Monday, 16 September 2013

Whimbrel migration

In May we were catching and colour-ringing Whimbrel as they headed north as part of a larger project set up by Tony Cross (see ruffledfeathers)  with the aim of trying to find out more about the migration of this transient species. So far we have only had one report of the 34 we ringed in Pembs in spring, a bird which unfortunately died after colliding with electric cables before managing to leave Pembs. Whimbrel have recently been passing through on their way back from their breeding grounds further north and during four routine ringing sessions at the Gann Estuary near Dale since early August 4 individuals have been caught. This total is surprisingly low given that 1498 were counted passing Strumble Head on 18th August (see Strumble blog).

Although the sample size is small it was noticed that the autumn birds were heavier than those in spring (average of 486g compared to 410g), presumably implying that although they pass through in good numbers in autumn, they don’t need to feed up, so many must carry straight on without stopping. Anyway, if anyone is out watching Whimbrel then it is worth looking for a numbered yellow colour-ring above the knee on the right leg and a green one below, as in the photo below.

Adult Whimbrel with colour-rings

6 Curlews have also been ringed and weighed this autumn and their weights were quite a bit lower than that expected for this time of year  with an average of 646g compared to the national average of 770g in autumn (BTO website), but  the sample size is still too small to draw any confident conclusions.

The Whimbrel study has had a very interesting ‘bycatch’ with the most recent session producing 40 waders of 10 species. Half of these were Oystercatchers which generated much discussion on how to age them correctly - in the end we think we sussed it! (see photos below). Also ringed were; 4 Curlew, 4 Dunlin, 5 Bar-tailed Godwit, 2 Redshank, and singles of Greenshank, Black-tailed Godwit, Common Sandpiper and Ruff.

Oystercatcher age code 3 - born this year

Oystercatcher age code 5 - born last year

Oystercatcher age code 7 - born two years ago
Oystercatcher age code 8 -  at least 3 years old
Male and female juvenile Bar-tailed Godwits - the female has the longer bill
Juvenile Black-tailed Godwit
male Ruff 
Juv Common Sandpiper
Paddy J and Paul W

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