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Coopers Hawk (Accipiter cooperi)
The Coopers Hawk (or
proper Cooper's Hawk) is North America's medium size Accipiter (about the same size as a crow). "Coops" breed throughout North America in forested areas. They do breed in deserts and other open areas, but must have trees to nest.
Male and Female Measurements
As noted in the Accipiters page, Coopers Hawks (COHA) are reverse size dimorphic, meaning that the females
are larger than the males.
Wheeler & Clark data are presumed to be primarily from eastern birds, Cape May, NJ migration monitoring.
We present data for wing chord and weight that we collected for both Eastern and Western Cooper's Hawks. We have found (as have others) that Eastern "Coops" are slightly larger on average than Western birds (see data below).
Eastern Cooper's Hawk Wing Chord*
Males: mean 236.1 mm (230-250)
Females: mean 262.6 mm (254-268)
Eastern Cooper's Hawk Weight
Males: mean 327.7 g (285-380)
Females: mean 488.7 g (456-600)
Western Cooper's Hawk Wing Chord*
Males: mean 224.9 mm (210-240)
Females: mean 255.4 mm (241-270)
Western Cooper's Hawk Weight (No Food in Crop)**
Males: mean 281.7 g (239-329)
Females: mean 424.7 g (326-549)
Western Cooper's Hawk Weight (Food in Crop)**
Males: mean 300.9 g (268-382)
Females: mean 453.3 g (360-556)
*Wing Chord is measured from from the wrist to the tip of the longest primary feather of one wing. The primary feathers have a natural camber (bend), and can be measured flattened or un-flattened. We always measure un-flattened wing chord.
**Raptors store food in a crop (pouch in the throat area). Food in the crop or stomach can effect the bird's weight. We can not know how much food is in the stomach, but we can
estimate the amount of food in the crop. We score the crop on a 0= no food in the crop to a 3 = full crop. A full crop in a Cooper's hawk could weigh as much as 60-70 grams. Keep in mind, we are not likely to capture birds
that are not hungry, so only a few birds have crops and very few birds have large crops.
Cooper's Hawk Diet
Cooper's Hawks prey mostly on small to medium sized birds and small mammals, but they also take other prey such as lizards, insects and frogs, but they occasionally try to take larger prey.
I have even pulled out a porcupine spine found stuck in a Cooper's Hawk! I don't know what the Coop was thinking or how big the porcupine was, but I doubt the porcupine attacked the Coop!
(Toland 1985), found the diet of Coopers Hawks in Missouri consisted of mostly of birds (87% of prey numerically and 65% by biomass) and mammals (34% biomass) and 1% was prey other than birds or mammals.
Nest
Usually 18 - 28 inches in wide and 7-30 inches deep, with an inner cavity of 7 inches diameter and 2 - 4 inches deep. The nest is made of sticks and twigs. The nest cup is lined with chips or flakes of bark (from pine or oak) and sometimes fresh greenery.
The nest is usually placed on horizontal branches against the trunk of coniferous trees, or in the crotch of a deciduous tree 20-60 feet above the ground. About 50% of nests are 35-45 feet high.
I have seen a Cooper's Hawk Nest that was only 12 feet above the ground in a Gambel Oak (Quercus gambelii). The area was a rolling open sage-brush area, with small patches of oaks in the washes.
Nest Construction usually begins in March or April.
Eggs
Clutch size is usually between 3-6 eggs. About half of nests have 4 eggs and about 25% of the nests have 5 eggs.
Average size: 49 X 38.5 mm. (Bent, 1937)
Eggs are usually bluish or greenish white, then fade to dirty white. Eggs can be un-marked or have some brownish spots.
Egg laying usually begins in early May to early June. Eggs are usually laid 30-48 hours apart.
Incubation Period
Incubation may not start until most of the eggs are laid and is usually about 24 days. If incubation began after all the eggs were laid, then all chicks would hatch in 24 or 25 days. If incubation begins with the 3rd egg of a 4 egg clutch, then incubation would last
an additional 1-2 days. If incubation begins with the 3rd egg of a 5 egg clutch, then incubation would last an additional 3-5 days for a total of 27-30 days.
The chicks usually hatch a few days apart.
Fledging
Chicks usually begin "branching" from the nest before they can fly at about 28-30 days, but make their first flight between 32-36 days after hatching. Fledging usually occurs between early July to
early August.
Cooper's Hawk Longevity Record
20 Years and 4 months; based upon known age of a wild Cooper's Hawk at banding and subsequent band recovery (Data from Bird Banding Lab (Klimkiewicz
2008).
Migration
Cooper's Hawks migrate from the Northern parts of the breeding range during late Autumn. There are many raptor migration sites where they can be viewed during Migration.
For anyone who is a Cooper's Hawk enthusiast, we highly recommend
The Cooper's Hawk: A Cross Timbers Chronicle.
An excellent read by an author passionate about his favorite bird.
). We highly
.
An excellent read by an author passionate about his favorite bird.
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