The vultures of Los Amigos

July 13, 2018

Normally when you go out looking for birds, you look for the most colorful ones, or listen for those with the most beautiful songs. We often forget that cryptic birds have a beauty of their own. Vultures are not terribly eye-catching but they serve an important role in the ecosystem as the clean-up crew.

Vultures are scavengers, which means they eat dead meat. They are more efficient at finding carrion compared to other scavengers. You can see them soaring all around in their search for food. Their soaring behavior takes advantage of thermals, air currents warmed by the sun that allows them to reach great altitudes without beating their wings. Once they have found their meal, their extremely acidic stomach destroys any bacteria or viruses established in the carrion. This prevents diseases from proliferating and spreading to other animals and humans. Don’t think that because they are the ecosystem cleaners they are dirty birds; on the contrary, their featherless heads are an adaptation to stay clean while eating.

Turkey Vulture (Cathartes aura) soaring around in search of food. | Photo by Alex Wiebe

Although the many species of vultures all over the world serve the same role and have similar appearances, they are divided into two unrelated guilds: The Old World Vultures (Accipitridae) and The New World Vultures (Cathartidae). Los Amigos is home to four of the seven species in the Cathartidae family. The Black Vulture (Coragyps atratus), Turkey Vulture (Cathartes aura) and King Vulture (Sarcoramphus papa) are widely distributed in tropical forests, open savannahs, and grassland, while the Greater Yellow-headed Vulture (Cathartes melambrotus) is restricted to tropical forests. These four species are often seen interacting during lunchtime.

Due to their highly developed olfactory sense, finding carrion is easy for the Turkey and Greater Yellow-headed vultures. They can find their meal as early as an hour after it has been disposed. You may think that this gives them an enormous advantage over our other vulture residents, but the King and Black Vulture have found a way of benefiting from their neighbors’ awesome sense of smell. Since they themselves cannot track carcasses through their smell, they rely on reaching altitudes of 100 feet or more to be able to follow the Turkey and the Greater Yellow-headed vultures to the food source. This behavior is especially apparent in undisturbed forests where the latter is solely responsible for locating carrion and serving as a guide for the other species. This could be due to an even more developed sense of smell than the Turkey vulture or because its wing structure allows them to maneuver better over the tree canopy.

The Black Vulture (Coragyps atratus) waiting for its neighbors to find the meal. | Photo by Alex Wiebe

But what happens when all these species come together for lunchtime? Although a dominance hierarchy between species does exist, most of the time there is not a direct aggression between them. The interaction could result in different species feeding at the same time from the same resource or in individuals leaving when a more dominant species is approaching. More intense aggression has been identified between individuals of the same species. Furthermore, the differences between species in size and bill length and the postures they adopt while eating could be a factor allowing the presence of more than one species at a time. These differences enable them to forage from different tissues of the carcass simultaneously, which may reduce direct competition.

Close to Los Amigos, the main threats that vultures seem to face are the misperception of people. People believe they attack their cattle ranch or that they are dirty birds. But as described here, they feed on dead meat and they even prevent diseases from spreading. Despite their unattractive appearances, vultures are interesting and important birds in our ecosystem. Here at Los Amigos we are excited to have this array of species taking care of the health of our forest.

If you see the King Vulture (Sarcoramphus papa) and Greater Yellow-headed Vulture (Cathartes melambrotus) from far, you can tell them apart based on the color of their breast plumage. | Photos by Alex Wiebe

For more references:

  • Gomez, L.G., Houston, D. C., Cotton, P. and Tye, A. 2008. The role of Greater Yellow-headed Vultures Cathartes melambrotus as scavengers in neotropical forest. IBIS Journal 136: 193-196
  • Houston, D.C. 1987. Competition for food between Neotropical vultures in forest. IBIS Journal 130: 402-417