Friday, 5 August 2016

Billinge: 1st August 2016

A somewhat belated post but hopefully still of interest. The new month started much as last month ended with a session at Billinge producing a decent total of 36 new birds and 3 retraps. Once again Willow Warblers were the most numerous species and they accounted for nearly half the total with 15 new birds and 3 retraps. I don't know of any other ringing site in the area where Willow Warblers can still be caught in such good numbers and can also match Chiffchaff in the ringing totals at the end of the season, give or take a few. Why Willow Warblers occur at Billinge in such good numbers is a bit of a mystery but the combination of the habitats, topography and elevation of the area clearly play a part in attracting and funneling Willow Warblers and a several other migrant species through the site.

Adult Willow Warbler, some of the adults have completed their moult like this bird.
The attraction the site has for birds on passage was also demonstrated by the capture of another 2 Sedge Warblers, this time an adult and a juvenile. If the occurrences of Sedge Warblers only involved the occasional juvenile it could be simply put down to post juvenile dispersal which is fairly random in direction initially and sometimes leads to inexperienced birds being out of habitat. The fact that I catch more than just the odd one and adults as well a juveniles suggests there is more to it than that.

Juvenile Sedge Warbler
Interestingly 5 of the 15 Sedge Warblers ringed over the last 3 autumns have been adults and this is a higher proportion of adults than you would expect to catch at a lowland reedbed site in autumn. There is still time to catch a few more Sedges this autumn so that proportion could change but if I just use the ages of the 10 birds caught in autumn 2014 and 2015 adults still made up 30% of the total. I know it is only a very small sample size but it is still intriguing that such a high proportion of adults is involved, especially as the migration of adult Sedge Warblers is known to be more direct and involve fewer stops compared to that of juveniles. 

Adult Sedge Warbler
It was another very quiet day on the tit front but 2 or 3 Willow Tits were heard and one was caught and ringed.

Juvenile Willow Tit, the first to be ringed this autumn.
Ringing totals (retraps in brackets) for 1st August 2015 were: Willow Warbler 15 (3); Chiffchaff 5; Sedge Warbler 2; Blackcap 4; Whitethroat 2; Dunnock 1; Robin 1; Willow Tit 1; Blue Tit 1; Goldfinch 3; Lesser Redpoll 1.

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