Date: 3/13/17 4:31 pm
From: Dave Brooke <davbrooke...>
Subject: Re: Allegheny County - Chickadees
I found your discussion about Black-capped vs Carolina quite interesting and
it led me to wonder if I was reporting my Chickadee observations correctly.
Interestingly, I just had this discussion with Gabi Hughes from the WPAS.
She stated that they saw a mix at Beechwood but we probably only see
Black-capped at Harrison Hills Park (where we were having this discussion).
Using the map tools available on Google Maps, I measured from the edge of
the contact zone sited in the Sibley article to North Park (5mi), to
Beechwood Farms (5.5mi), and to Harrison Hills (23mi). If in fact, the
contact zone has shifted north since the original map was created, North
Park and Beechwood could easily be within the zone while Harrison Hills
would remain a reasonable distance away.
I birded Harrison Hills today and feel pretty confident that all of the
Chickadees I saw were Black-capped. I'm a fairly new birder so I lack the
skills and experience of most of you posting to this list.
Those Chickadees from Harrison Hills can be seen here
https://www.flickr.com/photos/ddbphoto/shares/88sZ9N
Or on the Ebird checklist http://ebird.org/ebird/view/checklist/S35163129

Dave Brooke

-----Original Message-----
From: Bird discussion list for Pennsylvania
[mailto:<PABIRDS...>] On Behalf Of Alan Buriak
Sent: Monday, March 13, 2017 11:31 AM
To: <PABIRDS...>
Subject: Re: [PABIRDS] Allegheny County - Chickadees

Sameer and PA Birders,


I have been one of the primary eBird contributors for the North Park area
for the last 1-2 years, so I can speak to this topic.


First, if you check the map of the hybrid zone in the following link by
David Sibley, it places North Park just north of the top edge of the zone,
suggesting that pure Black-capped should be found there.

http://www.sibleyguides.com/bird-info/black-capped-chickadee/black-capped-ca
rolina-chickadee/

<http://www.sibleyguides.com/bird-info/black-capped-chickadee/black-capped-c
arolina-chickadee/>However that article was posted in 2010, and the data
used for the map was probably even older.


Pertaining to North Park, I have also absolutely observed that the chickadee
situation there has become very muddled. I haven't paid that close of
attention to how others are submitting them, but you will notice that for a
couple years, I have been submitting all chickadees in North Park from
Latodami Nature Center south as Carolina/Black-capped Chickadee. I observed
a gradual intrusion of Carolina physical traits and vocalizations that made
it clear to me that the hybrid zone had shifted north to engulf most of
North Park. I do, however, still observe birds in the upper field area, at
the northernmost part of North Park, that fit pure Black-capped Chickadee,
and I regularly still hear Black-capped songs around the field. I think it
is reasonable to say that the upper field is one of the last holdout areas
of pure Black-cappeds in North Park, both because it is at the northernmost
extreme part of the park, and also because it is at one of the higher
elevations vs most of the park. Doing a quick check of the Latodami Nature
Center hot spot, most of the recent checklists by people other than myself
also report the chickadees as Carolina/Black-capped Chickadee, although
there are a few that are listed as pure Black-capped. If you are seeing
that most reports are pure Black-capped, that might be including older data.
I actually made a comment in my January 13th checklist from Latodami Nature
Center that speaks directly to this topic:

http://ebird.org/ebird/view/checklist/S33645124

I live in Gibsonia, to the east and a little north of North Park's latitude.
I still have predominantly pure Black-capped Chickadees here, both in
physical appearance, song, and call. I have never heard a Carolina song
here yet, and can't see any obvious intrusion of Carolina physical traits.
I have, however, noticed an ever so slightly quickened call pace of a couple
single birds in the past few months, which makes we wary of the possibility
of hybrid intrusion. With all my observations on the issue locally coming
from my house and North Park, I personally would place the new top edge of
the hybrid zone somewhere east of North Park and just west of the Gibsonia
area. If you are wanting to go somewhere in Allegheny County where you
should have no problem seeing pure Black-capped Chickadees, Harrison Hills
County Park in Natrona Heights would be the place, as it is physically
located at the far northeast corner of the county, the farthest point from
the hybrid zone.

As for the birds you were seeing at North Park yesterday, I'd say that even
though they are singing Carolina and have Carolina physical traits, they are
likely hybrids. It seems certain that the hybrid zone has shifted north,
but not far enough north to place pure Carolinas regularly in North Park,
and as you alluded to, there is no reason to think that pure Carolinas would
be irrupting northward at this time of year. Admittedly, I often do not
attempt to discern individual birds within the hybrid zone, and often just
submit them as Carolina/Black-capped Chickadee. Catching pure birds of
either type irrupting northward or southward is dicey because the hybrids
themselves are so variable. The fact that you heard so many Carolina songs
is notable however, as I personally have still heard a lot of Black-capped
songs even in the main part of the park. This may be a very recent
development. You have certainly brought up a topic that I intend to keep a
closer eye on. If anything I have said here is incorrect or misrepresented,
somebody out there please call me out on it, but hopefully I have
contributed something useful!

Good birding,
Alan Buriak
Gibsonia, Allegheny County


________________________________
From: Bird discussion list for Pennsylvania <PABIRDS...> on
behalf of Sameer Apte <sameerapte1...>
Sent: Monday, March 13, 2017 1:20 AM
To: <PABIRDS...>
Subject: [PABIRDS] 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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