Coragyps atratus

Family : Cathartidae

 

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Text © Dr. Gianfranco Colombo

 

 

English translation by Mario Beltramini

   

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As emphasized by the scientific name, Coragyps atratus is an atypical vulture that recalls for many issues the crows. On one side for the gloomy colour, apart some white on the primary remiges and the reddish iris, and then that particular way to fly, with rapid lateral wing slides, agile wheelies and ripid pull-ups © Giuseppe Mazza

The Carrion crow or American black vulture ( Coragyps atratus – Bechstein 1793) belongs to the order of the Cathartiformes and to the family of the Cathartidae and is the only species of the genus Coragyps.

The order of the Cathartiformes groups in its interior all the five genera and the seven species of vultures living in the New World, after the separation from the order of the Accipitriformes where were included all necrophagous raptors present on our planet.

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Common in the New World, is present from East and South USA to Argentina and central Chile, less the Patagonian area and the southern part of the American continent © Giuseppe Mazza

To the new taxonomical classification still now not accepted by all, they have come after various evaluations that considered some characteristics typical of these birds that made them converge, due to some of their behaviours and morphological particulars, not only to the Falconiformes but also to the Ciconiiformes.

Central digits very elongated and partially webbed, habits of urinating on its feet for refreshing the body during the warm days, stretching of the wings during the stops for warming up and disinfecting the plumage with the sun rays, peculiarities typical of the storks combined of course to a body and a feeding of a necrophagous raptor.

Anyway the exact taxonomy of the American vultures is still now not well defined and it is not sure that with new studies and genetic researches, they get in the future to a new and again different classification.

Already the vulture activity deserves for these birds the very bad reputation of carrions devourer placing them in a category certainly not at the height of the other birds usually endowed of a nice livery and often of a remarkable singing capacity but this black vulture, alongwith its consimilar Turkey vulture or Turkey buzzard ( Cathartes aura ) are so much graceless and trivial when on the soil and so much deprived of colour to be locally called, confusing them with each other, turkey vultures.

Actually, their neck, as we shall see, has no feathers and is wrinkled and wattled like a turkey but to this characteristics it adds also the rocked and graceless gait.

The name urubù used locally in some South-American countries to indicate this vulture, come from a term in the Tupi language meaning simply black bird.

Still now, in fome areas of South America it is called cuervos = crow rightly to indicate it resemblance and behaviour.

The etymology of the scientific binomen gets its origins from the Greek for the genus, Coragyps, merger of the terms “corax” = crow and “gups” vulture to indicate the ambiguous characteristics of this bird. The name of the species atratus, conversely, comes from the latin “ater” = dark dressed, black, due to the colour of the livery.

Particular is the origin of the terminologies Cathartiformes - Cathartidae given respectively to the order and to the family of this raptor, terms taken from the Greek, “kathartes” = purifier, with a clear reference to the unpleasant task given to these birds, of eating and purifying the mankind from the infesting carrions of dead animals.

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The local people often call it turkey vulture due to the featherless neck, wrinkled and wattled, the swelling rounded to the sun to sterilize the feathers and its awkward gait © Giuseppe Mazza

In Europe it is called: Black Vulture in English, Urubu noir in French, Zopilote Negro in Spanish, Urubu-de-cabeça-preta in Portuguese, Rabengeier in German, Urubu dalla testa nera or Avvoltoio nero americano in Italian and in Japan, nicely, kurokondoru.

Zoogeography

The American black vulture is quite diffused all over the American continent, with a range covering most of eastern and southern USA and seamlessly up to Argentina and central Chile, ignoring the Patagonian area and the southern part of the continent.

It is a sedentary bird and does not make real migrations if not for short erratic movements looking for food or for avoiding temporary adverse meteorological situations.

It is easily mistaken with the cousin turkey vulture, with whom fully shares the range even if this last one widens further, occupying also the extreme part of Patagonia and totally the USA.

Three subspecies have been identified that respectively occupy the northern part of the range ( Coragyps atratus atratus ), then the Andes cordillera ( Coragyps atratus foetens ) and the southern par of the territory ( Coragyps atratus brasiliensis ).

It should be stressed that the turkey vulture, even if morphologically very similar, does not have characteristics related to our vulture and taxonomically belongs to the genus Cathartes.

Ecology-Habitat

Its activity as necrophagous bird is amply shared with its consimilar turkey vulture of which it exploits the incredible and now well established olfactory capacity that leads it to discover carrions also in the thickness of the tropical forests even only by flying over them at remarkable altitude.

It is thought that our vulture does not have such capacity, however fairly rare in the world of the birds but that it follows it assiduously during the aerial reconnaissance flights knowing its characteristics.

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It’s a social bird that usually lives in dense groups in particular in the dorms but also while feeding when it gathers numerous around the carrions © Giuseppe Mazza

Like all birds belonging to this group, it lives feeding of carrions that seeks methodically staying high in flight along with other negrophagous species, at times in very numerous groups sharing and helping in the search for carcasses. This vulture is able to kill the just born small animals and is often blamed and therefore hunted, for the alleged damages caused to the cattle farms. In fact, it appears to be able, gathering in numerous bands, to kill the small calves. It nourishes also of eggs stolen from the nests, small mammals, reptilians and terricolous birds.

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When looking for food often twirls oberving the other raptors, especially Cathartes aura, similar species, with often overlapped range, that has an exceptional nose for all kinds of carrions © Giuseppe Mazza

Though the ideal habitat of this bird are the arid and steppe zones, it lives in any ambient spacing without seemingly any problem from the highlands of the Andean cordillera, to the Amazonian forests, from the coastal areas to the human settlements.

In these last it has then found an ideal habitat as it does not fear absolutely the human presence thus taking advantage of the city dumps and of the scraps and wastes of the modern human activities.

In some cities of Central and South America has practically become a city bird with colonies permanently urbanized and at times dangerous for the air trafic when close to the airports.

Morpho-physiology

The American black vulture is a raptor of medium size, well far from the traditional and immense Euro-Asian vultures. However, the wingspan is of 160 cm, the weight of more than 2 kg and the length of 70 cm.

It has a strong manoeuvrability in flight, with rapid movements and ease of control of the thermals. Unlike the typical vultures, it has a less rigid and static flight and is able to perform rapid lateral wing swerving, agile wheelies and steep pull-ups that render it more similar to the big crows.

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But this surely not splendid American scavenger attacks also small mammals, reptilians and terricolous birds, not to forget the modern times with the dumps and the wastes of human activities © G. Mazza

Indeed, it has proportionally small wings if compared to its size, rather short and rounded and also a little pronounced tail.

The colour of the livery is not marked by particular colours but by an overall and gloomy blackish covering the body and, tending to olivaceous greyish, the bare parts of the neck, of the head and of the legs.

Only distinction is a white spot appearing when flying in correspondence of the primary remiges and the eye of a nice dark red colour of course visible only at close range.

The bare skin of the neck and of the head results very shrivelled and wrinkled since young, as if it were pockmarked and pustular, of unappealing appearance especially when still covered by leftovers and by the blood of the food just consumed.

The feet are wide and flat, with little nailed fingers of which the front two very elongated and as said, slightly webbed, therefore the paws are unsuitable for catching and seizing the prey.

The beak is not robust and solid as in the typical vultures but rather thin and tapered and somewhat similar to that of our Egyptian vulture (Neophron percnopterus), with hooked tip and perforate nostrils without septum that when collimated laterally, allow to have a glimpse of the opposite part.

The flight of the American black vulture is particular and characteristic, with very rapid beats with rigid wing interspersed with little linear glides spaced in their turn by sudden lateral slides, as can be seen in the European kites ( Milvus sp. ).

As did the old Egyptians with the Egyptian vulture that is shown in their hieroglyphs as sacred bird, also the Mayan people often cites the America black vulture in their old codices indicating it as symbol of death.

It has no syrinx therefore does not have the possibility to emit particular sounds or cries. Only noise is the typical defence hiss while eating and a coarse growl when in group or close to the nest.

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Coragyps atratus is a monogamous bird reproducing only once in a year © Giuseppe Mazza

Ethology-Reproductive Biology

Being a relatively small bird among the necrophagous ones, this bird often lies to suffer the pressure of its consimilars when on the feeding places and probably this has been the reason of the greater diversification of its feeding.

Often for defending from the attacks of predators or when feeling in danger, these birds regurgitate the gulped food for weakening the attack but also for lightening its own weight and thus facilitating the escape.

Also this is a behaviour borrowed from some seabirds when harassed by the attacks of the skuas ( Stercorarius sp. ).

It is a social bird and usually lives in dense groups in particular in the dormitories but also during the feeding when it gathers numerous around the carrions.

The American black vulture is monogamous and nidifies once a year, in variable dates depending on the latitude and the weather conditions of the sites where it lives.

It places the nest usually in caves on steep rocks never at appreciable heights or in woody ambients, in crannies of old trunks but also on the ground at the foot of a rock or of a big trunk.

Usually it does not take to the nest any material, benefitting directly of the substratum present but occasionally and in particular during these last decades, have been seen nests adorned with coloured pieces of plastic material or shiny metal objects of course without any purpose of protection.

It usually lays two whitish eggs spotted of dark brown that are brooded by both parents for about 40 days.

The chicks are nourished for about two months with regurgitated food but even if leaving the nest after such period, they are not yet totally independent in the flight and remain in proximity for some weeks.

Nidifying on the ground the broods are often subject, when are present eggs or just born chicks, to raids by terrestrial animals such as raccoons, foxes or coyote whilst when the chicks get stronger they become aggressive and rarely succumb to these attacks.

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Nest is always well hidden in caves on steep rocks or in the thick of the forest. 2 eggs are laid, brooded also by the male for 40 days. He chicks are nourished with rigurgitated food for about 2 months, but even if leaving the nest they are not yet fully independent in flight and keep close for some weeks © Giuseppe Mazza

Though present numerous in all the territory occupied and placed among the species with lowest risk, the American black vulture, due to its functions of “purifier” of the habitat, enjoys of good protection all over its range.

A curiosity already discovered also for other vultures, takes the observation that the dung of these birds spread on the ground, has the effect of a herbicide, damaging the vegetation and killing plants and shrubs.

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The nests on the ground are attacked by raccoons, foxes and coyote, but the species is not endangered and is accepted by the man as “purifier” of the habitat, according to the scientific names of Cathartiformes and Cathartidae given to the order and family of this small raptor, from the Greek “kathartes” rightly meaning purification © Giuseppe Mazza

 

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