Van Rossem's Gull-billed Tern

Now that I am no longer a servant of Least Terns (whose eggs and chicks are prey for Gull-billed Terns), I can now come out publicly and say that I'm a big proponent of Gull-billed Terns.

For many years I only saw them infrequently...it wasn't until taking a job near California's Salton Sea in 2007 that I saw them on the regular. They stood out in stark contrast to their bizarre, often disgusting surroundings; this incongruity made me pay special attention to them.


Aside from skimmers, Gull-billeds are pretty unique for a tern...you can find them hunting for insects, amphibians, reptiles, crustaceans, fish, bird eggs and young...they are truly opportunistic.

Gull-billed Terns are cosmopolitan, and found on multiple continents. In California, the local subspecies is Van Rossem's Gull-billed Tern, whose global population is thought to be around only 800 pairs. Despite this worrisome number, the U.S. Fish and Wildlife Service recently declined to add them to the Endangered Species List.

The good news is that while the Salton Sea population has been more or less stable over the last couple of decades, the San Diego population is slowly increasing.



What a slick-looking bird. Economy of style in full effect.

Along the shores of Imperial Beach, Gull-billed Terns specialize on grabbing mole crabs (aka "sand crabs") from a few inches of water, when the tide is right. When the tide isn't conducive to mole-crabbing, Gull-billeds may instead focus on terrestrial prey like lizards and bird chicks and eggs.

While normally devoured on the wing, they will occasionally land to take the time to properly demolish and choke down big ones.

Here's a juvenile. Note the marked "flag" dangling from its ankle. This population, which nests in the Salt Works of South San Diego Bay, hosts a number of birds with metal bands, field-readable flags, and even radio transmitters.

All of the photos here were taken between the mouth of the Tijuana River and Imperial Beach, CA.