The Northern Goshawk tends to remain close to forest cover where it can be seen coursing through open forest, crossing clearings, or soaring along mountain slopes. Like all accipiters, it is a "sit and wait" predator that perches in a concealed place, then dashes out quickly to capture its prey. It tends to hunt prey on the ground or in the lower canopy. When hunting prey on the ground, such as grouse, it courses low, alternating rapid wingbeats and glides, through open forest, using brush, hedgerows, and trees to conceal its approach. It attacks ferociously and will pursue prey through the thickest cover. It hunts only during daylight hours. It grasps prey with its powerful talons, usually killing the prey on impact or repeatedly grasping its victim until it finds vital organs. Prey is carried to a traditional plucking perch, where it is plucked and torn apart. Plucking posts are often within 160 feet (50 meters) of the nest during the breeding season.
On sunny days it often soars in thermals, like buteo hawks and eagles. During migration it uses thermals to gain altitude before flying off.
In the fall, the Northern Goshawk migrates between August and November, although some populations are resident. It tends to move as single birds and follows coastlines, lakeshores, and mountain ranges. Immatures tend to move southward earlier than adults. The extent of migration depends on prey availability. Northern populations may move "en masse" southwards during years with low snowshoe hare numbers, but remain relatively sedentary during years of high hare numbers. These southward incursions occur every few years, on average between nine and eleven years. The return spring movement occurs from late February through early May.
The Northern Goshawk is widely, but thinly distributed. Breeding pairs require relatively extensive tracts of habitat compared to other hawks. Breeding home ranges for pairs in different habitats ranged from 1.2 square miles (212 hectares) to 5 square miles (13 square kilometers). Densities of breeding pairs are higher in broken forests with more edge habitat than in deep, continuous forest. The estimated life span in the wild is about 20 years. Mortality rates are quite high in the first year, about 80 percent from all causes, then declining to about 40 percent annually thereafter. Starvation and illegal shooting is the leading cause of mortality. Some adults and young are killed at the nest by Great Horned Owls.
Courtship behavior is similar to other accipiters. Males establish territories, then try to attract females by soaring in broad circles over treetops with tail closed and undertail coverts flared. Males perform a "sky dance" by circling high in slow, undulating flight, then plunging into the trees. Slow speed display flights occur where both birds fly slowly with exaggerated wingbeats interspersed with glides with the wings held in a dihedral.
This hawk aggressively defends its nest site from predators and will strike large mammals, and even humans, who venture too close.
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Sexual size dimorphism (females larger than males) may have evolved to increase food supplies available to pairs during the breeding season, as in the other accipiters. The larger female tends to capture larger prey and the smaller male tends to capture smaller prey. In this way, mates do not compete for the same prey source, and can provide more food for their young.
This hawk is adapted for the quick pursuit of medium-sized forest birds and mammals. Their powerful wings and long tail allow for speed and maneuverability in dense forests.
