in areas that are hidden, in order to avoid predators. Other birds that are large or nest in
colonies may build nests in the open, since they are more capable of defending their young.
Young Birds and Parental Care
Parent birds usually incubate their eggs after the last one has been laid. In the 95% of
species which aremonogamous,(the species pair for the duration of the breeding season
or sometimes for a few years or until one mate dies) the parents take turns incubating. In
polygamousspecies, where there is more than one mate, one parent does all the incubating.
Brood parasitism, in which an egg-layer leaves her eggs in another individual’s nest, is more
common among birds than any other type of animal. The host bird often accepts and raises
the parasite’s eggs, at the expense of the host’s own offspring.
Some precocial chicks, like those of the Ancient Murrelet (Synthliboramphus antiquus), follow
their parents out to sea the night after they hatch, in order to avoid land predators. In most
species, however, the young leave the nest just before, or right after, they can fly, sometimes
making it necessary for them to walk until they have mastered flying.
The length and type of parental care varies widely amongst different species of birds. At one
extreme in a group of birds called the magapodes, parental care ends in hatching. In this
case, the newly-hatched chick digs itself out of the nest mound without parental help and
can take care of itself right away. At the other extreme, many seabirds care for their young
for extended periods of time, the longest being that of the Great Frigatebird, whose chicks
take up to six months to fledge (getting parental care until they are ready to fly) and then
an additional 14 months of being fed by the parents (Figure14.4).
Although male parental care is rare among most groups of animals, in birds it is quite
common, more so than in any other class of vertebrates. Often, the tasks of defense of
territory and nest site, incubation, and feeding of chicks are shared between the parents;
sometimes one parent undertakes all or most of a particular duty.
Given all the information so far about birds, what would you say is true about bird diversity?
Diversity of Birds
If you guessed that there is a lot of diversity in birds, you guessed correctly. About 10,000
bird species belong to 29 different orders, or groups, within the class Aves. They live and
breed in most terrestrial habitats and on all seven continents. The greatest biodiversity of
birds occurs in the tropics.
There is enormous diversity and a wide range of adaptations of various body parts, such as
beaks and feet, to the specific habitats of the birds. There is also enormous diversity in the
feeding habits of birds. The feeding habits of birds is related to the beak shape and size,