[birdky] Re: FW: [Fwd: [Va-bird] Black-capped Chickadees in northwestern Virginia (?)]
- From: "Mark Monroe" <markmonroe1@xxxxxxxxx>
- To: birdky@xxxxxxxxxxxxx
- Date: Sat, 8 Dec 2007 02:02:27 -0500
The thing is, the birds that come south on invasion years seem to be
from northern populations, probably coming from as far north as
Canada, as evidenced by the northern races we've documented during
past invasions and the large movements of them on the Great Lakes
during those years, not races that are along the hybridization zone
that don't tend to truly migrate. Since there is no hybridization
zone within Kentucky, it's less likely to have one of them here.
Incidentally, banding during past invasion years it was fascinating to
note how black-cappeds would essentially let you capture them by hand
(completely unlike local Carolinas), like they'd never seen people
before. I've seen this occasionally with other boreal
species/populations like Pine Siskins and Red-breasted Nuthatches
during those respective invasions.
But the real question to me is, are they really two different species
in the first place? Some genetics work has shown more variation within
each of the current species than between them. :P
Mark Monroe
On Dec 7, 2007 10:18 PM, Jackie Elmore <jackiebelmore@xxxxxxxxxxx> wrote:
>
> With recent sightings in Kentucky, should we consider this?
>
> Jackie B. Elmore
> near Stanford, KY
> Lincoln County
>
>
>
> ________________________________
> Date: Fri, 7 Dec 2007 14:04:10 -0500
> Subject: [Fwd: [Va-bird] Black-capped Chickadees in northwestern Virginia
> (?)]
> From: marcusb@xxxxxxx
> To: carolinabirds@xxxxxxxx
>
> With the apparent southward movement of Black-caps this year, the issue
> regarding separation from Carolinas in the field has resurfaced in Virginia,
> as noted in the string in VA-BIRD. Another commentary and reference below
> may be relevant to the complex situation in the southern Blue Ridge of NC
> and TN.
>
> M Simpson
> Advance, NC
> --------------------------------- Original Message
> ---------------------------------
> Subject: [Va-bird] Black-capped Chickadees in northwestern Virginia (?)
> From: Birdconsv@xxxxxxx
> Date: Tue, November 27, 2007 5:25 pm
> To: va-bird@xxxxxxxxxxxxx
> ------------------------------------------------------------------------------------
>
>
>
> Recently, there have been a number of postings concerning sightings of
> Black-capped Chickadees in northwestern Virginia and some useful discussion
> about how to distinguish them in the field. Unfortunately--and I hate to
> rain on the parade--but that region is a documented zone of hybridization
> between the subject species and the Carolina Chickadee. Work by Gene Sattler
> and associates, most notably the paper published in The Auk in April 2000,*
> demonstrate that a principal area of hybridization lies along the ridges
> that form the western wall of the northern Shenandoah Valley. Based upon a
> series of transects, especially one running northwest from Massanutten
> Mountain between Woodstock and Edinburg to a point just northeast of Liberty
> Furnace, Sattler and Michael Braun found that..."Genetic data revealed that
> at least 58% of the birds in the center of each transect were of mixed
> ancestry and that recombinant genotypes predominated among hybrids,
> demonstrating that hybrids are fertile." In the case of the transect
> described above, that center lies near Columbia Furnace on/near Little North
> Mountain. Moreover, their work showed that..."patterns of morphological
> variation were equivocal regarding introgression [hybridization] across the
> hybrid zone." In other words, there was no useful correlation between
> appearance--as shown in bird guides--and the genetic makeup of a given bird.
> The same situation obtained with song. The bottom line, in non-scientific
> language, is that as you can't tell a book by its cover, in this region you
> can't ID a chickadee by its appearance and/or song.
>
>
>
> These field studies were carried out during the breeding season, so are most
> pertinent for that period. There is strong reason to believe that pure
> Black-capped Chickadees do drift south or downslope into northwestern
> Virginia in the winter as do siskins, Purple Finches, Red-breasted
> Nuthatches, and other "winter birds." Accordingly, some of the chickadees we
> see in winter in that area--and which look like black-caps--probably are
> indeed black-caps. The problem is that short of genetic analysis we really
> can't determine which are truly black-caps and which are hybrids. Indeed, in
> that area we face the same problem with Carolinas, and some of the
> Carolina-looking birds we see in northwestern Virginia are likely also
> hybrids.
>
>
>
> My interest in this subject arose because I own property precisely in the
> zone of greatest hybridization. That is the site where we participate in
> Project Feeder Watch (since 1989) and, more recently, routinely submit data
> to eBird. Feeder Watch has provided a "mixed" category since the inception
> and eBird has just this fall added both a hybrid and a mix category, both of
> which we use all year for lack of a better option. However, if it comes down
> to a Life Bird call, it appears that there is no good (or legal) solution.
>
>
>
> Based on recent history on this web site, I expect that this information
> will probably annoy or even provoke some readers. All I ask is that you bear
> in mind that I am only the messenger and have no axe to grind here.
>
>
>
> With best regards to all,
>
>
>
> Dave Davis
>
> Arlington and Cedar Creek
>
>
>
> * Morphometric Variation as an Indicator of Genetic Interactions between
> Black-capped and Carolina Chickadees at a Contact Zone in the Appalachian
> Mountains. Gene D. Sattler and Michael J. Braun. The Auk 117(2):427-444,
> 2000.
>
>
>
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