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The following account, provided by Chris Wells, highlights some of the difficulties encountered by an individual Curlew, identified by the fitting of a colour leg ring.
In April 2021, an adult female Curlew was caught by Tony Cross and I at a traditional Curlew nesting site in Herefordshire. She was wearing a metal BTO ring that had been fitted by Dave Coker in October 2013 (2746 days previously) at Wibdon Wharf, Gloucestershire, on the Severn Estuary - assuming this is her regular wintering ground then this is only 45 km from the nesting territory. When we fitted the colour ring, we could see that the bird had suffered a broken right tarsus since being ringed in 2013, although the injury had since healed.
In years gone by, there were several nesting pairs of Curlew here. Although there isn’t a clear record of the exact number of pairs, it has been claimed that fifty years ago there were over twenty pairs. In 2018, there were just three pairs, and it is not known when the last chicks fledged here, certainly non since 2018.
At the beginning of May 2021, the colour ringed Curlew and her partner made a nest at the traditional site. However, she only laid a single egg before this was observed being predated by a Carrion Crow. Two days later, she made another nest, eventually laying a full clutch of four eggs, which were due to hatch on or around 10 June. On 29 May, one adult Curlew was still on the nest, indicating an active nest.
On the evening of 07 June, the colour ringed bird was seen by John Sanders on the Severn Estuary, not far from where she was first caught in 2013; it was presumed by the observer that the bird was a failed or non-breeder.
The nest was therefore visited that evening and the eggshell remains indicated it was predated a few days previously; a Fox was presumed to be the predator, although other mammals can’t be discounted.
Three evenings later, the colour ringed bird was again seen on the Severn Estuary, when it could be seen she had visible damage to her throat (see image below). Close examination of the image suggests she had a life-threatening experience whilst defending her nest and eggs.
This story clearly demonstrates the importance of colour ringing in providing data that help us understand the complex lives of Curlew, and the various threats they face. The fitting of an expensive GPS data tracker / retriever, which was not available, would have provided even more data.
There are several interesting facts that have come to light due to this female being caught in April and fitted with a colour ring, which would almost certainly have gone unnoticed otherwise.
1) We would not have known she had broken her tarsus between ringing
2) Presumably, this bird has nested and wintered on the same grounds since 2013, as we know Curlew are very site faithful
3) The colour ring observer may not have noticed the feather loss (he tends to focus on birds with colour rings)
4) I would not have known the nest had been predated until after the expected hatching date
Ed: We will be providing further details of Curlew colour ringing schemes, and how to read and report colour rings, on the CRP website soon.