Monday, February 23, 2009

Playa Las Hojas

I’m back in El Salvador for a couple of weeks. I’m here volunteering to assist principal investigator Oliver Komar with data processing of the Golden-cheeked Warbler data that I and others collected on the wintering grounds in Central America these past three winters.

In other words, office time. These days I don’t spend as much time in an office environment as I used to, but two weeks is totally fine for me. Plus, I get to do more birding in El Salvador in between.

Like yesterday, when Oliver, his wife Lorena and his daughter Yvonne and myself went to Playa Las Hojas, an estuary near the airport. Other SalvaNatura staff members Roselvy, Oscar and Lety joined us, to look for a rare gull photographed at this location two weeks earlier.

The gull was a dark-mantled, yellow-legged gull, most likely a Yellow-footed Gull. I saw photos of this bird a couple of weeks ago, and was keen on seeing it in the wild.

Well, we found a large concentration of shorebirds, herons, terns and gulls – Laughing Gulls – but no larger gull species among them.

Black-necked Stilts were quite numerous at this site. I think we saw more than a hundred. This bird came close enough for a photo.

Probably the most interesting sightings were of several single sulids, one of which appeared briefly – and barely – within the range of my camera. These photos are so heavily cropped that you can almost count the individual pixels, but all the same I think it should be possible to determine the species based on these photos. Shall we? (Please click on the photos for larger views.)

Let’s first determine the age of the bird, and review the possibilities. The bird in this photo appears to be an immature bird, although we should probably include adult Blue-footed Booby as a possibility. That’s a bird whose adult plumage isn’t as clean-cut as that of the other sulids. However, we can eliminate it on the basis of the dark head: an adult bluefoot would have a whitish head. Our bird has a mostly dark head, with mostly dark underwings but lighter underwing coverts. The tail on our bird is light, and there seems to be a bit of a light collar visible on the neck.

Brown Booby is a candidate, but it can be eliminated on the basis of the upperside: both adult and immature Brown Boobies have all-dark uppersides, including dark tails. Masked Booby can be eliminated on the tail pattern; it has a light rump but a dark tail. Our bird has a light tail. Red-footed Booby, another candidate, has all-dark underwing coverts, which our bird does not show.

Overall, the bird that fits much better is immature Blue-footed Booby. It is a large sulid, often seen from land. It has a mostly dark underwing, with light underwing coverts. It has a pale tail.

We saw three individuals in total, the other two even further away than this one. We were unable to identify them in the field, but the other two may have been the same species.

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