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The zone-tailed hawk ( Buteo albonotatus) is a medium-sized buzzard of warm, dry parts of the Americas. It is somewhat similar in plumage and flight style to a common scavenger, the turkey vulture, and may benefit from being able to blend into groups of vultures. It feeds on small terrestrial of all kinds.
The adult plumage is mostly blackish. The notable exception is that the flight are barred with lighter gray, which can appear solid silver-gray from a distance. The tail has three or four bands (the "zones" of the common name), white from below and light gray from above, of which the one second from the tip is particularly broad and conspicuous. The cere and legs are yellow, the lores are light gray and a light touch of white may be seen on the face. Immatures are similar except for small white spots on the breast and tails with narrow gray and black bands and a broad dark tip. The zone-tailed hawk adults resemble the common black hawk but are distinctly more slender in flight and overall small, and they have more white bars on the tail. Other Buteo hawks in their dark phase, especially the broad-winged hawk, may appear similar but often have more silvery coloration on the wings and are broader-winged.
The call is a loud scream, a somewhat typical Buteo call, dropping in pitch at the end, kra kree-kree-kree-kree. In at least some birds, there is an abrupt rise in pitch (like a break to a falsetto voice) in the middle and an equally abrupt drop back down. They are most often heard vocalizing when engaging in breeding displays at the beginning of the mating season. When disturbed at the nest, they may utter a long, lower-pitched raaaaauu.
They can adapt to various habitats across their broad range, including both closed and open ones and wet and dry ones. Often, the largest numbers are found in rocky areas with access to water. They often reside in coniferous or pine-oak forests as well as timbered canyonland, hilly riverine woods, dry open boscage and Shrubland, humid forests, and overgrown marshes. They may forage over ranches and even semi-desert, but always need at least scattered tree thickets for nesting. Furthermore, they may be distributed in elevation from sea level to , though are mainly found below in the north and in the southern reaches of the breeding range.
The clutch comprises one to three, typically two, white eggs, often marked with brown. Incubation lasts for around 28 to 35 days and typically the female incubates, while being fed by the male, although the male may occasionally incubate. The young are semi-altricial at hatching and are covered in gray down. They grow slowly for the first 7 days of life and then considerably faster from 7 to 21 days old. As is common in raptors the older sibling often kills the younger one or outcompetes it for food; only occasionally do both survive to adulthood. The younger hatchling is sometimes referred to as the "spare" one since it may be tended to more directly if the first dies. The young fledge at 42 to 50 days, though are not typically self-assured fliers until around a week later. They may remain in their parents' care until the following breeding season, though in migratory populations, the young and adults often separate. There have been no extensive reports on longevity and mortality in the species.
Distribution and habitat
Zone-tailed hawks range from parts of southern Arizona, New Mexico, and western Texas almost throughout inland Mexico and the central portions of Central America down into eastern Colombia, Ecuador, and more sporadically, into Peru, southern Brazil, Paraguay, Bolivia, and northern Argentina. In winter, they generally withdraw from the United States and northernmost Mexico, with these populations wintering mostly in Oaxaca and the Yucatán Peninsula. They are also native to the Caribbean island of Trinidad. The hawks of Central America may be seasonally migratory, although their movements are not well known. Zone-tails sometimes wander out of their normal range, and the bird was once recorded in Nova Scotia.
Behaviour and ecology
The bird's flight feathers closely resemble those of the turkey vulture. Zone-tailed hawks soar with their wings held in a dihedral angle position (pointing slightly upwards), rocking from side to side, a flight style that parallels that of turkey vultures. Bird guides caution against confusing them with the much more common turkey vulture, but at a reasonable distance, one can distinguish them from vultures by their smaller size, the typical hawk shape of the wings and head, and the pale stripe on the tail. Since vultures frequently can be seen flying in numbers (groups are called "kettles"), zone-tailed hawks can mingle with them and are perhaps most often missed by the human eye in such kettles.
Breeding
The mating season of the species varies geographically but is almost always in the first half of the year. In the northern reaches of the range, the breeding season is mid-April through July, whereas in Trinidad and Ecuador, it is February through June. Eggs have been found as late as August in Colombia, implying only a loose breeding season in the true tropics. The mating pair performs a courtship display, which may include engaging in aerial loops, dives, and rolls with each other. The nest is typical of hawks: a big, bulky assemblage of sticks, lined with green leaves, usually built on the top or the main fork of a tree, in this case at above the ground. Typically, tall trees such as cottonwood or pine trees are selected, and the nest may be in the open or concealed by foliage. Occasionally, nests are found on cliffs.
Food and feeding
Unlike turkey vultures that do not normally prey on live animals, zone-tailed hawks are active predators. Therefore, some ornithologists believe that this mimicry tricks potential prey animals into not being alarmed when a zone-tail flies overhead. This hawk mainly preys on small birds and mammals (including , , mice, ), Buteo albonotatus (Zone-tailed Hawk) but reptiles can be locally favored, including virtually any type of lizard, such as the common collared lizard, Yarrow's spiny lizard, the crevice spiny lizard, and the mesquite lizard. Among the rats preyed upon are the tawny-bellied cotton rat and the white-eared cotton rat. In the north, California quail, along with possibly other quail species, , and other seemed to be the favorite prey. Other birds preyed upon include red-shafted flickers, , , Steller's jays, yellow-rumped caciques, tropical kingbirds, and even eastern screech owls. Zone-tails also eat various young birds, having been observed preying on nestlings and fledglings of species as varied as and . Zone-tailed hawks snatch young birds from trees or the ground without landing. Second-hand reports of predation on , other , and may be cases of misidentification of common black-hawks. Zone-tailed hawks are very active foragers, hunting almost exclusively by transects and random quartering in low flight at around over the ground. When approaching the prey, the hawk may try to use obstructing cover such as trees until it is within of the prey, an easy striking distance. Outside the breeding pair bond, these hawks are wholly solitary and are not known to hunt in pairs.
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