As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Saturday 19 January 2013

BTO cuckoos update

Poor summer and difficult conditions meant very poor survival rates on migration
January 2013. The BTO expanded their cuckoo tracking project in the summer of 2012 to include males from Scotland and Wales to add to the birds they tagged in East Anglia in 2011. They were keen to discover if Scottish birds, numbers of which do not seem to be declining, might have different migratory strategies (which may just be the case -read on!) and to look for east-west differences between Norfolk and Wales.

Cuckoos called BB, Chance, Mungo, Roy and Wallace were tagged in Scotland, whilst David, Indy, Iolo and Lloyd began their journeys south from Wales. John and Reacher joined Chris and Lyster as BTO East Anglian Cuckoos.

Many 2012 birds didn't survive the migration
Most of the Class of 2012 failed to make it to the African wintering grounds - in complete contrast to the Class of 2011. Hopefully, as BTO analyse this year's data, and start to add in data from future years, they will better understand the rules of the game of ‘snakes and ladders' that Cuckoos face each autumn, winter and spring on their 10,000 mile round trips.

Wet summer may have been detrimental
The summer of 2012 was wet - very wet, with a real dearth of insects - and BTO were concerned that migratory birds may be in poor condition when it came time for departure. This was not the last of their problems, however, as the birds fared very badly over the autumn period. We can only speculate as to what proportion of the losses was associated with conditions on the ground in southern Europe and how much due to poor preparations in the UK.

Individual challenges
In 2011 migration was a relatively straightforward but in 2012 there were a number of cases where birds returned northwards, presumably because they could not find food. Lloyd sampled sites in north-western and north-eastern Italy as well as in south and southwest France before making it across the Mediterranean, whilst John gave up on Spain and returned to France. We guess that Indy's u-turn in the middle of the Mediterranean, as he flew back to northern Italy, must have been associated with running out of resources and going back to his last known feeding ground to refuel.

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