Northern goshawks are the largest species of the genus Accipiter. Males generally weigh between 630 and 1100 grams, average 55 cm in length, and have a wingspan ranging from 98 to 104 centimeters. Females are slightly larger, weighing, on average, between 860 and 1360 grams, and having a wingspan of 105 to 115 centimeters and an average length of 61 cm. (Squires and Reynolds, 1997)
Northern goshawks have a white grouping of feathers above the eye. These feathers are more pronounced in northern goshawks than in other members of the group to which they belong, the accipiters. The eye color of adult goshawks is red to reddish-brown, in juveniles eye color is bright yellow. (Squires and Reynolds, 1997)
Adult male and female goshawks range in color from blue-gray to black. Their backs, the tops of their wings, and their heads are usually dark, and their undersides are usually white with light gray horizontal bands. Their tails are light gray and have three or four dark bands. (Squires and Reynolds, 1997)
Young goshawks don't look like their parents. Their backs, the tops of their wings, and their heads are brown, and their undersides are white with vertical brown stripes. (Clark and Wheeler, 1987; Johnsgard, 1990; Wheeler and Clark, 1995)
Northern goshawks are found throughout the mountains and forests of North America and Eurasia. In North America they range from western central Alaska and the Yukon territories in the north to the mountains of northwestern and western Mexico. They are typically not found in the southeastern United States. (Clark and Wheeler, 1987; Johnsgard, 1990)
Northern goshawks can be found in coniferous and deciduous forests. During their nesting period, they prefer mature forests consisting of a combination of old, tall trees with intermediate canopy coverage and small open areas within the forest for foraging. During the cold winter months they migrate to warmer areas, usually at lower elevations. (Johnsgard, 1990; Squires and Reynolds, 1997)
When trying to find a mate, female goshawks will attract males in the area by performing "sky dances" and calling, or by perching in the nesting area and calling. Once she finds a mate, the two goshawks will build a new nest or rebuild an old nest. During this time they will try to mate many times a day.
Northern goshawks breed once per year between early April and mid-June. A mating pair of northern goshawks begins to prepare their nest as early as two months before laying eggs. Typically, the nest is located in an old growth forest, near the trunk of a medium to large tree and near openings in the forest such as roads, swamps, and meadows. Their nests are usually about one meter (39.4 inches) wide and one-half to one meter (19.7 to 39.4 inches) high, and are made of dead twigs, and lined with leafy green twigs or bunches of conifer needles and pieces of bark. (Squires and Reynolds, 1997)
The female goshawk lays two to four eggs, two to three days apart. The eggs are rough textured, bluish-white, 59 milimeters long and 45 milimeters wide. The eggs begin to hatch within 28 to 38 days of laying. Incubation of the eggs is mostly done by the female, but the male will sometimes take her place to allow the her to hunt and eat. Nestlings stay at the nest until they are 34 to 35 days old, when they begin to move to nearby branches in the same tree. They may begin to fly when they are 35 to 46 days old. Juvenile fledglings may be fed by their parents until they are about 70 days old. (Squires and Reynolds, 1997)
Female goshawks do the majority of egg incubation, but occasionally males will incubate the eggs to allow the female to hunt and eat. After the clutch has hatched, the female will not leave the nesting area until the nestlings are 25 days old. During this time the male is the primary provider of food for the female and her nestlings. When the nestlings reach 25 days old, the female will leave them for periods of time to hunt with the male. (Baicich and Harrison, 1997; Johnsgard, 1990; Squires and Reynolds, 1997)
When nestling goshawks reach 35 to 42 days old, they begin to move to branches close to the nest. Soon after this, practice flights begin to occur. Often fledglings participate in "play" which is thought to allow them to practice hunting skills which will be needed throughout their lives.
Young goshawks leave the nest about 34 or 35 days after hatching. They usually stay in the area of the nest until their feathers are completely developed. This happens about 70 days after they hatch. Most goshawks are completely independent by the time they are 95 days old. (Johnsgard, 1990; Squires and Reynolds, 1997)
Young goshawks reach sexual maturity as early as one year after hatching. (Squires and Reynolds, 1997)
There is little data on life span and survival of goshawks. One study found that the average length of survival for northern goshawks is about 10.7 months. Maximum lifespan is believed to be at least 11 years. Females have a higher rate of survival, mainly due to their larger size, which gives them an advantage during the winter months. (Squires and Reynolds, 1997)
Most goshawks remain in the same area throughout their lives. Only the goshawks that breed in the northern and northwestern parts of North America migrate. They fly south for the winter and then return home in the spring. (Johnsgard, 1990; Squires and Reynolds, 1997)
Northern goshawks live alone or in pairs and are diurnal.
The home ranges of male goshawks are generally larger than those of females. Home ranges often overlap, except for exclusive nesting areas. During nesting, home range sizes range between 570 and 3500 hectares. (Squires and Reynolds, 1997)
Goshawks, like other accipiters, depend upon vocalizations for communication in their forested habitats. They are especially vocal during courtship and nesting. Both sexes make equally varied sounds, however, the female's sounds are deeper and louder, while male goshawks tend to have higher and less powerful voices. There are also several specific calls, or wails, given by goshawks. (Squires and Reynolds, 1997)
As nestlings, young goshawks may use a "whistle-beg" call as a plea for food. It begins as a ke-ke-ke noise, and progresses to a kakking sound. The chick may also use a high pitched "contentment-twitter" when it is well fed. (Squires and Reynolds, 1997)
As adults, goshawks vocalize by way of wail-calls, which consist of "ki-ki-ki-ki" or "kak, kak, kak". This call varies with the action it represents. A "recognition-wail" is made by both males and females when entering or leaving the nest. A "food-transfer" call, which is harsh sounding, is made by males to demand food from the female. (Squires and Reynolds, 1997)
Northern goshawks also use postures and other physical cues to communicate.
Northern goshawks are carnivores. Their main prey are birds, mammals, invertebrates, and reptiles. Individual prey can weigh up to half the weight of the goshawk. Each individual goshawk preys on what is most available in its environment. The average diet consists of 21 to 59 percent mammals and 18 to 69 percent birds, with the remaining percentages being made up of reptiles and invertebrates. Some common prey include snow-shoe hares, red squirrels, ground squirrels, spruce grouse, ruffed grouse, and blue grouse.
Northern goshawks sometimes save prey on tree branches or a crotch of a tree for up to 32 hours. This is usually only done by adults while their chicks are nestlings. (Johnsgard, 1990; Squires and Reynolds, 1997)
There are few natural predators of goshawks. Great horned owls, hawks and eagles, martens, eagle owls, and wolves, have been known to prey upon goshawks, particularly nestlings, during times of low food availability. (Squires and Reynolds, 1997)
Northern goshawks are formidable birds and will attack trespassers in their nesting territories. (Squires and Reynolds, 1997)
Northern goshawks are important as predators in the ecosystems in which they live, especially to small mammal and bird populations. They are also host to internal and external parasites, including lice, cestods and trematodes. (Squires and Reynolds, 1997)
Because northern goshawks are threatened in some areas, conservation measures to protect them may negatively impact the logging industry. (Squires and Reynolds, 1997)
Northern goshawks have been used for centuries in falconry. More importantly, northern goshawks help to control populations of small mammal pests.
While not endangered, northern goshawks are listed in Appendix II of the CITES agreement, which means that they can be traded between countries under certain circumstances, but would be threatened by uncontrolled trade. Northern goshawks are also protected under the Migratory Bird Treaty Act. (Weidensaul, 1996)
Timber harvesting is a major threat to northern goshawk populations. In recent years, several states such as Michigan, Washington and Idaho have listed northern goshawks as a Species of Concern and have increased conservation efforts focused on these birds. (Squires and Reynolds, 1997; Weidensaul, 1996)
Northern goshawks are considered "management indicators" in many national forests. They are considered "sensitive to change", and their well being often can provide clues to problems with habitat change.
Lauren Pajerski (author, editor), Undergraduate Research Opportunity Program, University of Michigan, George Starr Hammond (editor), Museum of Zoology, University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web, Kari Kirschbaum (editor), Animal Diversity Web.
Baicich, P., C. Harrison. 1997. A Guide to the Nests, Eggs and Nestlings of North American Birds. San Diego: Academic Press Limited.
Clark, W., B. Wheeler. 1987. Peterson Field Guides, Hawks. Boston: Houghton Mifflin Company.
Johnsgard, P. 1990. Hawks, Eagles, & Falcons of North America. Washington: Smithsonian Institution Press.
Squires, J., R. Reynolds. 1997. Northern Goshawk. The Birds of North America, 298: 2-27.
Weidensaul, S. 1996. Raptors The Birds of Prey. New York: Lyons & Burford.
Wheeler, B., W. Clark. 1995. A Photographic Guide to North American Raptors. San Diego: Academic Press Limited.