Saturday, 27 September 2014

“BIRGIT" - a very useful osprey

Image: Google Earth. Data: LUOMOS Finland (University of Helsinki)
*West is up
What's the use of satellite tracking, anyway?

It's a question that regularly crops up on the non-science forums and social media sites. Those who ask it often load the question with some opinion to the effect that “we already know where these birds spend the winter, so what is the point of continuing to track them?” But the birds themselves provide the answer to this... 

Increasingly, ecological research is getting down to the fine details of animal behaviour: things that only advanced technologies – close-up video cameras and microphones, and high-resolution data gathering – can uncover. These days, and probably for the first time in history, we are beginning to study bird behaviour in the wild on the scales at which birds themselves operate. And the observations are revealing.

Osprey “Birgit” fledged from a nest in southern Finland in August 2014 and, as part of a programme run by the Natural History Museum of Finland, was fitted with a GSM datalogger / transmitter unit. She duly migrated south-west over the Baltic and decided to make a stopover near the Ijsselmeer in Holland. Birgit's “2nd generation” tracker unit is able to record her position, speed and altitude every two minutes, varying this sample rate automatically according to her level of activity.

Birgit found that the flat fields and canals of the Dutch polder were much to her liking, and began to hunt for fish there – probably the first time in her young life that she had done this. The detailed satellite tracking shows that Birgit has instinctively adopted the usual foraging strategy for an osprey. She has some favourite trees for roosting, but does not visit the same places every day to hunt for fish. Instead, Birgit has prospected over a corridor that is some 20km in length, from the towns of Lemmer in the north to beyond Emmeloord in the south.

The fact that even juvenile ospreys – though not the most effective hunters, due to their inexperience – do not repeatedly exploit a single food source is important information, and Birgit has provided confirmation of it. In an increasingly crowded world, people and wildlife can come into conflict, and one charge often levelled at ospreys by the recreational angling community is that they “eat all the fish and then move on, leaving none for us to catch.” But this is wrong, and the latest technological tools are helping conservationists to prove it.

Birgit's autumn sojourn in Holland is just as useful to us as it is (no doubt) to her.

Links: Finland Museum of Natural History (in English):
Osprey “Birgit” tracking page: