Update on head-started juveniles from Slimbridge

As well as monitoring and protecting Curlew nests in the Severn and Avon Vales and cooperating with farmers and landowners on whose land the birds nest, the WWT Severn Curlew Project has been following the movements of ‘head-started’ Curlew chicks – those raised in captivity and released (with colour rings) into the wild at Slimbridge. Most of the observations so far have been in the immediate surrounds of Slimbridge, though a couple of juveniles have moved a few miles down the Severn (see previous News posts on this website for details).

At the end of the breeding season, adult Curlews gather at a number of sites on the Severn estuary; the earliest birds (probably birds which did not actually nest, or which have lost their nests or chicks) arrive from June onwards; larger numbers join them later and they spend July and August carrying out their annual moult, generally staying in the same spot for the remainder of the winter, feeding on the mudflats at low tide (or on inland fields), and gathering at high tide in roosts along the shoreline. Since they are very wary birds, it is often difficult to approach these high tide roosts, though with guile, ingenuity and occasionally a portable hide, observers may get close enough to read their coloured or numbered rings.

At Slimbridge the usual group of Curlews has built up through the summer, with a high tide roost out on the edge of the Dumbles (the area of saltmarsh outside the seawall in the New Grounds at Slimbridge), often 300 or more together. Some of the juveniles released earlier in the summer have joined these adults in the roosts, or on the mudflats just before or after high tide, usually too far off to read the numbers on their rings.

The project team is obviously keen to collect as much information as possible on each individual juvenile released, with minimal disturbance to the roosts, and so a novel technique was employed to read rings: trail cameras were attached to old fence posts on the Dumbles. Initial results were not promising: the cattle rubbed against the posts and knocked the cameras over. But, once the cattle had been removed, the cameras proved very effective: before the big tides of last weekend (which flooded the Dumbles so that the cameras had to be retrieved) six of the juveniles were caught on camera, one of them a bird which had not been re-sighted since release, two of them birds which had been ’hard released’ (i.e. released directly from their aviary without an acclimatization period in a temporary aviary); the six had been released on a variety of dates too. All in all a reassuring sign that they are getting used to wild conditions.

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