Nature & Ecology Nature

Big Black Birds
By Larry Abrams
Photographs by Robert Shantz

Two vultures boarded an airplane, each one carrying two dead iguanas. The flight attendant looks at them and says, “Sorry guys, only one carrion allowed per passenger.”

Now some of you might think I just wanted to start off with a dumb joke, but the real reason is that I want you to know that there are two different kinds of vultures flying around together in Zihuatanejo’s skies, the Turkey Vulture and the Black Vulture.

The Turkey Vulture (we will call it a TV) has a wing span of six feet and the Black's (BV) wing span is five feet. There is no need to carry a ruler with you to tell them apart; the underside rear length of the TV’s wing is light gray and just the tips of the BV is light gray. Easy enough, but not always that easy. There is another bird that will sometimes sneak in the pack when they are soaring overhead. The Zone Tailed Hawk (ZTH) is very similar in flight to the TV with a light gray wing. It’s thought by some that this copy cat similarity of soaring with the vultures, might make it easier to surprise their prey. And we might as well look at one other big black bird soaring up there, the Magnificent Frigate bird (MF). You'll never mistake these for a vulture. They have a long forked tail, long narrow angular wings, and lots of white and or red underneath their bodies.

For those of you who want to practice their Spanish, the TV is Zopilote Aura, the BV is Zopilote común, the ZTH is Aguililla Aura, and the MF is Fregata Magnificens. For those who don't want to practice their Spanish, skip this paragraph.

There are a few other differences in the two vultures: the TV has a red head and reddish feet, the BV’s head is all black, its feet gray. Both have no feathers on their heads which helps keep them clean when they tear open and eat inside a carcass. The TV finds most of its food by smell, which means it pretty much eats only old dead animals. As for all you old people lying out there in the sun for hours on Playa La Ropa, there’s no need to worry—unless you’re dead of course. The BV eats carrion also but locates its food more by eyesight than by smell, and occasionally both, mainly the BV, will kill a live animal for food.

The TV, even though it’s larger, is lighter and usually rises earlier in the morning on rising air currents to be the first one out looking for food. The heavier BV needs a stronger air current so it will wait for the sun to warm the air a little more. This also gives them the chance to see where the TV’s are feeding and sneak in on an easy meal. Neither have voice boxes so there is no song or call, just a little soft hissing like a hot poker thrust in cold water. Both are monogamous, but may pair again upon the death of a mate. If something happens to the eggs in a BV nest, they will try to lay a new clutch, the TV will not re-lay a second clutch of eggs until the following year. They nest in caves and deep crevices on cliffs and can reuse the same nest for years. They usually lay two eggs, incubate them for thirty to forty days and the young leave the nest between eight and thirteen weeks. Every night they will go back to a community roosting area, probably in a large tree, not necessarily back to their nest.

A couple of interesting TV facts: They urinate on their legs when the temperature is over 70 degrees F. This process, called urohydrosis, cools their blood as it runs through the blood vessels in their legs. It’s a similar process to a dog’s panting, which will cools its blood as it circulates through its wet tongue.

Gas pipeline engineers know about the TV’s wonderful sense of smell. If they suspect a gas leak, they will pump a chemical that smells like rotting meat into the pipe and watch for the vultures to gather at the spot where the leak is, so the engineers can fix it.

Most every one knows of the swallows that return to San Juan Capistrano on or about the 19th of March every year. Hinckley, Ohio, has a similar occurrence on the 15th of March. That’s when thousands of Turkey Vultures return to their same breeding area each year. There are three other annual events that feature the TV. One is a month earlier in Branson, Missouri, and two in the fall, for the migratory passage, in Kern, California, in September, and Mankanda, Illinois, in October. In the summer, the TV is found all over the US and in some parts of southern Canada. The BV is more of a south and south eastern bird.

So now you know all about those big black birds soaring in the skies over Zihuatanejo; next month we'll look at the little black birds of Zihuatanejo.

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