The grasshopper warbler migration started about 10 days later than last year and has so far not reached the dizzy heights of previous years. In fact we have only been averaging 12 birds per day and this year have only ringed 147 birds; all of those have been juveniles. Sedge warbler numbers have been very good and today (10th August 2013) a catch of 272 birds (including 6 controls) was made up of 187 (including 3 controls) birds making the total for the year 647. This week an extraordinarily dark juvenile sedge warbler was captured.
|Dark Sedge Warbler Acrocephalus schoenobaenus (B.S Duffin)|
As can be seen from the pictures the bird was generally dark rusty brown in colour on both the upper and underparts, a truly striking individual.
|Underparts of Dark Sedge Warbler|
Surprisingly this is not the first time I have seen a bird with this colouration. In 2010 a similarly coloured reed warbler was trapped at the Haven during the autumn migration. This bird was different in that it seemed to have a brown sticky mess on its forehead, which suggested that the bird may have fallen into something, this did not appear to be the case with the sedge.
|Dark Reed Warbler A. scirpaceus from 2010|
The pattern of migration this year is again similar to previous years with sedge, reed and grasshopper warblers being the most numerous. Willow warbler numbers are now starting to build and today we ringed 17 new birds bringing the total to date to 50. All of the willows were again juveniles including a very pale washed out individual. According to Svennson northern populations are more greyish-white and generally lack any yellow tones.
|Juvenile Willow Warbler Phylloscopus trochilus of the northern/acredula type|
This bird was was exactly that, a pale greyish-white bird with no yellow tones. When compared with a typical willow warbler it was possible to see just how striking the bird was.
|Willow Warblers - both these birds had a wing length of 61.5 mm and therefore |
we thought that they were ideal for comparison. The pale left bird weighed 7.4 grams
whereas the normal right bird weighed 8.5
And if an unusual sedge and a northern willow wasn't enough, we were also treated to a very smart wood warbler. Every year we try for this species and have only ever caught a handful. Today's bird was the first for four years and added to what was an excellent days bird ringing.
|Wood Warbler Phylloscopus sibilatrix the first ringed at the haven for about four years|
Our tally today included six controls, three each of sedge and reed warbler. That brings our total of outstanding controls for the autumn to 18 including one French and one Spanish, and we are not even halfway through the season yet. Our total for new birds ringed stands at 1309 birds of 24 species, 108 birds have been retrapped.