page_title: Cooper's hawk
section_title: Development of young
hierarchical_section_title: Cooper's hawk / Breeding / Development of young
caption_attribution_description: English: ARIZONA - BIRDS of SANTA CRUZ County
context_page_description: Cooper's hawk is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus Accipiter, sometimes referred to as true hawks, which are famously agile, relatively small hawks common to wooded habitats around the world and also the most diverse of all diurnal raptor genera. 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. It is easily confused with the smaller but similar Sharp-shinned hawk.
  The species was named in 1828 by Charles Lucien Bonaparte in honor of his friend and fellow ornithologist, William Cooper. Other common names for the Cooper's hawk include: big blue darter, chicken hawk, flying cross, hen hawk, quail hawk, striker, and swift hawk. Many of the names applied to the Cooper's hawks refer to their ability to hunt large and evasive prey using extremely well-developed agility. This species primarily hunts small-to-medium sized birds, but will also commonly take small mammals and sometimes reptiles.
context_section_description: Sex ratio can skew towards male in eggs, nestlings and fledglings in about 54-60% in nests of Cooper's hawks in the region of Milwaukee. However the sex ratio corrected over time in the urban area to an even amount, though it is still skewed outside the city (skewed broods towards males occur in cases where the females may become too costly to bring up, needing longer development stages and more foods). There are similar cases of male skewed ratios recorded now in southwestern cities (i.e. Tucson and Albuquerque). Due to the female usually only beginning incubation with the third egg, the first three eggs often hatch on the same day, while the 4th and 5th eggs often hatch 1 (rarely up to 3) days later. New hatchling young average about 28 g (0.99 oz) in body mass and are about 9 cm (3.5 in) in total length. Hatchlings are covered in white natal down with blue-gray eyes and are tan to pink on many of the bareparts. While growth is slow for about 3 days, sexual dimorphism by size may begin by to be measurable by about 7 days of age. At about 10 days, the nestlings begin to engage in rather feeble standing and wing flapping. The bill (at around 11 days) grows about twice as fast as the tarsus (at around 22 days). At 13 days, the nestlings stretch their legs and often yawn, and at 16 days can be aggressive if the nest is breached by people. Down first becomes deep and fluffy around 2 weeks, the following week first feathers among dense down, feather production accelerates but growth slows in the 4th week after which both increase for the 5th week. By 16–18 days, the nestlings preen well, starts to rip at prey and flap well. Within first 2 weeks, the young Cooper's hawks begin to defecate over nest edge but often soil the edge of nest. At 3 weeks often begin to stand up and feed by themselves and often begin to mantle prey away from each other. The young grow is rapid for the period when they are 17 days old to about 23 days, growth then slows down abruptly before they nearly pause growth to feather out and then thereafter become fully grown. At the age of 3 weeks a female nestling may stand and be able to fully feed herself. Sometimes smaller, more agile male nest mates may snatch several bits of meat from their larger sister as if taking food from the mother. Siblicide rarely has been proven for this species, and may occur "accidentally" at times. Sometimes a younger sibling that has died from other means may be eaten by the siblings or by the parents.  In one case, an entire brood of 4 nestlings from 2.5 to 3.5 weeks old were found dead in the nest, apparently having died due to exposure after consistent heavy rains. Normal departure from nest is 30 days (up to 27 days) for males and 34 days for females, but averaged sooner in Oregon, at 27–30 days. Response to the parents after the young Cooper's becoming branchers depends on their hunger levels. Snyder and Wiley recorded feeding rates of 0.267 per hour for a brood of 2 and 0.564 per hour for a brood of 4. In New York and Wisconsin, the sex ratio of broods roughly even, but slightly male biased in Wisconsin (53.5% or 137 against 119). Food may be brought to the nest for the first ten days after the young leave it, as the young often return to rest on it or even to sun from it. Largely, the young are quiet until they leave the nest when they begin their loud, persistent hunger calls. Around this stage, the young hawks will frequently engage in play with sticks and pinecones. After they are about eight weeks old, they may start to hunt for themselves, but are usually still reliant on parents for food. The young Cooper's hawks are frequently loud, voracious and aggressive in procuring food from the parents. The parents soon seem to lose interest in feeding the young. Fledgling occurs at 27–34 days (males averaging earlier), but the young may often returns to nest and are not fully feathered until about 50–54 days. The siblings often stay within 4 m (13 ft) of each other even after leaving their parents range. Siblings before long-distance dispersal may hunt together, althoug
caption: A large nestling Cooper's hawk peers out of the nest.
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