Mystery Bird: Forster's Tern, Sterna forsteri

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[Mystery bird] Forster’s Tern, Sterna forsteri, photographed at Robbins Park, Smith Point, Texas. [I will identify this bird for you tomorrow]
Image: Joseph Kennedy, 12 June 2008 [larger view].
Nikon D200, Kowa 883 telescope TSN-PZ camera eyepiece 1/350s f/8.0 at 1000.0mm iso400.

Read how to identify this species below ..

Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:
A pretty picture, and well composed; with the bird’s head turned haughtily towards the observer, we can’t see the exact length and shape of the bill or the precise pattern of dark feathers on the head. So let’s start with what we can see.
Compare the overall shape of this Forster’s Tern with that of a Common Tern. They’re both “classic” Sterna terns, but Forster’s is noticeably more attenuated — not just the foreshortened bill, but the tail and legs are longer than those of Common Tern. In this view, note that the tail, just barely visible beneath the folded primaries, nearly reaches their tips; I’m not certain whether I can truly see a white outer vane or not, but if I could, that would distinguish this bird from Common with its dark-margined tail. What strikes me most of all in this image is the length of the tarsus. Just for fun, take this photo and the photo of Common Tern, and ask yourself which bird could straddle the other.
Though the full head is not visible, what we can see of the crown pattern tends to confirm the identification as Forster’s Tern. The top of the head is immaculate, and the eye mask is clearly defined.
Review all mystery birds to date.


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: Forster's Tern, Sterna forsteri

  1. Bob O'H says:

    Hmm. I’m guessing (and I know this is a wild stab in the dark) that this is a tern.

  2. ray says:

    Franklin’s Gull

  3. aedis says:

    Is it just my browser or are the yellow legs part of a different photograph?
    In which case, I’ll say Arctic tern.

  4. nope, the leg color belongs to this bird. i am not trying to trick you guys, i am trying to help you all learn to better identify birds.

  5. aedis says:

    Photograph looks a lot better now; maybe it was my browser.
    Now I can see that the legs actually belong to the bird!
    And now they’re red.
    Arctic tern.