Saturday, 17 September 2011

Flying South

Autumn migration is now in full swing, millions of birds are on the move. An estimated 19% of the world’s bird species make regular journeys from their breeding grounds mostly to spend time in areas where the climate is more to their liking and, most importantly, where there is a more readily available food supply. Millions of birds are leaving Northern Europe to spend the winter further south; many of them will be crossing the Sahara. For some the Algarve will be their final destination: huge numbers of waders, wildfowl and gulls are already arriving and there will soon be countless numbers of Chiffchaffs and other passerines. The Algarve will also be a staging post for those that intend to continue south into Africa.

Eurasian Whimbrel - wintering in the Algarve or on its way to West Africa?

For many birdwatchers this is the most exciting time of the year. It’s the time when rare birds are most likely to be found. Of course, ‘rare’ usually equates to ‘lost’ and it is no coincidence that the vast majority of rarities are juvenile birds that are migrating for the first time with no previous experience. That’s not to say that adult birds don’t lose their way and, if it is climate that is a main reason for migration, it is weather that is the mostly likely cause of problems along the way.

Juvenile Buff-breasted Sandpiper - lost in the Algarve

Over the last 100 years or so a great deal has been learned about migration from ringing birds but there are still huge gaps in our knowledge. We may know where a bird was ringed but unless that ring can be read again at some time in the future, either on a dead bird or as a result of re-trapping the bird, we are not much further forward. In terms of our knowledge of migratory movements most of what we are now getting from ringing studies is confirmation of what has already been demonstrated. What, for instance, has ringing told us so far about where Common Cuckoos migrate? The facts are that out of 6,452 birds ringed in the UK (up to the end of 2010) only one has been recovered south of the Sahara - a bird that was shot in Cameroon in 1930!

However, anyone reading this will surely be aware by now that the situation is changing and that the satellite tracking of five Cuckoos earlier this year has already told us more in three or four months about their migration than we have learned in 100 years of ringing. This has been made possible by technological advances which have led to miniaturisation of solar-powered transmitters. Satellite tracking is now a well-established means of studying the movements of birds that are large enough to carry the weight of the necessary transmitter and as the kit gets smaller, so the possibilities open up to study smaller birds.

Details of satellite tracking studies are all over the internet. One story that came to our attention this week concerned two Hudsonian Whimbrels, birds that were fitted with transmitters in 2008 and had been providing valuable information about migration routes between Canada and Brazil. These were birds that from experience of previous such journeys knew where they wanted to go, how to get there and where to stop on the way. However, as referred to earlier, their problem was the weather. More specifically, Tropical Storm Maria and Hurricane Irene were the problems and because of severe weather both birds ended up somewhere they hadn’t been before. But this was only their first problem. Read about them here and here and add Guadeloupe to the list that includes Malta, Cyprus and who knows how many other islands where the locals have fun killing migrating birds.

Hudsonian Whimbrel - wintering in Costa Rica or on its way to Brazil?

Last month’s Birdfair chose to support Born to Travel – The BirdLife Flyways Campaign. Illegal shooting and trapping is only one factor affecting migrating birds. Loss of habitat is undoubtedly one of the major ones. Birdwatching tourism is increasingly being promoted in quite a number of countries including Portugal and is to be commended but much more than fancy hides and boardwalks, birdwatching tourists want birds and now, more than ever, birds need what is left of important habitats, including migration stopover sites, to be protected and bird protection laws to be enforced.

Lagoa dos Salgados - one of the Algarve's many important sites for migrating and wintering birds

Incidentally, amongst the recommendations contained in the recent report of the Taxonomy Sub-Committee of the British Ornithologists' Union Records Committee is that Hudsonian Whimbrel Numenius hudsonicus and Eurasian Whimbrel Numenius phaeopus should be treated as separate species. We’ve been doing that for some time, haven’t you?

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