Reproduction in Birds
How do birds reproduce? We are all familiar with the classic chicken egg. So what is involved
in the process of a bird laying an egg? It all starts with courtship. Courtship involves some
type of courtship display, usually performed by the male, leading up to the breeding. Most
displaysinvolveatypeofsongandsomedisplaysareveryelaborateandmayincludedancing,
aerial flights, or wing or tail drumming.
One of the most distinguishing features of bird reproduction is internal fertilization and the
laying of eggs. The hard-shelled eggs have a fluid-filled amnion, a thin membrane forming a
closed sac around the embryo. Eggs are usually laid in a nest. How do you think where a
bird lays an egg might influence the egg color? If an egg is hidden in a hole or burrow, away
from predators, then the eggs are most often pale or white. Nests in the open have eggs that
are camouflaged, thus giving protection against predation (Figure14.3). However, some
species like the ground-nesting nightjars, have pale eggs, but the birds themselves provide
the camouflage with their feathers.
Figure 14.3: Nest and eggs of the common moorhen (Gallinula chloropus), showing camou-
flaged eggs. ( 30 )
The shape of birds’ nests varies quite a lot too. Most create somewhat elaborate nests,
consisting of such structures as cups, domes, plates, mounds or burrows. The albatross,
however, makes a nest that is simply a scrape on the ground. Still others, like the common
guillemot, do not use nests, instead they lay their eggs on bare cliffs. The male emperor
penguins are even more elaborate in the care of their eggs: they incubate the eggs between
their body and feet.
How else might a bird help protect its young from predators? Most species locate their nests