ID tips & tricks

Bird Watching (UK) - - March Id Challenge -

VARI­A­TION AND DI­MOR­PHISM

One of the con­fus­ing aspects of iden­ti­fi­ca­tion of birds of prey is vari­a­tion, par­tic­u­larly in plumage in the pop­u­la­tion (in­traspe­cific vari­a­tion). This is par­tic­u­larly preva­lent in Buz­zard and the rare Honey Buz­zard, where birds can vary from al­most white to dark brown with ev­ery­thing in be­tween. Many birds of prey are sex­u­ally di­mor­phic, mean­ing that males and fe­males look dif­fer­ent. In gen­eral (though not al­ways) fe­male rap­tors are big­ger than males. The har­ri­ers and the Kestrel also have dis­tinct adult male and fe­male plumages. Male Kestrels, for in­stance, have grey heads and largely grey tails, whereas fe­males are barred and streaked brown. Har­ri­ers are also greyer in the smaller males, browner in the fe­males. Tail feath­ers from a Kestrel (left: male right: fe­male)

FAL­CON OR ‘HAWK’

Di­ur­nal rap­tors come in two main broad groups, namely the fal­cons and the rest (very loosely, the hawks). Fal­cons are in a dif­fer­ent fam­ily and some tax­onomists think they are only very dis­tantly re­lated to the re­main­der. Fal­cons are gen­er­ally smaller, slim­mer, dark-eyed, neater, pointed winged speed mer­chants, and also in­clude the ha­bit­u­ally hov­er­ing Kestrel. The hawks, kites, har­ri­ers and ea­gles are broader winged, of­ten with dis­tinctly fin­gered pri­mary feath­ers. They vary from small (like the Spar­rowhawk) to very large (ea­gles), of­ten have pale eyes and are gen­er­ally slower fly­ing.

A White-tailed Ea­gle can be up to five times larger than a Spar­rowhawk (which is about 29cm long and a wing­span of 58cm). The largest recorded is 92cm long, with a wing­span of 240cm.

Dark-morph Buz­zard and pale-morph Buz­zard (in­set)

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