Eurasian goshawk

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Eurasian goshawk
Adult

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Accipiter
Species:
A. gentilis
Binomial name
Accipiter gentilis
Subspecies
  • Accipiter gentilis albidus
  • Accipiter gentilis arrigonii
  • Accipiter gentilis buteoides
  • Accipiter gentilis fujiyamae
  • Accipiter gentilis gentilis
  • Accipiter gentilis marginatus
  • Accipiter gentilis schvedowi (eastern goshawk)[2]
Range of A. gentilis
  Resident
  Non-breeding
Synonyms

Falco gentilis Linnaeus, 1758

The Eurasian goshawk (/ˈɡɒsˌhɔːk/; Accipiter gentilis) is a species of medium-large bird of prey in the family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harriers. As a species in the genus Accipiter, the goshawk is often considered a "true hawk".[3] The scientific name is Latin; Accipiter is "hawk", from accipere, "to grasp", and gentilis is "noble" or "gentle" because in the Middle Ages only the nobility were permitted to fly goshawks for falconry.[4]

This species was first described by Linnaeus in the 10th edition of his Systema naturae (1758) as Falco gentilis.[5]

It is a widespread species that inhabits many of the temperate parts of the

resident, but birds from colder regions migrate south for the winter.[6] As of 2023, the goshawks found primarily in North America are no longer considered Accipiter gentilis, but are now designated as the American goshawk (Accipiter atricapillus).[7]

Distribution

The Eurasian goshawk is distributed in

Tien Shan, in some parts of Tibet and the Himalayas (India and Nepal), western China and Japan.[6] In winter, Eurasian goshawks may be found rarely as far south as Taif in Saudi Arabia and perhaps Tonkin, Vietnam.[8]

Vagrants have been reported in Alaska in the United States, Newfoundland in Canada, Ireland,

southwest Asia (southern Iran, Pakistan), western India (Gujarat) and on Izu-shoto (south of Japan) and the Commander Islands.[6]

It is also the state animal of Punjab, India.[9]

Habitat

Adult goshawk showing its beak

Eurasian and American goshawks can be found in both

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.[3][6][10][11] 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.[12][13] 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.[14]

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.[6] 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.[15][16] 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.[17][18]

Description

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.

supercilia, which tends to be broader in northern Eurasian and North American birds.[6] 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.[6][8] 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.[8]

Although existing wing size and body mass measurements indicate that the

culmen is 20–26.3 mm (0.79–1.04 in) and the tarsus is 68–90 mm (2.7–3.5 in).[6][24][25][26]

Voice

Accipiter gentilis – Eurasian goshawk

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.[3][6] 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.[3][6][17] 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.[3] 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.[3][6][17][27][28] 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.[29] 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.[30]

Similar species

Juvenile in flight, the most likely age and condition to mistake a goshawk for another species
An adult goshawk shows its richly streaked plumage.

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.[8] 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.[31][32] 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).[6][33][34] 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.[6]

Taxonomy

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.[6][8]

Within the genus Accipiter, the Eurasian goshawk seems to belong to a

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.[36] 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.[8][36]

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.[37]

The term goshawk comes from the

Old English
gōsheafoc, "goose-hawk".

Subspecies

Typical adult with a strong brownish-gray cast, from the nominate subspecies, A. g. gentilis
A captive specimen of whitish large goshawk of Siberian origin, possibly part of A. g. albidus.

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

Bering Land Bridge. Fossil remains show that goshawks were present in California by the Pleistocene era.[38] 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.[8][39] 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.[8][40] Most modern authorities agree on listing nine to ten subspecies of northern goshawks from throughout its range.[6][17]

  • A. g. gentilis (Linnaeus, 1758) – The nominate race is distributed through most of the species current European range, excluding northern
    Asia Minor. It is a typically large subspecies, with high levels of sexual dimorphism. The wing chord of males ranges from 300 to 342 mm (11.8 to 13.5 in) and of females from 336 to 385 mm (13.2 to 15.2 in). Body mass is variable, range from 517 to 1,110 g (1.140 to 2.447 lb) in males and from 820 to 2,200 g (1.81 to 4.85 lb) in females. In some cases, the largest adult females (including some exceptionally big females which are the heaviest goshawks known from anywhere) from within a population are up to four times heavier than the smallest adult males, although this is exceptional.[6][23] The highest average weights come from central Fennoscandia, where the sexes weigh on average 865 g (1.907 lb) and 1,414 g (3.117 lb), respectively.[3] The lowest come from Spain, where goshawks of this race weigh a median of 690 g (1.52 lb) in males and 1,050 g (2.31 lb) in females.[41] The nominate race is generally a dark slaty-brown color on its back and wing coverts with a blackish-brown head. The supercilium is thin and the underside is generally creamy with heavy dark barring. On average, in addition to their smaller size, nominate goshawks to the south of the race's distribution have thinner supericilia and broader and denser barring on the underside.[6][40] An aberrant "isabelline" morph is known mainly from central and eastern Europe, where the goshawk may be a general beige color (somewhat similar to the pale birds from the races albidus and buteoides), but such birds appear to be very rare.[42][43]
  • A. g. arrigonii (Kleinschmidt, 1903) – This is an island race found on the Mediterranean isles of Sardinia and Corsica. It averages smaller and weaker-footed than goshawks from the nominate race. The wing chord measures 293 to 308 mm (11.5 to 12.1 in) in males and 335 to 347 mm (13.2 to 13.7 in) in females. This race is typically a more blackish brown above with almost fully black head, while the underside is almost pure white and more heavily overlaid with black barring and conspicuous black shaft-streaks. This subspecies is not listed by all authorities but is often considered valid.[6][44]
  • A. g. buteoides (
    Lena River. In the eastern portion of its distribution, many birds may travel south to central Asia to winter. This is a large race, averaging larger than most populations of the nominate race but being about the same size as the big nominate goshawks with which they may overlap and interbreed with in Fennoscandia. The wing chord in males ranges from 308 to 345 mm (12.1 to 13.6 in) while that of females ranges from 340 to 388 mm (13.4 to 15.3 in). The body mass of males has been reported from 870 to 1,170 g (1.92 to 2.58 lb), with an average of 1,016 g (2.240 lb), while that of females is reportedly 1,190 to 1,850 g (2.62 to 4.08 lb), with an average of 1,355 g (2.987 lb).[3][6] Usually, this race is an altogether paler colour than the nominate, being blue-grey above with a dusky-grey crown and a broad supercilium. The underside is white with rather fine blackish-brown barring. Pale flecking on the feather shafts sometimes result in barred appearance on the contour feathers of the nape, back and upper wing. Many birds from this subspecies also have a tan to pale brown eye color. These two characteristics are sometimes considered typical of this race, but individuals are rather variable. In western Siberia, about 10% of birds of this race are nearly pure white (similar to albidus) with varied indications of darker streaking.[6][8]
  • A. g. albidus (Menzbier, 1882) – This race of goshawk is found in northeastern
    Kamchatka. Many birds of this race travel south for the winter to Transbaikalia, northern Mongolia and Ussuriland. This race continues the trend for goshawks to grow mildly larger eastbound in Eurasia and may be the largest known race based on the midpoint of known measurements of this race, although limited sample sizes of measured goshawks shows they broadly overlap in size with A. g. buteoides and large-bodied populations of A. g. gentilis. The wing chord can range from 316 to 346 mm (12.4 to 13.6 in) in males and from 370 to 388 mm (14.6 to 15.3 in) in females. Known males have scaled from 894 to 1,200 g (1.971 to 2.646 lb) while a small sample of females weighed have had a body mass between 1,300 and 1,750 g (2.87 and 3.86 lb).[3][6] This is easily the palest race of northern goshawk. Many birds are pale grey above with much white about the head and very sparse barring below. However, about half of the goshawks of this race are more or less pure white, with at most only a few remnants of pale caramel flecking about the back or faint brownish markings elsewhere.[6][40][42]
  • A. g. schvedowi (Menzbier, 1882) – This race ranges from the
    Kuril islands. A. g. schvedowi averages smaller than the other races on the mainland of Eurasia, with seemingly the highest sexual dimorphism of any goshawk race, possibly as an adaptation to prey partitioning in the exceptionally sparse wooded fringes of the desert-like steppe habitat that characterizes this race's range. The wing chord has been found to measure 298 to 323 mm (11.7 to 12.7 in) in males and 330 to 362 mm (13.0 to 14.3 in) in females.[6] Body mass of 15 males was found to be merely 357 to 600 g (0.787 to 1.323 lb) with a mean of 501 g (1.105 lb), the lowest adult weights known for this species, while two adult females scaled 1,000 and 1,170 g (2.20 and 2.58 lb), respectively, or more than twice as much on average.[3][23] Beyond its smaller size, its wings are reportedly relatively shorter and feet relatively smaller and weaker than other Eurasian races.[45] In color, this race is typically a slate-grey above with a blackish head and is densely marked below with thin brown barring.[6][40]
  • A. g. fujiyamae (Swann & Hartert, 1923) – Found through the species' range in Japan, from the islands of Hokkaido south to the large island of Honshu, in the latter down to as far south as forests a bit north of Hiroshima. A fairly small subspecies, it may average slightly smaller than A. g. schvedowi linearly, but it is less sexually dimorphic in size and weighs slightly more on average. The wing chord is the smallest known from any race, 286 to 300 mm (11.3 to 11.8 in) in males and 302 to 350 mm (11.9 to 13.8 in) in females.[6] However, the weights of 22 males ranged from 602 to 848 g (1.327 to 1.870 lb), averaging 715 g (1.576 lb) while 22 females ranged from 929 to 1,265 g (2.048 to 2.789 lb), averaging 1,098 g (2.421 lb).[46] The coloration of this race is not dissimilar from A. g. schvedowi, but is still darker slate above and they tend to have heavier barring below, probably being the darkest race on average, rivaled only by the similar insular race from the opposite side of the Pacific, A. a. laingi.[6][40][46]

Behavior

Territoriality

Adult goshawks maintain territories with display flights.

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.[47] During display flight goshawks may engage in single or mutual high-circling.[6][48] Each sex tends to defend the territory from others of their own sex.[8] 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.[6] 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.[8][13][49]

Migration

Although at times considered rather sedentary for a northern raptor species, the northern goshawk is a

southern China, Taiwan, Ryukyu Islands and South Korea.[6][47][55]

Dietary biology

Hunting behavior

Goshawks are particularly agile hunters of the woodlands.

As typical of the genus Accipiter (as well as unrelated forest-dwelling raptors of various lineages), the northern goshawk has relatively short wings and a long tail which make it ideally adapted to engaging in brief but agile and twisting hunting flights through dense vegetation of wooded environments.

pigeons as prey and a largely urbanized environment in Germany explains the local prevalence of hunting from a soaring flight, as the urban environment provides ample thermals and obstructing tall buildings which are ideal for hunting pigeons on the wing.[61]

A juvenile goshawk beginning to pluck its prey, a likely rock dove

Northern goshawks rarely vary from their perch-hunting style that typifies the initial part of their hunt but seems to be able to show nearly endless variation to the concluding pursuit.

waterfowl).[28][63][64][65] Anecdotal cases have been reported when goshawks have pursue domestic prey into barns and even houses.[66]

Prey pursuits may become rather prolonged depending upon the goshawk's determination and hunger, ranging up to 15 minutes while harrying a terrified, agile

corvids was 63.8%.[8][71]

Prey spectrum

Northern goshawks most often prey on birds, especially in Eurasia

Northern goshawks are usually opportunistic predators, as are most

pigeons, grouse, pheasants, thrushes and woodpeckers (in roughly descending order of importance) among birds and squirrels (mainly tree squirrels but also ground squirrels) and rabbits and hares among mammals.[8][17][76]

Birds are usually the primary prey in Europe, constituting 76.5% of the diet in 17 studies. Studies have shown that from several parts of the Eurasian continent from

corvids and thrushes and then lastly to grouse, even though adults are also freely caught opportunistically for all these prey types.[8][79] This is fairly different from Vendsyssel, Denmark, where mostly adult birds were caught except for thrushes and corvids, as in these two groups, the goshawks caught mostly fledglings.[80]

Corvids

Overall, one prey family that is known to be taken in nearly every part of the goshawk's range is the corvids, although they do not necessarily dominate the diet in all areas. Some 24 species have been reported in the diet of Eurasian and American goshawks. The second most commonly reported prey species in breeding season dietary studies from Europe is the 160 g (5.6 oz)

Ural mountains (9% by number), the 245 g (8.6 oz) western jackdaw (Coloeus monedula) in Sierra de Guadarrama, Spain (36.4% by number), the 453 g (0.999 lb) rook (Corvus frugilegus) in the Zhambyl district, Kazakhstan (36.6% by number).[23][86][87][88][89] Despite evidence that northern goshawks avoid nesting near common ravens (Corvus corax), the largest widespread corvid (about the same size as a goshawk at 1,040 g (2.29 lb)) and a formidable opponent even one-on-one, they are even known to prey on ravens seldom.[8][23][78][90]

Pigeons and doves

Adult on Corsica with its fresh prey, a common wood pigeon

In

Germany-Netherlands border area (37.7% of 4125 prey items) and Wales (25.1% by number and 30.5% by biomass of total prey).[23][94][95] It has been theorized that male goshawks in peri-urban regions may be better suited with their higher agility to ambushing feral pigeons in and amongst various manmade structures whereas females may be better suited due to the higher overall speeds to taking out common wood-pigeons, as these typically forage in wood-cloaked but relatively open fields; however males are efficient predators of common wood-pigeons as well.[8][96] Studies have proven that, while hunting feral pigeons, goshawks quite often select the oddly colored pigeons out of flocks as prey, whether the plumage of the flock is predominantly dark or light hued, they disproportionately often select individuals of the other color. This preference is apparently more pronounced in older, experienced goshawks and there is some evidence that the males who select oddly-colored pigeons have higher average productivity during breeding.[97][98]

Gamebirds

Hawk and Black-Game (Bruno Liljefors, 1884), a painting of a goshawk at the moment of catching a black grouse

The Eurasian goshawk is in some parts of its range considered a specialized predator of gamebirds, particularly grouse. All told 33 species of this order have turned up in Eurasian and American goshawks' diet, including most of the species either native to or introduced in North America and Europe. Numerically, only in the well-studied taiga habitats of Scandinavia do grouse typically take a dominant position. Elsewhere in the range, gamebirds are often secondary in number but often remain one of the most important contributors of prey biomass to nests. With their general ground-dwelling habits, gamebirds tend to be fairly easy for goshawks to overtake if they remain unseen and, if made aware of the goshawk, the prey chooses to run rather than fly. If frightened too soon, gamebirds may take flight and may be chased for some time, although the capture rates are reduced considerably when this occurs. Pre-fledgling chicks of gamebirds are particularly vulnerable due to the fact that they can only run when being pursued.[3][8] In several parts of Scandinavia, forest grouse have historically been important prey for goshawks both in and out of the nesting season, principally the 1,080 g (2.38 lb) black grouse (Tetrao tetrix) and the 430 g (15 oz) hazel grouse (Bonasa bonasia) followed in numbers by larger 2,950 g (6.50 lb) western capercaillies (Tetrao urogallus) and the 570 g (1.26 lb) willow ptarmigan (Lagopus lagopus) which replace the other species in the lower tundra zone. The impression of goshawks on the populations of this prey is considerable, possibly the most impactful of any predator in northern Europe considering their proficiency as predators and similarity of habitat selection to forest grouse. An estimated 25-26% of adult hazel grouses in Finnish and Swedish populations in a few studies fall victim to goshawks, whereas about 14% of adult black grouse are lost to this predator. Lesser numbers were reportedly culled in one study from northern Finland. However, adult grouse are less important in the breeding season diet than young birds, an estimated 30% of grouse taken by Scandinavian goshawks in summer were neonatal chicks whereas 53% were about fledgling age, the remaining 17% being adult grouse.[8][23][99][100][101][102] This is fairly different from in southeastern Alaska, where grouse are similarly as important as in Fennoscandia, as 32.1% of avian prey deliveries were adults, 14.4% were fledglings and 53.5% were nestlings.[103]

Goshawks sometimes become habitual fowl killers. This juvenile was caught pursuing chickens inside a hen house.

Eurasian goshawks can show somewhat of a trend for females to be taken more so than males while hunting adult gamebirds, due to the larger size and more developed defenses of males (such as leg spurs present for defense and innerspecies conflicts in male of most pheasant species). Some authors have claimed this of male

ring-necked pheasant (Phasianus cochilus), but these trends are not reported everywhere, as in southern Sweden equal numbers of adult male and female ring-necked pheasants, both sexes averaging 1,135 g (2.502 lb), were taken.[8][23][104] While male goshawks can take black and hazel grouse of any age and thence deliver them to nests, they can only take capercaillie of up to adult hen size, averaging some 1,800 g (4.0 lb), the cock capercaillie at more than twice as heavy as the hen is too large for a male goshawk to overtake. However, adult female goshawks have been reported attacking and killing cock capercaillie, mainly during winter. These average about 4,000 g (8.8 lb) in body mass and occasionally may weigh even more when dispatched.[8][23][79][99][101] Similarly impressive feats of attacks on other particularly large gamebirds have been reported elsewhere in the range, including the 2,770 g (6.11 lb) Altai snowcock (Tetraogallus altaicus) in Mongolia[23][105] At the other end of the size scale, the smallest gamebird known to be hunted by northern goshawk was the 96 g (3.4 oz) common quail.[23][106] Domestic fowl, particularly chickens (Gallus gallus domesticus) are taken occasionally, especially where wild prey populations are depleted. While other raptors are at times blamed for large numbers of attacks on fowl, goshawks are reportedly rather more likely to attack chickens during the day than other raptors and are probably the most habitual avian predator of domestic fowl, at least in the temperate-zone. Particularly large numbers of chickens have been reported in Wigry National Park, Poland (4th most regular prey species and contributing 15.3% of prey weight), Belarus and the Ukraine, being the third most regularly reported prey in the latter two.[66][78][107][108]

In a study of British goshawks, the red grouse (Lagopus lagopus scotica), a race of willow ptarmigan, was found to be the leading prey species (26.2% of prey by number).[109] In La Segarra, Spain, the 528 g (1.164 lb) red-legged partridge (Alectoris rufa) is the most commonly reported prey species (just over 18% by number and 24.5% by weight).[23][106]

Squirrels

Among mammalian prey, indisputably the most significant by number are the squirrels. All told, 44 members of the

Sciuridae have turned up in their foods. Tree squirrels are the most obviously co-habitants with goshawks and are indeed taken in high numbers. Alongside martens, northern goshawks are perhaps the most efficient temperate-zone predators of tree squirrels. Goshawks are large and powerful enough to overtake even the heaviest tree squirrels unlike smaller Accipiters and have greater agility and endurance in pursuits than do most buteonine hawks, some of which like red-tailed hawks (Buteo jamaicensis) regularly pursue tree squirrels but have relatively low hunting success rates due to the agility of squirrels.[8][110] The 296 g (10.4 oz) red squirrel (Sciurus vulgaris) of Eurasia is the most numerous mammalian prey in European studies and the sixth most often recorded prey species there overall.[8][111] In Oulu, Finland during winter (24.6% by number), in Białowieża Forest, Poland (14.3%), in the Chřiby uplands of the Czech Republic (8.5%) and in Forêt de Bercé, France (12%) the red squirrel was the main prey species for goshawks.[112][113][114]

Hares and rabbits

Illustrating a goshawk attempting to catch a rabbit, by G. E. Lodge

Northern goshawks can be locally heavy predators of

Iberian peninsula, the native European rabbit (Oryctolagus cuniculus) is often delivered to nests and can be the most numerous prey. Even where taken secondarily in numbers in Spain to gamebirds such as in La Segarra, Spain, rabbits tend to be the most significant contributor of biomass to goshawk nests. On average, the weight of rabbits taken in La Segarra was 662 g (1.459 lb) (making up 38.4% of the prey biomass there), indicating most of the 333 rabbits taken there were yearlings and about 2-3 times lighter than a prime adult wild rabbit.[106][41] In England, where the European rabbit is an introduced species, it was the third most numerous prey species at nests.[109] In more snowbound areas where wild and feral rabbits are absent, larger hares may be taken and while perhaps more difficult to subdue than most typical goshawk prey, are a highly nutritious food source. In Finland, females were found to take mountain hare (Lepus timidus) fairly often and they were the second most numerous prey item for goshawks in winter (14.8% by number).[101] In some parts of the range, larger leporids may be attacked, extending to the 3,800 g (8.4 lb) European hares (Lepus europaeus), as well as the mountain hare.[115][116][117] In Europe, males have been recorded successfully attacking rabbits weighing up to 1,600 g (3.5 lb), or about 2.2 times their own weight, while adult mountain hares overtaken by female goshawks in Fennoscandia have weighed from 2,700 to 3,627 g (5.952 to 7.996 lb) or up to 2.4 times their own weight. Despite historic claims that taking prey so considerably larger than themselves is exceptional beyond a small region of Fennoscandia, there is evidence that as grouse numbers have mysteriously declined since 1960, adult mountain hare are increasingly the leading prey for wintering female goshawks, favoring and causing an increase of larger bodied females in order to overpower such a substantial catch.[8][118][119] Eurasian goshawks also take about a half dozen species of pikas in Asia, much smaller cousins of rabbits and hares, but they are at best supplementary prey for American goshawks and of unknown importance to little-studied Eurasian goshawks.[120][121]

Other birds

Some 21 species of

alcids and the Eurasian stone-curlew (Burhinus oedicnemus), the Eurasian oystercatcher (Haematopus ostralegus) and the long-tailed jaeger (Stercorarius longicaudus).[84][134][108][130][135][136][137][138]

Juvenile in Japan with a young bird prey item

Corvids as aforementioned are quite important prey. Although they take fewer passerines than other northern Accipiters, smaller types of songbirds can still be regionally important to the diet. This is especially true of the

emberizine sparrows, finches and Old World sparrows. Avian prey has even ranged to as small as the 5.5 g (0.19 oz) goldcrest (Regulus regulus), the smallest bird in Europe.[23][78] Among smaller types of passerines, one of the most widely reported are finches and, in some widespread studies, somewhat substantial numbers of finches of many species may actually be taken. Finches tend to fly more conspicuously as they cover longer distances, often bounding or undulating as they do, over the canopy than most forest songbirds, which may make them more susceptible to goshawk attacks than other small songbirds.[130][140] Non-passerine upland birds taken by goshawks in small numbers include but are not limited to nightjars, swifts, bee-eaters, kingfishers, rollers, hoopoes and parrots.[78][106][93][130][141][142]

Other mammals

A goshawk preying on a brown rat in a fairly urbanized area.

Outside of the squirrel family, relatively few other types of

meadow vole (Microtus pennsylvanicus) was the third most frequently reported prey species, the only known study where large numbers of microtine rodents were taken in North America.[123][148] Microtine rodents taken by goshawks have ranged in size from the 11 g (0.39 oz) western harvest mouse (Reithrodontomys megalotis) to the 1,105 g (2.436 lb) muskrat (Ondatra zibethicus).[149][78][150] Other miscellaneous rodents reported sporadically in the diet include dormice, porcupines, kangaroo rats, mountain beavers (Aplodontia rufa), jumping mice, Old World mice and rats, zokors, gophers and jirds.[81][86][143][151][152][153][154]

Ungulates such as deer and sheep are sometimes consumed by goshawks but there is no evidence that they prey on live ones (as much larger accipitrids such as eagles can sometimes do), but these are more likely rare cases of scavenging on carrion, which may more regularly occur than once thought in areas with harsh winter weather.[47][147][156]

Alternative prey

In a few cases, northern goshawks have been recorded hunting and killing prey beyond birds and mammals. In some of the warmer drier extensions of their range,

American southwest.[86][91][106][165][166] The only known location in the northern goshawk's range where reptiles were taken in large numbers was Sierra de Guadarrama, Spain, where the 77 g (2.7 oz) ocellated lizard (Timon lepidus) was the second most numerous prey species.[87][167] Amphibians are even rarer in the diet, only recorded more than singly in one study each from Spain and from England.[109][41] Fish are similarly rare in the diet, recorded twice each in Bavaria and Belarus.[108][140] A few pellets have included remains of insects, much of which may be ingested incidentally or via the stomachs of birds that they have consumed. However, there is some evidence they at times will hunt large ground-dwelling insects such as dung beetles.[94][147][168][169]

Interspecies predatory relationships

Chasing an osprey, most likely to rob it of food, but the osprey is even considered possible prey

Northern goshawks are often near the top of the avian food chain in forested biomes but face competition for food resources from various other predators, including both birds and mammals. Comparative dietary studies have shown that mean sizes of prey, both in terms of its size relative to the raptor itself and absolute weight, for goshawks is relatively larger than in most buteonine hawks in North America and Europe.[170][171] Studies show even buteonine hawks slightly larger than goshawks on average take prey weighing less than 200 g (7.1 oz) whereas average goshawk prey is usually well over such a mass. This is due largely to the much higher importance of microtine rodents to most buteonine hawks, which, despite their occasional abundance, are ignored by goshawks in most regions.[170][172] Similarly, mean prey mass for sharp-shinned and Cooper's hawks in North America is between about 10 and 30% of their own mass, whereas the mean prey of American goshawks is between about 25 and 50% of their own mass and therefore are the goshawks takes prey that is on average relatively much larger.[72][173] In many of the ecosystems that they inhabit, northern goshawks compete with resources with other predators, particularly where they take sizeable numbers of lagomorphs. About a dozen mammalian and avian predators in each area all primarily consume European rabbits and snowshoe hares alongside goshawks in the Iberian peninsula and the American boreal forest regions where these became primary staple foods. Like those co-habitant predators, the goshawk suffers declines during the low portion in the lagomorph's breeding cycles, which rise and fall cyclically every 10 to 12 years. However, even where these are primary food sources, the northern goshawk is less specialized than many (even Bubo owls, some of the more generalist avian predators become extremely specialized lagomorph hunters locally, to a greater extent than goshawks) and can alternate their food selection, often taking equal or greater numbers of tree squirrels and woodland birds. Due to this dietary variation, the northern goshawk is less affected than other raptorial birds by prey population cycles and tends to not be depleted by resource competition.[174][175][176][177][178]

Despite their propensity to pursue relatively large prey and capability to pursue alternate prey, northern goshawks can be locally outcompeted for resources by species that are more adaptable and flexible, especially in terms of habitat and prey. Most northern buteonine hawks largely take small rodents such as voles (which are usually ignored by goshawks) but can adapt to nearly any other type of prey when the staple local rodent prey populations go down.[170] Comparisons with goshawks and red-tailed hawk nesting in abutting areas of Arizona (other large common Buteos like Swainson's hawks (Buteo swainsonii) and ferruginous hawks (Buteo regalis) utilize open habitats and so do not come into conflict with goshawks) shows the red-tailed hawks as being able to take a broader range of prey than goshawks and nest in more varied habitats, the latter species being perhaps the most commonly seen, widespread and adaptable of diurnal American raptors.[179][180][181] On occasion, goshawks are robbed of their prey by a diversity of other birds, including harriers, other hawks, eagles, falcons and even gulls.[182][183][184]

Northern goshawks from North America are less prone to nesting outside of mature forests and take larger numbers of mammals as opposed to abundant birds than in Europe. This may be in part due to heavier competition from a greater diversity of raptors in North America. In Europe, the goshawk only co-exists with the much smaller sparrowhawk within its own genus, while in North America, it lives with the intermediately-sized Cooper's hawk. The latter species much more readily nests in semi-open and developed areas of North America than goshawks there and hunts a broad assemblage of medium-sized birds, whereas such prey is more readily available to male goshawks from Europe than to goshawks in North America. Although the Cooper's hawk usually avoids and loses individual contests against the larger goshawk, its adaptability has allowed it to become the most widespread and commonly found North American Accipiter.[8][185][186] The slightly larger goshawks of Europe have been shown, in some but not all areas, to outcompete and possibly lower productivity of the slightly smaller common buzzard (Buteo buteo) when their ranges overlap. Usually, however, the dietary habits and nesting preferences are sufficiently distinct and thus effect neither buzzard or goshawk populations. Both can mutually be very common even when the other is present.[8][187][188][189] On the other hand, American goshawks are slightly smaller on average than their European counterparts and can be up to 10% smaller in mass than red-tailed hawks. However, studies have indicated that the goshawk has, beyond its superior speed and agility, has stronger feet and a more forceful attack than that of the red-tailed hawk. All in all, individual competitions between red-tailed hawks and goshawks can go either way and neither is strongly likely to deter the other from nesting given their distinct nesting habitats.[8][190][191] Other raptors, including most medium to large-sized owls as well as red-tailed hawks and falcons, will use nests built by northern goshawks, even when goshawks are still in the area.[192]

Illustration of the formidable talons and beak, which are both proportionately large relative to their size, and give them a predatory advantage over many other raptors

To many other raptorial birds, the northern goshawk is more significant as a predatory threat than as competition. The northern goshawk is one of the most dangerous species to other raptors, especially to those considerably smaller than itself. In many cases, raptors of any age from nestlings to adults are taken around their nests but free-flying raptors too are readily taken or ambushed at a perch.

the Netherlands, the percentage of nest of European honey buzzards (Pernis apivorus), weighing on average 760 g (1.68 lb), predated by goshawks increased from a little as 7.7% in 1981–1990 to 33% in 2000–2004.[23][196] As their habitat preferences may overlap with goshawks, all other Accipiters encountered may be predated in multiple cases, including the 238 g (8.4 oz) Eurasian sparrowhawk, the 188 g (6.6 oz) levant sparrowhawk (Accipiter brevipes), the 136 g (4.8 oz) sharp-shinned hawk, the 122 g (4.3 oz) Japanese sparrowhawk (Accipiter gularis) and the 440 g (0.97 lb) Cooper's hawk.[23][134][125][135][81][197]

Other assorted accipitrids of up to their own size to be predated by goshawks include the 747 g (1.647 lb)

crested honey-buzzard (Pernis ptilorhynchus) and the 1,370 g (3.02 lb) lesser spotted eagle (Clanga pomarina).[23][203][206][207]

Outside of the accipitrid group, heavy predation on different varieties of raptorial birds by northern goshawks can continue unabated. Many types of

Eurasian kestrels, Eurasian sparrowhawks and long-eared owls, not only avoid goshawk activity where possible but also were found to have lower nest productivity any time they nested relatively close to goshawks per the study.[187] A similar phenomenon, with goshawks inadvertently providing shelter to small passerines, has been recorded in North America as well.[66]

Competition for northern goshawks can also come from

raccoon dog (Nyctereutes procyonoides), but it is not clear whether these were actual kills, as many may be encountered as already dead carrion.[18][135][216][217][218] The red fox is a surprisingly considerable competitor for resources with northern goshawks. It was found in Norway that goshawk numbers were higher when voles were at peak numbers, not due to voles as a food source but because foxes were more likely to eat the rodents and ignore grouse, whereas during low vole numbers the foxes are more likely to compete with goshawks over grouse as prey.[219] A decrease of the fox population of Norway due to sarcoptic mange was found result in an increase of grouse numbers and, in turn, northern goshawks.[220] In some areas, red foxes have been found to steal up to half of the goshawks' kills.[221]

Unlike the predators at the top of the avian food chain such as

Eurasian eagle owl and the great horned owl, which not only predate goshawks of any age and at any season but also opportunistically take over their own prior nests as their own nesting site.[8] Of the two, the American horned owl nesting habits are more similar to goshawks, which most often consists of tree nests whereas the eagle owl usually nests in rock formations. Thus, the northern goshawk is more likely to victimized by the great horned owls, which can stage nightly ambushes and destroy an entire goshawk family as they pick off both adults and nestlings.[17] In radio-tagging studies of adult and immature goshawks in the Great Lakes region and Arizona, up to half of the studied birds were killed by great horned owls at night, while the horned owls accounted for 40% of the nest failures in studies from Arizona and New Mexico.[82][222][223][224] In comparison, in Schleswig-Holstein, 59% of reintroduced eagle owls used nests built by goshawks and no goshawk pairs could successfully nest within 500 m (1,600 ft) of an active eagle-owl nest. 18% of nest failures here positively were attributed to eagle owl predation, with another 8% likely due to eagle-owls.[225] Other larger raptorial birds can threaten them. The golden eagle (Aquila chrysaetos) and the bald eagle (Haliaeetus leucocephalus) in North America, have killed wintering goshawks, but given the discrepancy in their habitat preferences, such cases are presumably rare.[47] Other avian predators known to have successfully preyed on goshawks including adults (usually in singular cases) include white-tailed eagles (Haliaeetus albicilla), Bonelli's eagles (Aquila fasciata), eastern imperial eagles (Aquila heliaca), snowy owls (Bubo scandiacus), Ural owls (Strix uralensis) and red-tailed hawks.[182][183][226][227][228][229][230]

The same mammalian predators that sometimes compete for food with northern goshawks also sometimes kill them, with the nestlings, fledglings and brooding females, all with impaired flight due to their wing feather moults, seemingly the most vulnerable. In one case, the

gray wolves (Canis lupus) and red foxes (Vulpes vulpes) as they may perch lower to the ground and are clumsier, more unsteady and less cautious than older birds.[17][238] In one case, a goshawk that was ambushed and killed at a kill by a mangy vixen fox was able to lethally slash the windpipe of the fox, which apparently died moments after partially consuming the goshawk.[239]

Apart from aforementioned predation events, northern goshawks have at times been killed by non-predators, including prey that turned the tables on their pursuer, as well as in hunting accidents. In one case, a huge group (or murder) of hooded crows heavily mobbed a goshawk that they caught in a relatively open spot, resulting in a prolonged attack that ended up killing the goshawk.[240] In another instance, a goshawk drowned while attempting to capture a tufted duck (Aythya fuligula).[241] One young goshawk managed to escape a red fox that had caught it with a chewed wing, only to drown in a nearby creek.[8] Another, and rather gruesome, hunting mishap occurred when a goshawk caught a large mountain hare and, while attempting to hold it in place by grasping vegetation with its other foot, was torn in half.[42]

Breeding

Egg Collection Museum Wiesbaden

The northern goshawk is one of the most extensively studied raptors in terms of its breeding habits. Adult goshawks return to their breeding grounds usually between March and April, but locally as early as February.[237][30][242] If prey levels remain high, adults may remain on their breeding ground all year.[174][199] Courtship flights, calls and even nest building has been recorded in Finland exceptionally in September and October right after young dispersed, whereas in most of Fennoscandia, breeding does not commence any earlier than March and even then only when it is a warm spring.[243][244] Most breeding activity occurs between April and July, exceptionally a month earlier or later.[6] Even in most areas of Alaska, most pairs have produced young by May.[237] Courtship flights typical are above the canopy on sunny, relatively windless days in early spring with the goshawks' long main tail feathers held together and the undertail coverts spread so wide to give them an appearance of having a short, broad-tail with a long dark strip extending from the center.[245] Display flights not infrequently escalate into an undulating flight, similar to a wood pigeon but with sharper turns and descents, and are sometimes embellished with sky-dives that can cover over 200 m (660 ft). One study found undulating display flights more than three times more often done by males than females.[246] After display flights have concluded, the male typically brings a prepared fresh prey item to the female as part of the courtship. In general, these displays are presumably to show (or reinforce) to the potential mate their health and prowess as breeding partner.[17][8][28] Copulation is brief and frequent, ranging up to nearly 520 times per clutch (on average about 10 times a day or 100-300 throughout the season), and may be the male's way of ensuring paternity since he is frequently away gathering food by the time of egg-laying, although extra-pair copulation is extremely rare. Female solicits copulations by facing away from male with drooped wings and flared tail-coverts. The male, wings drooped and tail-coverts flared, drops from a branch to gain momentum, then swoops upward and mounts her back. Both birds usually call while mating.[3][17][8][247][248] Fidelity studies from Europe show that about 80–90% of adult females breed with the same male in consecutive years, whereas up to 96% of males mate with the same female in consecutive years.[8] In California, 72% of males retained relationship with the same mates in consecutive years while 70% of females did the same.[249] Males intruding in Hamburg, Germany territories were in some cases not evicted and ended up mating with the female, with the male of the pair not stopping it.[250] In migratory, northernmost populations, mate retention in consecutive years is low.[3][249] Males are sometimes killed by females during courtship and encounters can be dangerous especially if he does not bring food to courtship and he often seems nervous withdrawing with a trill at a given chance.[251]

Nest characteristics

Nests are usually large structures placed quite high near the canopy on mature, tall trees, as seen on this birch in Norway

Nesting areas are indefinite, a nest may be used for several years, also a nest built years prior may be used or an entirely new nest may be constructed. When nest constructing, the pair will often roost together. Males construct most new nests but females may assist somewhat if reinforcing old nests. While the male is building, the female perches in the vicinity, occasionally screaming, sometimes flying to inspect the nest.

tamarack, wild cherry and willow. In some areas, the nests may be lined with hard pieces of bark and also with green sprigs of conifers.[3][8] Often the tallest tree in a given stand is selected as the nest tree and this is often the dominant tree species within the given region and forest. Therefore, hardwood trees are usually used as the nesting tree in the eastern United States while conifers are usually used in the western United States.[17][253][254] Most nests are constructed under the canopy or near the main fork of a tree and in North America, averaging nest height ranged from 5.8 m (19 ft) (in the Yukon) to 16.9 m (55 ft) (in New Mexico), elsewhere as in Europe average height is between 9 and 25 m (30 and 82 ft).[17][8][174][255] In the dwarf trees of the tundra, nests have been found at only 1 to 2 m (3.3 to 6.6 ft) off the ground, and, in the tundra and elsewhere, very rarely on felled trees, stumps or on the ground.[15][16][256][257] In some studies from North America up to 15% of nests are in dead trees but this is far rarer in Eurasia.[258] More significant than species is the maturity and height of the nesting tree, its structure (which should have ample surface around the main fork) and, perhaps most significantly, little to no understory below it.[8][10] Multiple studies note the habit of nests being built in forests close to clear-fellings, swamps and heaths, lakes and meadows, roads (especially light-use logging dirt roads), railways and swathes cut along power cables, usually near such openings there'd be prominent boulders, stones or roots of fallen trees or low branches to use as plucking points. Canopy cover averaged between 60 and 96% in Europe.[17][8] As is typical in widely distributed raptors from temperate-zones, those from cold regions faced south, 65% in Alaska, 54% in Norway and also in high latitudes such as sky-forests of the Arizona Rockies, otherwise usually nests face north and east.[237][259][260]

Nests, especially after initial construction, may average between 80 and 120 cm (31 and 47 in) in length and 50 to 70 cm (20 to 28 in) in width, and are around 20 to 25 cm (7.9 to 9.8 in) deep.[261][237][262] After many uses, a nest can range up to 160 cm (63 in) across and 120 cm (47 in) in depth and can weigh up to a ton when wet.[252][262] Northern goshawks may adopt nests of other species, common buzzards contributed 5% of nests used in Schleswig-Holstein, including unusually exposed ones on edges of woods and another 2% were built by common ravens or carrion crows, but 93% were built by the goshawks themselves.[187] While colonizing peri-urban areas in Europe, they may displace Eurasian sparrowhawks not only from their territories but may actually try to use overly small sparrowhawk nests, usually resulting in nest collapse.[8] One nest was used continuously by different pairs for a period of 17 years.[263] A single pair may maintain up to several nests, usually up to two will occur in an area of no more than a few hundred meters. One nest may be used in sequential years, but often an alternate is selected. During an 18-year-study from Germany, many alternate nests were used, 27 pairs had two, 10 had 3, 5 had 4, one had five and one pair had as many as 11. Other regions where pairs had on average two nests were Poland, California and Arizona's Kaibab Plateau. The extent of use of alternate nests is unknown as well as their benefit, but they may reduce significant levels of parasites and diseases within the nest.[17][8][13][199][192][264] In central Europe, the goshawk's nest area can be as small 1 to 2 ha (2.5 to 4.9 acres) of woods and less than 10 hectares are commonplace. Nests are not typically found near forest edges, and usually only one active nest occurs per 100 ha (250 acres), with active nests from different breeding pairs being seldom less than 600 m (2,000 ft) apart.[187][262] The most closely spaced active nests by a separate pair on record was 400 m (1,300 ft) in central Europe, another case of two active nests 200 m (660 ft) apart in Germany was a possible case of polygamy.[8][265]

Eggs

The eggs are laid at 2- to 3-day intervals on average between April and June (usually May), taking up to 9 days for a clutch of 3–4 and 11 days for a clutch of 5.[3][17][31] The eggs are rough, unmarked pale bluish or dirty white.[3] In A. g, atricapillus, the average dimensions of the eggs are reported at 57.76 to 59.2 mm (2.274 to 2.331 in) in height by 44.7 to 45.1 mm (1.76 to 1.78 in) in width, with ranges of 52–66 mm (2.0–2.6 in) x 42–48 mm (1.7–1.9 in).[39][256] In Spanish eggs, the average dimensions were 56.3 mm × 43 mm (2.22 in × 1.69 in) compared to German ones, which averaged 57.3 mm × 44 mm (2.26 in × 1.73 in). Goshawks from Lapland, Finland lay the largest known eggs at 62–65 mm (2.4–2.6 in) x 47–49.5 mm (1.85–1.95 in), while other Finnish goshawk eggs ranged from 59–64 mm (2.3–2.5 in) x 45–48 mm (1.8–1.9 in).[3] Weight of the eggs average 59 g (2.1 oz) in America, 63 g (2.2 oz) in Great Britain and 50 to 60 g (1.8 to 2.1 oz) in Poland and Germany, with extreme weights from the latter nations of 35 to 75 g (1.2 to 2.6 oz).[18][266][267] Clutch size almost always averages between 2 and 4 eggs, with a median around 3, rarely as few as 1 or as many 5–6 will be laid.[17][8][268] In combination spring weather and prey population levels seem to drive both egg laying dates and clutch size.[8] If an entire clutch is lost, a replacement can be laid within 15 to 30 days.[31]

Parental behaviour

Mother goshawk seldom leaves the nest in either the incubation or the brooding stage, until the young are about 2 weeks

During incubation, females tend to become quieter and more inconspicuous. The mother can develop a brooding patch of up to 15 by 5 cm (5.9 by 2.0 in) 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% of the observed incubation. The incubation stage last for any time between 28 and 37 days (rarely up to 41 days in exceptionally big clutches), varying in different parts of the range.

The Netherlands and typically these breeding attempts fail.[262][250]

Hatching and development

Nestling northern goshawks in Germany

Hatching is asynchronous but not completely, usually an average sized clutch takes only 2 to 3 days to hatch, although it may take up to 6 days to hatch a clutch of more than 4 eggs.

altricial (as are all raptors) at first but develop rapidly. Hatchlings measure about 13 cm (5.1 in) long at first and grow about 5 to 9 cm (2.0 to 3.5 in) in length each week until they fledge. The mothers typically brood the nestlings intensively for about two weeks, around the time grayer feathers start to develop through the nestlings' down. The most key time for development may be at three weeks when the nestlings can stand a bit and start to develop their flight feathers. Also at the three-week stage, they can reach about half the adults' weight and females start to noticeably outgrow the males. However, this growth requires increased food delivery so frequently results in lower nest attendance and, in turn, higher predation rates. Also rates of starvation at this stage can exceed 50% especially in the youngest of large clutches of 4 to 5.[8][66][273][274] Nestlings at four weeks are starting to develop strong flight feathers, which they frequently flap; also they can start to pull on food but are still mainly fed by female and begin to make a whistling scream when she goes to fetch food from the male. More active feeding behavior by nestlings may increase their aggression towards each other. By the 5th week, they have developed many typical goshawk behaviors, sometimes mantling over food, testing balance by extending one leg and one wing at edge of nest (called "warbling" by falconers) and can wag their tails vigorously. Starvation risk also increases at this point due to their growing demands and, due to their incessant begging calls, vocal activity may court predators. In 6th week, they become "branchers", although still spend much of the time by the nest, especially by the edge. The young goshawks "play" by seizing and striking violent at a perch or by yanking off leaves and tossing them over their back. Wing feathers do not develop highly dimorphically, but male branchers are better developed than females who have more growing to do and can leave the nest up to 1–3 days sooner. The young rarely return to the nest after being 35 to 46 days of age and start their first flight another 10 days later, thus becoming full fledglings.[3][8][273][274] Goshawk nestlings frequently engage in "runting", wherein the older siblings push aside and call more loudly and are thus are feed more often at food deliveries, until the younger siblings may either starve to death, be trampled or killed by their siblings (referred to as siblicide or "cainism"). There is some evidence that mother goshawks may lessen the effects of runting by delaying incubation until their last eggs are laid. Food supply may be linked to higher rates of siblicides and, in many locations with consistent prey levels, runting and siblicide can occur somewhat seldom (meaning the northern goshawk is a "facultative" rather than "obligate cainist").[8][273][275][276][277] Nonetheless, either by predation, starvation or siblicide, few nests produce more than 2 to 3 fledglings. One pair in North America was able to successfully fledge all four of its young.[273][278] Somewhat larger numbers of female fledglings are produced in Europe with their larger size, but the opposite is true in North America where sexual dimorphism is less pronounced. When food supplies are very high, though, European goshawks actually can produce somewhat more males than females.[8][279]

At about 50 days old, the young goshawks may start hunting on their own but more often eat carrion either provided by parents or biologists. Most fledglings stay within 300 m (980 ft) of the nest at 65 days of age but can wander up to 1,000 km (620 mi) before dispersal at between 65 and 80 days old in sync with the full development of their flight feathers. Between 65 and 90 days after hatching, more or less all young goshawks become independent. There is no evidence that parents aggressively displace the young in the fall (as other raptorial birds have sometimes been reported to do), therefore the young birds seek independence on their own.[3][8][66] Goshawk siblings are not cohesive together past 65 days, except for some lingering young females, whereas common buzzard broods are not recorded at their nests after 65 days but remain strongly cohesive with each other.[8][280] Five percent of radio-tagged young in Gotland, Sweden (entirely males) were found to disperse to another breeding area and join a different brood as soon as their flight feathers were developed enough. These seem to be cases of moving to a better food area. Parents and adoptive young seem to tolerate this, although parents do not seem to be able to tell the difference between their own and other young.[8] It is only after dispersal that goshawks typically start to hunt and seem to drink more often than older birds, sometimes spend up to an hour bathing.[3][8]

Breeding success rates

Nest success averages between 80 and 95% in terms of the number of nests that produce fledglings, with an average number of 2 to 3 fledglings per nest. About equal numbers of eggs and nestlings may be lost (6% lost in each the incubation and brooding periods per a study from

Yukon Territory found that average number of fledglings varied dramatically based on food supply based on the cyclical nature of most prey in these northern areas, varying from average success rates of 0 to 3.9 fledglings in the latter region. Similar wide variations in breeding success in correlation to prey levels were noted at other areas, including Nevada (where the number of fledglings could be up to seven times higher when lagomorphs were at their population peaks) and Wisconsin.[3][174][282][283]

Nesting failure

Poor weather, which consists of cold springs that bear late cold spells, snow, and freezing rain, causes many nests to fail, and may also hamper courtship and lower brood size and overall breeding attempts.[8][284] However, the most important cause of nest failure was found to be nest destruction by humans and other predations, starvation, then bad weather and collapse of nests in declining order.[8][281] On average, humans are responsible based on known studies for about 17% of nest failures in Europe. 32% of 97 nestlings in Bavaria, Germany died because of human activities, while 59% of 111 broods in England failed due to this factor.[8][13][285] Low food supplies are linked to predation, as it seems to cause greater risk of predation due to the lower nest attendance.[13] Lower densities of pairs may actually increase nesting success, as per studies from Finland where the highest median clutch size, at 3.8, was in the area with the lowest densities.[268] Similarly, in Schleswig-Holstein, nest failure was 14% higher where active nests were closer than 2 km (1.2 mi) apart compared to nests farther than this.[187] Age may also play a factor in nest success, pairings where one mate is not fully mature (usually the female, as males rarely breed before attaining adult plumage) is less than half as successful as ones where both were mature, based on studies from Arizona.[199][186] Overall, males do not normally breed at any younger than 3 years of age (although they are in adult plumage by two years) and females can breed at as young as 1 to 2 years old, but rarely produce successful, viable clutches. The age at sexual maturity is the same as other northern Accipiters as well as most buteonine hawks (eagles, on the other hand, can take twice as long to attain full sexual maturity).[17][8] 6–9 years of age seem to be the overall peak reproductive years for most northern goshawks. However, some females can reproduce at as old as 17 years old and senescence is ambiguous in both sexes (possibly not occurring in males).[8] Median values of brood success was found to be 77% in Europe and 82% in North America overall. Conversely, the median brood size is about half a chick smaller in North America than in Europe. In Europe, clutch size overall averages 3.3, the number of nestlings averages 2.5 and fledglings averages 1.9.[8][109]

Lifespan

Goshawks may be killed by collisions with man-made objects

The lifespan in the wild is variable. It is known that in captivity, northern goshawks may live up to 27 years of age.

AOU) of a 16-year, 4-month-old goshawk.[287] In Fennoscandia, starvation was found to account for 3-6% of reported deaths.[288] In Norway, 9% of deaths were from starvation, but the percentage of demises from this increased to the north and affected juveniles more so than adults.[289] In Gotland, Sweden, 28% of mortality was from starvation and disease.[8] Both bacterial and viral diseases have been known to cause mortality in wild northern goshawks.[222][290] Variable numbers of goshawks are killed by flying into man-made objects such as power lines and buildings and by automobiles, although lesser numbers are affected by powerline collisions than larger types of raptor.[17][109]

Status

The breeding range of the Eurasian goshawk extends over one-third of Asia and perhaps five-sixths of Europe, a total area of over 30,000,000 km2 (12,000,000 sq mi) for Eurasian and

IUCN, the global population of Eurasian and American goshawk is estimated to consist of 1 million to nearly 2.5 million birds, making this one of the most numerous species complex in its diverse family (the red-tailed hawk and black kite both may have a similar global population size, whereas the Eurasian sparrowhawk and common buzzard are possibly slightly more numerous than goshawks despite their smaller ranges).[1][293][294][295]

Mortality rates for first-year goshawks is often considerably higher than older birds. In studies from

gamekeepers, but in recent years it has come back by immigration from Europe, escaped falconry birds, and deliberate releases. The goshawk is now found in considerable numbers in Kielder Forest, Northumberland, which is the largest forest in Britain. Overall there are some 620 pairs in Britain.[6][8][304]

Juvenile goshawk from Poland

In the 1950s–1960s declines were increasingly linked with

pesticide pollution. Higher DDT levels seemed to have persisted quite recently in Europe. This was the case in Germany, especially in former East Germany where DDT was widely available until 1988, having been largely discontinued elsewhere after the 1970s.[305] Goshawks, which had increased in The Netherlands after World War II due to less persecution, new woodlands and increased pigeon numbers, were found to have suddenly crashed from the late 1950s on. It was later revealed that this was due to DDT, the number of breeding pairs decreasing 84% from 1958 to 1963.[306] As opposed to DDT, the main contaminant found to have reduced goshawks in Scandinavia during the 20th century were methyl mercury seed dressings used to reduce fungal attack in livestock.[307]

Falconer's bird in Scotland

Seemingly the remaining persistent conservation threat to goshawks, given their seeming overall resilience (at the species level) to both persecution and pesticides, is deforestation. Timber harvests are known to destroy many nests and adversely regional populations.[185][308][309] Harvest methods that create extensive areas of reduced forest canopy cover, dropping to cover less than 35-40%, may be especially detrimental as cases of this usually cause all goshawks to disappear from the area.[310][311] However, the mortality rates due to foresting practices are unknown and it is possible that some mature goshawks may simply be able to shift to other regions when a habitat becomes unsuitable but this is presumably unsustainable in the long-term.[17] A study from Italy and France shows that goshawks only left woodlots when the canopy was reduced by more than 30%, although the European goshawk populations have long been known to be adaptable to some degree of habitat fragmentation.[312]

Relationship with humans

Iranian falconer with a trained goshawk

Human culture

The northern goshawk appears on the flag and coat of arms of the Azores. The archipelago of the Azores, Portugal, takes its name from the Portuguese language word for goshawk, (açor), because the explorers who discovered the archipelago thought the birds of prey they saw there were goshawks; later it was found that these birds were kites or common buzzards (Buteo buteo rothschildi).[citation needed] The goshawk features in Stirling Council's coat of arms via the crest of the Drummond Clan.

Hawks are highly associated with Guru Gobind Singh in the Sikh community. According to ornithologists, he is believed to have kept a white Northern Goshawk. This is reflected in that the Northern Goshawk was made the official state bird of Punjab, India.[313][314][315][316]

In falconry

The name "goshawk" is a traditional name from

waterfowl, which are similar to much of the prey the species hunts in the wild. A notable exception is in records of traditional Japanese falconry, where goshawks were used more regularly on goose and crane species.[318] In ancient European falconry literature, goshawks were often referred to as a yeoman's bird or the "cook's bird" because of their utility as a hunting partner catching edible prey, as opposed to the peregrine falcon, also a prized falconry bird, but more associated with noblemen and less adapted to a variety of hunting techniques and prey types found in wooded areas. The northern goshawk has remained equal to the peregrine falcon in its stature and popularity in modern falconry.[319][320]

Goshawk hunting flights in falconry typically begin from the falconer's gloved hand, where the fleeing bird or rabbit is pursued in a horizontal chase. The goshawk's flight in pursuit of prey is characterized by an intense burst of speed often followed by a binding maneuver, where the goshawk, if the prey is a bird, inverts and seizes the prey from below. The goshawk, like other accipiters, shows a marked willingness to follow prey into thick vegetation, even pursuing prey on foot through brush.[319] Goshawks trained for falconry not infrequently escape their handlers and, extrapolated from the present day British population which is composed mostly of escaped birds as such, have reasonably high survival rates, although many do die shortly after escape and many do not successfully breed.[321] The effect of modern-day collection of northern goshawks for falconry purposes is unclear, unlike some falcon species which can show regional declines due to heavy falconry collections but can increase in other areas due to established escapees from falconers.[322][323]

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  312. ^ "Lost in flight: State bird of Punjab missing from the state!". Hindustan Times. 2017-09-14. Retrieved 2021-04-19.
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  319. ^ Oggins, R. S. (2004). The Kings and Their Hawks: Falconry in Medieval England. Yale University Press.
  320. JSTOR 3808727
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  321. ^ Kenward, R. E. (2009). Conservation values from falconry. Recreational Hunting, Conservation and Rural Livelihoods: Science and Practice, 181.
  322. S2CID 86633405
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External links

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