— How Many Leucistic PIWOs? --

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Since I bring up the issue of leucistic Pileateds with some regularity (including previous post) I'll repeat here what I recently posted over at a Facebook site (for the MANY who no longer patronize FB). Someone had posed the question, how many leucistic PIWOs are there? Not a question that can be answered with precision obviously, but I figured it would be fun (anal-compulsive?) to take a stab at it so did a li’l research, a li’ math, a li’l logic:

1)   Estimates are that 1 in 30,000 birds have some degree of leucism (though specific species could probably vary from that quite a bit; and the degree of leucism obviously varies).

2)  It’s estimated that there are 2.6 million total Pileateds in North America.

So using the 1-in-30,000 figure that would make for less than 90 total individual leucistic PIWOs (given the number that show up on YouTube & birding sites I suspect that figure may be LOW, but whatever, we’re just playin’ here).

3)  PIWOs have a wide range in N. America so perhaps less than half the total would be in the Southeastern United States (one might actually be able to use official spring & winter bird counts to get a better idea what proportion of PIWOs reside in say 8 -10 southeast states versus the rest of their range).

4)  So, assuming less than half of PIWOs reside in SE states, now we’re down to less than 50 leucistic individuals in possible IBWO habitat. And then, acknowledging that MOST leucistic PIWOs won’t look anything like an Ivory-bill, we’re really only interested in the small % of 50 who’s leucistic pattern might give them an IBWO-like appearance; likely a very small number of birds (5 or less) strewn across a LOT of acres. [ADDED: and actually a LOT of those acres would NOT represent good IBWO habitat.]

5)  Even allowing what I think are pretty conservative numbers here, leading to a quite small number of individuals, keep in mind that Pileateds can fly long distances and live 4 - 10 years, so even a single bird might actually account for quite a number of errant sightings over its full lifetime.

6)  Also, do not forget that there are several OTHER largish woodland birds (waterbirds, crows, raptors)  that could bear a leucistic pattern mimicking an IBWO in flight (we are not actually restricted to PIWOs, except when a mystery spotted bird can be confirmed as a woodpecker).

Anyway, this is all pretty speculative, intended as a sort of fun thought-exercise…. and a way to confirm for myself the possibility that a number of brief and/or distant IBWO claims (especially from the inexperienced, and those repeatedly instructed to focus on the white saddle or trailing edge) could be leucistic individuals.

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