Osprey mi­gra­tion

BBC Wildlife Magazine - - Q&A - BH

1 WHERE ARE BRI­TAIN’S OSPREYS NOW?

Most ospreys that breed in the north­ern hemi­sphere mi­grate south for win­ter, be­cause when lakes freeze they can’t fish. Bri­tish birds head to West Africa, mainly Sene­gal and Gam­bia, though a few now win­ter in Por­tu­gal and Spain. They have ex­cep­tion­ally long wings and can make longer sea cross­ings than other birds of prey, which man­age only a few hours over water.

One tagged osprey flew an amaz­ing 350km across the Bay of Bis­cay.

2 WHAT DO THEY DO IN WIN­TER?

Tag­ging stud­ies show that ospreys win­ter along coasts and es­tu­ar­ies, switch­ing their diet to salt-water fish. They have no trou­ble fish­ing in the sea. Food can be so plen­ti­ful that they spend over three­quar­ters of the day perched in trees by the shore, some­times in groups of sev­eral dozen. If hol­i­day­mak­ers on Gam­bian beaches look up, they may be treated to the mag­nif­i­cent sight of ospreys that hatched in Bri­tain fly­ing over­head to fish just off­shore.

3 WHEN WILL THEY SET OFF HOME?

Adult ospreys be­gin their re­turn jour­ney of over 4,500km in late Fe­bru­ary or March. Not only do they re­turn to the same nest, they use the same fa­mil­iar roost­ing trees at stop-overs dur­ing their mi­gra­tion. Ju­ve­niles linger in West Africa for at least two years be­fore mak­ing the maiden trip north to find a nest­ing area of their own. The Mediter­ranean has a few non­mi­gra­tory osprey pop­u­la­tions, in­clud­ing on Menorca and Cor­sica, where birds sur­vive on sea fish year-round.

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