Monitoring Bar-tailed Godwits on The Wash

Bar-tailed Godwits (Limosa lapponica) are large waders which have a wide distribution across several continents. Five subspecies are currently recognised plus a sixth recently proposed as yamalensis (Appleton 2021). Bar-tailed Godwits are long-distance migrants and one subspecies (baueri) makes an incredible non-stop migration from Alaska to New Zealand over the Pacific Ocean lasting many days.

Two populations of Bar-tailed Godwit use The Wash: lapponica breeds from northern Fennoscandia eastwards to western Russia and the Taymyr peninsula and moults on The Wash in autumn, with most birds staying to spend the winter; taymyrensis breeds further east reaching central Siberia and passes through The Wash on migration to its wintering sites, as far south as West Africa.

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Ten years of colour-marking Curlew on the Wash – what have we learnt?

Curlew use the Wash both as a passage site to moult during autumn and as a wintering location. On a global scale, they are ‘Near Threatened’ i.e. vulnerable to extinction and they are present in Internationally important numbers on the Wash. Declines in the UK breeding population have placed Curlew in the highest category of UK bird conservation concern; therefore, the species is a priority for the group in terms of long-term conservation monitoring. We started to mark a proportion of the population on the eastern shore of the Wash with unique leg flags in 2012. This allows us to accurately determine their survival and assess wintering habitat use.

Since then, a total of 478 birds have been marked and we have had over 5,000 re-encounters recorded by over 200 WWRG volunteers and members of the public. We regularly dedicate fieldwork hours to ensure we have sufficient resightings to determine survival and winter distribution. This steady stream of data has started to be used in scientific publications to describe the east Wash Curlew population. This blog is a summary of what we have learnt so far.

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Using data to make a difference

Birth, and copulation, and death.
That’s all the facts when you come to brass tacks:
Birth, and copulation, and death.
I’ve been born, and once is enough.

Although not involved in bird study, these lines from T. S. Eliot encapsulate our current studies of wader populations on The Wash. Bird populations are sustained by recruitment of fledged young into the adult population at an equal rate to the death of individual adults. More recruitment than deaths equals more birds. Unfortunately, the opposite is currently occurring in Eurasian Curlew, which is experiencing population decline. This could be due to not enough chicks being raised to adulthood from each nesting attempt, or alternatively, it could be due to increased death of adult birds. Knowing which factor is more important allows conservation efforts to be prioritised: do we need to protect Curlew nests to improve chick survival or do we need to enhance protection of wintering Curlew to improve adult survival? A recently published paper has explored one part of the equation – survival in Curlew – using data from The Wash, as well as other wader ringers around Britain and Ireland.

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The occurrence of Knot Calidris canutus canutus on the Wash

The Wash Wader Ringing Group recently received a recovery report from the BTO of a WWRG-ringed Knot caught in Guinea-Bissau: the first recovery of one of our Knot in that country. This fascinating recovery prompted a more-detailed look both at the circumstances of this bird’s capture and the historical records of Wash recoveries from western and southern Africa.

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Re-sighting during the Covid-19 pandemic

The lockdown imposed by the government in response to the Covid-19 pandemic lasted seven weeks during which fieldwork, including ringing and re-sighting, across the UK came to a standstill. WWRG had just completed their winter field work with the final catching weekend of the season having taken place in mid-March. Trips for several members of WWRG to Delaware and to Iceland were cancelled and opportunities for re-sighting on the Wash were all curtailed during the final weeks of spring 2020 as we were all told to stay at home. Garden ringing and local walks (hopefully entered into Birdtrack) became the norm.

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