The Vaux's Swift (Chaetura vauxi) is a small species resident from northwestern North America to Panama. Like many other swifts species, these birds are expert fliers, usually hard to identify unless you have excellent viewing conditions (prolonged close views in clear days with dark backgrounds). To photograph them is even harder, so in this post you'll see essentially Vaux's Swifts silhouettes.
Two subspecies occur in Panama: richmondi, a common breeder of the western highlands; and ochropygia, which is the common small swift over forested area in central Panama (pictured above).
I took the above photo in the Chiriqui lowlands. The identity of the birds occurring in the western lowlands of the Pacific slope is still a mystery; however, the best candidate is richmondi coming down from the adjacent highlands (this is what happens in the rest of its Mesoamerican distribution). The nominal vauxi, which breeds in North America is another possibility although there are no records of this migratory race south of Honduras. In any case, the pale area restricted to the throat discards vauxi, in which it extends to the belly.
Some consider richmondi a good species. The differences in rump patterns (less contrasting in richmondi than in ochropygia) could justify this split; however, more studies are needed. The above photo, from the western highlands, shows the stubby shape, short tail and paddle-shaped, short wings. In the next photo, the characteristic pale throat of this species is more evident. For these, and many others reason is why we chose the Vaux's Swift as our Bird of the Month.
1. Ridgely R, Gwynne J. A Guide to the Birds of Panama. Princeton University Press. 1989.
2. Chantler, P. (1999). Vaux's Swift (Chaetura vauxi). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2013). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved fromhttp://www.hbw.com/node/55311 on 1 July 2014).