Date: 3/12/17 10:20 pm
From: Sameer Apte <sameerapte1...>
Subject: Allegheny County - Chickadees
This afternoon, Aidan Place, Jack Chaillet, and I birded North Park, where
we searched for Black-capped Chickadee (which Jack and I needed for our
county year lists). Despite the many reports of exclusively BCCH at this
location, every chickadee we found either resembled a pure Carolina or
predominantly resembled Carolina in phenotype. One chickadee at lake
elevation (970') had extensive white on the tertials and on the cheek
patch, and several chickadees at the Latodami Nature Center (1110') were
clear phenotypic hybrids between Black-capped and Carolina. Although we
heard many Carolina songs, we did not hear a single Black-capped song, and
many of the hybrids certainly appeared to be possible backcrosses with
Carolina Chickadees.

With BCCH reaching their furthest range southward around this time of year,
it begs the question as to why almost every chickadee seen in North Park is
identified as BCCH on eBird. Are most of these reports are from a higher
elevation, where pure Black-cappeds are certainly plausible? Are Carolinas
(which are expanding northward) being dismissed as the traditional species
of Black-capped at this particular location and in other places north of
the Allegheny River (which I believe has been the demarcation line for the
last fifteen years or so)? Or was our sighting just highly unlikely and
exceptional?

I'd love to hear thoughts and experiences from people in the Pittsburgh
metro area about this paradox -- it seems like chickadee identification is
a thing that comes up once in a while, but maybe not as much as it should
in an area smack dab in the middle (or maybe not anymore) of the
hybridization zone. Perhaps it would be constructive to conduct a sort of
informal census of areas north of the Allegheny River to determine the
current demarcation line and hybrid zone of this species in the area.

And if anyone has any clue what exactly those mutt chickadees in North Park
really are, please let me know.

Thanks and good birding,
Sameer Apte
 
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