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Name: Stan Skelton
Location: N/A
Country: N/A
Date: N/A 

Hi...I have a question about RAPTORS (birds) that some of my students asked me many years ago and I have never been able to find the answer. Up in Dawson Creek BC, Canada, we observed hawks, owls and other birds of prey, flying around in temperatures of -40 to -54 degrees Celsius. We know their eyes have a thin protective membrane they can flick into place, but how do they keep their eyeballs from freezing. They must be flying at least 20 K/Hr and the wind, plus the low temperatures mean that they are in conditions that would freeze skin in less than one minute. Either this thin membrane is the worlds most effective insulator, or their eyeballs must be filled with antifreeze. Your answer will be most appreciated.

I assume that even at -40C (otherwise known as -40 F!) they are protected because the great majority of the volume of the eye is actually inside the body and metabolically heated. The bit of surface that is exposed is in constant motion, and the fluid covering it is constantly being replenished by blinking. But I'm guessing. Nobody here, even bird people, seems to know.


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