Nombre en español: Azor de Cooper
Nombre en ingles: Cooper’s Hawk
Nombre científico: Accipiter cooperii
El gavilán de Cooper o azor de Cooper (Accipiter cooperii) es una especie de ave accipitriforme de la familia Accipitridae propia de América del Norte y regiones del desierto de Sonora, México, si bien algunos ejemplares emigran hacia el sur, llegando a avistarse ejemplares incluso en Panamá. No se conocen subespecies.
La familia Accipitridae incluye a los milanos, aguilillas, gavilanes y águilas. Este gavilán sigiloso y solitario es un ave rapaz de cabeza grande. La especie es migratoria y de amplia distribución; los individuos de tamaño mediano con una longitud de 37-49 cm. Los machos pesan entre 235-300 gr y las hembras entre 413-598 gr. Su envergadura es de 9-99 cm, su cola larga y ligeramente redondeada (lo que ayuda a maniobrar en espacios reducidos); sus alas son cortas pero también redondeadas. Iris anaranjados a rojos; cere y patas amarillas a anaranjado pálido; corona y nuca negras, frente blancuzca, partes superiores azul grisáceo en el macho y café grisáceo en la hembra. Duermen sobre una pata con la cabeza oculta. En cuanto a su distribución en México, esta ave ha sido reportada para todos los estados del país. Habita principalmente bosques maduros, riparios, de coníferas maduros, de pino-encino, plantaciones de pino, bosques semiáridos, tierras con algunas partes abiertas y árboles espaciados, y en lugares cerca de ríos o lagos. Vive en climas templados subhúmedos, cálidos húmedos y subhúmedos y secos (BS, BW); y en altitudes desde 600 a más de 3,000 msnm. La extensión de su hábitat reproductivo se ha reducido considerablemente. Como todos los depredadores, puede tener un efecto regulador en las poblaciones de sus presas y en el mantenimiento de la diversidad local. Con respecto al estado de las poblaciones de esta especie en el país, no hay ningún estudio en México enfocado a evaluarlo; los trabajos regionales reportan poca información. En México no existen programas de manejo y conservación para esta ave. Se debe promover la reforestación de sus áreas sobreexplotadas así como evitar actividades forestales durante la temporada reproductiva. Asimismo, se debe controlar el uso de compuestos organoclorados y pesticidas organofosfatados en las actividades agropecuarias y evitar la cacería de estas aves. La NOM-059-SEMARNAT-2010 considera a la especie como Sujeta a protección especial y la IUCN 2019-1 como de Preocupación menor. Es necesario realizar estudios sobre esta especie en México.
También llamado Gavilán de Cooper. Accipiter proviene del latín Accipere y Capare (ambas significan agarrar, tomar). La especie se nombró en honor a William Cooper (1798-1864), zoológo y colector norteamericano.
Tamaño y forma
Los machos tienen un tamaño de 38-43 cm, las hembras de 43-51 cm. Patas y cera amarillas, ojos rojos o naranja. Encima es gris azuloso oscuro (la coronilla es más oscura en los machos), debajo tiene un color canela más o menos uniformemente barrado de blanco, infracaudales blancas, en la cola tiene 3 o 4 bandas negras y banda terminal blanca.
Los inmaduros tienen café encima, blanco opaco debajo fuertemente estriado de café, todo lo demás es similar al adulto.
Crían desde el Sur de Canadá hásta el norte de Mexico. Inverna en el Sur raramente hasta Costa Rica. En el país es una especie ocasional, registrado puntualmente al sur de Cundinamarca (Sumapaz) y en la ciudad de Bogotá.
Es un gavilán parcialmente migratorio. Los individuos migran desde la porción más norte de su distribución, pero algunas aves permanecen durante el invierno. En el otoño los juveniles son los primeros en migrar, (y las hembras dentro de cada categoría de edad) mientras en primavera los machos son los primeros. En la migración sus hábitos son similares a los del Accipiter striatus, pero se congrega en menores números. Puede migrar en grupos compuestos con otros azores o con otros gavilanes. No se conocen sus hábitos en Colombia.
The Cooper’s hawk (Accipiter cooperii), also known as the cooper hawk, is a medium-sized hawk native to the North American continent and found from Southern Canada to Northern Mexico. As in many birds of prey, the male is smaller than the female. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west. Other common names for the Cooper’s hawk include: big blue darter, chicken hawk, flying cross, hen hawk, quail hawk, striker, and swift hawk.
Cooper’s hawk was first described by French naturalist Charles Lucien Bonaparte in 1828. It is a member of the goshawk genus Accipiter. This bird was named after the naturalist William Cooper, one of the founders of the New York Lyceum of Natural History (later the New York Academy of Sciences) in New York. Other common names; big blue darter, chicken hawk, hen hawk, Mexican hawk, quail hawk, striker and swift hawk.
The average mass of an adult male ranges from 220 to 440 g (7.8 to 15.5 oz) with a length between 35 and 46 cm (14 and 18 in). The adult male is significantly smaller than the average female, which weighs 330 to 700 g (12 to 25 oz) and measures 42 to 50 cm (17 to 20 in) long. Its wingspan ranges from 62 to 94 cm (24 to 37 in). Individuals living in the eastern regions, where the sexes average 349 g (12.3 oz) and 566 g (20.0 oz), tend to be larger and heavier than those in the western regions, where the respective sexes average 280 g (9.9 oz) and 440 g (16 oz).
Cooper’s hawks have short rounded wings, the wing chord measuring 21.4–27.8 cm (8.4–10.9 in) long, and a relatively long tail, 17–20.5 cm (6.7–8.1 in) long, with dark bands, round-ended at the tip. As in most accipiters, the tarsus is relatively long, measuring 5.6–7.6 cm (2.2–3.0 in) long, and the bill is relatively small, with the culmen from the cere measuring only 1.5–2.1 cm (0.59–0.83 in). Adults have red eyes and have a black cap, with blue-gray upper parts and white underparts with fine, thin, reddish bars. Their tail is blue-gray on top and pale underneath, barred with black bands.
Immatures have yellow eyes and have a brown cap, with brown upper parts and pale underparts with thin black streaks mostly ending at the belly. Their tail is brown on top and pale underneath, barred with dark bands. The eyes of this hawk, as in most predatory birds, face forward, enabling good depth perception for hunting and catching prey while flying at top speeds. They have hooked bills that are well adapted for tearing flesh of prey. Immatures are somewhat larger than a sharp-shinned hawk and smaller than a northern goshawk, though small males nearly overlap with large female sharp-shinned hawks, and large female Cooper’s hawks nearly overlap with small male goshawks. Although the coloration is generally somewhat similar between sharp-shinned hawks and Cooper’s hawks, Cooper’s appear broader-chested and larger-headed, with generally more robust features. The crow-like size of Cooper’s hawks is sometimes distinctive from the sharp-shinned, but this can be less reliable in large female sharp-shinneds. Goshawks are usually more distinctive in their larger size and differing plumage markings, with the juvenile goshawk having broader, darker streaking below with more irregular patterns than the immature Cooper’s. The Cooper’s hawk appears long-necked in flight and has been described by birdwatchers as looking like a «flying cross». The Cooper’s hawk is seen mostly flying with quick, consecutive wing beats and a short glide, though they may also soar.
Distribution and habitat
Their breeding range extends from southern Canada to northern Mexico. They are generally distributed more to the south than the other North American accipiters, the sharp-shinned hawk and the northern goshawk. Birds from most of the Canadian and northern U.S. range migrate in winter, and some Cooper’s hawks winter as far south as Panama. The Cooper’s hawk occur in various types of mixed deciduous forests and open woodlands, including small woodlots, riparian woodlands in dry country, open and pinyon woodlands, and forested mountainous regions and also now nests in many cities. They were once thought to be averse to cities and towns, but are now fairly common urban and suburban birds. The cities provide plenty of rock pigeon and mourning dove for the Cooper’s hawk to prey on. Although more adapatable in habitat than the sharp-shinned hawk, studies have indicated that the species still more often than not prefers sizeable tracts of woodland for breeding and migrating to fragmented, developed areas.
These birds capture prey from cover or while flying quickly through dense vegetation, relying almost totally on surprise. One study showed that this is a quite dangerous hunting style. More than 300 Cooper’s hawk skeletons were investigated and 23% revealed healed fractures in the bones of the chest. Cooper’s hawks prey almost exclusively on small to midsized birds. Typical prey species include American robins, other thrushes, jays, woodpeckers, European starlings, quail, icterids, cuckoos, pigeons and doves. They may also prey upon the raptor American kestrel and other smaller raptors, including their cousin the sharp-shinned hawk. They have been known to rob nests and may supplement their diet with small mammals such as chipmunks, hares, mice, squirrels, and bats. Even more rarely, they may prey on lizards, frogs, or snakes. It normally catches its prey with its feet and kills it by repeatedly squeezing it and holding it away from its body until it dies. They have also been seen drowning their prey, holding it underwater until it stops moving. The hawks often pluck the feathers off their prey on a post or other perch. They also hunt songbirds at backyard feeders, perching nearby then swooping down and scattering the birds to single one out in flight. They may pursue prey on the ground by half running and half flying.
The Cooper’s hawks are monogamous, but most do not mate for life. Pairs will breed once a year and raise one brood per breeding season. Courtship displays include stylized flights with the wings positioned in a deep arc. During their flight displays the male will begin by diving toward the female. A slow speed-chase follows involving the male flying around the female exposing his expanded under tail coverts to her. The male raises his wings high above the back and flies in a wide arc with slow, rhythmic flapping. Courting usually occurs on bright, sunny days, in midmorning. After pairing has occurred, the males make a bowing display before beginning to build the nest.
Their breeding habitats are forested areas. The breeding pair builds a stick nest in large trees. Over a two-week period the pair builds the nest. The nests are piles of sticks around 70 cm (28 in) in diameter and 15–43 cm (5.9–16.9 in) high with a cup-shaped depression in the middle that is 20 cm (8 in) across and 10 cm (4 in) deep. Their nests are built in pines, oaks, Douglas firs, beeches, spruces, and other tree species usually on flat ground rather than on a hillside. The nests typically are about 7.6–15.1 m (25–50 ft) high off the ground, halfway up the tree, and out on a horizontal branch. The clutch size is usually 3 to 5 eggs. The cobalt-blue eggs average about 48 mm × 38 mm (1.9 in × 1.5 in) and weigh about 43 g (1.5 oz). The female incubates the eggs between 30 and 36 days. The hatchlings are about 28 g (0.99 oz) and 9 cm (3.5 in) long and are completely covered in white down. They are brooded for about two weeks by the female, while her mate forages for food. The fledging stage is reached at 25 to 34 days of age, though the offspring will return to the nest to be fed until they become independent around 8 weeks. Eggs and nestlings are preyed on, rarely, by raccoons, crows as well as other competing Cooper’s hawks. Adults rarely fall prey to larger raptors, namely red-tailed hawks, great horned owls, peregrine falcons, prairie falcons, bald eagles, golden eagles, Eurasian eagle-owls and northern goshawks.
Cooper’s hawks communicate using vocalizations and displays. Vocal is probably preferred over display, because the denseness of their habitat could prevent displays from being seen from a distance. Males are usually submissive to females and will listen for reassuring call notes the females make when they are willing to be approached. The males have a higher pitched voice than females.
Cooper’s hawks live as long as 12 years in the wild. The oldest known Cooper’s hawk was 20 years and 4 months old.
Status and conservation
At one time, Cooper’s hawks were heavily hunted in persecution for preying on poultry and were called chicken hawks. It is now known that predation by these hawks on domestic animals borders on negligible, and they are rarely hunted currently.
However, one threat facing Cooper’s hawks today is the degradation and loss of habitat. Management activities like logging may make their former habitat unsuitable for breeding. As a natural predator of almost any North American bird smaller than itself, the Cooper’s hawk may inadvertently deplete populations of rarer, conservation-dependent species. The American kestrel, whose populations have experienced considerable decrease, may be one species which has suffered from the extensive predation of the recovered Cooper’s hawk population.
The Cooper’s Hawk is a largely North American species that occurs as a breeder in the mountains of Mexico and in winter south to northern Central America. A medium-sized Accipiter, it has a long tail and rounded wings. Adults are gray above and banded rufous above, thus resembling the sympatric Sharp-shinned Hawk (A. striatus), from which they are distinguished by their larger size, dark cap, and more-rounded tail. Immatures are brown above and streaked white below, and are distinguished from immature Sharp-shinned by size, shape, and the narrower streaks on their underparts. The Cooper’s feeds largely on birds taken in an ambush or in active aerial pursuit, but also takes mammals. It builds a stick platform in a tall tree, often near a clearing.
Fuentes: Wikipedia/eBird/xeno-canto/WikiAves/Neotropical Birds