Accipitriformes

 

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Text © DrSc Giuliano Russini - Biologist Zoologist

 

 

English translation by Mario Beltramini

 

 

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Aggressive Buteo albicaudatus with typical sickle-like beak to tear the preys © Giuseppe Mazza

The well known and vast order of the Falconiforms ( Falconiformes ), defined also as of the Accipitriformes - Sharpe, 1874, includes the so-called “diurnal birds of prey”, which, together with the Strigiforms (Strigiformes), the “nocturnal bird of prey”, form the group of the birds of prey.

To this order belong more than 274 species of birds, among the most known to the laymen, such as eagles, hawks and condors.

The general characteristics of all members leading to the group of the diurnal raptors are attributable to morphological lines of adaptation and of general tendency.

These birds are characterized by the presence of a robust and hooked beak, with sharp edges, suitable for tearing the flesh and provided, at the base, with a particular cere, where are located the nostrils.

The head is flat with sloping forehead, sternum with two incisures or holes, quite strong wings and powerful flight.

The word “Falco”, for instance, comes from the Late Latin falco, falconis, which is close to falx, falcis ‘sickle’, due to the shape of the beak and of the claws.

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The long and sharp beak of Gyps fulvus is the best for dissecting big corpses © Giuseppe Mazza

The tail is usually formed by twelve tail feathers.

The legs are strong, often having feathered tarsi and a structure called “trousers”. The foot has four very mobile toes and the fourth one may be opposable. The claws, with which the toes end, are robust, very long and remarkably curved, in order to seize the preys.

Usually, the plumage is thick and hard.

There are substantial differences between the two sexes: the female is almost always bigger than the male.

They have a wing beats or gliding flight.

Finally, the alimentation, basically carnivo- rous, is formed by invertebrates and vertebrates, alive as well as dead (carrions).

Apart from the vultures, the falconiforms nourish of preys caught alive. The not digested remnants of their meals (bones and corneous structures) are ejected in the forms of “wads”, which, due to the powerful stomach acids, give however an imperfect idea of what has been eaten.

They nest on the tops of the trees as well as on the tops of the rocks, and, in some instances, even on the ground.

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We find it, with few changes, also in this Cathartes burrovianus © Giuseppe Mazza

The hatching begins from the deposition of the first egg, and this causes, in the polyovulatory species, a difference in age between the young.

The pullets come out covered by a down, but it is always an altricial-inept, that is nidicolous, offspring and their breeding, done by both parents, lasts at times long time, with peaks of 130 days.

Most species of this order are solitary or do live in stable pairs. But some of them are social and even nidify in colonies.

All diurnal birds of prey are far-sighted. This depends on the density of the cone cells on the retina which grants them a very sharp diurnal vision (called photopic), which is about ten of times bigger than in the man, contrary to the Strigiformes, the nocturnal birds of prey, which have a bigger retina density for the rod cells, as adaptation to the diurnal vision.

Possibly, the two diurnal birds of prey better endowed in the eyesight, are the Golden eagle ( Aquila chrysaetos ) and the Common kestrel ( Falco tinnunculus ), but also the Peregrine falcon ( Falco peregrinus ), as well as the various species of condors of the New and Old World and all the other diurnal birds of prey do not have a lower eyesight.

A classification is difficult to be done. It is sure that, in ecological terms, this adaptation is the cause of their nutrition modality.

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Like for this Polyborus plancus, the tail is usually formed by 12 rectrices © G. Mazza

But, talking evolutionarily, we have to wonder if it has been the type of environment where they have adapted to live, to generate, selecting them, the individuals with an increasingly sharp eyesight; this has allowed them to colonize and live on the tops of the mountains and of the trees, or in open barren areas, where animals like wild rabbits, hares, grouse pecking on the ground, or serpents and saurians, for instance, may quite well camouflage and, consequently, only animals having such a sharp vision (rightly, like for the birds, the diurnal raptors, and for the mammals, lynxes, wolves, foxes, hyenas, cheetahs, etc.) may survive.

The order of the Accipitriformes or Falconiformes, is subdivided into five families:

- The family of the Cathartids ( Cathartidae - Lafresnaye 1839 ), that is the New World vultures, which, in its turn, is subdivided into five genera: Vultur, Sarcorhamphus, Coragyps, Cathartes, and Gymnogyps.

Among the most known species, we find the Condor ( Vultur gryphus ) and the King vulture or Pope vulture ( Sarcorhamphus papa ).

The various species, leading to the five genera, have their home range between South and North America, up to Canada.

- The family of the Sagitarids ( Sagittariidae - R. Grandori & L. Grandori, 1935 ), which has just one genus Sagittarius and only one nominal species or holotype, the Secretary bird ( Sagittarius serpentarius ), endemic to the sub-Saharan Africa.

- The family of the Accipitrids ( Accipitridae - Vieillot 1816 ), which has 64 and more genera with about 208 species and hundreds of subspecies or races.

Among the various genera, we remind the Elanus, Pithecophaga, Aegypius, Gyps, Pseudogyps, Gypaëtus, Circus, Gymnogenys, Ichthyophaga, Buteo, Milvus, Accipiter, Heliaëtus, Harpia, Aquila, etc.

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Excellent eyesight. Nothing escapes to this Fish eagle (Haliaeetus vocifer) © Giuseppe Mazza

Among the various species, we remind the Red kite ( Milvus milvus ), the Black-winged kite ( Elanus caeruleus ), the Eurasian, or Northern, sparrow hawk ( Accipiter nisus ), the Common buzzard ( Buteo buteo ), the Harpy eagle ( Harpia harpyja ), the Golden eagle ( Aquila chrysaëtos ), the Sea eagle ( Heliaëtus albicilla ), the White-head Sea eagle or Bold eagle ( Heliaëtus leucocephalus ), symbol of the United States of America, etc.

The about 208 species of diurnal birds of prey which form the rich family of the Accipitrids ( Accipitridae ), are spread over almost all lands of the world, but Sahara, Antarctic and some island of Oceania.

- The family of the Pandionids ( Pandionidae - Linnaeus, 1758 ), has one genus only, the Pandion, which has one only species, the Fish hawk ( Pandion haliëatus ), embedded, by some biologists into the family of the Accipitrids ( Accipitridae ).

- The family of the Falconids ( Falconidae - Vigors, 1804 ), which has 13 genera, to which correspond several tens of species, fifty-eight, to be precise.

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The hunting trained Falco peregrinus reaches the 300 km/h © Giuseppe Mazza

The genera are: Herpetotheres, Micrastur, Daptrius, Milvago, Phalcoboenus, Polyborus, Spizapteryx, Gampsonyx, Polihiërax, Microhierax, Neohierax, Falco, and Laracidea.

General description of the five families

- Family of the Falconids ( Falconidae )

Among the most known species, we find the Peregrine falcon, or Falcon ( Falco peregrinus ), the Brazilian polyborus or Caracara ( Polyborus plancus ), the Kestrel ( Falco tinnunculus ), the American kestrel ( Falco sparverius ), the Eleonora’s falcon ( Falco eleonorae ), and the Hobby ( Falco subbuteo ).

From time to time, each species will be treated in the relevant texts.

For this family, as an example, we take the Falcon, which, as it happens for other members of the Falconids ( Falconidae ), tends to live in the entire world.

They settle in the most varied places, along the coasts as well as in the hinterland, in the plains and in the mountains; they are particularly numerous in the woods both with conifer (Taiga) and with latifoliate-caduceous trees, but this doesn’t mean that they are absent in locations where are mostly present barren rocks, where they nest; they live well also in old buildings (country houses, obsolete agricultural sheds, stables), in the wastelands as well as in the populous cities.

Several species are migratory; others are more or less erratic (see text Falco peregrinus ).

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A Geranoaetus melanoleucus. Accipitriformes wingspan is often huge © Giuseppe Mazza

All the falconids have an extraordinary mastery of the air, similarly to the members of the other families.

Their flight, particularly elegant, exhibits really remarkable rapidity and agility.

Their ability in flying has been exploited by the humans, since historical times, for hunting activities, such as, for instance, for hunting hare, fox, etc.

Such a procedure, mainly in the Middle Age, developed much in Europe, contributing to the creation of true and proper schools of falconry, especially in Italy, France, England and Spain, but also in the East, particularly in Persia (the present Iran) and in Mesopotamia (the present Iraq).

The falconids, when flying, sometimes assume a position defined as that of the “Holy Spirit”, typical of the common kestrel.

When observing them from the ground, while they glide with the open wings taking advantage of the ascending warm air currents, they look, in fact, like a spirit gliding in the sky. This is a name originated by the travellers, who, in the medieval times during their pilgrimages, often did observe these evolutions, ascribed to benign spirits.

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The Bonelli’s eagle (Hieraaetus fasciatus) is now rare in Italy © Giuseppe Mazza

Usually, on the ground, all the Falconidae walk keeping the body horizontally in respect to the soil, but they are not completely comfortable and go ahead helping themselves with the wings.

Some species lay the eggs even on the ground, but most of them prefer to settle in a nest abandoned by another raptor, or to build a rudimentary nest on rocky peaks or on the top of a big tree.

Also the most primitive species of the group, such as the Laughing falcon ( Herpetotheres cachinnans ), which mainly eats reptilians, autochthonous to the tropical forests of South America, do have a similar behaviour. The eggs laid are, in almost all the species, are incubated by both parents, who, always together, breed the young.

The diet of the falconids is based on vertebrates: birds, small mammals, reptilians and fishes, but they nourish also of insects, molluscs and crustaceans, without disdaining the carrions.

The members of the Falconidae have the characteristic of seizing their preys only while flying, or at least while resting on the branch of a tree, whilst find hard to capture a pigeon while this one is walking on the ground.

Other falcons, besides the true ones of the genus Falco, which groups most of the species, 39 precisely, lead to various genera, such as Microhierax, Polioheirax and Spiziapteryx, having quite small species, but with an almost identical biology.

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The Grasshopper Buzzard (Butastur rufipennis) eats mainly insects © G. Mazza

- Family of the Accipitrids ( Accipitridae )

As briefly stated before, this family counts 208 species with quite variable dimensions.

The Lammergeier ( Gypaetus barbatus ) is 1,10-1,50 m long, with a weight of about 6 kg, whilst a small kite of the genus Gampsonyx is only 19 cm long, per 500-600 g of weight, but the two resemble on the anatomical point of view: the nostrils are separated (that is, independent), the digestive tract has caecal appendixes, and the first toe is significantly developed.

These particularities distinguish the accipitrids from the cathartids.

Other caratheristics such as the shape of the beak, of the nostrils, the number of the cervical vertebrae, from 14 to 17, separate them, on the contrary, from the falconids.

The eagles are the biggest and strongest species belonging to this family.

Their wingspan, as an average, may exceed the metre and twenty, and their weight varies from 1 to 7 kg.

Other genera of accipitrids, such as Aquila, Hieraetus, have a much ample distribution, whilst others are located only in some continental zones, like, for instance, the Harpy eagle ( Harpia harpyja ), of Central and South America, and the Monkey-eating of Philippine eagle ( Pithecophaga jefferyi ), is nowadays present only in the Philippines archipelago.

Some species live in the forests, like the Booted eagle ( Hieraetus pennatus ), other live in the steppes, such as the Tawny eagle ( Aquila rapax ), but all do hunt remarkably sized preys.

The biggest ones are caught by the Golden eagle ( Aquila chrysaetos ), which, for instance, attacks in Scotland the young and by the Harpy eagle ( Harpia harpyja ), which nourishes of monkeys and sloths in the Venezuelan forests.

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Atypical accipitrid, Eastern chanting goshawk (Melierax poliopterus) hunts running in the savannah © Mazza

The unjustified and prolonged persecution of these wonderful birds done by the man in the so-called “civilized” countries has obliged them to take shelter in the least accessible regions, like the mountains.

The eagles build a nest of dry branches placed on a tree or on a rocky ledge.

Their reproduction rate is unluckily very low: 1-3 eggs, speckled with brown, on a whitish background, are hatched for 40 to 50 days and often the new born eaglets do not all go to “fruition”, because the more robust brothers eliminate the frailest ones.

The biggest eagles fly heavily, but they may glide with great ability.

In Italy, we still find the Golden eagle ( Aquila chrysaetos ) and in Sardinia, and maybe also in Sicily, the Bonelli’s eagle ( Hieraaetus fasciatus ).

The buzzards are close to the eagles, to which they resemble also in the shape, but they get far from them due to the relatively weak legs and because, in spite of their far from negligible size, they are content with small preys (rodents, and other gnawers, repti- lians, landbirds), which they seize mainly in ambush and by surprise.

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The Harris hawk (Parabuteo unicinctus) lives in Arizona, Texas and Argentina © Giuseppe Mazza

These diurnal raptors glide quite well. The main genera are Buteo, Butastur (Africa and Asia), Parabuteo, Buteogallus (America), etc.

The Common buzzard ( Buteo buteo ) is one of the most common raptors in Italy.

Most of the Goshawks and Sparrow hawks (genera Accipiter and Urotriorchis ), have a plumage transversally barred on the lowest part of the body, short and rounded wings and finally a rather long tail.

Amongst all accipitrids, they are the fastest in the flight. In fact, they base their hunting technique in pursuing the birds at high speed, which, however, are capable to maintain only on short distances.

Notwithstanding the rather modest dimen- sions, thanks to their particular temper, they are in condition to catch also preys of their same size.

The smallest accitripids are located in the group of the sparrow hawks, such as the Little sparrow hawk ( Accipiter minullus ), African, present into the red list of the IUCN, which measures just 21 cm.

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The Long-crested eagle (Lophaetus occipitalis) lives south to Sahara © Giuseppe Mazza

The unusual songbirds, of the genus Melierax, the so-called chanting goshawks: the Dark chanting goshawk ( Melierax metabates ), the Pale chanting goshawk ( Melierax canorus ) and the incredible Eastern chanting goshawk ( Melierax poliopterus ), lead an aberrant kind of life. In fact, they hunt running in the savannah utilizing their tarsi, which are rather long.

Sparrow hawk and goshawk still nest in some parts of Italy.

The harriers, genus Circaetus and the Snake eagles, genera Dryotriorchis, Spilornis and Terathopius, are big diurnal raptors with a length varying from 46 to 62 cm, specialized in catching the reptilians.

They look for their victims overflying a long time the hunting grounds or waiting for them when passing by.

These birds lay one egg only and the incubation is much long.

The Short-toed snake eagle ( Circaetus gallicus ) still nidifies, even if not frequently, in Italy and migrates in Africa.

The Harriers of the genus Circus divide in 10 species, and other two genera have an average length of 45 cm.

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Short-toed snake eagle (Circaetus gallicus) eats reptilians and still nests in Italy © Giuseppe Mazza

These birds are easily recognized due to their elongated appearance and their flying low with slow wing beats which alternate with glides or with slips.

Furthermore, unlike the raptors described so far and the others of which we shall treat later, they nest electively on the ground, in the prairies, in the fields, in the swamps and in the steppes, which form their typical environment.

Usually, the plumage is pale (mixed grey, dirty white), but at times dark, as it happens in the case of the Western marsh-harrier ( Circus aeruginosus ).

The sexual dimorphism is quite evident, especially due to the colouration.

More than a few species of the temperate regions are migratory.

They nourish of small preys (insects, rodents, sciurids, small birds, lizards, small serpents), which they seize on the ground.

The western marsh-harrier and the Montagu’s harrier ( Circus pygargus ) still nest in Italy.

The Kites (13 species leading to the genera Milvus, Haliastur, Ictinia, Harpagus, etc.) are birds of reasonable size, for instance 60 cm of length for the Red kite ( Milvus milvus ), ), but little gifted for active hunting.

The ornithological biologists have often remarked that they content of injured animals, such as fishes, rodents, birds or of carrions, and that at least one species is parasitic of other more powerful raptors, being specialized in the stealing of preys, carried by the last ones to the nests for nourishing their progeny.

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Nubian vulture (Torgos tracheliotus) eating © Giuseppe Mazza

The species of the American genus Ictinia are mostly insectivores. The kites prefer the closeness of the water streams and of the lakes, where they may find part of their food.

Five species do have a bifurcate tongue.

The Black kite ( Milvus migrans ) and the Red kite ( Milvus milvus ) still nest in Italy.

The sea eagles resemble to the true and proper eagles due to their huge size, weight 4-6 kg and length up to 90 cm in the Common sea eagle ( Haliaeetus albicilla ).

There are two genera : Haliaeetus ( Haliaeetus vocifer and Haliaeetus leucocephalus ) and Ichthyophaga (two species).

They all live by the sea, or on the lakes or along the banks of the rivers and of the great streams of fresh water, where they seize the fishes and collect dead or dying animals.

At times, the young of the sea eagles are found also in the Mediterranean.

The Honey buzzards belonging to the genus Pernis, are insectivorous raptors in spite of their remarkable size. The Western or Common honey buzzard ( Pernis apivorus ) may reach, for instance, the 50 cm.

This group includes also the genus Henicopernis, and others, but those of the genus Pernis are the most specialized, with adaptations to diets based on stinging insects, especially Hymenopterans ( Hymenoptera ).

So, the raptors of the genus Pernis have the nostrils slit-shaped, edge of the beak and of the eyes covered by small scaly feathers, very thick, and little curved nails suitable for digging the soil to uncover the nests of the Bumble bees ( Bombus ) and of the wasps.

The only migratory honey buzzards are those autochthonous to the temperate regions.

The Common, or Western, honey buzzard ( Pernis apivorus ) nidifies in Italy.

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Is often helped by African white-backed vulture (Gyps africanus) © Giuseppe Mazza

To the group of the honey buzzards connects some raptors with similar diet: genera Chondrohierax and Leptodon in the New World and Avicea in the Old one.

The white kites are small birds (for species of America and of the Old World) which distinguish for their definitely clear colouration (grey and white, with black zones) and their insectivorous diet.

The Swallow-tailed kite ( Elanoides forficatus ), American, resembles much to them.

The Bat hawk, belonging to the genus Machaerhamphus, subfamily of the Machaerhamphinae, of Africa and eastern Asia, deserves a particular citation due to its monophagous or stenophagous diet: this species seizes almost exclusively the bats that in the evening take off getting out from the dens where they have spent the day.

Thus, this raptor, if compared to the previous ones, has crepuscular habits and keeps idling during the day.

Finally, two unusual birds of the genus Rostrhamus, with thin and much curved beak, mostly, if not exclusively, nourish of gastropod molluscs and live in America.

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1,60 m wingspan Egyptian vulture (Neophron percnopterus) is an Old World scavenger © Giuseppe Mazza

The Old World vultures (14 species) have been, for long time, placed in a standing alone family by the ornithological biologists, that of the Egipids ( Egiipidi ), justifying such classification with their biology.

They are big birds.

The smallest one, the Egyptian vulture ( Neophron percnopterus ), measures a wingspan of 1,60 m. The greatest one is the Lammergeier ( Gypaetus barbatus ), with the black, brown and beige, at times mostly white, plumage, with very long and broad wings which allow them to glide extremely well.

All, but the lammergeier, have the head and the neck without feathers, covered only by a more or less scattered down.

The legs have feet with weak fingers and suitable for walking.

The vultures live in the poor, desert and mountainous regions.

They are “necrophagous” and the presence of herds of ungulates is one of the conditions of their existence, as they nourish almost exclusively of the corpses they may sight.

The Palm-nut vulture ( Gypohierax angolensis ), African, eats also fruits.

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Cathartes burrovianus has same size, but cares the New World carrions © Giuseppe Mazza

The lammergeyer, on the contrary, nourish almost exclusively of bones.

Four species do live in Europe, 8 in Asia and 9 in Africa.

Only one white with brown dots egg is laid and the incubation lasts from 46 to 53 days, depending on the species.

The Griffon vulture ( Gyps fulvus ), race ( Gyps fulvus fulvus ), is still found in Sardinia, whilst it has recently disappeared from Sicily.

The Egyptian vulture should still live in the central-southern Appennines, and finally the lammergeier might still be present in Sardinia.

- Family of the Pandionids ( Pandionidae )

It has the only species Fish hawk ( Pandion haliaëtus ). This bird is, as aforementioned, still nowadays placed by many ornithological biologists into the family of the Accipitridae, but its morphology and its biology, absolutely special, has prompted the taxonomical biologists to allocate him a proper one. Actually, it is the only diurnal raptor nourishing exclusively of fishes which it catches by diving into the water.

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With more than 3 m wingspan, Condor (Vultur gryphus) stands among the biggest extant raptors © Mazza

The legs with bare tarsi end with toes whose surface is covered by corneous spiculae, particularly suitable for holding scaly and slimy preys.

Furthermore, we have also to note that the outer toe is reversible, that is, it may be led further back than the outer finger of many other species and this further facilitates the grip.

The fish hawk is found practically all over the world, but South America.

It does not nest any more in Italy. Perhaps some pairs are still nesting in Corsica, whilst in the peninsula, during the pass, some individuals may be observed while stopping especially along the main rivers.

Unluckily, they are often killed by the hunters.

- Family of the Cathartids ( Cathartidae )

This family includes the vultures of the New World which are much resembling to those of the Old World, family Accipitridae.

There are two species of Condors, leading to two distinct genera Vultur and Gymnogyps, and four vultures. The genera Sarcorhamphus, Coragyps and Cathartes, have however some anatomical characters which distinguish them significantly: these are the tendons of the toes, the nostrils, the “uropygial” gland, the nails (quite less curved) and the vocal apparatus, which is absent.

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Like cranes and bustards, the Secretarybird (Sagittarius serpentarius) has terrestrial life habits © Mazza

The Andean condor ( Vultur gryphus ) and the famous California condor ( Gymnogyps californianus ) are the biggest known raptors, respectively with a wingspan of 3,15 m for the first species and 3,20 m for the second one and a length, for both of them, of 1,25 m.

The various Urubu, such as the Coragyps atratus and the colourful King vulture ( Sarcoramphus papa ), are smaller, usually 60-72 cm of length. There are only two species located in North America.

- Family of the Sagitarids ( Sagitariidae )

The unusual Secretary bird ( Sagittarius serpentarius ), of the African savannahs forms, alone, this family.

Due to its hooked beak, the diet based on small vertebrates (reptilians, batrachians, and small rodents) and its mode of reproduction, this bird is definitely a raptor.

If, however, we consider its long legs (whose toes are fused at their base by means of an interdigital membrane, “syndactylous foot”) and the habits and the style of life, mostly terrestrial, we might be led to think that its similarities with birds such as the bustards and the cranes are remarkable.

Among the other odd characters, the secretary bird, which measures 1,15 m of length and 2,10 m of wingspan, there is that of having median rectrices much elongated, that exceed the other feathers of 13-15 cm and an occipital crest which earned it the English name of secretary (Secretary bird), referring to the habit the secretaries had, once, of settling down the pen on the ear. It has a grey-black plumage.

 

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The photographic file of Giuseppe Mazza

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Haliaeetus vocifer - Parabuteo unicinctus - Aquila nipalensis

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Aquila nipalensis - Juvenile form of Parabuteo unicinctus - Haliaeetus vocifer

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Haliaeetus vocifer

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Haliaeetus vocifer

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Gyps africanus - Aquila nipalensis - Neophron percnopterus - Lophaetus occipitalis - Torgos tracheliotus

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Cathartes burrovianus - Vultur gryphus - Falco peregrinus

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Falco peregrinus

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Falco peregrinus - Buteo albicaudatus - Circaetus gallicus - Butastur rufipennis - Sagittarius serpentarius

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Gyps fulvus - Geranoaetus melanoleucus - Hieraaetus fasciatus - Melierax poliopterus - Parabuteo unicinctus - Polyborus plancus

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Falco cherrug

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Falco cherrug - Geranoaetus melanoleucus - Harpia harpyja

© Giuseppe Mazza

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