Accipiter nisus
Eurasian sparrowhawk

The ideal habitat for Eurasian sparrowhawks is in dense cover next to an open hunting ground, and often near a stream or river. However, habitats can include parks, agricultural fields and other open areas as well. They live in various wooded areas, but prefer conifers or mixed woodlands. Eurasian sparrowhawks can also be found in pure broadleaf forests or in scrub forests. Breeding habitats range from extensive forests to clearings, valleys, high wooded slopes, and broken woodlands. During the winter, migratory populations can be found in various diverse habitats, and are more widely distributed in open areas without trees. (Ferguson-Lees and Christie, 2001; Harrison and Greensmith, 1993)

Eurasian sparrowhawks are one of the smallest diurnal raptors in Europe, and exhibit sexual dimorphism with females much larger than males. Adult males weigh 110 to 196 g and adult females weigh 185 to 342 g. Wingspan ranges from 59 to 64 cm in males, and from 67 to 80 cm in females. Males are between 29 and 34 cm long, while females are between 35 and 41 cm. (Ferguson-Lees and Christie, 2001; Harrison and Greensmith, 1993; Kelly and Bland, 2006)

Accipiter nisus has a small head, slim body, and relatively short wings combined with a long tail that is squared or notched at the tip. These characteristics allow for maneuverability and speed. This species also possesses long legs and a sharply hooked beak, which is used for plucking feathers and pulling prey apart. The male is dorsally gray-blue, while ventrally it exhibits fine red bars. Females are dorsally brown or gray-brown, and brown barred ventrally. Additionally, females have a pale spot on the nape behind the head. Juveniles resemble females but are brown above, with brown barring or spotting ventrally. (Ferguson-Lees and Christie, 2001; Harrison and Greensmith, 1993; Kelly and Bland, 2006)

Pairs of Eurasian sparrowhawks are monogamous during each breeding season, but may change mates from year to year. Typically, males attract females through aerial display or by diving at females perched in trees or on branches. Populations of sparrowhawks consist of territorial breeding pairs and non-territorial non-breeding individuals, which are called floaters. Floaters are unable to acquire nesting territory because of the defensive behavior of established nesting pairs. However, it has been shown through removal studies that when breeding pairs vacate their territory, the nesting area is quickly inhabited by a floater. The floater may then breed in the same year. (Newton and Marquiss, 1982; Newton and Rothery, 2001; Petty, et al., 1995; Reid, 1988)

Breeding pairs often stay together from year to year and return to the same nesting area, although they build a new nest each year. Several factors such as food supply and breeding success contribute to whether or not a pair will remain together or return to the same territory. It is less likely that a breeding pair will return in subsequent years in poor territories with a limited food supply. Unsuccessful breeding pairs are less likely to remain together for another year, while older pairs that have successfully bred are more likely to stay together. The two members of a breeding pair are often of a similar age. This could be due to natural preference or a limited number of unpaired older birds. Factors such as breeding success and mortality affect pair composition and long term monogamous pairings. (Newton and Marquiss, 1982; Newton and Rothery, 2001; Petty, et al., 1995; Reid, 1988)

Every year, breeding pairs of Eurasian sparrowhawks breed in early spring and lay eggs between late April and early June. Pairs that lay their eggs earlier in the season produce more young than pairs that lay later in the season. Additionally, pairs that have access to the most abundant supply of food or are better hunters are able to produce the earliest and the largest clutches of eggs. Pairs that have limited access to food or are inferior hunters lay smaller clutches later in the season and are more apt to desert their eggs. (Ferguson-Lees and Christie, 2001; Newton and Marquiss, 1984)

The ability to successfully breed is directly related to the body weight of the female. The body weight of the female depends upon food supply, and this is correlated with an efficient male hunter. Females who gain more weight early in the season are able to lay their eggs earlier. On average, females lay four to five eggs per year, and it takes 33 days of incubation for the eggs to hatch. Nestlings weigh an average 20 grams at hatching. After hatching there are 24 to 30 days until fledging, and another 20 to 30 days before independence. (Ferguson-Lees and Christie, 2001; Newton and Marquiss, 1984)

Breeding success is also highly correlated with the age of the female. In females, almost all aspects of breeding improve with age, including clutch size and number of surviving offspring. However at some point, breeding success peaks and then begins to slowly erode with further age.

Typically, both males and females reach sexual maturity in one to three years. (Newton and Rothery, 2002)

The platform, stick nest is constructed primarily by the male. Following hatching, the altricial chicks are cared for by the female and fed food provided by the hunting male. As the chicks grow and more food is needed, the hen is often also forced to hunt in order to create an additional source of food. Approximately 26 days after hatching the young are able to leave the nest, and begin perching and learning to fly. After another 26 days the parents stop provisioning their young with food, which forces them to become independent and forage on their own. Most mortality in young occurs within three days of hatching and most deaths are due to young being dragged out of the nest by the hen. Also, some downy chicks may die of starvation, perhaps due to competition with other chicks or from a lack of food provided by the parents. (Newton and Marquiss, 1981; Newton and Moss, 1984; Newton, 1976)

In addition to caring for the young, the female sparrowhawk defends the nest from intrusions by other sparrowhawks and from predators. Northern goshawks sometimes attempt to prey upon sparrowhawk chicks, but the female is often able to successfully protect the nest. (Vedder and Dekker, 2004)

The oldest recorded Eurasian sparrowhawk was a banded twenty year old individual found in Denmark. Typically, sparrowhawks live for three to four years, but this average is skewed due to fledgling mortality. The highest rate of mortality occurs in young males. This is due to their small size early in life, which limits hunting range and size of prey. Smaller prey means that young males cannot go as long between meals, and this leads to a higher rate of mortality. (Kelly and Bland, 2006; Newton and Moss, 1984)

Accipiter nisus is generally secretive and solitary except when living as a nesting pair. Individuals live either in a monogamous breeding pair or as solitary non-breeding individuals. Breeding pairs defend their nesting territory from intrusions from other A. nisus. Generally, this species nests in trees and hunts in woodlands where it is able to catch its prey unawares. It is normally found perched upright and under cover, but is sometimes more exposed. High circling is often observed as a preamble to hunting.

The flight stroke of this species is characterized by a flap, flap, glide motion, which results in fast beats and short glides. (Ferguson-Lees and Christie, 2001; Gotmark and Post, 1996; Reid, 1988)

The range of A. nisus depends upon several factors including food availability, food needs, and breeding considerations. In general, ranges are larger in habitats where food is more scarce, or when more food is necessary (when feeding young). The center of a bird's home range is its nest; however, non-breeding individuals are not restricted to roosts or specific nest areas. For mated pairs, range varies throughout the year. Ranges are smallest when the nest has to be attended, that is, from before the laying of eggs to the brooding period. In general, females exhibit a larger range than males, but females are more sedentary when attending to the nest. Ranges have been recorded up to 3500 ha. (Ferguson-Lees and Christie, 2001; Harrison and Greensmith, 1993; Marquiss and Newton, 1982)

Eurasian sparrowhawks are often silent when away from the nest, however, they may call to contact other members of their species. A call is also used when birds are threatened by a territorial intruder or humans. A softer call is used when bringing in prey or calling to another member of the species that is the opposite sex. The main call varies in speed based upon circumstances and is described as a shrill cackling. Females use a distinctive call when a male is bringing them food.

Males may perform a sky dance in the presence of females in order to attract a mate. This includes shallow and deep dives, upward swings, and high circling. Also, males may dive at females who are perched or flying to gain attention during the mating season. (Ferguson-Lees and Christie, 2001)

Sparrowhawks exhibit exceptional eyesight which is instrumental in capturing its characteristically small and quick prey. Excellent eyesight is achieved through an abundance of rods and cones; more sensory cells means better vision. Accipiter nisus also possesses binocular vision which allows for excellent depth perception, and it can see in color which helps with identification of prey. Eurasian sparrowhawks possess a limited sense of smell, but an acute sense of taste is used to detect foods that could possibly be harmful. Also, a sense of hearing is used to sense auditory calls made by members of the same species, and tactile senses are used when catching prey animals. Like all birds, Eurasian sparrowhawks perceive their environments through audio, visual, tactile and chemical stimuli. (Ferguson-Lees and Christie, 2001; Gotmark and Post, 1996)

Accipiter nisus is a carnivore that subsists on animal prey, which can consist of up to 97% small birds, but also can include mammals such as young rabbits, voles, shrews, squirrels, and other small animals. Occasionally, lizards and amphibians are taken. Very rarely, insects and carrion are also eaten. Eurasian sparrowhawks prey upon all ages of birds. The most common bird prey are ground feeders such as finches, warblers, thrushes, and robins. However, most resident small birds can be prey. Juvenile hawks have been shown to prey predominantly on fledgling birds, but the overall diet is similar to that of adults. (Ferguson-Lees and Christie, 2001; Gotmark and Post, 1996; Kelly and Bland, 2006)

Usually, the larger game birds are reserved for females who can capture prey up to 150 g, while males hunt smaller prey up to 40 g. However, the primary hunter during the nesting period is usually the male sparrowhawk, which provides food for its mate and offspring. Prior to egg laying, the male catches food for his mate up until the time when the young demand more food, and at this point the female also begins to hunt. Typically, males hunt in the woods under more cover while females hunt in more wide open areas. (Ferguson-Lees and Christie, 2001; Gotmark and Post, 1996)

Sparrowhawks use a plucking post that is about 30 m from the nest. This is usually a log or stump where the prey's feathers are removed. Primary hunting habitats are deciduous forests, forest edges, and semi-open areas including farms and villages. When hunting, A. nisus remains hidden at a perch or moves from perch to perch until its prey draws close. The hawk then breaks from cover and chases and captures its prey by flying fast and low to the ground. A. nisus makes frequent hunting visits to an area when a profitable prey source is identified. (Ferguson-Lees and Christie, 2001; Gotmark and Post, 1996)

Accipiter nisus has few predators; however, northern goshawks have been known to attack nests in order to prey on nestling sparrowhawks. In these situations, the mother sparrowhawk has been observed to successfully defend the nest from attack while the male observes and sometimes makes distress calls. (Vedder and Dekker, 2004)

Accipiter nisus is a major predator of small birds and mammals in its habitat, and serves to regulate the populations of its prey species. A. nisus is a host for several blood parasites including Leucocytozoon toddi, species of the genus Haemoproteus, and of the genus (Plasmodium). (Gotmark and Post, 1996)

Accipter nisus preys on small mammals that are sometimes harmful to agriculture. (Gotmark and Post, 1996)

Accipiter nisus often comes into conflict with humans because it preys on popular bird populations, especially game birds, songbirds, and racing pigeons. However, its effect on pigeons and songbirds is often exaggerated. Eurasian sparrowhawks preying upon bird populations has led to the conscious destruction of sparrowhawk populations by landowners and gamekeepers. However, because of the high number of non-breeding individuals the sparrowhawk population has been able to recover quickly. (Holloway, 1996; Newton, et al., 1977)

Under the IUCN Red list A. nisus is classified as being of least concern. This species is one of Eurasia's six most common and widespread raptors. Populations are stable or increasing in most parts of Europe in spite of human persecution by hunters and landowners, and the use of pesticides. During the 1950's and 1960's the use of pesticides such DDT led to a catastrophic crash in populations. DDT causes the shells of eggs to be too thin, which results in eggs breaking during incubation. Also, overdoses of pesticides led to deaths in many individuals, but a ban on harmful pesticides as well as a more enlightened public attitude toward sparrowhawks has led to a recovery. The population is now estimated to exceed one million breeding pairs worldwide, in addition to many non-breeding individuals. In England, population densities have been measured to be from 10 to 72 pairs per 100 square kilometers. Populations worldwide are now viewed as stable and Eurasian sparrowhawks currently face no major threats. (Ferguson-Lees and Christie, 2001; Holloway, 1996)

There are six recognized subspecies of A. nisus. They are A. nisus nisus, A. nisus nisomilis, A. nisus melaschistos, A. nisus wolterstorff, A. nisus granti, and A. nisus punicus. (Ferguson-Lees and Christie, 2001)