Mystery Bird: Flying Sandwich Tern, Sterna sandvichensis

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[Mystery bird] Sandwich Tern, Sterna sandvichensis, photographed flying over Quintana and Bryan Beach, Texas. [I will identify this bird for you tomorrow]
Image: Joseph Kennedy, 26 August 2008 [larger view].
Nikon D200, Kowa 883 telescope TSN-PZ camera eyepiece 1/640s f/8.0 at 1000.0mm iso400.

Below the fold is a detailed analysis for how to identify this species ..


Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:
Does anybody else remember The Book of Terns? My favorite was the sketch of a rugged beach, each rock topped by one of the eponymous seabirds: and the caption reading “We’ve left no stone unterned.”
The identification of these often subtle birds sometimes makes me want to turn the pun on its head and to leave no tern unstoned. But the quiz bird isn’t difficult, though there is an obvious pitfall if, following the old Petersonian system, we rely solely on this bird’s bill.
The photo shows a relatively heavy, solid black bill, the classic field mark of Gull-billed Tern. But that widespread species–it breeds on six continents–just doesn’t look like this. Gull-billed is short-tailed, fat-footed, broad-winged, squat-bodied, square-headed, and even thicker-billed; the head markings in non-breeding plumage are usually better-defined and restricted to the auriculars, rather than creating a “shawl” effect on the nape, as here. Our bird is longer, leaner, with narrower, more classically tern-like wings; the first thing I noticed was the long, elegantly curved neck–making us think immediately of Sandwich Tern.
But what about the bill? Well, look close. If I shade the monitor, squint hard, and already know it’s supposed to be there, I can see a clear yellow bill tip, a distinctive feature for Sandwich Tern but more often than not invisible in the field. Even then, though, the bill is noticeably straight-edged, lacking the huge “gull-like” gonydeal angle so conspicuous on a real Gull-billed Tern.
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About GrrlScientist

grrlscientist is the pseudonym of an evolutionary biologist and ornithologist who writes about evolution, ethology, and ecology, especially in birds. After earning a degree in microbiology (thesis focus: virology) and working at the Fred Hutchinson Cancer Research Center in Seattle, she earned her PhD in zoology from the University of Washington in Seattle, where she studied the molecular correlates of testosterone and behaviour in white-crowned sparrows. She then worked a Chapman Postdoctoral Fellow at the American Museum of Natural History in New York City, where she studied the speciation and distribution of lories and other parrots throughout the South Pacific Islands. A discarded scientist, she returned to her roots: writing. Formerly hosted by The Guardian (UK), she now writes about science for Forbes and for the non-profit think tank, the Evolution Institute and she writes podcasts for BirdNote Radio. An avid lifelong birder and aviculturist, she lives with a flock of songbirds and parrots somewhere in Germany.
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0 Responses to Mystery Bird: Flying Sandwich Tern, Sterna sandvichensis

  1. Cliff Miles says:

    Gull-billed Tern

  2. Joel says:

    Gull-billed Tern

  3. Jer says:

    Sandwich Tern. Unless I’m seeing things, the yellow-tipped bill rules out any other species. Nice pic.

  4. Fia says:

    Sandwich tern. I very much like these birds 😀

  5. Tristan says:

    Well, it is definitely not a Gull-billed or Sandwich Tern…

  6. bobk says:

    Sandwich Tern.
    You may be interested to know that this bird is not in Peterson’s Western Birds (1990).

  7. bobk says:

    I can do without the Reebok pop up.
    NEW BALANCE has a complete selection of widths. Remember fit is everything. And if you want to be cool, NIKE is the only choice. “Reebok sucks.”

  8. i agree regarding that damned ad! i’ve been complaining for a day now, and it’s still there. i am ready to write a nasty blog entry about that brand of shoes, just because that pop-up ad has made me so mad!

  9. bobk says:

    Devorah,
    You continue to impress and now we know you have good taste. Has anyone contacted you recently about a Vice Presidency?
    Bob
    PS – has anyone ever seen a birder in Reeboks? I doubt it.

  10. david says:

    pidgin

  11. ray says:

    Sandwich Tern: black bill, yellow tip; black feet

  12. JohnB says:

    Sandwich Tern, for the reasons Ray gives above.