Sunday, December 20, 2009

It's an ill wind.....



This female great spotted woodpecker has been a frequent visitor to the garden bird feeders during the current cold snap

At the moment it's still very wary, but I'm attempting to coax it into closer camera range by drilling holes in an old piece of tree trunk and plugging them with sunflower hearts and other goodies....meanwhile, it spends most of its time on the peanuts and on the black sunflower seed feeder



Something I hadn't realised until I looked at these photos is that woodpeckers close their eyes when they're about to deliver a hammer-blow with that beak. Compare the photo above with the one below (double-click for a larger image), where you can see the bird's third eyelid (the nictitating membrane - see http://en.wikipedia.org/wiki/Nictitating_membrane) shielding the eye just before it makes contact with the nuts. I guess this is to protect the eye against flying splinters, and apparently it prevents the bird's eyes from literally being shaken out of their sockets under the force of the impact. It must mean that once it begins to deliver the blow the woodpecker is - for a moment - blind...


8 comments:

  1. Thanks for that photo and explanation of the nictitating membrane. I have at least one woodpecker photo that shows the same thing.

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  2. Interesting observation Phil. Makes sense when you think about it.

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  3. Hi Wilma, the only time I can remember ever noticing a bird's eyelids in real life, rather than in a photograph, was when watching dippers that have white eyelids - so everytime they blink the effect is quite striking - http://cabinetofcuriosities-greenfingers.blogspot.com/2009/04/goosander-and-dippers.html

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  4. Hi Keith, I seem to recall reading that herons blink just before they hit their prey too...

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  5. What a great visitor to have. I only had one fleeting glimpse of a juvenile quite a while ago. Fascinating fact about the eyelid.

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  6. Hi John, winter can be tough on birds but it certainly brings some interesting visitors unto gardens.

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  7. Hi Phil: I wonder if they are getting commoner in gardens. Up until about 5 years ago I'd never seen one in my urban garden but now they are occasional visitors all year round.
    The flying eyeball idea may not be so far fetched - see http://standandstare-nyctalus.blogspot.com/2009/11/on-merits-or-otherwise-of-head-banging.html for my (small)contribution on this topic. I'm still not entirely convinced by the explanation of why they don't knock themselves out.

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  8. Hi Allan, they do say that Dutch elm disease is the best thing that ever happened to woodpeckers because it created a bonanza of beetle larva-infested dead wood and plenty of dead trees to nest in. Their numbers do seem to have increased over the last couple of decades.

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