First let me preface that in no way was I addressing the identification
of the West Machester birds. I have no seen a photograph nor to
this moment seen a physical description of the size of the pale bird.
I only brought up the matter of pale variants within the context of
this recent sighting.
A few more words on Eurasian collared-doves (ECD, Streptopelia
decaocto) to add to Paul Gardner's and Vic Fazio's remarks. I'm sure Vic
does not advocate identifying the West Manchester piebald bird based on
its size alone, or suggest that plumage characteristics aren't important
in the identification of ECD.
Not at all. The standard characters in field guides will lead you to
what we know to be Eurasian Collared-Doves. My point was that
automatically attributing these piebalds to something else is
confusing the issue, especially when bringing into the discussion
the much smaller Ringed Turtle Dove (African if you wish but
following commonly available field guides to which one may
refer to follow this discussion I will stick to Ringed Turtle-Dove).
And what apparently is a lack of attention to size ... as that is
a distinguishing mark (given the often ready side-by-side
comparison with Mourning Doves) .. or can someone point me to
a reference indicating that Ringed/Africans can exceed a Mourning
Dove in heft.
I had a look at two of my European field guides on Eurasian collared
doves, Mullarney et al. (1999) and Jonsson (1992), with English titles
'Birds of Europe.' Both are, I believe, pretty much up to date and very
highly regarded, and would not fail to mention important plumage
variations in the species they treat. The ECD has been there since the
'70s, and Europe's many excellent observers are more familiar than
Americans with it by now; as far as we know, Europe is the source of our
ECDs. Both guides illustrate and describe a single set of plumage
characteristics, just as do Sibley, the National Geographic guide, etc.,
on this side of the pond. I don't know of any North American field guide
that mentions plumage variations for this species such as Vic hints at.
I granted the point regarding "original stock" and suggested that some
recent genetic mechanism may be at play.
I've made numerous trips to Florida, the Ground Zero of this species'
invasion, since the '80s, and have never noticed aberrant ECD plumages
in thousands of sightings.
For 14 years I made twice yearly trips to Sanibel I. where relatives
own property. I've spent hrs watching roosts, numbering up to
500 by 1999. And not once have I seen the variation that I see in
Oklahoma.
If there are documented records of wild S.
decaocto exhibiting obvious variations from treatments in reputable
field guides, then it's time someone wrote a paper formally describing
them for ornithology.
I think it would be helpful to point out that of the Oklahoma birds
the species was an accidental as recently as 2000. By 2001, there
were perhaps a 2-3 dozen in Lawton, OK. By 2004, one could find
that many in a neighborhood, and 5-10 in surrounding communities.
By 2006, for the first time, the species could be saifd to be
common and widespread. I estimate their Lawton numbers tripled
in 2007. In other words the variation I speak of has been only
seen for 3 years.
Ringed turtle-dove and Streptopelia 'risoria,' terms now abandoned by
the AOU in favor of African collared-dove S. roseogrisea, denoted a
domesticated form in N. America (there are minor differences in opinion
on this, with the AOU maintaining there are three small self-supporting
colonies, and the ABA that it's not viable anywhere in the wild in N.
America), quite tame and easily kept in captivity.
Then someone needs to go to Oklahoma City. You can find this form
around Lake Overholser for example. Dr. Joe Grzybowkski showed me
several there in 2002 and was not surpsied at their presence.
These birds were no where near a residence. Furthermore waching these
birds made apparent differences in flight style and profile owing to
the slender build. A Eurasian Collared-Dove can be picked out from
a half mile in silhouette by its unique (in North America at least)
courtship flight and approach to landing.
It is often released, ad some individuals can closely resemble ECDs because so many
phenotypes have been fostered by breeders--see the web address Paul
offers. Unfortunately, hybrids--some of them doubtless
confusing--between this pet form and the wild ECD exist and have been
widely reported in the literature, and are bound to increase as the
latter occupies North America.
Further complicating matters is the recent report of the possible
offspring of the union between Rock Pigeon and Eurasian Collared
back-crossing with Eurasian Collared Dove*. Where might such a
pairing take place ... why at the fringe of the population expansion
in this case in South Dakota.
* Martin, R. 2007. Spring Migration: March through May 2007. North
American Birds. p. 467-468.
As to evidence of hybridization within these pale variants, I made
no suggestion that any immediate pairing was involved. And as Bill
Whan indicates, a bird exhibiting HYBRID charcaters is no
Eurasian Collared-Dove. What I do suggest is that with a history
of introgression of genetic material from S. roseogrisea, that in
circumstances where Eurasian Collared-Doves find themselves
prone to pairing with close relatives (e.g. at the periphery of an
expanding population) that it may be possible to see the expression
of variation from the original stock ....
... so brow beat me with all those European treatises all you like ... :-)
they are rendered moot by the brave New World that S. decaocto
finds itself in, in all likelihood arriving here through a genetic
bottleneck (relatively few birds within the founding population),
upon which natural slection now acts ...
cheers
Vic Fazio
Shaker Hts, Oh
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