Date: 3/15/17 9:41 am
From: Barry E. Blust <barryblust...>
Subject: Re: Allegheny County - Chickadees
Very interesting discussion. I'll add my two cents.

I live in Chester County, two miles from the Great Marsh where Bob Curry and
his team has conducted a considerable amount of Chickadee studies. Although
this is now squarely in the Carolina Chickadee breeding zone, it wasn't when
the studies began. I try to scrutinize the plumages of chickadees in my
area of southeast PA and, unless it's strongly suggestive of Carolina or
Black-capped, I'll record it in eBird as Carolina/Black-capped. (My
differentiation of the songs is very weak so right now I don't use that to
ID down to species.) Of course including photos (or recordings) of
individuals in eBird reports is helpful.

I know many birders who automatically assume and mark Carolina for this
area. On the other hand there are others who just mark
Carolina/Black-capped because they don't know the plumage or song
differences or aren't willing to take the time to look & listen to each
chickadee. That is their prerogative. And on the West Chester CBC, which I
compile, I warn people to not assume all chickadees are Carolina. In fact
this winter there's been a significant incursion of Black-caps in southeast
PA, affording us the opportunity to compare individuals, but also increasing
the chance to misidentify a bird that is a Black-capped for those who always
report Carolinas.

Given that the visual and aural cues are not necessarily accurate indicators
of which species is being observed it's still important to report these when
possible. As I explained to a couple of people recently, I feel the
reporting down to species by plumage (or voice) when possible, even if the
genetics of the individual bird may be strongly mixed or even the opposite
of the plumage and voice ID, is of value to whomever may choose to use this
data for future studies. Simply assuming Carolina/Black-capped causes some
information to be lost.

Many birders, particularly novices, are not aware of the possibility of two
different species in the same area and of the hybridization issue. Making
them aware of these things and of the challenges of identification can go a
long way towards more accurate reporting even if it is coming to the
realization that you may not know the ID every time and simply report

Barry E. Blust
21 Rabbit Run Lane
Glenmoore, PA
Upper Uwchlan Township, Chester County

"When we try to pick out anything by itself, we find it hitched to
everything else in the Universe."
-- John Muir

-----Original Message-----
From: Bird discussion list for Pennsylvania
[mailto:<PABIRDS...>] On Behalf Of Paul Hess
Sent: Wednesday, March 15, 2017 10:25 AM
To: <PABIRDS...>
Subject: Re: [PABIRDS] Allegheny County - Chickadees

Hi all,

As others have already said, we all owe thanks to Sameer Apte, Alan Buriak,
Aidan Place, et al. who have posted important comments on the Allegheny
County chickadee situation. They are all correct. Too many chickadees are
being identified as Black-capped when they are actually hybrids or perhaps
even "good" Carolinas. The problem is that many birders don't realize how
swiftly the northern Carolina limit has advanced during the past few

This has been a continual problem with the CBC, the breeding bird atlas
results, and other reports since at least the early 1980s. Long before that
in 1940, even the great W.E. Clyde Todd admitted in Birds of Western
Pennsylvania that, early on, he had been not fully aware of Carolina
Chickadees' distribution in southwestern Pennsylvania. (So, maybe we
shouldn't feel too embarrassed.)

For now, I have an important caveat about the northeastern corner of the
county. It is no longer strictly Black-capped country. I live in Natrona
Heights, about 3 miles south of Harrison Hills Park. The chickadee hybrid
belt has clearly advanced north into to my neighborhood during the past two
years. It is a fascinating continuance of the range advance, and I now
regularly hear vocalizations and see plumages that represent apparent
intergrades by plumage and sound.

During the past year I have also observed and heard apparent intergrades at
Harrison Hills Park. Birders should no longer to automatically consider all
chickadees to be Black-capped there. I would love to know what you see and
hear. I've birded at the park regularly and often since 1970, and the
chickadees are now among the most interesting birds to watch. In addition,
I've heard for several years that there is an isolated pocket of "good"
Carolinas north of the park near Freeport at a low elevation along the
Allegheny River, but I have never had a chance to check it out.

There are many weird plumages and songs as the contact zone moves north in
the county. One of the classic intergrade vocalizations I often hear in my
neighborhood is a four-note DEE-de-de-de, as reported during intensive
surveys of the contact zone in southeastern Pennsylvania by Bob Curry and
grad students at Villanova. Deb Grove and Scott Weidensaul mentioned those
studies in their recent posts. Others have pointed out that a chickadee may
look like one species but sing and call like the other.

This whole Allegheny county phenomenon was first recognized in the early
1980s when Kenneth Parkes, late curator of birds at the Carnegie Museum, and
two brilliant young birders named Bob Mulvihill and Ted Floyd reported an
advance of Carolinas into the Pittsburgh area in the Audubon Society of
Western Pennsylvania Bulletin, I think in 1983. Today's young birders are
clearly on the same observant path as Bob and Ted were in their teens.

I wrote an extensive analysis of the northward Carolina advance in
southwestern PA particularly in Allegheny County between 1974 and 1994,
submitted it to the Wilson Bulletin for publication, but priotrities
intruded and I never got around to making the reviewers' requested changes.
The data suggested that the northward movement of the hybrid belt was
occurring at about a mile a year. That was approximately the same as the
Curry teams' studies found in southeastern PA.

The true width of the overlap and active hybrid belt is unknown in
southwestern PA; it probably fluctuates. Neither is the distance of
decreasing genetic introgression past the active zone known. As Curry and
his associates pointed out in their exhaustive research, genetic signatures
of both species occur many miles from the center of the contact zone in
southeastern PA. The same thing is likely true in southwestern PA, and I
have long wished someone with such research interest and resources as
Curry's would study the hybrid zone in our southwest.

This should not discourage birders from contributing to our knowledge by
their eyes and ears. I would elaborate on an important point Geoff Malosh
mentioned. In the absence of genetic data, we can still help to track the
hybrid zone's movements, at least in general and importantly not only in the
northern areas but also in the southern areas of the contact zone, by
carefully studying every chickadee's plumage and song. In the absence of
genetic evidence, as the Carolina range limit advances and the Black-capped
range retreats, the only way we can have any idea what's going on is by
looking and listening - and reporting as much visual and vocal evidence as

Meanwhile, I have a one-foot-high box of chickadee references and my own
past findings if anyone is interested in having it.

Paul Hess

Natrona Heights, PA

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