Sunday, 31 May 2015

47 and still counting

Since the last post, several visits have been made to the wheatear RAS site to try and bling up an acceptable minimum sample size of  50 individuals and this year success looks very likely; thanks to the dedicated efforts of Mike and Theresa we only now need to catch another three individuals to add to the total of 16 re-sightings and 31 new birds caught so far. Mind you, to reach this total we have had to accept "immigrants" - Teifi RG immigrants at that! The last individual to be added to the tally was a female wheatear originally ringed as a juvenile on 4th July 2014 at Carn Ingli by Karen (Teifi RG). It is only 8km as the crow flies from Carn Ingli and the date and age of the bird suggests that it was presumably born very locally to Carn Ingli before settling to breed within a few km here at Carn Breseb (v
ia Africa). This is the only recorded movement away from the site despite ringing 312 wheatears since 2008. It is also very appropriate that the bird was ringed by Karen who often makes the long foot-slog up the Preselis to help with the project.  Luckily the politics of the group welcomes migrants!

Karen's wheatear with added colours

The 2015 wheatear season is running much later that last year and is more on a par with 2013, an exceptionally cold spring with delayed breeding and small broods. Following a very sunny April, May has been relatively cold and quite windy so perhaps this has caused females to delay egg-laying, or even abandon and start again. So far no fledglings have been seen. Another potential cause of nest failure is predation. Wheatear nests are completely safe from corvids and at this site from foxes too - who often try to dig them out unsuccessfully, but it was clear from the response of three male wheatears that they absolutely panic in the presence of weasels. During one of the visits a weasel was seen systematically searching any crevice or hole it could find and up to three male wheatears were in attendance, all hovering within a foot or two and giving off a very agitated rattle-like alarm call. The weasel didn't seem to find anything and it later became clear that very close by a female wheatear must have been incubating a clutch that escaped predation.

A weasel on the prowl - probably looking for voles but three male wheatears were in a panic

Another unusual record this spring was a wheatear caught on 29th May in full moult - this normally starts at the end of |June or mid-July following breeding, but this bird must have started by 20th May. Whether this was caused by the cold weather combined with a failed early breeding attempt is not clear, but it is extremely unusual for an adult of any migrant passerine to be in moult this early.

Male wheatear in full moult on 29th May

Adult male

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