Monday, July 18, 2011

Strong westerly and northwesterly winds again raised hopes that a few scarcer seabirds might pass by, and they did, at Strumble Head. Here the number of Manx Shearwater logged topped 3,000 but the majority of birds passing were probably of local origin, indeed only a few Common Scoter and Gannets must have come from further afield. A couple of Purple Sandpipers and Dunlin have now joined the small numbers of Whimbrel, Common Sandpiper and Redshank whilst the Curlew flock has topped 50 on a couple of dates. Inland there has been little change but the hard work put into the Heligoland extension seems to be paying off with some nice catches. For example the Willow Warbler, Stonechat and Whitethroat pictured below were caught in a single go.

Willow Warblers have been well studied on Bardsey. This young bird probably hatched on the Island and has begun its partial post-juvenile moult. This bird will probably start its epic migration towards the end of this moult, a full couple of weeks or more prior to the adults departing. The adults undergo a full moult and this is probably why they depart later. But this does not mean the adults will arrive on the wintering grounds later. Studies of fat deposits have shown that younger birds only accumulate enough of an energy reserve to fuel short distance flights whereas the adults, presumably more experienced at feeding, can fuel themselves up for longer non-stop journeys. This may explain why many ringed juveniles are re-trapped on the south coast of Britain having not travelled too far whilst adults are often not seen again, perhaps crossing the Channel in one night. (c) Richard Brown

Although only three pairs of Stonechat are breeding this year, they are all currently incubating third broods. This youngster has been fortunate enough to be born on an Island lacking ground-based predators. This absence may explain why, as of last year, the oldest known Stonechat had been recorded here. A juvenile ringed 1 October 1987 was still alive 4 years 11 months and 15 days later on 16 September 1992. (c) Richard Brown

This young Whitethroat is also undergoing a partial post-juvenile moult. There is good evidence from ringing that young birds may return to the island in subsequent years. For example a bird ringed as a chick on 2 July 1989 was re-trapped as an adult male in May and July 1991 and on 26 May 1992 having crossed the Sahel each spring and autumn. (c) Richard Brown

This particular first-summer Kittiwake has been spotted associating with both Herring Gulls and Oystercatchers. A lot of first-summer Kits spend this time of year in their wintering grounds between the Sargasso Sea and the Azores so this is the rarer of the plumages that we are seeing on the birds around the island. Incidentally the Sargasso Sea is the only sea without shores. (c) Richard Brown

The Poplar Hawkmoth caterpillars continue to grow at a steady speed. They have already undergone three moults, the last being only a week or so ago (above). During the moult their head casing pops off and, once they have emerged from their old skin, they proceed to eat it. When they are about to moult they stop eating and stay motionless on a leaf for a day or two and during this time the head again begins to protrude, soon to pop off. (c) Richard Brown

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