Saturday, 10 September 2011

The Satellite Tracked Cuckoos

Interesting reading about the satellite tracked Cuckoos which are now in their wintering grounds south of the Sahara.  You can read about it on Birdguides here.  Basically the project caught five Cuckoos and tagged them with a tracking device.  Expensive tracking devices mind.  The results were this.  We know of course that Cuckoos winter in Africa south of the Sahara but some Cuckoos took a westerly route through Spain and some took a more easterly route through Italy but they all, upto now, have ended up in the same general area.

General approximated migration routes.
Notice the blue route, the Cuckoo stopped in Senegal for
some time (probably refuelling) before relocating to the "correct" wintering grounds.
Also notice the red Cuckoo naturally avoiding Malta.

I questioned why such behavior should occur.  Birds must migrate using a combination of magnetic north, the sun, the moon, the stars (?) etc yet using any of the last three would also mean a explicit comprehension of time, i.e. set off a month later and the sun is in a different position, nay, set off an hour later and the sun is in a different position!  Instinct?  Instinct is widely used in the animal kingdom, less so in humans, frogs returning to their places of birth to breed, Salmon likewise, insects copying the behavior of their oft long dead parents.  Is instinct genetic?  It must be.

The blue Cuckoo must be taking the route one of it's parents took, the red Cuckoo likewise.  Both parents were successful (i.e. they arrived and returned fit and well to provide offspring) so instinct surely tells the offspring that this journey is the way to go.  No one way is the "right" way to go, different means, same outcome i.e. both routes finish in the general target area.  This project is fundraising to be able to sat-track these birds for another year (and beyond).  I'd wager the blues and the reds take the same west or east routes when they migrate next year, both to and from England although the blue will surely take a more direct route when going north.

Something's just occurred to me.  The blue route actually skirts the Sahara!  It doesn't cross the Sahara directly, it follows the cooler coast then when south of the desert, cuts east to the target area.  This could be an individual thing, i.e. the Cuckoo itself starts to cross the Sahara and doesn't feel strong enough at that time, so skirts it and refuels in downtown Senegal before heading east.

Instinct in animals is well known yet we as humans feel we learn instead of it being genetic.  Since we cracked the genome this has changed somewhat with some studies showing that instinct is indeed genetic even in humans, for example a gene on chromosome 7 actually turns on an instinct for learning grammar!  Amazing brilliant stuff.  But not everything is genetic in humans.  You would've thought that a fear of snakes is a natural in-built deterrent.  It's not, something like that has to be learnt.  Imagine your 8 month old daughter, she'd poke and prod at a huge spider that's near her, yet your 4-year old would run off!  True, this is a generalisation and not all would run off, but if you have a mother, say, that warns your little girl of spiders, in turn your little girl will learn to run from spiders.  It's the done thing.  Mummy taught me subconsciously.

So, instinct is built-in genetically.  So what?  Well, apply this to vagrant birds.  It has been questioned before whether vagrants who do this "reverse migration" are maybe challenged genetically.  Indeed the Cornwall Varied Thrush was of a form very rarely observed even in the U.S. so the chances of it arriving here seems minute!  Unless of course it was genetically programmed to "go the wrong way" and to have strange plumage then this would greatly increase it's chances of turning up here.  If the next one is of this form then proof therein!

Could we combine the two (main) subjects above?  i.e. Could we sat-tag 100 Yellow Brows in Asia and watch 99 of them winter in Indo-China whilst watch the poor lone genetically challenged mite arrive dumped in Kilnsea churchyard?  Then the fun would really start!  Where would the Yellow Brow go next?!  What amazing viewing.  If it had done this reverse-migration thing then what would be the chances of it trying to continue north or west?  To watch it's signal lurch out into the Atlantic continuing it's supposed journey to it's wintering grounds "target area" only to sadly lose the signal 200 miles out would be quite something.  Not for the Yellow Brow of course.  I'm guessing, but who knows?  It would and could be one of the greatest ornithological projects, although expensive.  I for one would put into the fund to see it happen.  Would you?

I suppose it would be quite a long shot to actually tag a vagrant.  Also is the equipment too large for a Yellow Brow?  I presume so.  Miniturisation.  Maybe in a few years?

Please leave comments, I'm interested in opinions on this.

And you thought I couldn't go a whole post without doing a childish cock joke or adding some stupid picture.  Well there you go, I am sensible after all.  It was even about birds!

Finally have a look at this interesting flight migration route of the last sat-tracked Cuckoo. See how it ends up wintering somewhere in north east Germany!

I've spoilt it now.
That was quite a good post (for me) until then.


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