SWIFT V HIRUNDINES
Many beginner birdwatchers get confused between the swallows and martins (aka hirundines) and the Swift. They are all long winged, mostly fork-tailed birds which do just about all of their feeding in continuous flight. But distinguishing them is actually pretty straightforward. Hirundines are actually perching birds (passerines), whereas Swifts are in a separate order, the Apodiformes (which, curiously, they share with the hummingbirds as well as the tree swifts). One characteristic of the Apodiformes is that they have very short legs and, in the case of the Swift, they are so short that a grounded Swift can find it extremely hard or impossible to take off. So, if you see either a hirundine or a Swift perched on a wire, or fence, or in a tree, or on the ground, it will be a hirundine. Swifts only come back to earth at the nest sites, where they disappear into a roof before you can even see them perched! Swifts are all dark, very long winged and much larger than our hirundines. A Swift is up to 18.5cm long with a wingspan of 40-44cm and a House Martin is 15cm long with a wingspan of 26-29cm.
They are all long winged, mostly fork-tailedbirds which do just about all of their feeding in continuous flight