Azor Común

Identificación

The Eurasian goshawk has relatively short, broad wings and a long tail, typical for Accipiter species and common to raptors that require maneuverability within forest habitats. For an Accipiter, it has a relatively sizeable bill, relatively long wings, a relatively short tail, robust and fairly short legs and particularly thick toes. Across most of the species' range, it is blue-grey above or brownish-grey with dark barring or streaking over a grey or white base color below, but Asian subspecies in particular range from nearly white overall to nearly black above. Goshawks tend to show clinal variation in color, with most goshawks further north being paler and those in warmer areas being darker but individuals can be either dark in the north or pale in the south. Individuals that live a long life may gradually become paler as they age, manifesting in mottling and a lightening of the back from a darker shade to a bluer pale color. Its plumage is more variable than that of the Eurasian sparrowhawk (Accipiter nisus), which is probably due to higher genetic variability in the larger goshawk. The juvenile Eurasian goshawk is usually a solid to mildly streaky brown above, with many variations in underside color from nearly pure white to almost entirely overlaid with broad dark cinnamon-brown striping. Both juveniles and adults have a barred tail, with 3 to 5 dark brown or black bars. Adults always have a white eye stripe or supercilia, which tends to be broader in northern Eurasian and North American birds. In Europe and Asia, juveniles have pale-yellow eyes while adults typically develop orange-colored eyes, though some may have only brighter yellow or occasionally ochre or brownish eye color. Moulting starts between late March and late May, the male tends to moult later and faster than the female. Moulting results in the female being especially likely to have a gap in its wing feathers while incubating and this may cause some risk, especially if the male is lost, as it inhibits her hunting abilities and may hamper her defensive capabilities, putting both herself and the nestlings in potential danger of predation. The moult takes a total of 4–6 months, with tail feathers following the wings then lastly the contour and body feathers, which may not be completely moulted even as late as October.<p>Although existing wing size and body mass measurements indicate that the Henst's goshawk (Accipiter henstii) and Meyer's goshawk (Accipiter meyerianus) broadly overlap in size with this species, the Eurasian goshawk is on average the largest member of the genus Accipiter, especially outsizing its tropic cousins in the larger Eurasian subspecies. The Eurasian goshawk, like all Accipiters, exhibits sexual dimorphism, where females are significantly larger than males, with the dimorphism notably greater in most parts of Eurasia. Linearly, males average about 8% smaller in the North American species, and 13% smaller than females in Eurasia, but in the latter landmass can range up to a very noticeable 28% difference in extreme cases. Male Eurasian goshawks are 46 to 63 cm (18 to 25 in) long and have a 89 to 122 cm (35 to 48 in) wingspan. The female is much larger, 58 to 69 cm (23 to 27 in) long with a 108 to 127 cm (43 to 50 in) wingspan. Males average around 762 g (1.680 lb) in body mass, with a range from all races of 357 to 1,200 g (0.787 to 2.646 lb). The female can be up to more than twice as heavy, averaging from the same races 1,150 g (2.54 lb) with an overall range of 758 to 2,200 g (1.671 to 4.850 lb). Among standard measurements, the most oft-measured is wing chord which can range from 286 to 354 mm (11.3 to 13.9 in) in males and from 324 to 390 mm (12.8 to 15.4 in) in females. Additional, the tail is 200–295 mm (7.9–11.6 in), the culmen is 20–26.3 mm (0.79–1.04 in) and the tarsus is 68–90 mm (2.7–3.5 in).<p>Northern goshawks normally only vocalize during courtship or the nesting season. Adult goshawks may chatter a repeated note, varying in speed and volume based on the context. When calling from a perch, birds often turn their heads slowly from side to side, producing a ventriloquial effect. The male calls a fast, high-pitched kew-kew-kew when delivering food or else a very different croaking guck or chup. The latter sound has been considered by some authors similar to that of a person snapping the tongue away from the roof the mouth; the males produce it by holding the beak wide open, thrusting the head up and forward, then bringing it down as the sound is emitted, repeated at intervals of five seconds. This call is uttered when the male encounters a female. Two calls have been recorded mainly from brooding females in the race A. a. atricapillus: a recognition scream of short, intense notes (whee-o or hee-ya) which ends in harsh, falsetto tone; then a dismissal call given when the male lingers after delivering food, consisting of a choked, cut-off scream. Meanwhile, the adult female's rapid strident kek-kek-kek expresses alarm or intent to mob towards threatening intruders. This is often done when mobbing a predator such as a great horned owl (Bubo virginianus) and as it progresses the female's voice may lower slightly in pitch and becomes harsh and rasping. As the intensity of her attacks increases, her kakking becomes more rapid and can attain a constant screaming quality. Females often withdraw into the treetops when fatigued, and their calls are then spaced at longer intervals. Males respond to interlopers or predators with a quieter, slower gek gek gek or ep ep ep. A call consisting of kek...kek.kekk kek kek-kek-kek is used mainly by females in advertisement and during pre-laying mutual calling. Both sexes also may engage in kakking during copulation. Vocalizations mainly peak in late courtship/early nesting around late March to April, can begin up to 45 minutes before sunrise, and are more than twice in as frequent in the first three hours of daylight as in the rest of the day. Occasionally hunting northern goshawks may make shrill screams when pursuing prey, especially if a lengthy chase is undertaken and the prey is already aware of its intended predator.<p>The juvenile plumage of the species may cause some confusion, especially with other Accipiter juveniles. Unlike other northern Accipiters, the adult northern goshawk never has a rusty color to its underside barring. In Eurasia, the smaller male goshawk is sometimes confused with a female sparrowhawk, but is still notably larger, much bulkier and has relatively longer wings, which are more pointed and less boxy. Sparrowhawks tend to fly in a frequently flapping, fluttering type flight. Wing beats of northern goshawks are deeper, more deliberate, and on average slower than those of the Eurasian sparrowhawk. The classic Accipiter flight is a characteristic "flap flap, glide", but the goshawk, with its greater wing area, can sometimes be seen steadily soaring in migration (smaller Accipiters almost always need to flap to stay aloft). Rarely, in the southern stretches of its Asian wintering range, the northern goshawk may live alongside the crested goshawk (Accipiter trivirgatus) which is smaller (roughly Cooper's hawk-sized) and has a slight crest as well as a distinct mixture of denser streaks and bars below and no supercilia.

Taxonomía

The genus Accipiter contains nearly 50 known living species and is the most diverse genus of diurnal raptors in the world. This group of agile, smallish, forest-dwelling hawks has been in existence for possibly tens of millions of years, probably as an adaptation to the explosive numbers of small birds that began to occupy the world's forest in the last few eras. The harriers are the only group of extant diurnal raptors that seem to bear remotely close relation to this genus, whereas buteonines, Old World kites, sea eagles and chanting-goshawks are much more distantly related and all other modern accipitrids are not directly related.<p>Within the genus Accipiter, the Eurasian goshawk seems to belong to a superspecies with other larger goshawks from different portions of the world. The American goshawk, found in North America, was previously considered conspecific with Eurasian goshawk, formed the species complex "northern goshawk". Meyer's goshawk, found in the South Pacific, has been posited as the most likely to be the closest related living cousin to the Eurasian goshawk, the somewhat puzzling gap in their respective ranges explained by other Palearctic raptors such as Bonelli's eagles (Aquila fasciata) and short-toed eagles (Circaetus gallicus) that have extant isolated tropical island populations and were probably part of the same southwest Pacific radiation that led to the Meyer's goshawk. A presumably older radiation of this group may have occurred in Africa, where it led to both the Henst's goshawk of Madagascar and the black sparrowhawk (Accipiter melanoleucus) of the mainland. While the Henst's goshawk quite resembles the northern goshawks, the black sparrowhawk is superficially described as a "sparrowhawk" due to its relatively much longer and finer legs than those of typical goshawks but overall its size and plumage (especially that of juveniles) is much more goshawk than sparrowhawk-like.<p>Outside of the presumed superspecies, the genus Erythrotriorchis may be part of an Australasian radiation of basal goshawks based largely on their similar morphology to northern goshawks.<p>The term goshawk comes from the Old English gōsheafoc, "goose-hawk".<p>The northern goshawk appears to have diversified in northern, central Eurasia and spread both westwards to occupy Europe and, later on, eastwards to spread into North America across the Bering Land Bridge. Fossil remains show that goshawks were present in California by the Pleistocene era. Two non-exclusive processes could have occurred to cause the notably color and size variation of northern goshawks throughout its range: isolation in the past enabled gene combinations to assort as distinct morphs that suited conditions in different geographical areas, followed by a remixing of these genotypes to result in clines, or subtle variation in modern selection pressures led to a diversity of hues and patterns. As a result of the high variation of individual goshawks in plumage characteristics and typical trends in clinal variation and size variations that largely follow Bergmann's rule and Gloger's rule, an excessive number of subspecies have been described for the northern goshawk in the past. In Europe (including European Russia) alone, 12 subspecies were described between 1758 and 1990. Most modern authorities agree on listing nine to ten subspecies of northern goshawks from throughout its range.

Nombre científico

Astur gentilis

Autoridad

(Linnaeus, 1758)

Orden

Accipitriformes

Familia

Accipitridae

Género

Astur

Distribución y hábitat

The Eurasian goshawk is distributed in Eurasia. It is found in most areas of Europe excluding Ireland and Iceland. It has a fairly spotty distribution in western Europe (e.g. Great Britain, Spain, France) but is more or less found continuously through the rest of the continent. Their Eurasian distribution sweeps continuously across most of Russia, excluding the fully treeless tundra in the northern stretches, to the western limits of Siberia as far as Anadyr and Kamchatka. In the Eastern Hemisphere, they are found in their southern limits in extreme northwestern Morocco, Corsica and Sardinia, the "toe" of Italy, southern Greece, Turkey, the Caucasus, Sinkiang's Tien Shan, in some parts of Tibet and the Himalayas (India and Nepal), western China and Japan. In winter, Eurasian goshawks may be found rarely as far south as Taif in Saudi Arabia and perhaps Tonkin, Vietnam.<p>Vagrants have been reported in Alaska in the United States, Newfoundland in Canada, Ireland, North Africa (central Morocco, northern Algeria, Tunisia, Libya, Egypt); the Arabian Peninsula (Israel, Jordan, Saudi Arabia), southwest Asia (southern Iran, Pakistan), western India (Gujarat) and on Izu-shoto (south of Japan) and the Commander Islands. <p>It is also the state animal of Punjab, India. Eurasian and American goshawks can be found in both deciduous and coniferous forests. While the species might show strong regional preferences for certain trees, they seem to have no strong overall preferences nor even a preference between deciduous or coniferous trees despite claims to the contrary. Compared to American goshawk, the Eurasian goshawks especially in central Europe, may live in fairly urbanized patchworks of small woods, shelter-belts and copses and even use largely isolated trees in central parts of Eurasian cities. Even if they are far more wary of human presence than the Eurasian sparrowhawk, Eurasian goshawks are known to live in some relatively densely wooded areas of large cities of Central Europe, such as Berlin and Hamburg; it is a relatively new phenomenon that started in the 20th century.<p>The Eurasian goshawk can be found at almost any altitude, but recently is typically found at high elevations due to a paucity of extensive forests remaining in lowlands across much of its range. Altitudinally, goshawks may live anywhere up to a given mountain range's tree line, which is usually 3,000 m (9,800 ft) in elevation or less. The northern limit of their distribution also coincides with the tree line and here may adapt to dwarf tree communities, often along drainages of the lower tundra. In winter months, the northernmost or high mountain populations move down to warmer forests with lower elevations, often continuing to avoid detection except while migrating. A majority of goshawks around the world remain sedentary throughout the year.

Migración

Complete migrants

Comportamiento

The northern goshawk is always found solitarily or in pairs. This species is highly territorial, as are most raptorial birds, maintaining regularly spaced home ranges that constitute their territory. Territories are maintained by adults in display flights. During nesting, the home ranges of goshawk pairs are from 600 to 4,000 ha (1,500 to 9,900 acres) and these vicinities tend to be vigorously defended both to maintain rights to their nests and mates as well as the ranges' prey base. During display flight goshawks may engage in single or mutual high-circling. Each sex tends to defend the territory from others of their own sex. Territorial flights may occur throughout most of the year, but peak from January to April. Such flights may include slow-flapping with exaggerated high deep beats interspersed with long glides and undulations. In general, territorial fights are resolved without physical contact, often with one (usually a younger bird seeking a territory) retreating while the other approaches in a harrier-like warning flight, flashing its white underside at the intruder. If the incoming goshawk does not leave the vicinity, the defending goshawk may increase the exaggerated quality of its flight including a mildly undulating wave-formed rowing flight and the rowing flight with its neck held in a heron-like S to elevate the head and maximally expose the pale breast as a territorial threat display. Territorial skirmishes may on occasion escalate to physical fights in which mortalities may occur. In actual fights, goshawks fall grappling to the ground as they attempt to strike each other with talons.<p>Although at times considered rather sedentary for a northern raptor species, the northern goshawk is a partial migrant. Migratory movements generally occur between September and November (occasionally extending throughout December) in the fall and February to April in the spring. Spring migration is less extensive and more poorly known than fall migration, but seems to peak late March to early April. Some birds, up to as far north as northern Canada and central Scandinavia, may remain in their territory throughout the winter. Northern goshawks from northern Fennoscandia have been recorded traveling up to 1,640 km (1,020 mi) away from first banding but adults are seldom recorded more than 300 km (190 mi) from their summer range. In Sweden, young birds distributed an average of 377 km (234 mi) in the north to an average of 70 km (43 mi) in the south. In northern Sweden, young generally disperse somewhat south, whereas in south and central Sweden, they are typically distributed to the south (but not usually across the 5-km Kattegat straits). On the other hand, 4.3% of the southern Swedish goshawks actually moved north. Migrating goshawks seem to avoid crossing water, but sparrowhawks seem to do so more regularly. In central Europe, few birds travel more than 30 km (19 mi) throughout the year, a few juveniles have exceptionally been recorded traveling up to 300 km (190 mi). In Eurasia, very small numbers of migratory northern goshawks cross the Strait of Gibraltar and Bosporus in autumn but further east more significant winter range expansions may extend from northern Iran &amp; southern Turkmenia to Aral &amp; Balkhash lakes, from Kashmir to Assam, extreme northwestern Thailand, northern Vietnam, southern China, Taiwan, Ryukyu Islands and South Korea.

Conservación

Tendencia poblacional

unknown