Tuesday, April 03, 2007

How different is too different?

An excellent question appeared in the comments section of the previous piece which featured the little albinistic Dark-eyed Junco. A reader asked,"Does an albino bird have trouble convincing potential mates and territorial intruders of his or her species?"

As I said, an excellent question, but as far a I can tell, a question without an excellent answer as yet, because the answer is ,"It probably depends."

First of all a true albino bird is quite rare so very little research has been done solely on that group. I'm told the only problem an albino Red-tail seems to have is that her pink eyes are more sensitive to light therefore giving her a first possible strike against survival and reproduction due to a possible diminishment of hunting success unless of course she's gifted genetically in another way that over rides that aspect. And second of course there are the unenlightened with guns who can see an albino bird more easiler and therefore take pot shots more at her more frequently then they do at her pigmented cousins.

But what about albinistic birds, those with only patches of non-regularly pigmented feathers? When does the difference become too different and interfer with the regular functions of eating, inclusion in a flock for protection and reproduction?

A hight contrast colored lion is considered a better catch than one without with the ladies. In the lion's case the color change is due to excellent and abundant diet. The lion displays his hunting expertise and preferable territory in his coat.

When it comes to White-throated Sparrows, there are two types, those with the bright white stripes on their heads and those in which the lighter stripes are more beige. Scientists have found that the female White-throats find the beige guys preferable in almost every case to the bright white striped males. Why? Are the beige stripes or a tendency towards them, genetic? Or is there some nurtritional aspect that is enticing as in the case of lions? The Girls aren't talking.

How do we know just what the other juncos see that is imperative for Junco-ness? Might it be the case that if it sounds like a Dark-eyed Junco and it moves like a Dark -eyed Junco and it has the manners of a Dark-eyed Junco then he must be a Dark-eyed Junco. That is if the albinistic patches make any impact at all.

This area of Wisconsin is full of albinistic individuals. In fact the Krideri Red-tails may well be a form of albonism that affords a plus in survival due to the many months of snow in this locale.

When we watched the Trump Red-tail nest from Little Hill in Central Park, one day there appeared a young albinisitic House Sparrow. He had a couple of white tail and primary feathers. The other sparrows didn't seem to treat him differently in the flock than any others but then again what do we know of the intricacies of House Sparrow heirarchy.

And later that year when walking down Central Park South, who should I spy but our little albinistic sparrow friend on the sidewalk with a brood of three juveniles chasing him about as he hunted food for them. Did he end up with a less desirable mate or territory? Or as he is obviously an individual that can be recognized did he catch the eye of a local resident who made a point of throwing him a handful of snacks as she came home from the bakery every day? When there was snow, did his handful of white feathers cause his shape to be less obvious to predators so he was passed over on the hunt?

Note that this "normal" male also has white areas, including a white belly and frosted wing edges at rest. And when he takes off there are those two telling white bars on his tail.

How different is too different? At least in birds, all other things being equal, it appears that albinistic birds do just fine in the identity and inclusion in reproduction aspects of life.

Otherwise, the albinistic gene would have a tendency to be weeded out over time and around here that certainly isn't the case at all.

Donegal Browne

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