[CT Birds] Possible hybrid Ibis
David F Provencher
david.f.provencher at dom.com
Fri Aug 7 15:37:15 EDT 2009
On average White-faced Ibis are larger than Glossys but there is marked size difference between male and female in each species. So Roy's comment is very germane. The fact is if the White-faced is female, it will be significantly smaller than SOME of the Glossys. Conversely, if the W-faced is male, it will be significantly larger than SOME of the Glossys. So dealing with a single individual White-faced simply means that the only thing that can be said is that size is of no help other than to suggest which sex it is when compared directly to a large number of Glossys.
As for hybrids, they have been recorded in the wild but are by no means common. At colonies in Louisiana, Alabama, and Texas, both species breed with no known hybridization (unless there is newer info than I have). It isn't just appearance that keeps hybridization between similar species uncommon or rare. There can be specific courting behaviors or visual triggers that are different between similar species that cause pair bonding to occur virtually always with the same species. Who knows what Mrs White-faced finds more attractive in Mr White-faced than in Mr Glossy eh?
There is believed to have been isolation between the two species for some time allowing genetic differences to develop. Glossys are believed to have spread from the old world to North America less than 200 years ago (Palmer 1962). So are the two conspecific or not? Most authorities say no, and importantly for us, AOU currently considers them distinct species. The is an article on White-faced Ibis x Glossy Ibis hybrids found in Oklahoma published in North American Birds (2003) available at http://elibrary.unm.edu/sora/NAB/v057n01/p00136-p00139.pdf
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