Let me add a comment to the chickadee question.  About distribution.

Even ignoring obvious hybrids, there is a distinct cline in Black-capped
Chickadees with northern birds (even in the east) being brighter.
Southern birds, such as those in western Maryland, are duller and much
closer to Carolina Chickadee in appearance.  It is also claimed that
Black-capped Chickadees from western Maryland do NOT wander East.  Thus
out of range Black-capped Chickadees in central and eastern Maryland
should be northern birds and should be easier to identify than one would
guess from studying Chickadees in our western counties.

Also of interest, is that there are shadows in the Maryland distribution
of Black-capped Chickadees erupting out of the north.  They are caused
by a combination of the Delaware and Chesapeake bays and the reluctance
of the migrating birds to cross large expanses of water as they head
southwest.

I don't know how wide or deep these shadows are but Black-capped
Chickadees are a lot more common during an invasion north of the bays in
Cecil, Harford, and Carroll counties than they are further south and
east.  I've been told that there are a few well-documented records of
Black-capped Chickadees from *western* Talbot and *western* Dorchester
counties so some make it onto the Eastern shore, probably deflected
south by the Chesapeake bay.  However, there is at least some evidence
that these shadows are very dark.  Fifty years ago, a large banding
project at Ocean city was operating during a major chickadee eruption
and no Black-capped Chickadees were netted.

Experience with Black-capped Chickadees for most Maryland birders is
primarily from our western counties.  The combination of expecting an
out-of-range Black-capped Chickadee to be more similar to Carolina than
it actually is and a lack of appreciation for how much less common they
become as one heads south and east probably results in a number of
mis-identifications.  It's a pity the records committee doesn't request
documentation for Black-capped Chickadees in this part of the state.  It
would encourage documentation and help determine their true distribution
in Maryland.

Dave
-- 
David Mozurkewich
Seabrook, PG MD
mozurk at bell atlantic dot net