Living the Scientific Life (Scientist, Interrupted)

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[Mystery bird] Western Kingbird, Tyrannus verticalis, photographed at Smith Point, Chambers County, Texas. [I will identify this bird for you in 48 hours]

Image: Joseph Kennedy, 1 November 2009 [larger view].

Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/750s f/8.0 at 1000.0mm iso400.

This lovely North American species shouldn’t be too difficult for most of you to ID (maybe you can hold your enthusiasm in check for a few hours, David?)

Please name at least one field mark that supports your identification.

Review all mystery birds to date.

Comments

  1. #1 Michael
    December 12, 2009

    Well, it’s one of the yellow-bellied Tyrannus flycatchers. Of the four such species on the Texas checklist, we can rule out Cassins (T. vociferans) as this specimen lack white tips to the tail feathers.

    The posture of the bird relative to the camera makes it difficult to consider the relative size of the bill – largest in Tropical (T. melancholicus), smallest in the Western (T. verticalis) and intermediate in Couch’s (T. couchii).

    I don’t think the tail feathers are spread enough for me to properly assess how much white edging is present on the outermost retrices.

    The Cornell site has a good page contrasting these three look-alikes.

    I’ll leave it to others to drill deeper into this problem.

  2. #2 notedscholar
    December 12, 2009

    Based on another blog post I just read, I’m saying Ostrich.

    Cheers and good wishes for the holiday season,
    NS

  3. #3 John Callender
    December 12, 2009

    Agreed that it’s a kingbird, and probably one of Tropical, Couch’s, Cassin’s, or Western, but which one is kind of a tossup for me. I think I’m going to go with Couch’s Kingbird, basing that mainly on the back being more olive green, less gray, than Sibley’s illustrations of the Cassin’s and Western (as well as the lack of a terminal band on the tail that would hopefully be visible for Cassin’s, as Michael pointed out), and with the Sibley range map making Couch’s seem more likely than Tropical.

  4. #4 David
    December 13, 2009

    Grrl, I waited 24 hours… may I?

  5. #5 David
    December 13, 2009

    Assuming he took a series of photos which will indicate confirming field marks, I think the definitive answer will have to come from the photographer, however based upon some of the work kindly attached by Michael above, together with comparisons of confirmed ID photos (with varying angles of head/bill and wing shape) of all four species mentioned so far (Tropical, Couch’s, Cassin, and Western), I believe this to be a Western Kingbird (Tyrannus verticalis).

    Mark #1: I agree with both Michael and John that Cassin can be eliminated for the lack of white on the tip, but when one magnifies the image of the tail (greater than the auto function) the extent of the white edging becomes a lot clearer, and while some specimens of Tropical and Couch’s do have a “light” edging, the example here is plainly more white and does extend markedly along the length of the tail- I feel that the “brightness” of the white reflects the “depth” of white- i.e. probably from the outer edge medially to the feather shaft.

    Mark #2: looking at overall relative size of the entire bird, the Western is markedly more compact- the image above reflects this, taking into account tail length relative to body length, but to further confirm this intuition, I measured the relative length of bill size to overall head length on the specimens in the Cornell photo, and 5 images of each species, and found that although not exactly what one would call rigorous investigation, overall Tropicals had bill lengths that averaged 41% of the length from tip of the bill through the eye to back of the head, Couch’s 38%, and Westerns 25%- mathematically any foreshortening should maintain relative ratios so measuring the image above I found the bill to be 23.5%.

    Mark #3: as the most migratory species, Westerns show a greater projection of the primaries out from the secondaries in the folded wing as compared to the other species which I think is also indicated above- a distinctly “pointed” appearance.

    Mark #4: although this will vary in many circumstances, the shape of the end of the tail can be recognised above and looks much more “square” than any similarly-angled photo I could find for Tropical or Couch’s.

  6. #6 psweet
    December 13, 2009

    I agree — Western Kingbird, based largely on two marks — the relative lack of olive on the back — Tropical and Couch’s should be much brighter there, with more contrast with the head — and the shape of the tail. On a Tropical or Couch’s, the outer tail feathers should be longer than the inner ones, and on these, the inner tail feathers (on top on the folded tail) appear to be the longest part of the tail. I’m having trouble finding anything I could call white edging on the tail, but this shot was taken on 1 November, during migration, so the white edging is likely to be minimal at best due to wear. The same may well apply to the pale tip on Cassin’s, but a Cassin’s should show a distinct pale malar contrasting with a darker gray face.