On Sat, 2011-03-05 at 10:36 -0500, Jeff Shenot wrote:
> I've also wondered if there may be a possibility that one is a hybrid
> (BC x Carolina cross).  Does anyone know if Carolina breeds with
> Black-capped?  I know out in western MD there is an overlap with their
> range somewhere around Sideling Hill (I think in the western
> Washington and eastern Allegany area).  At some point they certainly
> share habitat, but presumably these birds are year-round residents and
> do not migrate.  Any comments on feasibility of hybrids?  The
> Chickadees (and all the other early breeders!) were singing mightily
> this morning.

Jeff,

Since I didn't see any replies, I'll take a stab at this.  Black-capped
and Carolina Chickadees hybridize freely in the narrow overlap zone
through southern PA and western MD.  They are considered separate
species because the hybrid zone is narrow and long-term stable.  The
hybrids do well only in the hybrid zone; there is no appreciable gene
flow between the two species.

However, you will often hear the claim that *all* of the Black-capped
Chickadees that move south during one of these invasions are from way up
north (as in Canada).  Assuming that claim is true, you should not be
seeing a hybrid in SE PG.

Although I am sure there are others, I am aware of only one report of an
intermediate-type chickadee far from the hybrid zone.  I believe that
was in Harford County and reported on this list a few years ago.  If you
can get good photos of your intermediate bird, it would be worthwhile
documenting it.

Dave
-- 
David Mozurkewich
Seabrook, PG MD

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