Wednesday 26 November 2014

Migration madness

I’ve been back on Islay for a month now – and it’s flown by! The most exciting thing about this autumn has been the chance to catch up with our GPS tagged white-fronts from last year, hopefully combined with downloading their valuable data gathered over their summer away.

Is it bad to have favourites? Tag 21

The initial joy at finding an old friend alive, well and back on Islay with the tag still attached quickly changes to an extremely nervous wait once the downloading kit is unpacked and pressed into action. Is the tag still working? Will it send me the data? Will it painfully cut out halfway through a download? When the numbers start whirring through on the computer screen and the magic words "all data imported J" flash up (yes, it really does give you a J!) there might have been a bit of a fist pump and a little jig; anyone who’s ever seen me dance will know that’s not a pretty sight - hopefully no one was watching..

Migration data! Spring-Autumn 2014
Different birds = different colours. Tag 21 is red, 22 is dark blue

The good news is that 6 birds willingly parted with their data, giving us a remarkable insight into their migration routes, Icelandic staging areas and remote West Greenland breeding areas – this location data from the tags really is the next best thing to actually being there.

West Greenland happenings

It’s revealed some trials and tribulations associated with migration – and strategies the birds use to overcome them. The return leg from Iceland to Islay this year seems to have been particularly arduous – almost entirely due to the weather. Tag “BLO 19” (before anyone says anything I know she needs a proper name..!) left her journey really late, only leaving Iceland on the 10th of November. She got her timings horribly wrong though, as she quickly met a series of Gale Force South Easterlies once she was out over the North Atlantic. Rather than pressing on into such a strong headwind and wasting precious energy, she ditched and sat on the sea for at least 6-8 hours. She did this twice more over the next 2 days before she made it to South Uist on the evening of the 13th. Here she over-nighted before heading on down to Islay in the morning. To put this 4-day marathon in perspective, Tag BLO 27 completed the same journey (just less than 1500km), three weeks earlier, in 16 hours. Clearly, though, this strategy worked for BLO 19 – maybe if she’d ploughed into the headwind for 3 days she wouldn’t have made it at all – definitely  better late than never!

BLO 19 back to Islay. Circles indicate lengthy stopovers at sea

Wind map of the 12/11/2014 - middle of BLO 19's Iceland - Islay leg

Other birds tried a different tactic: just go with the flow! Two of these windsurfers were tags BLO 21 and 22. They were both blown off course on amazingly different paths back to Islay, 21 was up way north of the Faroes at one stage (look at first picture - northernmost red line), whilst 22 was well to the North West of the Irish coast (south-westernmost blue line). Other Greenland white-fronts clearly experienced similarly tricky conditions; a bird from Loch Ken in Dumfries and Galloway was seen in Norway, for instance.

In terms of ditching at sea these 3 Tundra bean geese in the North sea have life sussed though: not just taking a rest from flying, but catching a lift at the same time!

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