Friday, 19 September 2008

Buzzards drift by

Last weekend saw an influx of Honey Buzzards into the county. These rather unusual birds of prey are very rare breeders within Britain but larger numbers may sometimes pass through on their autumn migration. Although the numbers reported over the weekend suggest a sizeable arrival, no doubt driven by prevailing easterly winds pushing the birds west of their normal migration route, it is unlikely to match the influx seen in 2000, when between 500 and 1,500 birds were thought to have drifted over. The Honey Buzzard is a long distance migrant, breeding predominantly in Russia, eastern Scandinavia, Germany and France (with fewer than 100 pairs breeding in Britain). Arriving here from late April, the birds face a short breeding season before setting off south again to the wintering grounds in the tropical woodlands that lay to the south of the Sahara. Unusually for a bird of prey, the staple food items are the larval stages of wasps and bees, obtained as the birds break open the nests of these social insects.

Adult Honey Buzzards depart from the breeding grounds some two weeks earlier than the young and migrating individuals are normally seen singly; that is, unless you happen to be watching at one of the main points where birds gather to make a crossing of the Mediterranean. At Gibraltar, many hundreds may be seen together, utilising thermals to gain the height needed to make their gliding flight over the sea.

Picking out and identifying migrating Honey Buzzards is not straightforward. Similar in size to the more familiar Buzzard (itself now fairly well established within the county), the Honey Buzzard shows a great deal of variation in its plumage. As such, you have to place greater emphasis on the structural characteristics of the bird rather than expecting to see clearly-patterned underparts. The wings of a Honey Buzzard are proportionally longer and narrower than seen in Buzzard and are held horizontally, or even slightly dipped, when in gliding flight. Watch a gliding Buzzard and you will see that it invariably holds its wings in a shallow ‘V’. Another useful feature is the head which, in Honey Buzzard, appears small in relation to the size of bird. I have heard the head referred to as being rather ‘cuckoo-like’ and this is a pretty fair description of both its size and the way it protrudes so prominently. Young Honey Buzzards show a greater degree of variation in their plumage than adults. Dick Forsman, a leading expert on raptors, reckons that juvenile Honey Buzzards are probably the most often misidentified birds of prey in Europe. As such, you can see why you need to be pretty sure of what you have seen before calling one in.

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