Godwit breeding season has strict deadline

Geolocators lead to new insights

Godwit breeding season has strict deadline

Godwits always start a second nest if the first one fails. However, they stop trying after May 18, making no further attempts to replace the brood they lost. Why they do this is a mystery.
21 April om 16:30 uur.
Laatst gewijzigd op 22 November 2020
om 16:20 uur.
April 21 at 16:30 PM.
Last modified on November 22, 2020
at 16:20 PM.


Door Rob Siebelink

21 April om 16:30 uur.
Laatst gewijzigd op 22 November 2020
om 16:20 uur.

By Rob Siebelink

April 21 at 16:30 PM.
Last modified on November 22, 2020
at 16:20 PM.

Rob Siebelink

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The discovery was made during research by ecologists on professor of migratory bird ecology Theunis Piersma’s research team. The study made use of so-called geolocators, small computer chips that record light intensity every five minutes, as well as the exact date and time. 

These geolocators have shed new light on the breeding season. The chips are attached to the godwits’ legs and were originally intended to show where the birds were going and when they were leaving. But PhD candidate Mo Verhoeven used them differently in his research, he writes in an article in the Journal of Avian Biology.

Dark 

The locators also record when it is in the dark during the day, he says. That occurs when the birds are nesting and have tucked their legs under them. This allows researchers to much more accurately pinpoint when birds are nesting than when they personally observe the birds.

Until recently, they assumed that only 20 to 45 percent of godwits started a second nest after the first one failed. Verhoeven suspects that earlier researchers assumed many second nests were actually first nest, while other second nests weren’t identified as such at all. 

The research showed another remarkable occurrence: after May 18, not a single godwit would try for a second nest, meaning godwits hold to a deadline for the breeding season. ‘That’s extremely cool.’ It’s not clear why they do so. Verhoeven: ‘I’d love to find out, though.’

Longer breeding season

The fact that all godwits have another tempt at a nest means the breeding season is much longer than people initially assumed. This will have consequences for how to protect the meadow birds.

‘Their second attempt tends to be less successful than the first, but they’re still important’, says Verhoeven. In protected areas, farmers wait to mow their fields until somewhere in July. ‘But the chicks that hatched from that second nest could still be with their parents in early July.’

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