rorýs kostarický Chaetura fumosa

Smallest swift in most of range. All dark gray with contrasting pale rump and paler throat, both of which can be difficult to see in many viewing conditions. A good look at the rump is necessary for a firm visual identification, otherwise Vaux’s Swift can look very similar. However, in some parts of its range (the Osa Peninsula, for example) this is the only small Chaetura swift. Makes twittering calls similar to many other swifts. Usually found in flocks over forests and more open areas.