Osprey Migration Q and A, 29th Oct

Some great questions coming in to our ospreys@swt.org.uk address about osprey migration- do you have a question not answered by our FAQ’s ( tab at top of this page)?

Q: Did Blue YZ overshoot her destination and will she make her way back to the Senegal area where so many others seem to gather?

A: We do not know Blue YZ’s exact “destination” and neither might she! Although we know young ospreys tend to migrate to the same latitude as their parents, this is not to a fixed point. We believe they reach the general area and then wander to wherever they can find a winter territory without too much competition from other birds. Senegal seems to be a common UK osprey destination, but not the only one- birds have been recorded in over 20 different west African countries (based on ringed birds recovered or sighted) .

Q:  Do we know if there are ospreys where she is – she must be feeling very lonely.

A: Yes we have had reports of ospreys in Guinea Bissau before and even further south. We know slightly less about ospreys in this area, compared to the relatively better studied countries to the north, partly because of the turbulent recent political history here which has made research more difficult.

Q: Emma’s latest blog says about Blue YZ’s position that “this area is not densely populated, but none the less hazardous for a bird like ours”. Is there any area in Africa which would be pretty safe for an osprey to “take up residence” in?

A:  All Osprey wintering grounds come with hazards and West Africa is no exception. As well as natural hazards such as bad weather, drought, starvation, and predators (such as crocodiles, eagle owls etc) the birds have to contend with many man made hazards.  Things such as power lines, fishing net entanglement and shooting are very real in Africa just as in Europe. In addition, much of the region is heavily dependent on seasonal rains, and subsistence fishing meaning human competition for food and waterways busy with traffic and nets. The legendary abundance of these tropical coasts and rivers mean that the hazards are generally outweighed by the advantages for our birds.

Q: Is Blue YZ the furthest south osprey from the UK?

A: No, Roy Dennis tells me he has tracked birds recently to Sierra Leone and the Ivory Coast. Previous ringed recovery’s of ospreys have been as far south as Cameroon and Gabon.

Q:  Why do ospreys migrate or in deed any bird? Ospreys seem to spend the bulk of their time in areas which seem to cater for all their needs yet then undertake a hazardous migration for a brief breeding season only to undertake the equally hazardous return migration and for fledglings to undertake this hazardous trip having hardly learned to fly. It makes no sense to me. Could someone please explain?

A: Migration is still one of the mysteries of nature- scientists and nature lovers are still discovering the why, where and how for many species, and technology such as satellite tracking is revolutionising our understanding.

Basically, migration just means moving with the seasons and birds migrate for several reasons: To avoid bad weather (e.g.  frozen Scottish lochs in winter for a fishing osprey) , to make use of better food availability ( e.g. geese going to artic to eat the summer grass glut or swallows following insects ) or avoid predators or find safer nesting areas. One crucial factor is daylight length: here in Scotland we have nearly 22hours of daylight in summer breeding season which means  a lot more time to fish and support a family. If an osprey stayed in West Africa to breed, it would have only the same 12hours of daylight all year and more predators to deal with too.

It is thought that long distance migration has evolved over millennia, by gradual ‘stretching’ of more local seasonal movements as climate changes.

Q:  I wonder if the swan which was spotted some time ago with wire & a fish hook hanging from it’s mouth has been seen recently? Hopefully it survived the ordeal.

A: This swan has survived but is still noticeably disadvantaged. We hope it can survive the winter and we will do everything we can to support it- including intervening if it becomes weak or ill enough to catch.

Ranger Emma

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Some great questions coming in to our ospreys@swt.org.uk address about osprey migration- do you have a question not answered by our FAQ’s ( tab at top of this page)? Q: …

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