Among the best fliers in the avian world
Their streamlined bodies and long, thin, swept-back wings enable them to spend most waking hours in the air, with their small but wide bilis agape to catch insects. They can briefly sleep and even copulate on the wing.
Their short legs are poorly developed and they never land on the ground because they would have difficulty taking off. Instead, they have strong feet, and perch and nest on vertical cliffs and buildings from which they can easily glide off.
Costa Rica has 11 species, all mainly dark gray or black, so me with white or brown markings. The largest and most common countrywide is the white-collared swift (vencejón collarejo; Streptoprocne zonaris ), which is 22cm long and has a slim white collar and a square or slightly notched tail. The 13cm-long lesser swallow-tailed swift (macua; Panyptila cayennensis ) also has a white collar, which extends over the chin and upper breast. It has a deeply forked tail and is found below 800m on the Caribbean and up to 1000m on the south Pacific slope.