Cooper's Hawk
Accipiter cooperii
Summary 2
Cooper's hawk (Accipiter cooperii) is a medium-sized hawk native to the North American continent and found from Southern Canada to Northern Mexico. As in many birds of prey, the male is smaller than the female. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west. Other common names for the Cooper's hawk include: big blue darter, chicken hawk, flying cross, hen hawk, quail hawk, striker,...
Behavior 3
The Cooper's hawk is a typical Accipiter in all respects. This species tends to be active earlier in the morning than sharp-shinned hawks and Eurasian sparrowhawks (Accipiter nisus) and is generally much more likely to be active in the morning than in the afternoon. These hawks may readily take to conifers to roost, generally sleeping with their heads tucked in. During daylight hours, they tend to preen while sitting on a perch about 11 times a day, and may take about 1–20 minutes to do so. When attaining water to drink, Cooper's hawks appear to prefer to come to relatively secluded waterways. In more arid regions, Cooper's hawks may seek out artificial bodies of water to drink from (especially in passage). Although a rare behavior, there are now several records of juvenile hawks of the species proning wherein they lie on their backs along a branch (or rarely the ground), apparently as a form of sunning. Cooper's hawks may come to walk on ground to gather nesting materials as well as to hunt. Cooper's hawks have a well-developed muscle mass that powers their flight, especially helping with acceleration during hunts and when carrying heavy prey. However, some other non-raptorial birds may have similar muscularity relative to their mass, such as the Canada goose (Branta canadensis) and even pied-billed grebes (Podilymbus podiceps), and these ample muscle masses may be correlated with migratory (rather than hunting) behavior. Cooper's hawks have been recorded as engaging in an exaggerated, nighthawk-like flight in non-courtship circumstances, such as during migration or by recent fledglings. During the late nesting stage, parent Cooper's hawks were recorded during daylight in Utah to engage in soaring flight 8.4% for males and 8.1% of the time for females with a further 6.4% and 2.8% of the time in different kinds of flights, perching the remainder of the time (about 2–6 minutes at each perch interspersed with brief flights). Another study found 13.7% and 10.7% of daylight at this later breeding stage to be in flight, the rest of time perching, with occasional inactive perching spells of around 15–40 minutes. However, that inactivity could last up to 5 hours during heavy rainfall. Breeding adults generally engage in agonistic behavior when an interloper of their sex is present; 11 responses showed that males responses consisted 64% of the provocations, 9% of the time by females and both members 27% of the time. Frequent aggressive interactions were recorded between females, often yearling and 2nd year vs older females. The Cooper's hawk’s threat display appears to consist of them lowering their heads, raising their "crest" (capital tract), stretching out their wings, spreading the tail and engaging in vocalizations. Stress levels, as indicated by a study of corticosterone levels, were considered quite high when hawks are being handled by researchers, particularly in males (indicating that they experience higher levels of stress than females). The Cooper's hawk is subject to frequent mobbing by various birds and some mammals, with good cause, but evidence shows that even main prey types like jays will sometimes shy away from engaging in full-fledged mobbing of a Cooper's, perhaps due to the risk in closely approach this very agile predator, which can in an instant suddenly turn and kill a member of the mob. Therefore less dangerous hawks such as Buteos are mobbed more vigorously than the more dangerous Cooper's. Many potential prey will confine their response to a hawk of this species to vocal scolding and/or attempt escape before an attack occurs.
Like a majority of diurnal birds of prey in the Northern Hemisphere, the Cooper's hawk is a partial migrant. They tend to be most migratory in the north and largely to partially sedentary elsewhere. With individual exceptions, hawks of the species largely migrate out of nearly all of their range in southern Canada as well as cooler parts of the Pacific Northwest, essentially all of Montana and northern parts of surrounding states, the Dakotas (but for southern South Dakota), the northern parts of the Great Lake states, northern New York and much of New England. Despite being classed as sedentary, banding studies have revealed that many Cooper's hawks south of the typical migratory populations engage in some variety of seasonal winter movements. Migrants in the Florida Keys were determined via stable isotopes to have originated from mid-Atlantic states and the southeastern United States both (largely) south of the typical migratory range. While females in the urban areas of Tucson were sedentary (99%), about 6% of the females outside of the urban areas did not remain on their breeding grounds during winter. In British Columbia, many adults are non-migratory but juveniles do tend to migrate. From the Great Lakes region in particular, migrants appear to disperse in multiple directions to the south. Multi-directional movements, even to the north as well as potentially any other direction, are more common than previously thought in this and other migratory raptors, which has been previously described as “inefficient and indirect method of 'homing'”. However, reaching regions where appropriate habitat and prey is available is probably far more significant in seasonal movements to birds of prey than climatic concerns. Fairly strong evidence has been found of habitual northbound migration by Cooper's hawks from Central and Southern California, usually over fairly short distances, often less than 320 km (200 mi). However, the three longest distance movements from southern California were all northbound, i.e. 616 to 993 km (383 to 617 mi). Cooper's hawks originating from Northern California do generally migrate south, mostly wintering in Mexico though sometimes covering up to 1,637 km (1,017 mi) to Central America. In Lansing, Michigan, evidence has been found of individual Cooper's hawks being annually devoted to the same wintering grounds, presumably due to their high quality.
Migratory movements in the autumn are generally between late August to mid-October, peaking at the end of September and beginning of October in the east, but sometimes migration extend into November. Meanwhile spring northward migration may be any time from the end of February to May, with the last ones leaving Mexico in April and very late individuals were passing over south Texas in late May. Generally, spring migration is more dispersed and less consistent than fall migration. There is evidence from the Great Lakes region that spring migration is occurring sooner due to warming temperatures in recent years. Passage appears to be timed to coincide with that of their main prey, medium-sized birds. In migration, first-year juveniles precede two-year-old hawks which themselves precede adults when moving south in fall. Furthermore, females of all ages tend to migrate sooner and spend longer in winter quarters than like-age males, the latter staying relatively north and traveling back again earlier. Interestingly, the sharp-shinned hawk (despite the even more dimorphic migration times between sexes) showed no strong difference in distance on migration between the sexes, unlike female Cooper's which sometimes can move considerably further than males. At regular western migration sites, the average difference of passage timing for Cooper's hawks of the earlier females and later males of like-age was 5 days. In the Marin Headlands, migration of the sexes differed by 6 days in juvenile, first-year females and males and by 11 days in older females and males. Like other Accipiters (but unlike falcons), Cooper's appear to not start moving until day is warmer and thermals can be used. During migration they favor mountain ridges and coastlines, which coincide with migratory raptors routes in general. This species can seem to cross some bodies of water unlike most sharp-shinned hawks but seldom do so over wide bodies of water. However, they have been seen to turn up in such oceanic vicinities as the Florida Keys and Cuba, and so are capable of crossing larger than usual bodies of water. It is thought that Cooper's hawks also avoid the Great Plains while migrating as well. Like many other raptors, Cooper's hawks favor strong northwesterly winds during autumn passage.
At coastal migration sites like Cape May, first year Cooper's hawks are far more regularly encountered than older individuals, with the juvenile Cooper's accounting for 92.7% of recorded individuals of the species (juveniles of various other raptor species also generally seem to favor coastal over montane migration when it is available). In Cape May, Cooper's hawks are the third most commonly recorded raptor species in passage behind the sharp-shinned hawk and the American kestrel (Falco sparverius) but are far less than numerous in migration or in winter in the nearby Delaware Bayshore locations of New Jersey than various other raptor species. Interestingly, in the Manzano Mountains and Goshute Mountains, juvenile sharp-shinned hawks were roughly twice as numerous as juvenile Cooper's hawks but the number of adults seen passing through of the two species was roughly the same. At the hawkwatch in Cedar Grove, Wisconsin, the Cooper's hawk was not among the most regular species, being the 6th most frequently most recorded species. In central and southwestern Idaho, Cooper's hawk accounted for relatively few of the recorded raptors, i.e. 3.45% of 748 migrating raptors. A similarly low volume was observed relative to other bird of prey species in Yellowstone National Park, where the Cooper's was only the 9th most frequently observed out of 17 species and averaged only 50 hawks in passage over the course of autumn. Nonetheless, the Cooper's hawk was second only to sharp-shinned hawk as the most frequently recorded species seen migrating at nine major hawkwatchs throughout the western United States (and 1 in Canada) and, unlike the sharp-shinned, has shown a trend of increase in numbers overall in recent decades, despite some declines in numbers at Lipan Point and Bridger Range. The Cooper's hawk was the 7th most often recorded raptor at four migration sites along the Gulf Coast, being much more frequently identified in the site at Veracruz, Mexico than the ones in the United States, but showed an annual stability of numbers that many of the more numerous raptors (including sharp-shinned hawks) in passage did not. Along the Kittatinny Ridge in Pennsylvania, studied Cooper's hawks that were migrating from further north spent only 12% of the day actually migrating, devoting the remainder of their time to perching and hunting along their passage. Fat stores were measured to consist of 4-12% of the body mass of migrants, being higher in autumn than in spring, and higher on average in adults over younger hawks and in females over males. Migration speeds appear to be largely similar to those of other raptors, with average speeds of 33.6 to 88 km/h (20.9 to 54.7 mph), but one migrating from Colorado was recorded to cover about 26 km (16 mi) per day. Typically Cooper's hawk migrate singly but sometimes can be seen in in groups of 2 to 5. Flocking is not typically engaged in by raptors who migrate using powered flight, such as Accipiters, falcons and harriers, but many Buteo hawks do form loose flocks. 96.3% of 806 observed Cooper's hawk seen migrating in Johnson County, Iowa were solitary, although 30 migrating pairs were seen together.
Behavior 3
The Cooper's hawk is a typical Accipiter in all respects. This species tends to be active earlier in the morning than sharp-shinned hawks and Eurasian sparrowhawks (Accipiter nisus) and is generally much more likely to be active in the morning than in the afternoon. These hawks may readily take to conifers to roost, generally sleeping with their heads tucked in. During daylight hours, they tend to preen while sitting on a perch about 11 times a day, and may take about 1–20 minutes to do so. When attaining water to drink, Cooper's hawks appear to prefer to come to relatively secluded waterways. In more arid regions, Cooper's hawks may seek out artificial bodies of water to drink from (especially in passage). Although a rare behavior, there are now several records of juvenile hawks of the species proning wherein they lie on their backs along a branch (or rarely the ground), apparently as a form of sunning. Cooper's hawks may come to walk on ground to gather nesting materials as well as to hunt. Cooper's hawks have a well-developed muscle mass that powers their flight, especially helping with acceleration during hunts and when carrying heavy prey. However, some other non-raptorial birds may have similar muscularity relative to their mass, such as the Canada goose (Branta canadensis) and even pied-billed grebes (Podilymbus podiceps), and these ample muscle masses may be correlated with migratory (rather than hunting) behavior. Cooper's hawks have been recorded as engaging in an exaggerated, nighthawk-like flight in non-courtship circumstances, such as during migration or by recent fledglings. During the late nesting stage, parent Cooper's hawks were recorded during daylight in Utah to engage in soaring flight 8.4% for males and 8.1% of the time for females with a further 6.4% and 2.8% of the time in different kinds of flights, perching the remainder of the time (about 2–6 minutes at each perch interspersed with brief flights). Another study found 13.7% and 10.7% of daylight at this later breeding stage to be in flight, the rest of time perching, with occasional inactive perching spells of around 15–40 minutes. However, that inactivity could last up to 5 hours during heavy rainfall. Breeding adults generally engage in agonistic behavior when an interloper of their sex is present; 11 responses showed that males responses consisted 64% of the provocations, 9% of the time by females and both members 27% of the time. Frequent aggressive interactions were recorded between females, often yearling and 2nd year vs older females. The Cooper's hawk’s threat display appears to consist of them lowering their heads, raising their "crest" (capital tract), stretching out their wings, spreading the tail and engaging in vocalizations. Stress levels, as indicated by a study of corticosterone levels, were considered quite high when hawks are being handled by researchers, particularly in males (indicating that they experience higher levels of stress than females). The Cooper's hawk is subject to frequent mobbing by various birds and some mammals, with good cause, but evidence shows that even main prey types like jays will sometimes shy away from engaging in full-fledged mobbing of a Cooper's, perhaps due to the risk in closely approach this very agile predator, which can in an instant suddenly turn and kill a member of the mob. Therefore less dangerous hawks such as Buteos are mobbed more vigorously than the more dangerous Cooper's. Many potential prey will confine their response to a hawk of this species to vocal scolding and/or attempt escape before an attack occurs.
Like a majority of diurnal birds of prey in the Northern Hemisphere, the Cooper's hawk is a partial migrant. They tend to be most migratory in the north and largely to partially sedentary elsewhere. With individual exceptions, hawks of the species largely migrate out of nearly all of their range in southern Canada as well as cooler parts of the Pacific Northwest, essentially all of Montana and northern parts of surrounding states, the Dakotas (but for southern South Dakota), the northern parts of the Great Lake states, northern New York and much of New England. Despite being classed as sedentary, banding studies have revealed that many Cooper's hawks south of the typical migratory populations engage in some variety of seasonal winter movements. Migrants in the Florida Keys were determined via stable isotopes to have originated from mid-Atlantic states and the southeastern United States both (largely) south of the typical migratory range. While females in the urban areas of Tucson were sedentary (99%), about 6% of the females outside of the urban areas did not remain on their breeding grounds during winter. In British Columbia, many adults are non-migratory but juveniles do tend to migrate. From the Great Lakes region in particular, migrants appear to disperse in multiple directions to the south. Multi-directional movements, even to the north as well as potentially any other direction, are more common than previously thought in this and other migratory raptors, which has been previously described as “inefficient and indirect method of 'homing'”. However, reaching regions where appropriate habitat and prey is available is probably far more significant in seasonal movements to birds of prey than climatic concerns. Fairly strong evidence has been found of habitual northbound migration by Cooper's hawks from Central and Southern California, usually over fairly short distances, often less than 320 km (200 mi). However, the three longest distance movements from southern California were all northbound, i.e. 616 to 993 km (383 to 617 mi). Cooper's hawks originating from Northern California do generally migrate south, mostly wintering in Mexico though sometimes covering up to 1,637 km (1,017 mi) to Central America. In Lansing, Michigan, evidence has been found of individual Cooper's hawks being annually devoted to the same wintering grounds, presumably due to their high quality.
Migratory movements in the autumn are generally between late August to mid-October, peaking at the end of September and beginning of October in the east, but sometimes migration extend into November. Meanwhile spring northward migration may be any time from the end of February to May, with the last ones leaving Mexico in April and very late individuals were passing over south Texas in late May. Generally, spring migration is more dispersed and less consistent than fall migration. There is evidence from the Great Lakes region that spring migration is occurring sooner due to warming temperatures in recent years. Passage appears to be timed to coincide with that of their main prey, medium-sized birds. In migration, first-year juveniles precede two-year-old hawks which themselves precede adults when moving south in fall. Furthermore, females of all ages tend to migrate sooner and spend longer in winter quarters than like-age males, the latter staying relatively north and traveling back again earlier. Interestingly, the sharp-shinned hawk (despite the even more dimorphic migration times between sexes) showed no strong difference in distance on migration between the sexes, unlike female Cooper's which sometimes can move considerably further than males. At regular western migration sites, the average difference of passage timing for Cooper's hawks of the earlier females and later males of like-age was 5 days. In the Marin Headlands, migration of the sexes differed by 6 days in juvenile, first-year females and males and by 11 days in older females and males. Like other Accipiters (but unlike falcons), Cooper's appear to not start moving until day is warmer and thermals can be used. During migration they favor mountain ridges and coastlines, which coincide with migratory raptors routes in general. This species can seem to cross some bodies of water unlike most sharp-shinned hawks but seldom do so over wide bodies of water. However, they have been seen to turn up in such oceanic vicinities as the Florida Keys and Cuba, and so are capable of crossing larger than usual bodies of water. It is thought that Cooper's hawks also avoid the Great Plains while migrating as well. Like many other raptors, Cooper's hawks favor strong northwesterly winds during autumn passage.
At coastal migration sites like Cape May, first year Cooper's hawks are far more regularly encountered than older individuals, with the juvenile Cooper's accounting for 92.7% of recorded individuals of the species (juveniles of various other raptor species also generally seem to favor coastal over montane migration when it is available). In Cape May, Cooper's hawks are the third most commonly recorded raptor species in passage behind the sharp-shinned hawk and the American kestrel (Falco sparverius) but are far less than numerous in migration or in winter in the nearby Delaware Bayshore locations of New Jersey than various other raptor species. Interestingly, in the Manzano Mountains and Goshute Mountains, juvenile sharp-shinned hawks were roughly twice as numerous as juvenile Cooper's hawks but the number of adults seen passing through of the two species was roughly the same. At the hawkwatch in Cedar Grove, Wisconsin, the Cooper's hawk was not among the most regular species, being the 6th most frequently most recorded species. In central and southwestern Idaho, Cooper's hawk accounted for relatively few of the recorded raptors, i.e. 3.45% of 748 migrating raptors. A similarly low volume was observed relative to other bird of prey species in Yellowstone National Park, where the Cooper's was only the 9th most frequently observed out of 17 species and averaged only 50 hawks in passage over the course of autumn. Nonetheless, the Cooper's hawk was second only to sharp-shinned hawk as the most frequently recorded species seen migrating at nine major hawkwatchs throughout the western United States (and 1 in Canada) and, unlike the sharp-shinned, has shown a trend of increase in numbers overall in recent decades, despite some declines in numbers at Lipan Point and Bridger Range. The Cooper's hawk was the 7th most often recorded raptor at four migration sites along the Gulf Coast, being much more frequently identified in the site at Veracruz, Mexico than the ones in the United States, but showed an annual stability of numbers that many of the more numerous raptors (including sharp-shinned hawks) in passage did not. Along the Kittatinny Ridge in Pennsylvania, studied Cooper's hawks that were migrating from further north spent only 12% of the day actually migrating, devoting the remainder of their time to perching and hunting along their passage. Fat stores were measured to consist of 4-12% of the body mass of migrants, being higher in autumn than in spring, and higher on average in adults over younger hawks and in females over males. Migration speeds appear to be largely similar to those of other raptors, with average speeds of 33.6 to 88 km/h (20.9 to 54.7 mph), but one migrating from Colorado was recorded to cover about 26 km (16 mi) per day. Typically Cooper's hawk migrate singly but sometimes can be seen in in groups of 2 to 5. Flocking is not typically engaged in by raptors who migrate using powered flight, such as Accipiters, falcons and harriers, but many Buteo hawks do form loose flocks. 96.3% of 806 observed Cooper's hawk seen migrating in Johnson County, Iowa were solitary, although 30 migrating pairs were seen together.
Behavior 3
The Cooper's hawk is a typical Accipiter in all respects. This species tends to be active earlier in the morning than sharp-shinned hawks and Eurasian sparrowhawks (Accipiter nisus) and is generally much more likely to be active in the morning than in the afternoon. These hawks may readily take to conifers to roost, generally sleeping with their heads tucked in. During daylight hours, they tend to preen while sitting on a perch about 11 times a day, and may take about 1–20 minutes to do so. When attaining water to drink, Cooper's hawks appear to prefer to come to relatively secluded waterways. In more arid regions, Cooper's hawks may seek out artificial bodies of water to drink from (especially in passage). Although a rare behavior, there are now several records of juvenile hawks of the species proning wherein they lie on their backs along a branch (or rarely the ground), apparently as a form of sunning. Cooper's hawks may come to walk on ground to gather nesting materials as well as to hunt. Cooper's hawks have a well-developed muscle mass that powers their flight, especially helping with acceleration during hunts and when carrying heavy prey. However, some other non-raptorial birds may have similar muscularity relative to their mass, such as the Canada goose (Branta canadensis) and even pied-billed grebes (Podilymbus podiceps), and these ample muscle masses may be correlated with migratory (rather than hunting) behavior. Cooper's hawks have been recorded as engaging in an exaggerated, nighthawk-like flight in non-courtship circumstances, such as during migration or by recent fledglings. During the late nesting stage, parent Cooper's hawks were recorded during daylight in Utah to engage in soaring flight 8.4% for males and 8.1% of the time for females with a further 6.4% and 2.8% of the time in different kinds of flights, perching the remainder of the time (about 2–6 minutes at each perch interspersed with brief flights). Another study found 13.7% and 10.7% of daylight at this later breeding stage to be in flight, the rest of time perching, with occasional inactive perching spells of around 15–40 minutes. However, that inactivity could last up to 5 hours during heavy rainfall. Breeding adults generally engage in agonistic behavior when an interloper of their sex is present; 11 responses showed that males responses consisted 64% of the provocations, 9% of the time by females and both members 27% of the time. Frequent aggressive interactions were recorded between females, often yearling and 2nd year vs older females. The Cooper's hawk’s threat display appears to consist of them lowering their heads, raising their "crest" (capital tract), stretching out their wings, spreading the tail and engaging in vocalizations. Stress levels, as indicated by a study of corticosterone levels, were considered quite high when hawks are being handled by researchers, particularly in males (indicating that they experience higher levels of stress than females). The Cooper's hawk is subject to frequent mobbing by various birds and some mammals, with good cause, but evidence shows that even main prey types like jays will sometimes shy away from engaging in full-fledged mobbing of a Cooper's, perhaps due to the risk in closely approach this very agile predator, which can in an instant suddenly turn and kill a member of the mob. Therefore less dangerous hawks such as Buteos are mobbed more vigorously than the more dangerous Cooper's. Many potential prey will confine their response to a hawk of this species to vocal scolding and/or attempt escape before an attack occurs.
Like a majority of diurnal birds of prey in the Northern Hemisphere, the Cooper's hawk is a partial migrant. They tend to be most migratory in the north and largely to partially sedentary elsewhere. With individual exceptions, hawks of the species largely migrate out of nearly all of their range in southern Canada as well as cooler parts of the Pacific Northwest, essentially all of Montana and northern parts of surrounding states, the Dakotas (but for southern South Dakota), the northern parts of the Great Lake states, northern New York and much of New England. Despite being classed as sedentary, banding studies have revealed that many Cooper's hawks south of the typical migratory populations engage in some variety of seasonal winter movements. Migrants in the Florida Keys were determined via stable isotopes to have originated from mid-Atlantic states and the southeastern United States both (largely) south of the typical migratory range. While females in the urban areas of Tucson were sedentary (99%), about 6% of the females outside of the urban areas did not remain on their breeding grounds during winter. In British Columbia, many adults are non-migratory but juveniles do tend to migrate. From the Great Lakes region in particular, migrants appear to disperse in multiple directions to the south. Multi-directional movements, even to the north as well as potentially any other direction, are more common than previously thought in this and other migratory raptors, which has been previously described as “inefficient and indirect method of 'homing'”. However, reaching regions where appropriate habitat and prey is available is probably far more significant in seasonal movements to birds of prey than climatic concerns. Fairly strong evidence has been found of habitual northbound migration by Cooper's hawks from Central and Southern California, usually over fairly short distances, often less than 320 km (200 mi). However, the three longest distance movements from southern California were all northbound, i.e. 616 to 993 km (383 to 617 mi). Cooper's hawks originating from Northern California do generally migrate south, mostly wintering in Mexico though sometimes covering up to 1,637 km (1,017 mi) to Central America. In Lansing, Michigan, evidence has been found of individual Cooper's hawks being annually devoted to the same wintering grounds, presumably due to their high quality.
Migratory movements in the autumn are generally between late August to mid-October, peaking at the end of September and beginning of October in the east, but sometimes migration extend into November. Meanwhile spring northward migration may be any time from the end of February to May, with the last ones leaving Mexico in April and very late individuals were passing over south Texas in late May. Generally, spring migration is more dispersed and less consistent than fall migration. There is evidence from the Great Lakes region that spring migration is occurring sooner due to warming temperatures in recent years. Passage appears to be timed to coincide with that of their main prey, medium-sized birds. In migration, first-year juveniles precede two-year-old hawks which themselves precede adults when moving south in fall. Furthermore, females of all ages tend to migrate sooner and spend longer in winter quarters than like-age males, the latter staying relatively north and traveling back again earlier. Interestingly, the sharp-shinned hawk (despite the even more dimorphic migration times between sexes) showed no strong difference in distance on migration between the sexes, unlike female Cooper's which sometimes can move considerably further than males. At regular western migration sites, the average difference of passage timing for Cooper's hawks of the earlier females and later males of like-age was 5 days. In the Marin Headlands, migration of the sexes differed by 6 days in juvenile, first-year females and males and by 11 days in older females and males. Like other Accipiters (but unlike falcons), Cooper's appear to not start moving until day is warmer and thermals can be used. During migration they favor mountain ridges and coastlines, which coincide with migratory raptors routes in general. This species can seem to cross some bodies of water unlike most sharp-shinned hawks but seldom do so over wide bodies of water. However, they have been seen to turn up in such oceanic vicinities as the Florida Keys and Cuba, and so are capable of crossing larger than usual bodies of water. It is thought that Cooper's hawks also avoid the Great Plains while migrating as well. Like many other raptors, Cooper's hawks favor strong northwesterly winds during autumn passage.
At coastal migration sites like Cape May, first year Cooper's hawks are far more regularly encountered than older individuals, with the juvenile Cooper's accounting for 92.7% of recorded individuals of the species (juveniles of various other raptor species also generally seem to favor coastal over montane migration when it is available). In Cape May, Cooper's hawks are the third most commonly recorded raptor species in passage behind the sharp-shinned hawk and the American kestrel (Falco sparverius) but are far less than numerous in migration or in winter in the nearby Delaware Bayshore locations of New Jersey than various other raptor species. Interestingly, in the Manzano Mountains and Goshute Mountains, juvenile sharp-shinned hawks were roughly twice as numerous as juvenile Cooper's hawks but the number of adults seen passing through of the two species was roughly the same. At the hawkwatch in Cedar Grove, Wisconsin, the Cooper's hawk was not among the most regular species, being the 6th most frequently most recorded species. In central and southwestern Idaho, Cooper's hawk accounted for relatively few of the recorded raptors, i.e. 3.45% of 748 migrating raptors. A similarly low volume was observed relative to other bird of prey species in Yellowstone National Park, where the Cooper's was only the 9th most frequently observed out of 17 species and averaged only 50 hawks in passage over the course of autumn. Nonetheless, the Cooper's hawk was second only to sharp-shinned hawk as the most frequently recorded species seen migrating at nine major hawkwatchs throughout the western United States (and 1 in Canada) and, unlike the sharp-shinned, has shown a trend of increase in numbers overall in recent decades, despite some declines in numbers at Lipan Point and Bridger Range. The Cooper's hawk was the 7th most often recorded raptor at four migration sites along the Gulf Coast, being much more frequently identified in the site at Veracruz, Mexico than the ones in the United States, but showed an annual stability of numbers that many of the more numerous raptors (including sharp-shinned hawks) in passage did not. Along the Kittatinny Ridge in Pennsylvania, studied Cooper's hawks that were migrating from further north spent only 12% of the day actually migrating, devoting the remainder of their time to perching and hunting along their passage. Fat stores were measured to consist of 4-12% of the body mass of migrants, being higher in autumn than in spring, and higher on average in adults over younger hawks and in females over males. Migration speeds appear to be largely similar to those of other raptors, with average speeds of 33.6 to 88 km/h (20.9 to 54.7 mph), but one migrating from Colorado was recorded to cover about 26 km (16 mi) per day. Typically Cooper's hawk migrate singly but sometimes can be seen in in groups of 2 to 5. Flocking is not typically engaged in by raptors who migrate using powered flight, such as Accipiters, falcons and harriers, but many Buteo hawks do form loose flocks. 96.3% of 806 observed Cooper's hawk seen migrating in Johnson County, Iowa were solitary, although 30 migrating pairs were seen together.
Sources and Credits
- (c) Jim Johnson, some rights reserved (CC BY-NC-ND), uploaded by Jim Johnson
- Adapted by Tricia LeBlanc from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://hub.toolforge.org/P3151:5112?lang=
- (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Cooper's_hawk
