[texbirds] Re: Article on Solitary Vireo complex
- From: Matt Heindel <mtheindel@xxxxxxx>
- To: upupa@xxxxxxxxxxx, texbirds@xxxxxxxxxxxxx
- Date: Fri, 3 May 2013 18:36:45 -0400 (EDT)
Martin, Peter et al
Martin's questions and comments involve a broader issue, so let me dispense
with Peter's question first. He asked whether I had a view on Don Roberson's
notion of the darker lores being a Cassin's feature. Why, yes, I do! It is
intriguing and the duller crown of Cassin's might help explain the reason Don
was working on this feature. But, I could not find any consistency to this
feature in specimens or pictures. Many Cassin's lack darker lores, just as do
many Blue-headed, so you can't say if it is a Cassin's, it has this mark.
Further, you can find Blue-headed pictures with either darker lores or at least
the area immediately in front of the eye being darker, so you can't say if it
has this feature, it cannot be a Blue-headed. So in the end, I just cannot use
this mark in helping with an identification, even though it might be bolder on
Cassin's on average.
Martin's observations are quite detailed and it is impossible to answer them
without some delving into detail. So, if the notion of this is unsettling,
please hit delete! (I know I want to!!) I don't want to answer the points
individually as what I think is covered in the article or field guides. (I
wrote the piece for the NGS Complete Birds of NA (which was used in the later
NGS guides) and had the good fortune of talking through SOVI ID with David
Sibley, so nothing in those works are things I would disagree with.) But, let
me take a broader view and then conclude with what I think can work, and
acknowledge that I am not the last word or authority on this problem.
Adifficulty with the Solitary Vireo complex is that the features
thatdistinguish these taxa are subjective and grade from one end of a continuum
tothe other. So, while I discuss the throat malar contrast as a feature, it is
a matter of degree and too complex to simply categorize them as having or not
having a distinct border. Even a dull Cassin'shas contrast in the malar, so we
are talking about a subjective adjective toimpart a degree of sharpness. It is
impossible to have this subjectivity and not have some problems with putting
birds in one of two boxes. The same can be said with color. There is a
continuum from blue-gray to gray to green-gray and observers have to make a
subjective judgment of when one fits in one box or the other.
Martin wonders if our intermediate birds are, well, intermediate, as in the
populations I mention from Alberta and nearby environs. This is possibly true,
but I worrythat this solution is too simplistic. Itry to simplify things for an
article or for these types of discussions, butthat glossing over is not helpful
with someone like Martin who has the brainpower and interest to lookfor the
details. Let me give two different problems- other than Canadian
Rockyintergrades- that could also result in ambiguous birds in our area.
TheAppalachian taxon (alticola) is a fascinating beast whose winter
rangedelineation from nominate solitarius is poorly understood. The ad males
can be remarkably uncolorful, having more slate instead of blue-gray, and less
of thebright green and yellow of its more widespread brethren. Females look
more likesolitarius, just more muted- hey, that sounds more like a Cassin's,
right? Weknow alticola winters in the southeast US, but have a poor
understanding of itslimits, especially those at the western edge of its range.
They still tend toexhibit a bold malar contrast, but coloration is not as an
effective criterion. Might some of more muted birds reported as Cassin's
involve alticola?
A secondchallenge has had me stumped for a while and I am not even sure to this
day how to bestcategorize these birds. In the Smithsonian collection, there are
a few birdscollected from Idaho that are odd and I can't tell if they are
solitarius/cassiniiintergrades from further north, or if they are
plumbeus/cassinii intergrades.Plumbeus is a boldly contrasting bird, like
solitarius, but generally lackingthe "pretty" aspects. Meld this with the color
of Cassin's and you canget a bird that is a tad muted for solitarius but highly
contrasting (more malar contrast and whiter underparts). If thesebirds were
collected in ID, they might be something we would see in TX. And, if there are
a few in a museum, there must be a decent population of them somewhere.
Relatedto this, one day many summers ago, Kimball Garrett told me he had
justcollected a Cassin's like vireo in Plumbeous country in eastern CA. He was
quite excited with this discovery. On my next trip to LosAngeles County Museum
to look at it, he had since decided it must be a colorfulPlumbeous after all;
yet I was (and am) stumped over where to properly classifythis thing. This was
a specimen in our hand, and it created ID questions. Thereare too many examples
of problematic specimens for me to get real confident withthese birds.
So, wecould be getting some alticola; and, we could be getting some of the
intermediatePLVI X CAVI things; and we are almost certainly getting Canadian
Rockiesintermediate birds. If you go back to the broader population, there are
real obvious ones and then there are some exhibiting intermediate characters.
As for trying to determine what is "pure" in Martin's words, that is beyond my
pay grade. A challengewith this complex (and other avian challenges) is that we
have thiscontinual desire to place things in a box, and indeed that drive is
what makes so many birders good as they work to better learn the fine details.
But, then we admit that some of thesecannot be placed in a box (can't we have a
box for these unidentified things?).Such a system as Martin proposes (call
birds with X pure Cassin's) can easily be done, but I'm not sure if it
reallyhelps us or hurts us by acting like we know what we are talking about. We
aretalking about a lot of gene flow so it is not only possible, but
guaranteed,that birds that would qualify to be in one box would have genes from
a taxa inanother box. It is somewhat like deciding what one wants to call
Thayer's Gullversus Iceland Gull. On the extremes, they are fairly
straightforward, but thevast middle ground is a mess. So, where Thayer's are
expected and Iceland is not, the bird has to be far more extreme Iceland to be
readily accepted as one. The same thing with this group. We can say everything
in x range that has ycharacteristics is a z vireo. That certainly makes it
easier for birders and Ido not throw that out flippantly, as there is value in
birders communicatingusing similar definitions. But, that does not mean the
bird being called Z was reallythe taxa involved.
Inshort, im female Cassin's have a more uniform green, with or without some
grayish that is not duplicated bysolitarius. On the other end, ad male
solitarius have a bold, colorfulness thatis not matched by cassinii. Sadly, we
have not eliminated anything in the middleof this bell curve. If one is able to
properly age a bird, certain deductionscan be made relative to brightness,
color, etc. So, when I mention Peter and Iarrived at similar conclusions on
some CA birds, we were using the markspreviously identified and the birds were
seemingly judged not to be in the overlap zone. We felt good about those
identifications and can defend them. It doesn't mean we were right, though!!!
I am farfrom the authority on what should or should not be called a vagrant
SolitaryVireo and I know I frustrate some people by not being willing to label
some of thesevireos. My non-scientific bias is that this was a poor taxonomic
split. I defend my criticism because the powers that be did not look at the
entire superspecies, and that makes no sense to me. The fact we cannot easily
identify them in itself has little to do with whether they are valid species,
but this is all us field birders have at our disposal. Regardless of whether
this is a superspecies with the species as currently sorted, or if they are
subspecies, they are distinct taxa, exhibiting average differences in certain
field marks. What I found with this complex, however, was: the more I learned
aboutthem, the more frustrating it was to label an individual bird that was
outsideof its "normal" range. So, I comfortably have a large box of things I do
not try to identify. Maddening, right?
Matt Heindel
Fair Oaks Ranch, TX
-----Original Message-----
From: Martin Reid <upupa@xxxxxxxxxxx>
To: texbirds <texbirds@xxxxxxxxxxxxx>
Sent: Thu, May 2, 2013 10:46 am
Subject: [texbirds] Re: Article on Solitary Vireo complex
Dear All/Matt,
I'd like to thank Matt for providing an update on his feelings about this ID
conundrum. No doubt most of my claimed CAVIs are those which Matt would take
issue with! :-)
I would like to ask Matt to comment on a feature that for some reason I seem to
be fixated on: the border/divide between the pale throat and the dark
neck-sides. Looking at pics from the west coast I think I see some CAVIs (fall
males?) with a fairly clean division in this area, however the only pics of
BHVIs from further east that have a less-clean division also seem to have some
equivocal features (i.e. I see no bright, dark-headed, yellow-flanked birds
with
a less than clean division). Then there are those birds which have pale gray
heads such that the lores is darker than the rest of the head - these birds
typically have the first few millimeters of the throat/neck divide somewhat
clean, with the rest being fuzzy.
Another feature that I thought was strong but may not be is the extent of (or
lack of) "dirtiness" on the throat, chest and breast area: I had the
impression
that (especially in Fall when all birds are fairly fresh-plumaged) BHVIs are
immaculate on the underparts - ? This may be complicated by intergrades from
Alberta, which based on an over-simple assumption of migration routes are
likely
to pass through the center/east of Texas...
I guess I have some questions - most of which are more for the purposes of
starting a discussion rather than in hope of there being a simple answer:
1) Can pure BHVI have a fuzzy neck/throat divide?
2) - if no, then what about the pale-headed birds with only a partially-clean
divide?
3) Is it likely that the majority of birds with fuzzy divides seen in the
eastern half of Texas are intergrades between BHVI and CAVI?
4) Assuming that intergrades are the best explanation for birds with some CAVI
features, can we draw a line on what qualifies for a good CAVI, accepting that
some birds that fall short of this line could well be "pure" CAVIs - ?
Regards,
Martin
---
Martin Reid
San Antonio
www.martinreid.com
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