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As common as it is there is not a lot of information about the family life or breeding biology of the Black Vulture a.k.a. American Black Vulture (Coragyps atratus). Black Vulture’s nests, eggs, and chicks are well known, but most of this information comes from a relatively small number of nests.
Black Vultures have a discreet and reclusive family life. This article goes over some interesting facts about the way Black Vultures find a mate, select a nest site, incubate the eggs. It also goes over the appearance of the egg, chicks, and the development of the young vultures.
Do Black Vultures mate for life?
Yes, Black Vultures mate for life but will re-mate with another individual if one member of the pair dies.
Mating for life appears not to be an absolute arrangement among birds thought to mate for life. Bird studies of paired birds in long-term relationships showed that some pairs split for no apparent reason. As if both members of the pair part ways in a friendly and civilized way.
While Black Vultures are thought to mate for life, friendly pair splits may also occur among Black Vultures as well.
Mated vulture pairs stay together, or in the same flock and in the general area during the breeding season and outside the breeding season. Perching together, roosting in close proximity, and flying together is often an indication that those two birds are part of a mated pair.
Mating of Black Vultures is an event rarely seen in nature.
What do they do to find a mate?
Apart from the general conditions, such as being in good health conditions and having an “acceptable status” in the flock, it is difficult to tell the fine-grain features that vultures use as cues to find a mate.
First-time pair formation and getting ready for the breeding season among mated pairs involves several courtships displays including:
- Aerial chases, which consists of one bird, the male, diving at the prospective female. This behavior is perhaps the most easily observed. While in flight, the male gains a higher altitude than the prospective female. Then, he dives at her and she dives away resulting in a fast descending chase downwards that can last 3 to 4 seconds.
- Circling Display, which consists of the male circling a standing female with its neck stretched out forward as he emits hissing sounds.
- Open wing facing, which consists of the pair facing each other with their open wings as they bob their heads up and down.
The success of this display behavior is generally conducive to a pair formation or reinforce an existing relationship as a prelude to start breeding.
How can one tell a male from a female Black Vulture?
You can’t. The Black Vulture is a monomorphic species, which means that there is no difference in appearance between males and females.
Both sexes are uniformly black. Adult and fully-grown immature birds measure about:
- 25” from the tip of the bill to the tip of the tail,
- 59” of wingspan, or length between the tips of the spread wings, and
- weigh about 4.4 lb (2,000 grams).
Where do Black Vultures nest?
They nest in a variety of secluded places most of which have in common resembling a small cave. The majority of nests are placed on the ground under thickets.
Other nests are placed in rock crevices, underbrush piles, under fallen tree trunks, abandoned buildings, or other places that have a cave-like appearance.
The nesting pair assesses the safety of the nesting for a period of 4 to 6 weeks prior to committing to a nest site. Both birds spend hours perched together near the prospective nest site apparently checking for the traffic of possible predators and other risks to the eggs and chicks.
Ground nesting birds, in general, are at higher risk of predation than birds that nest off the ground.
How many eggs do Black Vultures lay?
They normally lay two eggs on a small depression on the ground or other surface, without an actual nest. In rare occasions, they lay 3 eggs or a single egg per nest.
Eggs are laid either in two consecutive days or two to three days apart.
How long does it take an egg to hatch?
The eggs normally hatch in 38.5 days with a span of 38 to 39 days. The chicks usually hatch one or two days apart depending on when vultures start incubating the eggs.
Black vultures sometimes begin incubating the eggs as soon as she lays the first egg. Other times she waits until the second egg is laid to start incubating the eggs.
The initiation of incubation of the eggs makes a difference in the time it takes for each egg to hatch.
Both parents share the incubation duties nearly equally with multiple changeovers during the day.
What does a Black Vulture egg and chicks look like?
While the egg color and pattern may differ geographically, the appearance of young Black Vultures is consistently similar.
The egg of a Black Vulture is pale bluish or pale greenish with brown spots. The size and density of brown spots on the eggshell vary geographically. However, the wider side of the egg consistently appears to show a higher concentration of brown spots.
Newly hatched Black Vultures have a coat of dense beige or light brown down. They hatch with their eyes open. The eyes are dark with the skin on their face and the bill being black in color. This baby vulture is about 15 days old.
By the 17th day after hatching feathers begin to grow under the coat of down. Feathers are not noticed until the young bird is about 30-35 days old when some of the down begins to fall off. This young vulture is about 60 days old.
Not many people have seen an actual egg and chick Black vulture because nests are well hidden. The parents do not give away many leads towards the location of the nest.
Ornithologists purposely studying the nesting biology of Black Vultures know the clues that reveal the birds have a nest at a location nearby.
How long it takes a baby vulture from the time of egg-laying to fledging?
On their studies on Black Vulture development, ornithologists Thomas (1928) and Mchargue (1981) determined that it takes approximately 79 days from the time an egg is laid to the time a young vulture takes its first flight.
The approximate sequence is as follows:
- Egg-laying to hatching (incubation period): Approximately 38.5 days.
- Feathers begin to appear: 17-23 days.
- Young fully feathered: 65 days.
- First flight: Between 75-80 days of age.
Because the eggs hatch at different days, one chick is generally larger than the other. This difference in size and development results in one chick attaining each milestone earlier than the other.
In about a month after hatching the young vultures begin to take steps at or near the nest.
Once they fledge the nest, young vultures remain in the vicinity of the nest location for approximately 10 days performing practice flights.
After the flying muscles are ready and they have acquired some experience the family unit moves on to look for food away from the nest site.
Adult Black Vulture feeding young.
What are baby black vultures fed?
Newly hatched young vultures are fed pre-digested liquid food. Both parents will make a special liquid food from the food they normally eat.
At a feeding visit, one of the parents reaches the bill of a young vulture, which reacts to the stimulus by raising its head up so that the flow of liquid from the parent to the chick begins.
After only 15 days, the food type goes from liquid to semi-solid. As the chicks get older the parents bring solid food in their crops and deliver it to the chicks in the nest directly bill to bill.
Food delivery, during approximately the first 10 days happens at a frequency of approximately 15 to 20 times per day. As the chicks get older, the feeding frequency diminishes to a point that is only 2-4 times per day and consists of solid food.
Black Vultures are remarkable birds with a very important role in nature; they promptly get rid of dead animals that may smell for weeks and help reduce the spread of diseases.
Knowing some of the interesting facts about their family lives brought up in this article may help to understand them a little better.
- Gill, Frank (1995). Ornithology. New York: W.H. Freeman.
- Mchargue, L. A. (1981). Black Vulture nesting, behavior, and growth. Auk 98:182-185.
- Thomas, E. S. (1928). Nesting of the Black Vulture in Hocking County, Ohio. Ohio State Mus. Sci. Bull. 1:29-35.