The nest site varies widely depending upon local topography and vegetation. In forested areas, the nest is typically placed in the upper canopy of tall trees within woodlots or other fragmented forest clumps. It may be located within large tracts of unbroken forest. The nest tree may be taller than surrounding trees or on a higher slope. The nest tends to be placed near the edges of dense stands with more open rather than closed canopies. In areas where trees are scarce or absent, cliff faces, or artificial structures providing elevation above the landscape are used. Saguaro cacti is used in some desert locations. A common trait of nest sites is an unobstructed access from above and a good view of the surrounding landscape.
Both sexes build or refurbish the nest. The main nest is generally sticks and twigs from 0.5 to nearly 1 inch (1.3 to 2.5 centimeters) in diameter. The lining may include strips of bark, greenery, catkins, herbaceous plant materials, lichens and so forth. Typically, nests are over 30 inches in diameter and more than 15 inches high. The bowl is 4 to 5 inches (10.2 to 12.7 centimeters) deep and about 14 inches wide (35.6 centimeters). Nests may be refurbished and reused in subsequent years and so may become a little larger over time. Two or more nests may be built and not used.
The clutch size varies from one to four but is usually two or three eggs. The size averages about 2.4 by 1.9 inches (61.0 by 48.3 millimeters) with some geographic variation. The eggs are smooth and non-glossy, white, and may have a light buffy wash. They may be sparsely, or heavily-marked, with blotches that vary from reddish-brown, dark brown, or purple. These may be indistinct and combined with fine speckling. Clutch replacement may occur within three to four weeks of the loss of the first eggs and rarely, a third set may be laid. Egg-laying in the southern United States occurs as early as February but for much of the range south of the 49th parallel, March is typically the month for laying. In Canada, and the northern states, late March through early May is typical depending upon latitude and local climate, whereas in Alaska, laying occurs from April through late May.
Incubation begins before completion of the clutch or with the first egg that is laid and is undertaken by both sexes. The incubation period is variously estimated at 28 to 35 days. The female probably does the incubating at night and most of the daytime sitting as well. She will depart to hunt while the male incubates.
Hatching occurs over a two to four day period with fledging reported from 42 to 50 days but likely closer to 46 days on average. The young are active by the second day as they issue soft calls and bounce and wave their wings. By day seven, the young will peck at prey in the nest and spend less time bobbing and peeping. The young will sit up by day 15 and show aggression towards intruders at day 16. Striking with talons and wings will occur by day 21 and regular exercise and wing-stretching take place by day 30. The female will brood the young until the oldest is about 30 to 35 days old.
After about 46 days, the young leave the nest but stay close for several days. They may remain quite sedentary or chase the parents begging for food. The young stay in the vicinity of the nest for 18 to 25 days with sustained flight possible about 18 days after fledging. The parents typically supply all of the food for the first three to four weeks after fledging. Capturing of small vertebrate prey occurs at about six to seven weeks but parents may still provide food until the eighth week after fledging. Association with the parents may last for 10 weeks in southern migratory populations and up to six months in non-migratory populations. After dispersal from the nesting territory, immatures from several territories may aggregate in an immature staging area.
Cooperative breeding involving two females and one male attending a single brood has been recorded at least twice. In both cases, the male provided food to the females who in turn fed the young. Reproductive success generally, depends upon prey abundance, perch density and distribution as well as the proximity of nests to congeners. Weather and its impact on hunting may impact reproductive success.
#Which species lays this egg?;question\Q32\Q32.wav
