The namesake bill is bright yellow with a black tip and a black band along the ridge of the culmen.
[6]
The species is somewhat similar to the larger yellow-billed pintail, but has a darker head, shorter neck and plain grayish sides.
[7]
Taxonomy
Mitochondrial DNAsequence data is most similar to that of the very different-looking green-winged teal.[note 1] Apart from the mystifying relationship with the red-and-green-headed teals, it altogether most resembles the Indian Ocean radiation of teals. However, the yellow-billed teal's unicolored underside and namesake bill are unique, as is to be expected from a species that evolved half a world apart from Bernier's or the grey teal.[2]
This species is also unique among its relatives in some aspects of its post-copulation behavior: After dismounting, the drakes stretch themselves up high and swim around and alongside the females.[4]
Sharp-winged teal, Anas flavirostris oxyptera (Meyen, 1834) – highlands of central Peru to northern Chile and Argentina.
Chilean teal, Anas flavirostris flavirostris (Vieillot, 1816) – southern South America as far north as southern Brazil and northern Argentina. Also in the Falkland Islands.
Previously, this species and the Andean teal formed the superspecies speckled teal, but increasingly taxonomists consider the two species distinct.[8]
^ abCarboneras, Carles (1992). "77. Speckled Teal". In del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi (eds.). Handbook of Birds of the World, Volume. 1: Ostrich to Ducks. Barcelona: Lynx Edicions. pp. 603, plate 45. ISBN84-87334-10-5.
