Date: 3/15/17 10:14 am From: Matt Webb <matthewmichaelwebb...> Subject: Re: Allegheny County - Chickadees
This thread has, indeed, been very interesting to follow. For the past four years, Bob Mulvihill and I have been banding chickadees (as part of the Smithsonian Institute and National Aviary's Neighborhood Nestwatch project) at numerous sites throughout the Pittsburgh region. We have long talked about how we have been collecting data on these birds, and have the ability to collect samples for genetic analysis, but we have not yet pursued this...
At some sites over the four years, we've caught and banded birds that measure/appear very much Black-capped, and the next year (and subsequent years) we would only catch birds that measure/appear very much Carolina. In the Pittsburgh region, the "hybrid zone" most likely covers our whole area and measurement and appearance are not enough to go by, but I have noticed that it is not as simple as saying "North of here, we'll only get Black-capped..." etc. I've caught birds in some areas that appear and measure very Black-capped, and then go several miles north of there the next day and catch birds that only appear and measure Carolina. We do, however, tend to see that birds in northerly parts of the region tend to appear/measure Black-capped, and those in the south tend to appear/measure Carolina, but it's never very clear.
When I say "measure", I'm referring to page 335 in Peter Pyle's 1997 Identification Guide to North American Birds. I recommend that birders begin to carry this guide and a (small) wing rule when going into the field to clear up any ID problems. I am, of course, kidding, but I just wanted to say that even with the added ability to have the bird in-hand and measure both wing and tail, there is no real clear "hybrid zone" line.
Also, to add an interesting note, just this past fall, we caught and banded 15 Carolina Chickadees at Powdermill Nature Reserve, the highest number ever caught there. We have only sporadically caught and banded 1 or 2 a year, if that, in the past.
Someone (hmmm...) should study this further!
Thanks and happy chickadee-ing, Matt Webb Carnegie Museum of Natural History Pittsburgh, PA