WHAT IS A BIRD?
Two-legged, bipedal vertebrates, distinguished from other living vertebrates by feathers. All birds have bills, and they have a 4-chambered heart. ~ after Gill, F. B. 1995. Ornithology
Second edition. Freeman, New York
There are about 10,000 bird species, found in every shape and size. All birds lay eggs to incubate their young. All birds have wings; while most use their's for flight, some are land dwelling animals that can't fly, like the ostrich and penguin. Living birds are divided into two groups: (1) Paleognathae, the large flightless ostrichlike birds, which have a flat sternum with poorly developed pectoral muscles, and tinamous, and (2) Neognathae, all other birds, nearly all of which are flying birds that have a keeled sternum to which powerful flight muscles attach.
Flight
Bird bodies are constructed with stringent strucutal requirements to stay airborne. All adaptations for flying is acomplished by two things: more power and less weight. Feathers are very lightweight and are remarkably tough. Birds feathers each bears numerous barbs which hold tiny barbules. These barbules connect barbules of another barb in a zipper like fashion which allows the bird to have a wing instead of seperate individual feathers. When these barbs become seperated, the bird uses its bill to comb the barbs back together; this process is called preening, which keeps its feathers in perfect condition.
Molting
Feathers, like mammalian hair, is a dead structure. Feathers are discarded gradually to avoid appearance of bare spots. Flight and tail feathers are lost in pairs, one on each side, to maintain balance. While most lose their feathers gradually, many water birds (ducks, geese, loons, and others) lose all their primary feathers at once and are grounded during molt. During this time, the bird is very vulnerable to predators, therefore it will move to isolated bodies of water where they can find food and more easily escape enemies. Nearly all birds molt at least once a year, usually in late summer after nesting season.
Migration
Migration, or seasonal movements, is an activity in which species of birds take place in in order to seek warmer grounds and more food during winter seasons. In regrads to migration, birds can be classified as belonging to one of four groups:
- Permanent Residents, non-migrating birds who remain in their home territoy year round, such as the House Sparrow.
- Summer residents, Purple Martins, arrive during the spring, nest during the summer, and return south to wintering grounds in the fall.
- Winter residents, are birds who reside in Canada for much of the summer and "fly south" for the winter in to our backyards. White-throated Sparrows are winter residents.
- Transients, are only seen while "passing through". These birds nest farther north than our neighbors and winter farther south.
Song birds travel mostly at night; during the day, they spend their time resting and gathering and eating food. These birds stop many times on their way to their destination; these places they stop are called stopover sites or staging sites. The time they remain at the staging site various greatly depending on how much fat they have stored and weather conditions.
Other birds, are short distance migrators only migrating as far as they need to find food such as insects, berries, or seeds.
Build your own Nesting Box at:
Sources:
Allaboutbirds.com
National geographic website and field guide book
