http://www.ck12.org Chapter 12. Understanding Biodiversity: Animals: Birds
Evolution
Wings may have evolved from a bird ancestor that leapt into the air to avoid predators. Therefore, bird wings
are modified arms that may have helped them leap higher. Birds are thought to have evolved from a group of
bipedal dinosaurs called theropods. The ancestor of birds was probably similar to the theropod called Deinonychus.
Deinonychus was a dinosaur that is considered to be one of the closest non-bird relatives of modern birds. It lived in
North America about 110 million years ago.
Ecology
Mockingbirds are omnivores, which means they eat both plants and animals. Their main diet is insects, seeds, berries,
earthworms, sometimes small animals, and small crustaceans. They help disperse seeds. They affect the population
of species that they eat by eating them, so the population of those species decreases. Northern mockingbirds host
several ectoparasites, which are parasites on the skin or feathers. These parasites include blowfly larvae (family
Calliphoridae), fleas and mites. Finally, three Molothrus are brood parasites of northern mockingbirds. This means
that the cowbirds lay eggs in the northern mockingbirds’ nests. Sometimes the northern mockingbirds will incubate
the egg and raise the cowbird chicks along with their own chicks.
Anatomy and Physiology
After the eggs are laid, it takes eleven days to two weeks for them to hatch. It takes them 10 to 12 days to leave the
nest. They reach sexual maturity in one year. They breed in spring and early summertime. They can live eight years
in the wild and twenty years in captivity.
Mockingbirds have four chambers in their heart. Their crop stores food for later, which they process for their
nestlings. They have something called a gizzard, which they use for grinding/chewing their food. They have a two-
cycle respiratory system, unlike mammals, which only have one. Their feathers are made of keratin, which is a type
of protein that wears down easily and it has to be replaced.
Behavior
The mockingbird mimics fifty other birds. It usually sits on fences or telephone wires, runs or hops on the ground.
They are alone or in pairs throughout the year. They aggressively chase off intruders in their territory. They perform
thirty-nine songs and fifty calling notes. They can also imitate certain sounds such as dogs barking, pianos, sirens
and squeaking. Songs are important in mating. Males sing to attract females and to defend their territory against
other males. They sing often, at night and during the day.
References