Owls lay between one and thirteen eggs, depending on the species and also
on the particular season; for most,however, three or four is the more common
number. The eggs are rounded and white; there is little need for cryptic
markings given the concealed nature of most nest sites, and the vigour with
which they are defended.
Incubation of the eggs usually begins when the first one is laid, and lasts,
in most species, for around thirty days. Because eggs are laid over a
period of several days, the hatching is also staggered. This means that
there is always a gradation in the size of the chicks in the nest, the
larger and more active individuals invariably getting more food from the
parents than their smaller, weaker siblings. As a result, it is rare for
all the chicks that hatch from a clutch to survive, except when food is
plentiful.
A pair of Grass Owl chicks in their ground-level nest.
One of a pair of owl youngsters calls for the
attentions of its parents.
In their first few days of life owlets are almost completely helpless, the
eyes of the hatchlings barely opened, and were it not for their secure
nest site and the attentions of their parents, they would be vulnerable to
attack.
In most seasons the youngest chicks starve, or are sometimes even killed by
their brothers or sisters. This seemingly brutal approach to the rearing of
young has in fact positive survival advantages for the family as a whole: it
ensures that, whatever the food availability, some offspring will always
survive and produce another offspring. If all the young were fed equally,
there would be a chance that all might starve in years of poor food supply.
