Bird variations

Female blackbirds are brown but the males are glossy black

There are nearly 10,000 species of bird in the world and there are probably over 100 billion individual birds. None is exactly the same as any another. Every species is different, and every individual bird is unique.

Family ties

Some families, including parrots, pigeons and hummingbirds have over 300 species. Others, such as the ostrich, have just one or two. A family evolves as many different species as the environment can support. Each one has a slightly different adaptation.

Thrushes are a good example. The blackbird feeds on worms and berries on lawns and in gardens and woodlands; the song thrush feeds mainly on slugs and snails; the mistle thrush feeds more on fruit; and the rare ring ouzel lives on mountainsides. Some thrushes, redwings and fieldfares, migrate to Britain for the winter, while the ring ouzel heads south from its snowy mountains.

Male or female?

Male and female birds rarely look quite the same either. In some species the differences are tiny, such as the slightly thicker belly stripe on a male great tit. In others, they are much more obvious – such as blackbirds, where the female is brown. The differences depend on their behaviour: most male ducks have colourful feathers for courtship display; most female ducks have brown feathers to camouflage them on the nest.

Size can also differ. A female sparrowhawk is almost one third larger than the male. This means the female can catch birds as big as song thrushes whereas the males can only manage smaller birds such as blue tits. This stops the two of them competing for prey.

Colours for all seasons

Birds also change their colours at different times of year, by moulting their old worn feathers. Many have one breeding plumage and one different non-breeding plumage. For instance, a male wheatear in spring has a handsome pink breast, blue-grey back and black face mask. By autumn, he has become brownish all over – just like the female.

Being different

Even within one species, each individual bird is slightly different from every other. This is usually hard for us to spot, but in a few birds it’s more obvious. Some birds of prey, such as buzzards, can also vary greatly. Watch your regular birds at school or home. If you do it enough, you may get to recognise individuals.

Scientists ring birds that they want to study. This gives each one its own individual identity.