In winter 2015-16, the British Trust for Ornithology (BTO) caught a number of Curlews with cannon nets at the mouth of the Usk, where that river flows into the Severn near Newport, Wales. These birds were marked with colour rings, so that individual birds could be distinguished from one another in the field. They were also marked with battery-powered GPS tags. The batteries last about a month and give during this period an indication of where the birds are spending their time. The tags confirmed what had already been recorded for other wintering birds in the area: they are extremely site-faithful, and feed on a small area of mudflat, retiring to roosts on the edge of the water at high tide.
This was not in fact the first time that BTO had carried out a colour-ringing programme in this general area: from autumn 2010 to 2013, about 160 birds were marked with a series of colour rings a little higher up the Severn estuary near Wibdon in Gloucestershire and, even before that, a number of Curlews had been marked with metal rings. Recoveries from these ringing programmes have shown that Curlews wintering on the Severn estuary in south-west England and Wales migrate to breed in a great arc, running from the upper reaches of the Severn estuary, right across northwest Europe to Finland, up to the Russian border (none so far recovered in Russia, but one will no doubt turn up one day!); indeed a surprisingly large proportion of the recoveries do come from Finland in May and June. The map below shows a selection of Curlews colour-ringed in winter on the Gloucestershire section of the Severn, and recovered on their breeding grounds.
It was therefore not exactly a surprise, rather a welcome confirmation, when the BTO received a report from the Finnish Ringing Office of one of the Usk birds on the breeding grounds in Finland, together with a photograph of the ringed bird, which had a black ring on the left tibia and a red ring over a black ring on the right tibia; there was a yellow ring over a white one on the left tarsus, to show that the bird had come from the Severn, and a metal ring inscribed with a number on the right tarsus (see picture). The bird had been reported on 5 May 2018 by Veijo Nissilä, at Hailuoto 65.01N, 24.74E, near the head of the Gulf of Bothnia.
The picture made it possible to identify the bird as colour ring Black Red Black, marked by the BTO team on the Severn Estuary in Wales on 15 December 2015. The exact location was Lighthouse Beach, Usk Estuary, Wales 51.32N 2.59W. The last record of the bird by GPS tag was in mid-January 2016 at the Usk estuary. No other re-sightings of the bird had been reported until the Finnish record. The metal ring number was FA 95820 and the bird was ringed as an adult; sex not known (but the picture suggests it may have been a female, from the long bill).
Observers who report rings often have additional information of interest so, in the response to the Finnish Ringing Office, we commented: “It would be interesting to know more about the habitat in which it was seen, and whether it was definitely breeding; do you know if it bred successfully this year? Our experience is that Curlews are extremely site-faithful, returning to the same wintering area each winter, and to the same breeding site (often the same field) each spring/summer.”
In response, we have just received the following information from Dr Markus Piha of the Finnish Ringing Office who has kindly translated Veijo Nissilä’s comments from the Finnish:
“I saw this curlew during 3-4 days. Around my home there are fields where at least two curlew breeding attempts were successful. The chicks sometimes ran at my yard as well. One nest was located near the location where the colour-ringed individual was seen so it is likely that the bird is the female of this nest. The bird probably started migration soon after the egg-laying, but this is naturally not 100% sure. The birds that are guarding the chicks now (July 9th) are males. Best regards, Veijo Nissilä”
This note confirms several points which we have observed on Curlews in Britain: the females do quit the nesting grounds early, leaving the males to guard the growing chicks; and if they have already left Finland by 9 July, this explains why they arrive back so early on moulting and wintering areas in the south-west of their range. Many thanks to Veijo and Markus.