Migration Update 24th Sept

What a fascinating story our two satellite tacked youngsters have revealed so far! Who would have thought that we’d have two such different birds: one a late hatchling but so very confident and a long distance achiever; the other a bit of a stay at home and a short haul specialist.

Both birds are still doing well ( amazing in and of itself given the odds stacked against them) and continuing their chosen paths.

Blue 44 as still at Etang Blanc as of yesterday afternoon (23rd)  on the southern shore where he has been staying over the last week or so.

Blue YD was roosting at 7am this morning (24th) near the north side of the Dam in Morocco.

We’ve had some great questions to ospreys@swt.org.uk about our birds migration so far, such as:

 Q: How long will the autumn migration take?  Why is Blue YD ahead when he left later?

A: This journey can take anything from 12 days to 6 weeks or more in young birds.  There does not seem to be any particular reason some birds fly faster than others, or why some go further than others ( for example it is not late birds who have to go furthest to find a spot as in some other bird species) .

Q: Will Blue 44 still be flying with his dad?

A: Probably not.  In studies by A.F. Poole, it was found that   young ospreys migrate more slowly than their parents, even if they leave at the same time. 

Q: Is Blue 44 going to overwinter in France because his mum (or his dad) do so?

A: This is a strong possibility but there is no way of knowing which, as neither of his parents is ringed or tagged so we can’t indentify them on their wintering grounds. .Scientific studies all hint at the juveniles inheriting at least the general area of their winter destination from their parents, but we don’t know yet how this works.

For example, A. F. Poole states: “Familiarity with the migration route is not a critical advantage for an osprey and this in turn  suggests that inherited navigational direction, not learned landmarks, guide migrants ospreys ( Gwinner 1986)” . “Neither age nor migration schedules seem to influence where ospreys winter. [Ringing] recoveries suggest that juvenile ospreys winter at similar latitudes , on average, as their parents ( Osterlof 1977).

Roy Dennis states in his book ‘A Life of Ospreys’: “Migrating juveniles show much more variation [than adults]. They are making their first journeys relying only on their genetic information. We also know that some juveniles move about in winter, suggesting that they are searching for the best possible wintering sites”.  Alternatively they could be  being chased off and forced to look elsewhere by territorial adults who claim the best wintering areas every year ( adults on juvenile aggression in ospreys has been seen in Africa).

Q: How common is it for ospreys to overwinter in southern Europe?

A: From Roy Dennis again:  “Greater numbers of the birds are now wintering in the Iberian Peninsular instead of west Africa. There are probably several hundred birds [from all over Europe] that do this. This appears to be a growing phenomenon and may be due to warmer winters caused by climate change. Even further north in France, a few birds have overwintered over the last ten years in Southern Brittany.”

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What a fascinating story our two satellite tacked youngsters have revealed so far! Who would have thought that we’d have two such different birds: one a late hatchling but so …

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