World Book Trivia Challenge Advanced--12/26--birds

In many parts of the world, the foods that birds eat become scarce during certain seasons of the year. Many birds, such as insect eaters, would starve if they had to remain in such places through the unfavorable season. This situation is especially true of regions with cold, snowy winters. The majority of birds that nest in these regions migrate to warmer climates in fall.

Unlike most other vertebrates, living birds lack teeth. Instead, they have a hard bill, or beak, which they use in getting food and for self-defense. A number of the earliest birds possessed teeth, but these species no longer exist.

lso, the use of pesticides, especially DDT, contaminated the food of the bald eagle, the osprey, and the brown pelican in some areas. Since 1972, DDT has been prohibited in many countries. Populations of bald eagles, ospreys, brown pelicans, and peregrine falcons are now breeding successfully again in once-polluted areas of North America.

The smallest bird is the bee hummingbird, which grows only about 2 inches (5 centimeters) long. The largest living bird is the ostrich, which may grow up to 8 feet (2.4 meters) tall. The largest bird that ever lived was the elephant bird, which died out hundreds of years ago.

A bird cares for its feathers chiefly by cleaning and smoothing them with its beak, a process called preening. A bird uses its feet to preen its head and other hard-to-reach parts. Most birds oil their feathers while preening.

Like mammals, and unlike amphibians and reptiles, birds are warm-blooded—that is, their body temperature always remains about the same, even if the temperature of their surroundings changes.

The flow of air over the wing produces an upward force called lift. Lift enables birds to overcome gravity, rise, and remain airborne.

Birds produce their songs with a unique vocal organ called the syrinx. The syrinx of most birds occurs where the main airway, or trachea, branches into the two smaller air passages, called the bronchi, which go to the lungs. Many birds can produce two different songs at the same time, one with each side of the syrinx.

Most newborn chicks are blind, practically featherless, and so weak-legged they cannot stand. Such birds are called altricial. In other species, the newborn chicks can see, and they have a covering of fine down and strong legs. These birds are called precocial. Precocial young can walk from the nest and start to hunt for food a few hours or days after hatching. Altricial young must remain in the nest far longer and be cared for by their parents.

Birds move from one place to another chiefly by flying. Only a few kinds cannot fly. Some of these flightless birds are cassowaries, emus, kiwis, ostriches, rheas, and penguins