A songster from the east

I spent part of the weekend (the dry part) manning the British Trust for Ornithology stand at a wildlife event in north London. The event, held annually in the Lea Valley, took place at a disused water treatment works, the old filter beds now managed to provide a range of habitats for wildlife.  As the sun shone, small parties of sand martins bounced low over the filter beds, feeding on the many small flies that were readily available, while the first of the summer’s reed warblers rattled out their songs.

The highlight, however, came from one of our more secretive summer visitors – the lesser whitethroat. Throughout the day, two of these delightful little birds issued short bursts of rattling song from the deep cover of the many tumbling brambles. Lesser whitethroats are warblers, closely related to the blackcap, garden warbler and whitethroat. Unlike their cousins, these lesser whitethroats will not have arrived from the south but will, instead, have travelled in from eastern Africa and the eastern end of the Mediterranean. They are one of very few of our summer migrants to winter in Eritrea, Ethiopia, Chad and the Sudan. This choice of wintering location has spared them some of the problems caused by the Sahel drought (which hit Whitethroats and other species wintering in West Africa) but, while they have fared well long-term, things have been more difficult of late.

The lesser whitethroat can be admired for being one of our most attractively marked warblers; however, it is rarely seen well. While newly arrived males may sing from obvious song-posts it is not long before they switch to singing from deep cover. The males arrive during the second half of April, followed a week or so later by the females. The adults are highly site faithful, most returning to the site at which they bred the previous year and even the young return to the same general area. The adults pair up quickly and get down to the business of making a nest and laying their clutch of four to six eggs. The nest itself is usually placed in bramble or hawthorn, low to the ground and extremely well-hidden. As the breeding attempt progresses so the amount of song diminishes; if you hear a lesser whitethroat singing well in June then this is likely to be an unpaired male. It seems that just as soon as the breeding season has started then it is over, with most lesser whitethroats departing in August, heading southeast towards the wintering range. Researchers have found that the birds build up enough fat reserves to see them reach northern Italy (some 770km away) where they make a stopover before making the final hop to Africa.