Hi All,

I happen to have been working on the atlas book accounts for the 
chickadees over the last two weeks. In general I agree with Matt 
Hafner's comments on the chickadees. There are two regions of contact 
between these two chickadees in Maryland: one is western Washington 
County, and the other is northwestern Frederick and northeastern 
Washington County atop the South and Catoctin Mountain ridges. The 
overlap zones are very tough places to attempt an ID of these 
chickadees. Black-capped and Carolina Chickadees learn each other's 
songs when they are in close proximity and there is well-documented 
hybridization in contact areas leading to blending of otherwise useful 
outward field marks. There has been a recent detailed account of the 
Black-capped and Carolina Chickadee hybrid zone northwest of 
Philadelphia in the most recent issue of "The Auk" (by Matthew Reudink, 
Stephen Mech, Sean Mullen, and Robert Curry). The authors report that 
the hybrid zone is expanding northward and moving uphill (hybrids were 
reported from the Kittatinny Ridge at Hawk Mt.) in favor of Carolina 
Chickadee.

The 2002 to 2006 Maryland atlas map suggests that this retreat by 
Black-capped Chickadee has also occurred in the Catoctin/South Mt. area 
as well, and that Carolina-type Chickadees are now more evident in 
western Washington County. Although it is hard to call the ID of any 
individual chickadee with certainty in the known areas of overlap, it is 
likely that declines in either form indicate that one vocal and plumage 
type is becoming scarcer. On the eastern slope of the Appalachians, 
including on our atlas project, this appears to be the Black-capped-types.

Sideling Hill is approximately the western edge of the overlap area for 
intergrading chickadees. To the east of Sideling Hill birds identified 
as Black-capped Chickadees were reported in sixteen atlas blocks in 
western Washington County to just east of Clear Spring. Black-capped 
Chickadees were also reported in four blocks near the Pennsylvania line 
on Catoctin/South Mt. with none reported more than four miles south of 
the state line. Both chickadee species were reported by observers in 
twenty blocks. Although this might not prove the presence of pure 
Black-capped Chickadee (or Carolina) it does show where the two species 
might well be hybridizing and influencing each other's sounds and 
appearance. Although Carolina Chickadee was reported from two Potomac 
valley blocks in Allegany County in the 1980s, none were reported in 
Allegany County in 2002-2006.

I agree with Matt that birds on the C & O near Hancock are more likely 
to be Carolina than Black-capped Chickadees. This is especially so in 
the light of apparent gains by Carolina-type birds in the Hancock area 
on the atlas map. Black-cappeds or intergrades would be more likely at 
upper elevations, such as the upper slopes of Tonoloway Ridge.

Good birding,

Walter Ellison

23460 Clarissa Rd
Chestertown, MD 21620
410-778-9568

Observing Nature is like unwrapping a big pile of presents every time 
you take a walk.


David Smith and Melody Nevins wrote:
> Hoping for some input on the range of the two species of chickadees in 
> Maryland.
>
> We haven't birded western MD very much and were wondering at what point 
> the range of the Carolina Chickadee transitions to Black-capped Chickadees. 
> We hiked about 12 miles of the C&O Canal towpath yesterday starting in 
> Hancock (Washington County) and moving west. Along the way, we studied 
> some groups of chickadees, trying to determine if we thought there were any 
> Black-capped Chickadees. Of course, all of the chickadees' feathers were fairly 
> worn. At times, we had ones with very gray secondaries and at other times, 
> ones with more white on the secondaries.
>
> We've always seen Black-capped Chickadees out of state where Carolinas 
> were not present, making it a little easier. Is it possible we were seeing a bit 
> of both species in this area of Maryland?
>
> Thanks!
>
> mln and dcs
>
>
>