Mystery Bird: Flying Gull-billed Tern, Sterna nilotica

tags: , , , ,

[Mystery bird] Gull-billed Tern, Sterna nilotica, photographed flying over Bolivar Flats, Texas. [I will identify this bird for you tomorrow]

Image: Joseph Kennedy, 6 June 2008 [larger view].

Nikon D200, Kowa 883 telescope TSN-PZ camera eyepiece 1/2000s f/8.0 at 1000.0mm iso400.

Read a detailed analysis for identifying this species below the fold ...

Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:

Compare this bird's shape and structure to the Sandwich Tern in a recent quiz. You'll notice right away that the legs are thick and the bill heavy, broad, and powerful -- from this angle, especially noticeable at the base. Instead of the elongated body and "swan neck" of Sandwich , this bird is nearly terete -- like the cardboard tube from a toilet paper roll -- with a massive, thick neck and a decidedly angular head.

All classic features of Gull-billed Tern, as is the broad dark trailing edge of the primaries. Bill color is a nice supporting mark in this photo, but it's worth noting that Olsen and Larsson's Terns warns that the extreme tip of the bill can be pale.

In the field, Gull-billed Terns stand out nicely because of their habitat and habit. They aren't often seen over the ocean, preferring instead to hunt the salt marshes. And that hunting is accomplished not by plunge-diving, the usual mode of attack of large terns, but by swooping and skimming, plucking crabs and other small invertebrates from the ground as they pass.

Review all mystery birds to date.

More like this

I'm thinking Gull-billed tern. The black hood, the lack of a yellow tip to the beak, the black beak...

Gull-billed Tern because of the thick apparently all black bill, black legs and feet, all light tail without any darker color, and lacking the longer outer tail of a Common, Arctic, Roseate, or Forster's Tern which I think would even show up when the tail is fanned. The underwing pattern eliminates some of the more exotic terns. Sandwich Tern would have a more slender bill with a yellow tip. The location falls within Gull-billed's expected range.

I say gull-billed tern too.

I'm gullible too, so I'll agree with everyone else.

Make that five for Gull-billed. Since it's a June photo, it would be in breeding plumage.

By Bill Voss (not verified) on 25 Sep 2008 #permalink

Not present.
OK, everything else looks like a Gull-billed but that bill just doesn't say Gull to me. I remember the first time I saw a Gull-billed and I thought wow that really does look like a gull's bill. And also, There seems to be too much black, too far below where I think the eye is and too broad around the back of the neck. And the black seems to have white intrusion on the side of the neck like a Roseate Tern. I wish the tail wasn't flared - it's hard to tell how deep the notch is. Sense I wasn't here to make an earlier ID, I think I'll stall and take the glory if it's not a Gull-billed (who said there's no politics in bird watching).

One good tern deserves another, so will we see one like this tomorrow? The bird-en is on GrrlScientist to put down her Avian water and get to work. But don't overdo it. Remember, three shrikes and you're out....