About Gampsonyx swainsonii Vigors, 1825
The pearl kite (scientific name Gampsonyx swainsonii Vigors, 1825) measures 20.3–23 cm (8.0–9.1 in) in length and weighs 80–95 g (2.8–3.4 oz). It is the smallest raptor found in the Americas, and one of the two smallest accipitrids in the world—only the little sparrowhawk shares this distinction. Another Neotropical species, the tiny hawk, reaches a slightly higher average weight than the pearl kite. Adult pearl kites have black crowns, upperparts, wings, and tails; a white collar edged with rufous; yellow forehead and cheeks; mostly white underparts; and yellow legs. Immature birds have a similar appearance to adults, but with white and chestnut tips on their back and wing feathers, a buff collar, and some buff marking on their otherwise white underparts. When in flight, this species appears mainly black on its upper side and white on its underside. The northern subspecies G. s. leonae differs from the nominate subspecies G. s. swainsonii by having rufous flanks. This tiny kite breeds from Panama, Colombia, and Venezuela south to Bolivia and northern Argentina, with an isolated, non-migratory population in Nicaragua. Its range is expanding; breeding on Trinidad was first confirmed in 1970. It was first reported in Costa Rica in the mid-1990s, and is now fairly common along the country's Pacific slope up to 1000 m elevation.
