The Red-tailed Hawk

Telling the sexes apart

The most reliable criterion is weight, with size, not eye colour and not plumage. The North American bird manual no longer accepts sexing of red-tails by banders because the ranges overlap so heavily, but falconers still make good educated guesses. The extremes run 26 to 44 ounces for males and 36 to 70 ounces for females, averaging about 34 ounces male, 49 ounces female. Females also tend toward larger, more powerful thighs and feet, broader heads and a blockier build. There is definitely sexual dimorphism in the species; anyone who says otherwise is answering the wrong question.

Behaviourally the males are more spirited and more temperamental; the females crash into heavy cover more willingly but lack the males' quickness and aerial dexterity. Neither sex is preferred: when the exam asks whether males are preferred over females, the answer is none of the above.

The New York year

• Eggs are laid in March or early April. Incubation averages 30 days and is shared by both sexes.
• On average two young are successfully fledged.
• Eyases leave the nest at about 45 days, roughly six weeks, and often stay in the area into early summer.
• Climb the nest tree and the adults usually call from a distance rather than attack. Eastern red-tails almost never strike an intruder at the nest; western birds are sometimes bolder.

They do not nest only in trees. Western birds use cliffs, Arizona birds use saguaro cactus, and city birds use building ledges, famously in New York City.

Diet and hunting style

The wild style is perch and wait, not waiting-on and not attacking from above. The diet is rabbits and rodents, but when those run short the red-tail becomes a genuinely competent bird hawk, feared by waterfowl and upland game birds, and will take crows, ravens, gulls, owls and other buteos. In western deserts it lives on rattlesnakes and other reptiles as much as on rodents. It is also the raptor most likely to kill its prey with its powerful grip, in contrast with the falcons.

Variation

There are many varieties: up to 14 described subspecies, plus the pale Krider's Hawk of the west, the very dark Harlan's Hawk of British Columbia and the southern Yukon, and localised leucistic birds. Falconers will tell you no two red-tails look alike anyway.

Trapping the passage bird

In fall migration, the best place to set a bow net or mist net is atop a ridge running northeast to southwest, because migrants ride updrafts from ridge to ridge on that axis. Red-tails begin moving about two weeks after the equinox, and the first cold front brings them through by the dozen. The best day is a fine cold day after foul weather, though too much wind makes them hard to coax out of a soar. Trapping stays good into November.