Swifts | Apodiformes

Gierzwaluwachtigen | Vencejos

Worldwide this order also includes the treeswifts of Southeast Asia. The birds of this order share tiny, weak feet unfit for walking or hopping, and a wing skeleton with a short upper arm bone and long forearm and hand bones that allows extremely fast, agile wingbeats. Almost all food is taken on the wing, which with a small body and a high metabolism makes for a large daily demand for energy. In cold weather or overnight that metabolism can slow sharply, a form of torpor that conserves energy. The clutch is small and the eggs are white; the naked chicks stay in the nest until fully grown.

Families in this order

Swifts | Apodidae5 speciesAlmost everything happens in the air. Insects are sieved from the airstream with the mouth held wide open, water is scooped up in a low pass over a lake, and even the nest material — feathers, plant down, dry twigs — is caught in flight or snapped off a branch on the wing. In the breeding season the salivary glands swell, and with that sticky saliva the twigs are glued into a half-cup and fixed to a vertical surface inside a chimney, a hollow tree or under an overhanging rock. There the birds cling with four toes that can all be turned forward, braced by stiff tail feathers whose shafts project as spines. In long spells of cold, wet weather, when no insects are flying, the nestlings' metabolism drops away and they survive for days without food, so that fledging may be delayed by weeks. Around sunset hundreds of birds may funnel down into a chimney in a spiral; the voice is a dry, rapid chittering.
Hummingbirds | Trochilidae19 speciesThe vivid, metallic colours of the plumage do not come from pigment but from the fine, layered structure of the feather barbs, which bend and interfere with light; seen from a different angle, the same feather can flip from brilliant to dull. The long, forked tongue works as a pump that draws nectar in by capillary action, reaching deep into flower tubes out of reach for other animals. The female builds the nest, incubates and raises the young entirely alone, while in North America the male performs steep display dives in which the tail feathers vibrate in the airstream to produce a sharp, mechanical sound. In some species the length and curve of the bill closely matches the shape of the flowers that grow in its range, so that different species sharing an area draw on largely separate food sources.