Bird Family Life

• For birds, the process of reproduction and raising young is quite complicated, usually involving courtship and nest construction.
• Courtship is the male bird attempting to attract a mate.
• Males are more colorful than females.

• Birds are oviparous, producing amniotic eggs.
• Male transfers his sperm into the cloaca of the female (internal fertilization).
• Females have a single ovary for ova production.
• Fertilization occurs within the oviduct.

• Embryo appears as a small nucleus in the yolk.
• Yolk is coated with protein-containing substance called albumen (the white part of the egg). 
• Encased in a shell.
• The shell may range in color from white to almost black, and it may have markings like spots, splotches, or streaks. While a bee hummingbird egg is the size of a pea, an ostrich egg may weigh 1.5 kg (3.3 lb) and could hold 4700 of the small hummingbird eggs.

• Eggs and young birds require parental care.
• The egg require incubation. Usually one or both parents do it.
• There are two types of chicks after they hatch:
• Altrical chicks
• Precocial chicks
• Altrical chicks
• Hatch in less than two weeks and emerge naked, blind and helpless.
• All they can do is open their mouths and eat.
• Parents produce less than 6 eggs at a time.

• Precocial chicks
• Longer incubation period, sometimes as long as a month.
• When hatched, they are well developed, alert and able to move.
• Covered with soft down.
• Stay close to parents for protection.

• Most birds have a reproduction cycle of one year, each year with a different mate. 
• Some birds mate for life.
• Eagles and penguins.

Migration

• The ideal place for raising offspring may not provide suitable year-round conditions. Some birds overcome this dilemma by migrating.
• Almost 1/2 of all bird species in the Norther Hemisphere travel south in the winter and north in the summer. 
• Seasonal, predictable, and repeatable on an annual basis.
• Why migrate?
• They can live all year in warm climates where there is lots of food.
• Best environment for raising young.
• The time, route, destination, and other aspects of bird migration are inborn.
• Mechanism for navigation not completely understood.
• Might use landmarks, but some fly over open water.
• Birds have an instinctive sense of direction.
• Some detect magnetic poles
• Some use stars and sun
• The arctic tern covers the greatest distance.
• 17,700 km from the Arctic Circle to Antarctica.