Birds: How do birds behave?

Choosing partners
Although birds are warm-blooded creatures like mammals, they do not give birth to live babies. They lay eggs like cold-blooded creatures such as lizards. Unlike most reptiles, the shell of a bird's egg is hard. The baby bird grows inside the egg and after a few weeks, breaks out, or hatches.
Birds in cold climates usually have a breeding season once a year in the spring. Migratory birds can have two springs and two mating seasons in a year. So can birds that live in hot climates.

When the breeding season arrives, the birds choose partners. Some birds are mated for life, like married couples. These birds include pigeons, geese, and cranes. Other birds look for new partners each year and sometimes a male bird or cock will have several wives.

For birds that choose new mates, part of the breeding season is display. The male bird will do all sorts of things to attract females. These include singing, dancing, showing off the feathers and building a beautiful nest. Some male birds have splendid feathers for attracting females. The most famous is the peacock who can spread the feathers above his tail into a huge fan.

A peacock display

Sarus Crane. Many cranes make dancing movements to attract their mate.

Emu nest.

A nest of House Sparrows

NestingOnce the birds have found partners, they find a suitable place to lay eggs. The idea of what is a suitable place differs between species, but most build bird nests. Robins will make a beautiful little round nest of woven grass and carefully line it with feathers, bits of fluff and other soft things. Swallows like to nest near other swallows. They make nests from little blobs of clay, often on a beam near the roof of a building where it is well sheltered. Many birds like a hollow tree to nest in. Eagle's nests are often just piles of dead wood on the top of the tallest tree or mountain. Scrub Turkeys scratch together a huge pile of leaves that may be 10 metres across. Guillemots lay their eggs on rock shelves with no nest at all. Their eggs are shaped so that they roll around in circles. A cuckoo doesn't make its own nest. It lays its egg in the nest of another bird and leaves it for them to care for. The cuckoo eggs are camouflaged to look like the host's eggs.

When the nest has been prepared, the birds mate so that the eggs are fertilised and the chicks will start growing. Unlike mammals, birds only have one opening as the exit hole for body fluids. The opening is called the cloaca. A female bird, called a hen has two ovaries, of which the left one usually produces eggs.

Most male birds have no sex organs that can be seen. But inside the male are two testes which produce sperm which is stored in the cloaca. Birds mate by rubbing their cloacas together, although with some birds, particularly large water birds, the male has a sort of a penis inside the cloaca.

HatchingOnce the hen has mated, she produces fertile eggs which have chicks growing inside them. She lays the eggs in the nest. There might be just one egg or a number of them, called a clutch. Emus might lay as many as fifteen huge dark green eggs in a clutch. After the eggs are laid, they are 'incubated, or kept warm so the chicks form inside. One of the good things about the fact that most birds stay together for the whole nesting time is that the work is shared. The birds generally take turns sitting on the eggs, so that both can feed.

This is not always the case. With Emus, the male does all the sitting and all the baby-minding. With Emperor Penguins it is also the male that cares for the egg. There is only one egg, which he keeps on his feet and under his feathers, standing in a big group of males without feeding until the chick is hatched. While the eggs are hatching, the females are at sea, feeding, so that they can care for the chicks when they return.

With birds that build mounds, the heat to hatch the eggs comes from the sun on the rotten leaves. The parents leave the mound. When the chicks hatch, they are strong enough to feed themselves.

Many types of birds take 2-4 weeks to hatch eggs. Albatrosses take 80 days. During this time the female loses a lot of her body weight.

The quickest hatching time is for the Cuckoo. Some types of cuckoos take only 10 days. This means that when they hatch in the nest of their "foster parents", the eggs that the parents have laid are not yet ready. Newborn cuckoos are naked, blind and ugly, but they are very strong. They get under any eggs that are in the nest and throw them out before they hatch. That means that the cuckoo has the whole care of both parents. Baby cuckoos grow fast and are often soon bigger than the parents who feed them.

When baby birds hatch, in most types of birds, they are fed by both parents, and sometimes by older aunties as well. Their mouths are open all the time and are often very brightly coloured so the parents can easily see where to put the food. For birds that eat grain and fruit, the parents eat and partly digest the food for the babies. It is then vomitted carefully into the babies mouth.

A Black Redstart feeding chicks. photo Stefan-Xp