The big excitement on my trip with Andrey and Steven to Pavones was caused by a hybrid Golden-winged Warbler (Vermivora chrysoptera) that turned out to be a backcross (?) adult male Brewster’s Warbler (Vermivora chrysoptera ?) that associated with other warblers up at the top of the Torre Alta Lodge property. Steven Aguilar managed a couple of rather blurry photos but they nonetheless would seem to confirm the very rare sighting:
We knew it was a Golden-winged Warbler, but an unusual one!
Hello! The Brewster’s peers down at us and is recognisable despite the difficult backlighting
Hybrids in themselves confuse me, but a backcross? It turns out that this is the product of a Golden-winged Warbler and a Brewster’s hybrid. Golden-winged/Blue-winged warbler hybrid forms are termed “Brewster’s” (mostly light-grey) or “Lawrence’s” (mostly golden in colour). If your’re interested, see the following link for a very detailed explanation of the situation with hybrids plus a detailed discussion of the reasons for the recent population crisis with chrysoptera.
Here’s a clear view of a Golden-winged male banded down at CATIE some years ago:
Male Golden-winged Warbler showing black throat patch absent on the Brewster’s.
These photographs have been submitted to eBird for confirmation (we hope) and detailed expert comment.
Birds for Beer 