The most obvious external features of birds are shown here in a number of British birds. Birds like the starling, great tit, tree sparrow and tree creeper are typical passerines – small perching birds feeding on seeds and insects. The merlin, Falco columbarius (O. Falconiformes), is the smallest falcon found on moors of Scotland feeding on small birds such as chaffinches and tits caught in flight. The budgerigar (O. Psittaciformes) is originally an Australian bird but is now a very common pet and bred in captivity in Britain.

1. Starling, Sturnus vulgaris; 2. A pair of great tits, Parus major; 3. Tree sparrow, Passer montanus; 4. Tree creeper, Certhia familiaris; 5. Budgerigar, Melopsittacus undulatus; 6. Merlin, Falco columbarius.