Pinning down the Cocoa woodcreeper

The February 17th bird-banding at the CATIE ended with a woodcreeper that was fairly puzzling at first.  It looked like a big version of the Streak-headed and Spot-crowned woodcreepers that had so kindly and conveniently fallen into the nets a little while back, but it wasn’t immediately obvious what species it was.  Here’s a first photo.

Straight bill?

We eventually plumped for Cocoa woodcreeper (Xiphorhynchus susurrans), but things were complicated first by nomenclature, because the above names, even the Latin one, don’t figure in Stiles & Skutch.  Instead, you get the Buff-throated woodcreeper (Xiphorhynchus guttatus), the illustration of which shows a buff throat with malar stripe and considerable streaking on the back.  None of these features seem to fit our bird here.

Here’s another look:

Back streaks?

I left the Buff-throated alone and turned to the Cocoa, split from the Buff-throated, which is now considered a South American species only, I believe) and what seems like its sole competitor, the Spotted woodcreeper (Xiphorhynchus erythropygius), which supposedly has an indistinct eye-ring and ‘olive underparts with buffy spots’ (Garrigues & Dean).  All others can be excluded on the grounds of size or plumage, can they not?  If you demur, please drop me a line!

Here are the underparts, or at least the breast:

Breast streaks or spots?

Ah well, I’m definitely sure of one thing, and that is that I would never be sure of an identification of these guys in the field.  Alejandra weighed our bird at 41 grams, which fits the Cocoa, though we didn’t know it at the time, while the
Spotted should weigh in at a good ten grams more.  And so Cocoa woodcreeper (Xiphorhynchus susurrans) is the final pronouncement.  Now all we need is the Spotted in our net tomorrow for comparison!

Here’s a final picture:

Final view and off he flew

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