The nesting year

When disturbance costs the most

Desertion is most likely just prior to egg laying. Once eggs are on the ground, most raptors will stick with the clutch despite disturbance, though not all. That gradient is the biological reason the nestling take season opens on May 1 rather than in early spring.

Double clutching

If a first clutch is destroyed soon after laying, many hawks and falcons will lay a second clutch. Propagators exploit this deliberately to maximise the output of a breeding pair. The caution attached is real: some wild raptors disturbed on eggs will abandon the nest and shut their reproductive systems down for the whole season.

Who does what

The male generally returns from migration first, chooses the nesting area, and provides most of the food after the young hatch. In most falcons the male does nearly all the hunting for roughly the first two weeks after hatching. Once the young grow past what he can supply, the female hunts as well.

Territory scales with size

Bigger birds need more ground. Golden Eagle territories in Europe have been measured at 16 square miles, Gyrfalcon territories in the north at 14 to 15. Northern Harriers, Cooper's Hawks and American Kestrels are unlikely to need more than one.

The bird most likely to breed in captivity

A parent-raised (raptor-raised) eyas. Imprints and passagers are far less likely to breed naturally in captivity, and captive-bred raptors from parent-raised stock now account for large numbers of young produced in the United States.