Colour-ringed Curlews in Wales: the joys of ring reading 1

In winter 2015/16 a team from the British Trust for Ornithology (BTO) and the Wildfowl and Wetlands Trust (WWT) colour-ringed about 40 Curlews on their wintering-ground in the Usk estuary, near Newport in south Wales. The reason for ringing the Curlews (and some other species of waders and Shelduck too) was to find out more about their local movements and use of low tide mudflats, ahead of the possible construction of tidal lagoons for power production in the Severn Estuary. The Curlews were also marked with radio tags which recorded their movements until the tags fell off about a month later.

After the initial observations that winter, there have been very few attempts to observe these birds and to track their long term movements (though two were recorded on their breeding grounds, one in Poland in April 2018 and another in Finland in May 2018 – see earlier posts on this website). Colour-ringed Curlews are occasionally noted on Goldcliff Lagoon in the Newport Wetlands and reported on the Gwent Ornithological Society website. From this autumn greater attention has been paid to these colour-ringed birds (both at Goldcliff and along the Usk estuary) and about a dozen of the original 40 individuals have so far been recorded, thanks to the unique combination of colour rings on their legs; it is planned to continue these observations, which are of great value in calculating the survival of adult Curlews. Experience at other Curlew wintering sites suggests that these Curlews are likely to be highly site-faithful, and that many, if not all of them, will be observed every winter on and around the Usk estuary.

Interestingly, however, at least one bird seems to have had other ideas; it provides a good illustration of the difficulties of reading colour rings, and the patience required.  On 14 September 2019 a picture was taken of a colour-ringed Curlew, not on the Usk but some 40 miles to the west, at the WWT Llanelli centre on the Loughor estuary into the Burry Inlet. The picture was taken at the time of a very high tide for, on normal high tides, Curlews stay much too far away from the observation hides to be seen or pictured at close range: that morning however, conditions were right, a ringed bird was seen, and a photo taken; it clearly showed that the bird carried an orange ring on its left tibia (upper leg) and two colour rings, white over red, on the right tibia. This suggested strongly that it was Orange White Red, ringed with metal ring FA 95842 on 14 January 2016 near the Usk estuary; but, but, to be certain, we would need to see the two other colour rings on the left tarsus, or lower leg: if the bird had come from the Usk it should (like all the other Usk ringed birds) have had an orange ring over a white ring on the left tarsus: but it was standing in a few centimetres of water, so that these rings were invisible – and of course the bird never moved out of the water before flying away. Nothing daunted, WWT staff and volunteers from Llanelli, together with members of the Carmarthenshire Bird Club, kept looking, but for some weeks there was no tide high enough to push the Curlews close enough to the observation hides. Next cycle of spring tides: on 2 October a colour-ringed Curlew seen – Orange White Red above, two colour rings below; but they were reported not as Orange over White, but as Yellow over Orange; if this was correct, they could not have been from the Usk.  Check back with the observer: aha! It was not Yellow over Orange but Orange over Yellow. Still not absolute certainty, but white rings do discolour and begin to look like yellow after a certain time, so the observation is 99% certain. However, it would be really good to reach 100% on the next high tide cycle, if at all possible, with a photo.

Of course, the question then arises as to whether this bird had moved to Llanelli just for the present winter, or whether it had been a regular winter visitor to Llanelli for several years; without regular observations there is no way of telling. There are few records of Curlews changing from one wintering ground to another: it may occur more frequently than previously thought, but without more observations it is impossible to tell. So, more observations please, and as many photographs as possible!

Many thanks to Brian Briggs and Tom Wright of WWT Llanelli and members of the Carmarthenshire Bird Club for the background information in this fascinating story.

Mike Smart

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