Red-tailed hawk After 28 to 35 days of incubation (averaging about three days longer in the Caribbean as does fledgling as compared to North American red-tails), the eggs hatch over 2 to 4 days.[2][306] Like most raptorial birds, the nestlings are altricial and nidicolous at hatching.[9][135] Hatchlings average 58 g (2.0 oz) in body mass with no difference in sizes of the sexes until the young are about 29 days old for mass and 21 days or so for external linear standard measurements such as bill and talon size.[307] The female broods them while the male provides most of the food to the female and the young, which are also known as eyasses (pronounced "EYE-ess-ez"). The female feeds the eyasses after tearing the food into small pieces. The young red-tails are active by the second day when they issue soft peeping calls, bounce, and wave continuously with their wings. By day 7, the bouncing and peeping begin to wane, and young start to peck at prey in their nest. Nestlings emit high whistling notes (usually in response to adults overhead) by day 10, sit up on tarsometatarsi by day 15, become aggressive toward intruders by day 16, strike out with talons and wings by day 21, begin to stretch wings and exercise regularly by day 30. After 42 to 46 days, the eyasses begin to leave the nest and tear apart prey for themselves.[9][135] The amount of food brought to the nest daily varies considerably, based on brood size and prey availability. In Alberta, an average of 410 to 730 g (14 to 26 oz) is brought each day for 1 to 3 nestlings while in Washington, it was estimated a minimum of 520 g (1.15 lb) per day for 1 surviving nestling and in Wisconsin, an estimated 219 g (7.7 oz) was needed for 1 nestling and 313 g (11.0 oz) for 2.[257][253][308] Brooding is strenuous for parent red-tails and both members of the pair usually lose some weight, especially the female. Some females may lose over 100 g (3.5 oz) between hatching and fledging.[9] During brooding the female may become aggressive to intruders, including humans. In the east, red-tailed hawk females rarely defends nests from humans but historically in California and quite often still in Alaska, some female will dive repeatedly and "savagely", sometimes snapping off large branches in her temper, occasionally stunning herself or inadvertently knocking down her own youngster if it is attempting to fledge. Apparently, the less extensive prior exposure they have to humans may make mature females more aggressive towards humans near the nest.[5][15][94] Although development is asynchronical in most nests, runting may sometimes be recorded and even siblicide may occur, with the parents feeding the weaker, younger chicks less so and both the siblings and parents occasionally aggressively pecking the “runts” of the nest. Ultimately, the runt in such cases does not usually survive and may be either be found crushed in the nest, discarded out of the nest after starvation or consumed by the parents or the siblings. However, as a whole, such killings are fairly rare and only when food supplies are extremely low, often this being in sync with poor spring weather (such as overly rainy or cold conditions).[5][258][308] If there is too much food, such as California ground squirrels in California, the parents will discard remains after a day or two since decomposition of their prey invites infection, other diseases and blood-sucking insects to the nest that may endanger the nestlings. However, after about four weeks, the female often stops discarding leftover prey and the increased presence of flies may form somewhat of a risk to disease in the young but may also merely get the young to leave the nest sooner.[15][135] One nest in California had two females and one male attended to, the male performing his usual function but both females would brood and tend to the nest.[309] Additionally, bald eagles have been recorded to occasionally adopt red-tail fledglings into their nests. As recorded in Shoal Harbor Migratory Bird Sanctuary located near Sydney, British Columbia on June 9, 2017, a juvenile red-tailed hawk was taken by a pair of bald eagles back to their nest, whereupon the chick, originally taken as prey, was accepted into the family by both the parents and the eagles' three fledgelings. After surviving six weeks amongst the eagles, the fledgling, nicknamed "Spunky" by birdwatchers, had successfully begun learning to hunt and fly, showing that the aggressive hawk was able to survive amongst a nest of much larger adoptive siblings.[310][311]

Question: when do red tail hawks leave the nest