bird breeds in the Arctic in the summer and flies to tropical habitats in winter.

Scientists believe shrinkage in body size is a response to climate change in different animals.

The latest research, published in the journal, Science, looked at the red knot (Calidris canutus).

The wading bird is one of the record-breakers for long distance flight, being able to cover about 5,000 km without stopping.

Image copyright
© Jan van de Kam – Netherlands

Image caption

Foraging red knots in Mauritania

An international team studied the bird over 30 years at its stop-off point in Russia.

“We see a change in body size and also a change in body shape,” said lead researcher Dr Jan van Gils of the Royal Netherlands Institute for Sea Research and Utrecht University.

He told the BBC’s Science in Action programme: “What is peculiar about this is that we have strong evidence that this is an effect of climate change and people have seen in other species changes in body size in response to climate change.”

The study was the first to show that shrinking in response to climate change was a disadvantage to an animal, because the smaller birds had a lower survival rate, he added.

Paying the bill

The scientists found that over the course of 30 years, the date of the snow melt in the Arctic had advanced by more than two weeks.

Meanwhile, the birds produced smaller and smaller offspring – probably because the chicks missed the main food supply at the time of the thaw.

Image copyright
© Jan van de Kam – Netherlands

Image caption

Flying red knots

The birds pay the price when they arrive in Africa after their long flight.

Analysis of the diet of the red knot in its winter home found that individuals with a longer bill could delve into the mud for molluscs.

However, those with a shorter bill could not reach the shellfish, and were forced to eat less nutritious food.

“There are only a few birds nowadays that make it to adulthood – those are the ones that are small and have a relatively long bill,” Dr van Gils explained.

The study shows that long-term changes in the body architecture of Arctic wading birds can affect their survival in their tropical wintering range, said Martin Wikelski of the Max Planck Institute for Ornithology in Germany.

“Thus, changes in one habitat may have important ecological consequences in habitats halfway around the world,” he said in an editorial in Science.

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