May Quiz: Answer

To refresh your memory, here is the photo from May’s Bird Quiz. It was taken in Puerto Rico during the month of May. Don’t read any further if you want one last chance to identify these birds.

5 May_BoqueronPR_20100523_LAH_3752

As I’ve mentioned in previous posts, bird identification usually begins with determining which family the bird belongs to. Most good field guides list the birds in taxonomic order. Remember taxonomy from your biology class? Birds are in the phylum Chordata (having a spinal cord), class Aves (the birds). Next comes the order, then family, genus, and finally species. There is a hierarchy to these based on how each bird species is related to the other species. As a new birder, I discovered that the key to quickly finding a bird in my field guide was to learn the main characteristics of the various bird families.

Sometimes it’s difficult to distinguish between a finch and a sparrow, or a vireo and a warbler, but the birds pictured above are easy to place. I’m sure you already know they’re in the family that includes gulls and terns, called the Laridae. Now comes the tricky part.

The first step is to decide if these are gulls or terns. Gulls tend to have round heads, thick, hooked beaks, and broad wings. They like to sit on the water, hoping a fish will come by. Terns often have flattened heads, pointy beaks, and thin, pointy wings. They zoom over the water, then dive almost straight down to grab a fish for dinner. In general, terns are also smaller than gulls.

So, are these birds gulls or terns? We can’t see them flying or hunting, but we do have a clear view of their heads and beaks. Yup, they’re terns. Now what?

Here is the same species as above, but in breeding plumage.
Here is the same species in breeding plumage.

Except for breeding Black Terns (which are, appropriately enough, largely blackish), most terns look pretty much alike. They have gray and white bodies with or without black on their wingtips. During the breeding season they wear vivid black berets. The rest of the time, or in the case of an immature bird, that black recedes to either a small spot or a fringe (which makes them look like balding old men, don’t you think?). So how does one tell them apart?

It’s almost as if God got tired when He got around to making terns. I imagine him sitting there with a pile of beaks (in four colors) and feet (in two colors), and he just arranged them in different combinations to make the different species. Then he added some black feathers to the head and called it a day.

When you encounter a tern, these are the three parts of the body to look at—the head, the beak, and the legs. You can skip the head if the bird is in its breeding plumage; otherwise note the extent of the black “hat.” Then check to see how big the beak is, and whether it’s black, yellow, orange, or a flaming orange-red (or a combination of these). Finally, note the legs and feet—are they black or orange?

Now check your field guide to see what you’ve got. (At this point I should mention that juvenile birds don’t always resemble the adults.)

These birds have the “old man” fringe of black feathers, orange beaks, and black legs. There’s only one bird found in Puerto Rico with this combination of features. Yup, they’re Royal Terns.

Royal Tern_BonSecourNWR-AL_LAH_8931-001To verify your ID, check the rest of the bird. Terns also vary in how forked their tails are. At left, you can see that the tail on a Royal Tern is deeply forked.

Also, check the range map. Apparently, Royal Terns are expected in Puerto Rico. (The fact that there are two birds in my photo is a good indication that we don’t have a rare sighting, and indeed, there were lots of Royal Terns in the area.)

Let’s compare Royal Terns to some similar species, so you can see the differences:

Breeding Caspian Tern
Breeding Caspian Tern

Caspian Terns (left) are the ones with the big, bright, orange-red beaks, as you can see. Common Terns have black at the end of their orange beaks, and orange feet. Elegant Terns though very similar, are distinguished by having more black on their heads. Also, they’re found along the Pacific coast, not in Puerto Rico.

See how easy that was?





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