Spizaetus ornatus

The ornate hawk-eagle (Spizaetus ornatus) is a fairly large bird of prey from the tropical Americas. Formerly, some authorities referred to this species as the crested hawk-eagle, a name that may cause some confusion as it is more commonly used for an Asian eagle species. Like all eagles, it is in the family Accipitridae. This species has a feathered tarsus that marks it as a member of the Aquilinae or booted eagle subfamily. This species is notable for the vivid colors and bold markings of adults, which differ considerably from the far more whitish plumage of the juvenile bird. The ornate hawk-eagle ranges from central Mexico south through much of Central America and in a somewhat spotty but broad overall range into South America, including in the west apart from the Andes and broadly on the Atlantic side especially Brazil down to as far as Southeast Brazil and northern Argentina. This species is found largely in primary forests with tall trees, although can be found in many forest types. The ornate hawk-eagle female lays almost always a single egg and the species has a fairly prolonged breeding cycle like many tropical raptors, especially due to a lengthy post-fledging stage on which juveniles are dependent on their parents. It a diversified and exceptionally powerful predator which takes a range of prey, usually led by various medium-to-large-sized birds and small-to-medium-sized mammals as well as occasional reptiles. Like many forest-dependent raptors, especially those in the tropical and subtropical regions, this species is likely under the pressing threat of deforestation. The decline of forest habitat in this species range, especially the Amazon rainforest, led the IUCN to uplist the ornate hawk-eagle as Near Threatened in 2016. The ornate hawk-eagle is a member of the booted eagle subfamily, with the signature well-feathered tarsus present on both tropical and temperate species (and shared, presumably through convergent evolution, with a pair of buteonine hawks). It is one of four living members of the Spizaetus species of “hawk-eagle” native to the neotropics. At one time Old World hawk-eagles, native to various southern areas of Asia, were also included in the Spizaetus genus. However, genetic studies have shown the Asian group of species to be paraphyletic, resulting in the Old World members being placed in Nisaetus (Hodgson, 1836) and separated from the New World species. The history of the American Spizaetus genus has been indicated by the diversity of hawk-eagles found in the fossil records in the United States and Mexico. At least five such species have been described, having presumably radiated from basal hawk-eagles of Asian origin across the Bering Land Bridge. Studies have indicated that some of these are ancestors of modern Spizaetus species, with the genera having been present in North America at least since the Pliocene. Some forms were considerably more massive than any extant hawk-eagle and indeed were likely to have exceeded the size of any living booted eagle. Fossil species such as Spizaetus willetti may have grown to similar sizes as the modern harpy eagle (Harpia harpyja). Studies based on the genetic markers indicated the black-and-white hawk-eagle (Spizaetus melanoleucus) and, especially, the black-and-chestnut eagle (Spizaetus isidori) are closely related to the ornate hawk-eagle, resulting in their respective former genera of Spizastur and Oroaetus being eliminated. The fourth neotropical hawk-eagle, the black hawk-eagle (Spizaetus tyrannus), has been found to be basal to the other extant species. Per genetic research, the ornate hawk-eagle and black-and-chestnut eagle are considered as sister species. The ornate hawk-eagle has been diagnosed to include two subspecies. The nominate subspecies (S. o. ornatus) occupies a good deal of the South American range of the species, including eastern Colombia, Venezuela and all of the species range in Brazil and points south. The second subspecies, S. o. vicarius, has been described to inhabit the discontinuous northern part of the range, extending from Mexico and Central America down through much of western Colombia and western Ecuador down as far south as El Oro. The subspecies seem to differ mostly in the plumage characteristics of adults. Whereas nominate birds are a more cinnamon-hued color on the neck with slightly paler ground color and sparser markings about the head and undersides, S. o. vicarius, tends to be darker overall, with a richer, deeper more rufous color around the neck, denser and darker markings overall and broader bands on the tail. This is a medium-to-large sized species of raptor but a fairly small eagle. In the ornate hawk-eagle, the sexes are similar in appearance and overlap in size but like most birds of prey do show reverse sexual dimorphism, in which females outsize males to the contrary of most non-raptorial birds. The biggest female ornate hawk-eagles are 13% larger than biggest males, with an average of about 8% greater in nominate race. In Central America, in extreme cases, the largest females are as much as 50% heavier than the smallest males. The species is slightly smaller than the largest members of widespread raptor genera such as the largest Buteo and Falco species but is usually larger than other forest raptors in its range apart from vultures and other eagle species. The total length of full grown ornate hawk-eagle is 56.0 to 68.5 cm (22.0 to 27.0 in). Average total length is estimated at 60 cm (24 in) for males and 63 cm (25 in) for females. The wingspan may range from 117 to 142 cm (3 ft 10 in to 4 ft 8 in). Body mass can vary in males from 835 to 1,215 g (1.841 to 2.679 lb) and in females from 950 to 1,760 g (2.09 to 3.88 lb). The average weight of five adult males was 1,009 g (2.224 lb) while another five males averaged 1,035 g (2.282 lb). The average weight of four adult females was 1,421 g (3.133 lb) while a sample of 11 averaged 1,452 g (3.201 lb). Among standard measurements, wing chord measures from 312 to 360 mm (12.3 to 14.2 in) in males and 320 to 405 mm (12.6 to 15.9 in) against S. o. vicarius in which wing chord is known to measure 337.8 to 349.3 mm (13.30 to 13.75 in) in males and 353.3 to 388 mm (13.91 to 15.28 in). In tail length, males vary from 244 to 268 mm (9.6 to 10.6 in) and females from 266 to 290 mm (10.5 to 11.4 in). The culmen from cere measures 25.5 to 29 mm (1.00 to 1.14 in) in males and 27 to 31.5 mm (1.06 to 1.24 in). In tarsus length, males may measure 87 to 92 mm (3.4 to 3.6 in) and females may measure 89.5 to 100 mm (3.52 to 3.94 in). Average wing chord lengths from Guatemala (S. o. vicarius), showed 7 males to average 339.8 mm (13.38 in) and 8 females to average 377.8 mm (14.87 in). Meanwhile, in the same sample, mean tail length was 255.6 mm (10.06 in) in males and 281.6 mm (11.09 in) in male and mean tarsus length was 89 mm (3.5 in) and 94.1 mm (3.70 in), respectively. The largest rear talon (or hallux claw) present on all accipitrids (usually the main killing tool in these predator’s arsenal) is particularly enlarged on the ornate hawk-eagle relative to its size, averaging about 36.7 mm (1.44 in) in males and 39.1 mm (1.54 in) in females from Guatemala, with an average foot span for both sexes measuring around 13.5 cm (5.3 in). Ornate hawk-eagles largely perch within the tree canopy, but will sometimes be out on exposed branches especially earlier in the morning. Usually soaring activity peaks in the late morning. Brown & Amadon (1986) described the species are “rather stolid and buteonine, despite the long tail and crest”. Adults are largely distinguishable by their rufous cowls and bold barring below. Furthermore, all ornate hawk-eagles bear a long erectile crest, which may variously be laid flat against the head, protrude straight up like a spike or sometimes hang at a slight curve. Adults when perched have an obvious black crown, crest and malar stripes (continuing to sides as isolated streaks) sets off by the rufous color on their cheeks, ear-coverts and sides of the neck and chest (sometimes completely covering their upper chests), the rufous shading into a somewhat browner rufous nape. On the upperside, they are barred blackish to dark brown with usually apparent white tips on the mantle and lesser wing coverts. Meanwhile, on the underside, they have a whitish base color which, other than the often plain throat, is boldly overlaid with black barred. This barring extends down to the abdomen and legs, while the crissum is spotted black. Like many forest raptors, the species has relatively short wings and a longish tail. When perched, their wing tips slightly exceed their tail base. The tail is blackish with a creamy whitish tip and three broad pale bands, which are greyish above and whitish below, the basal bar often being obscured. According to Brown & Amadon “the perched bird seemingly has legs set very far forward, almost under the chest, thus giving the impression of posed readiness. The position of the black crest hints at the bird's temper at the moment”. Juvenile differ conspicuously in many respects, generally lacking most of the pigment visible in adults. Juveniles lack the adults’ rufous collar, malar stripes and underside barring. Instead, the juvenile’s whole head and underparts are white excepting thin black streaks on the crown and the tip of their crest. Some juvenile ornate hawk-eagles do, however, show variable, light dark brown barring and spotting on the flanks and thighs, at even may manifest a vestigial moustache on the face. The juvenile’s back and wings are dark brown with white-tipped blackish shoulders. The tail is somewhat similar to the adult’s but has a broader white tip and at least 4-5 thinner bands, which like those of the adult are greyish above and whitish below. By their 2nd year, the young hawk-eagles enter an intermediate or subadult plumage that quickly starts to resemble that of the adults but is rather more faded in appearance. The subadult’s face is a sandy to pale rufous color with an indistinct malar stripe, while the flanks, belly and legs increasingly start to manifest barring and spotting. The subadult’s back is still largely dark brown but tends to appear increasingly blackish. Adults have orangish-yellow eyes, with a dull greenish to grey color on the cere and bare lores, while the feet are rich cream to pale yellow. Juveniles have white to whitish-yellow eyes, a yellow to bluish-grey cere and brighter yellow to orange feet. Apparently, the legs of juveniles are often less thickly feathered than those of adults. In flight it may appear intermediate in size, being large relative to most forest raptors but rather small and slender-bodied for an eagle. The flying ornate hawk-eagle is prominent headed with short, broad rounded wings that show an emphasis on the bulging secondaries and pinch in at the bases of the trailing edges. Flight of the species is deep and powerful with the wings held flattish and pressed slightly forward, while the tail may be closed to slightly spread. From above, adult has a rufous cowl, a blackish mantle and a slightly brownish black back and wings with white-tipped shoulders and tail coverts. Below the underwing is paler looking relative to body with flecking or speckling only on the hand and thinly barred flight feathers. In flight, the juvenile ornate hawk-eagle is mainly dark brown above with whitish scaled blackish-brown shoulders. Below, the juvenile’s wings have scattered spots on the axillaries and great wing-coverts, blackish tips to the white based outer primaries and thin barring on the other flight feathers, at times matching the patterning of the tail. By the 2nd year, there is an only moderate increase to the flecks and spots on the wing linings, as the flight feathers and tail are the last to molt away from the juvenile-like look to those like adults. While adult ornate hawk-eagles are obviously distinctly marked from most other raptors, one species strikingly resembles this predator, the juvenile of the gray-bellied hawk (Accipiter poliogaster) which is extremely different looking from the respective plumage of adults. While not definitely proven, this is quite possibly a case of mimicry, as is known in other raptor assemblages wherein a less powerful species (the hawk) mimics a more powerful species (the hawk-eagle) presumably to mitigate potential predatory attacks. Distant gray-bellied hawks are best told apart by their very different proportions and build both in flight and perched. The gray-bellied hawks are typical of an Accipiter, having broader and much shorter wings, relatively more elongated tail and signature flap-flap-glide flight style. Although the gray-bellied hawk is by a slight margin the largest member of that genus in South America, it is still considerably smaller than the hawk-eagle, averaging about a third smaller in length. At close range, it may noticeably differ, beyond the size discrepancy, by the hawk being crestless and bearing relatively long, featherless and yellow legs. Black hawk-eagles are fairly similarly shaped and similarly sized as the ornate hawk-eagle when seen in flight but are slightly larger in appearance, being longer tailed and longer winged. Nonetheless, the ornate hawk-eagle usually is slightly heavier on average than the black hawk-eagle and may appear chestier in perched birds than the more gracile black species. Confusion with the adult black hawk-eagle is unlikely given that it is always much darker, appear solidly soot colored apart from its heavily barred wings. Juveniles and late first years stages of the black hawk-eagle are most likely to be confused in distant flight with perhaps a subadult ornate, however the juvenile black hawk-eagle is always much more heavily barred below with dark cheeks separating the white supericilia and throat. Haverschmidt (1968) mentioned a 'dark morph' of the ornate hawk-eagle that he said was 'nearly impossible' to distinguish from the black hawk-eagle but this is considered most likely to have been a misidentified black hawk-eagle in intermediate plumage. The juvenile ornate hawk-eagle is potentially confusable with the black-and-white hawk-eagle but the latter is smaller with boxier wings, shorter crest, a bold orange cere, a strong black mask and a blacker upper-body with white leading edges. Also the black-and-white bears no spots or barring on its wings and has a plain white underbody. The black-and-white species is more similar to an Accipiter in proportions than the ornate species, having relatively less expansive wings and somewhat more elongated looking tail. Juveniles are told from the similar juvenile black-and-chestnut eagle by their smaller size and by having more extensive spots and barring on the under wing (giving the differences in altitudinal range, overlap in distribution is likely very minimal). Juvenile hook-billed kite (Chondrohierax uncinatus) are also potentially confusable with juvenile ornates but the kite is much smaller and more dumpily built with more paddle-shaped wings, a squarer tail, with clearer bars on remiges and rectrices and bare tarsi. Another kite, the gray-headed kite (Leptodon cayanensis) can be considered similar in plumage in its adult plumage to the juvenile ornate but it is rather smaller with very different shape in all respects (especially in its small, pigeon-like head), completely different underwing pattern and unmarked body but for grey crown and nape. Pale juvenile crested eagles (Morphnus guianensis) appear much larger and longer tailed than juvenile ornate hawk-eagles with dark grey rather than dark brown backs, unbarred flanks and have a less marked hand in flight contrasting with more boldly barred primary quills. Despite the ornate species not infrequently being described as “slim”, in actuality, the much bigger looking crested eagle is much lighter for its size and only averages about 30% heavier than the ornate (i.e. other eagle species around the same total length as the crested eagle weigh about three times as much as the ornate species). Despite its somewhat similar plumage and appearance to the crested eagle, the harpy eagle is far more massive than the ornate hawk-eagle (nearly five times heavier on average) and unlikely to be confused with any plumage of the smaller species. The main call known for the ornate hawk-eagle is a series of loud piping whistles. It is emitted by the soaring bird, usually male, and is often transcribed as whi whee-whee-wheep, the whee repeated anywhere from 2 to 9 times. Numerous variations are known are given in terms of transcription but most sources describe in roughly similar ways. Unlike the call of the black hawk-eagle, similarly done in flying display, the ornate hawk-eagle the introductory series of notes is more hurried and the last note more drawn out. It has been noted by some authors that the ornate species’ call in nearly a reverse of the pattern of the calling black hawk-eagle which calls huwee-whee-whi-whi-wi-wi-wi, the first note being longest and slurred, second note highest, followed by descending short notes. While perched, ornate hawk-eagle may let out a ca-lee-oo followed by an accelerating series of excited sounding laughing notes. Other reported call include a qu-ouw reminiscent of a limpkin (Aramus guarauna) call and a cat-like scream when disturbed. Perched juveniles have a food begging call consisting of a loud, clear whistle, which is repeatedly irregularly and transcribed aswheeu or wheee. While nesting, the male when arriving with food announces his presence with a pitpit call repeated four times. The most common form of call by the female during the call is the food begging hui, which is usually repeated about four times. She may also call out a sharp fli-fli-fli-flio when being mobbed by small birds. A further call was once attributed to an ornate hawk-eagle that was hunting a guan was a very deep growl, reminiscent of a big cat, to such a degree that the witnesses initially thought the guan was being pursued by a jaguar (Panthera onca). However, further analysis has indicated that it was the guan itself that had let out the big cat-like growl (possibly in an effort to startle the predator and perhaps successfully as the guan escaped) and not, in likelihood, the hawk-eagle itself.