Family life

In some ways, the family lives of birds are much like our own. More than 90 per cent of bird species are “monogamous”, which means that males and females form stable couples that work together to raise a family. In some species, such as swans, couples may stay together for life. But despite the appearance of stability and harmony, family life among birds is full of hardship, deceit, and even cruelty. Birds almost always lay more eggs than will reach adulthood, and from the moment they hatch, chicks face a struggle to survive that only the strongest can win.

Divorce rate. Family life in birds can be as complicated as in humans. Swans might appear to be a model of the perfect family, but DNA tests reveal that parents often cheat on their partners and lay eggs “out of wedlock”. And if a couple has problems breeding they may get “divorced” so each can try mating with a different partner.

Growing-up. Young birds fall into two main types. Ground-nesting birds such as ducks and geese have “precocial” young, which are downy and can walk and feed themselves within hours of hatching. In contrast, tree-nesting birds have “altricial” young, which are tiny, naked, and helpless. Their parents face the exhausting challenge of feeding the young until they can leave the nest.

Imprinting. Newly hatched ducklings follow their mother, whose voice and appearance become permanently “imprinted” in their brains. If the mother isn’t present, ducklings imprint on whatever else they can follow.

Programmed to kill. Young birds learn some survival skills from their parents, but most knowledge is instinctive. A cuckoo never meets its parents, yet it knows how to kill the other chicks in the nest within hours of hatching.

Sibling rivalry. Birds of prey often have more chicks than can survive. The parents give most of the food to the strongest chick and turn a blind eye when it begins to bully the others. Often the well-fed chick ends up killing and eating its brothers and sisters, but sometimes the parents eat the weakest or most sickly chicks themselves.

Insatiable appetite. Birds that feed their young work non-stop to meet their chicks’ needs. A wren may make 1.000 feeding trips in a single day, and a swift may fly 1.000 km daily to gather enough food. Black terns spend three or four weeks flying to and from their nests, which are hidden on rafts of floating vegetation in lakes.

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