The Northern Goshawk

The northern goshawk, known by its scientific name accipiter gentilis, is a medium-to-large raptor in the family accipitridae, which are raptors active in the daytime, such as eagles, buzzards and harriers.
Considered a “true hawk,” the northern goshawk has relatively short, broad wings and a long tail, common to raptors that require maneuverability within forest habitats. For an acipiter, it has a relatively sizable bill, relatively long wings, a relatively short tail, robust and fairly short legs and particularly thick toes. Those found in California are blue-grey above or brownish-grey with dark barring or streaking over a grey or white base color below. These birds usually become paler as they age, manifesting in mottling and a lightening of the back from a darker shade to a bluer pale color. In North America, juveniles have pale-yellow eyes, and adults develop dark red eyes usually after their second year, although nutrition and genetics may affect eye color as well.
Molting starts between late March and late May.
The male tends to molt later and faster than the female. Molting 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 molt takes a total of four-to-six months, with tail feathers following the wings, then lastly the contour and body feathers, which may not be completely molted even as late as October.
The northern goshawk is on average the largest member of the genus accipiter. The northern 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 percent smaller in North America and 13 percent smaller than females in Eurasia, but in the latter landmass can range up to a very noticeable 28 percent difference in extreme cases. Male northern goshawks are 18 inches to 24 inches long and have a 35-inch to 41-inch wingspan. The female is much larger, 23 inches to 27 inches long, with a 43-inch to 50-inch wingspan. In a study of North American goshawks, males were found to average 22 inches in total length, against females which averaged 24 inches. Males from six subspecies average around 1.680 pounds in body mass, with a range from all races of 0.787 pounds to 2.646 pounds. The female can be up to more than twice as heavy, averaging from the same races 2.54 pounds with an overall range of 1.671 pounds to 4.850 pounds. Among standard measurements, the most oft-measured is wing chord which can range from 11.3 inches to 13.9 inches in males and from 12.8 inches to 15.4 inches in females.
Northern goshawks generally vocalize only 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 males produce it by holding the beak wide open, thrusting the head up and forward, than 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 from brooding females are known, a recognition scream of short, intense notes – whee-o or hee-ya – which ends in a 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 genders may also 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 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.
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 via display flights. During nesting, the home ranges of goshawk pairs are from 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. Each gender tends to defend the territory from others of their own gender.
Though somewhat sedentary for a northern raptor species, the northern goshawk is a partial migrant. Migratory movements generally occur between September and early December and February to April. Spring migration is less extensive, peaking in late March to early April.
Northern goshawks are opportunistic predators, targeting insects, fish, small to medium-sized mammals such as reptiles and amphibians, tree squirrels and ground squirrels, rabbits and hares among mammals and birds found in forests, edge and scrub habitats, extending to corvids, pigeons, doves, woodpeckers, ducks, grouse and cormorants.
Males construct most new nests but females may assist somewhat if reinforcing old nests. Trees used for nesting include spruce, fir, larch, pine and hemlock. Broadleaf trees used include ash, alder, aspen, beech, birch, elm, hickory, hornbeam, lime, maple, sycamore, oak, poplar, tamarack, wild cherry and willow. While the male is building, the female perches in the vicinity, occasionally screaming, sometimes flying to inspect the nest.
Eggs are laid at 2-to-3-day intervals on average between April and June, most usually May, taking up to 9 days for a clutch of 3–4 and 11 days for a clutch of 5. The eggs are rough, unmarked pale bluish or dirty white. During incubation, females tend to become quieter and more inconspicuous. The mother can develop a brooding patch of up to 5.9 inches by 2 inches on her underside. She may turn the eggs as frequently as every 30 to 60 minutes. Males may incubate as many as 1 to 3 hours, but usually less than an hour, early in incubation but rarely do so later on. During daylight, females can do as much as 96 percent of the observed incubation. The incubation stage lasts for any time between 28 and 37 days, though rarely up to 41 days in exceptionally big clutches. After hatching occurs, the male does not come directly to the nest but instead just delivers food, usually already plucked, beheaded or otherwise dismembered, to a branch near the nest which the female tears apart and shares between herself and the nestlings. Food deliveries by the male can be daily or as infrequent as every 3 to 5 days. In turn, the female must feed the young about twice a day in order for the chicks to avoid starvation. Caching of food has been recorded near the nest, but only before the young start feeding themselves
Accipiter in Latin means “hawk,” from accipere, “to grasp.” Gentilis is “noble” or “gentle.” In the Middle Ages only the nobility were permitted to fly goshawks for falconry.
This species was first described under its current scientific name by Linnaeus in his Systema naturae in 1758.
From Wikipedia,,

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