Biology Reference
In-Depth Information
The reproductive lives and nesting habits of the two species differ considerably, which isn't surpris-
ing in view of their divergent social habits. As befits their gregarious nature, crows tend to raise their
young in an extended-family atmosphere, not unlike that of a wolf pack on a very small scale. That is,
younger, unmated family members help the older, mated pair to build a nest and feed the young.
Crows construct a large nest of sticks and twigs, lined with soft materials such as grass and feathers.
Given a choice, they usually select a site in an evergreen tree, mostly high up but occasionally lower.
The eggs, normally four to six, are greenish with dark brown spots.
The young crows leave the nest after about three weeks. Thereafter, for a considerable time, they
beseech their extended family to feed them, importuning them with reedy, pathetic-sounding little caws
that resemble what one might imagine are the last, feeble utterances of a dying crow. Although their
parents and other family members respond to these pleading calls to some degree, they gradually force
the youngsters to fend for themselves, and their calls grow more adult in nature.
Ravens may mate when they're as young as three years old. On the other hand, some may not mate
until they're as much as seven years of age. This behavior makes more sense when longevity is taken
into account; ravens can live for as much as fifty years, although few in the wild survive to such an
advanced age.
Ravens, unlike crows, have generally been considered to mate for life and to be completely mono-
gamous. Like other animals that supposedly mate for life, however, the survivor will promptly mate
again if its partner dies. Furthermore, subordinate males have been observed copulating with the female
when the dominant male leaves the nest site. Evidently marital fidelity can't be taken for granted in
either man or beast.
As might be anticipated from their more or less solitary nature, a raven pair builds its nest and raises
its brood without the sort of help from an extended family that crows enjoy. Their preferred nesting site
is a shelf beneath an overhang on the side of a cliff. Where suitable cliffs are absent, as they often are,
ravens make do by placing their nest high up in a tall conifer.
The nest is made of sticks and is quite an impressive structure, roughly two and a half feet in diamet-
er. The nesting hollow inside is about a foot wide and lined with a variety of soft materials, such as fur,
shredded bark, and feathers. The eggs, numbering from four to seven, are a little smaller than a hen's
egg. Their background color is greenish blue, but they're spotted and blotched to varying degrees with
dark brown.
The nestling period is about forty days, which is unusually long. As soon as they leave the nest, the
young ravens embark on a period of learning for the next month and a half to two months. During this
span they follow their parents about, acquiring the knowledge of hunting and foraging necessary to sur-
vive. Then they begin to disperse, setting out to lead their own lives.
Birdwatching is reputed to be America's fastest-growing activity, and millions of North Americans,
from the most dedicated birder with a life list to the casual observer of a backyard feeder, enjoy the
