Monday, November 24, 2008

Quick Question: Birds and Color Vision with Anders Ödeen

The other day I was rewatching the "Signals and Song" episode of The Life of Birds and took special interest in the section about avian eyesight.  David Attenborough, ye giver of knowledge, explained that many birds possess color vision far superior to our own, often allowing birds to see light in the UV spectrum.  The ability to see UV light means that in some cases - examples in the program include Budgerigar and European Starlings - birds appear to each other much different than they appear to us.

This got me thinking, then, about whether or not it matters what colors birders wear in the field.  My winter coat is bright red, and sometimes I wonder whether I'm scaring birds away unnecessarily.  I got in touch with Anders Ödeen, an animal ecologist at Uppsala University in Sweden who has done work with birds' color vision, and asked him about whether or not the color of birders' clothes matters.  Turns out, it probably does.  Here's Anders:

"Birds have a more advanced colour vision system, with one more class of photoreceptor involved in colour vision and a wider spectral sensitivity than humans. The conspicuousness appears to be correlated between vision systems. A colour contrast conspicuous to a human will in most cases also be conspicuous to a bird. For all practical purposes, we can therefore assume that most colours that blend into the background for humans do so also for birds. There are some combinations of foreground and background colours where the difference will be much greater for birds than humans. They will however depend on the specific combination and requires spectrophotometry and retinal modelling to identify. However, human camouflage might differ from the background with respect to ultraviolet reflection, to which we are blind but birds in general, Passerida passerines and psittaciforms in particular, are sensitive. The biggest difference between passerine and raptor colour vision seems to lie in the UV spectral range."

So, just as it would for humans, my bright red winter jacket will make me conspicuous to birds in the field.  It seems obvious, but it really isn't something that had ever crossed my mind before.  Looks like someone is going to have to put "camouflage coat" in his Christmas list...


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