The Lives Of Birds

The behaviour of birds is closely connected to the seasons. To survive, birds must prepare for the arrival of Autumn and winter and adjust their behaviour accordingly. Gliding over the oceans, a wandering albatross, for example, travel anywhere from 2,900-15,000 km (1,800-9,300 mi) in single day in search of food. When the times comes to choose a partner, the behaviour of males is different from that of females: males employ a variety of tactics to win over females and convince them of their fitness. Some bird couples stay together forever, whereas other birds change partner every year. As for caring for chicks and building nests, in most species both parents participate.

How They Communicate

Sound is an important form of expression in the lives of birds. Birds' sounds can be of two types: calls and songs. The former have simple acoustic structure, with few notes. They area associated with coordinating the activities of a group, extablishing communication between parents and their young, maintaining contact between birds during migration. Songs, on the other hand, are more complex in rhythm and modulation. They are controlled by the sex harmones, primarily the male harmones. For this reason, males produce the most varied melodies. Songs are linked to sexual behaviour and territorial defence. In general, birds either inherit or learn them.

Nuptial Parade

Finding a mate is not easy for any species. For birds, the exhibition of plumage with bright colours, the presentation of offering and gifts, and the performance of dances and highly elaborate flight patterns are some of the particular behaviours seen during this period. They are known as nuptial or courtship displays. The males resorts to all these strategic gestures to attract the female's attention and prevent her from paying attention to other males. Some of these ritual are extremely complicated; other are very tender and delicate.

Home Sweet Home

Most birds lay their eggs in a nest, where they are incubated by the body heat of an adult sitting on them. To build a nest, the couple normally uses mud mixed with saliva, small tones, branches and feathers. When the nest is in visible location, the bird covers it with lichens or loose twigs to hide it from predators. Nest shapes are very according to the bird group: they can take the form of a bowl, a hole in a tree (woodpeckers) or an excavated burrow on a slope of sand or soil. There are even birds that use nests built by other species.

First, the Egg

Birds may have inherited their reproductive method from their predecessors, the theropod reptiles. In general, the lay as many eggs as they can care for until the chicks become independent. Highly adapted to the environment, the eggs of the same species have varying shapes and colours. These variations help keep them safe, from predators. They also vary greatly in size: the egg of an ostrich is 2,000 times bigger than that of a humming bird.

Birth in Detail

When a chick is about to hatch, it starts to make itself heard from inside the egg. These allows it to communicate with its parents. It then starts to peck at the shell with its tiny egg tooth, which is lost after birth. Next, it turns inside the egg and opens a crack with new peforations, at the same time pushing with its neck and legs until it manages to stick out its head. This job demands a lot of effort and can take 30 to 40 minutes or, in the case of kiwis and albatrosses, even three to four days. In most species, newborn chicks ar eblind and naked, and they can open their bills only to receive food.

Postnatal Development

Chicks develop at highly variable rates after hatching. Some birds are born with their eyes open and with a thick layer of down feathers. These birds can also feed themselves. That is why they are called precocious, or nidifugous. Ducks, rheas, ostriches and certain beach birds can walk and swim as soon as they are born. Other species are born naked and develop their feathers later. They need to stay in the nest until they have sufficiently developed, so adult birds must care for them. These birds care called nidicolous. The most helpless chicks are the young of songbirds and hummingbirds, because they need warmth from their parents to grow strong.