Birding folklore maintains that you seldom see a large arrival of migrant birds after a clear night, nocturnal migrants just keep going in those conditions and don’t make landfall. It is also believed that a full moon exacerbates the situation, allowing the migrants to see far ahead and cross the Channel without having to stop. Of all the wind directions, the north-west is generally considered to be the most unhelpful, so when I left home at 0500 to a chilly 8 C, a north-west breeze, a clear sky and a full moon I was resigned to catching just a handful of birds at Durlston.
How wrong could I be! The ringing totals for the morning were:
- Willow Warbler -78
- Common Whitethroat – 50
- Grasshopper Warbler – 10
- Garden Warbler – 8
- Sedge Warbler – 6
- Chiffchaff – 4
- Redstart – 3
- Blackcap – 2
- Lesser Whitethroat – 2
- Tree Pipit – 1
- Reed Warbler – 1
- misc common species – 10
Total 175 birds – fortunately Mick Cook joined me, that would have been a lot to cope with on my own.
Interestingly the Willow Warblers had longer wings than ones we have been trapping recently, presumably indicating a different origin.
There wasn’t time for much photography, but I could resist this side by side comparison of an adult and first year Grasshopper Warblers.
The adult (on the right) has not moulted since the winter and shows considerable abrasion to its plumage which causes a greyish unkept appearance. Also note the richer colour of the iris.
The abraded wings and tail of the adult (here on the left) can be clearly seen
Unlike Acrocephalus and Locustella warblers, most adult Sylvias, like this Lesser Whitethroat, undergo a complete moult after breeding. As both adults and first years have fresh plumage, details of the iris and tail feather colouration are used for ageing.
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