[2] The International Ornithological Committee (IOC) recognizes these five subspecies of the white-crested elaenia:[2] The South American Classification Committee of the American Ornithological Society (SACC), the Clements taxonomy, and BirdLife International's Handbook of the Birds of the World (HBW) recognize a sixth subspecies, E. a. chilensis (Hellmayr, 1927), that the IOC treats as the Chilean elaenia.

Their flight feathers have narrow whitish or yellowish edges with dusky bases on the inner pairs.

The white-crested elaenia's habitat has been studied for all subspecies except E. a. modesta, and it is assumed to have similar requirements to the others.

[6][7][8][9][10][excessive citations] Subspecies E. a. modesta breeds west of the Andean crest and moves to the east side of the range for the austral winter.

Flocks of up to 100 have been reported during migration, but as is the case with vagrants to the Falklands they could have been the highly migratory Chilean elaenias.

[6] The oldest known white-crested elaenia from banding studies was eight years and two months old, though it is uncertain whether this represents the maximum potential longevity of the species.

The white-crested elaenia's vocalizations apparently differ somewhat among the subspecies, though not all have been studied in detail.

The dawn song of E. a. griseigularis is "a series of deep, burry, falling-rising djeewee notes interspersed with occasional per'brr'djwee notes" and its calls are "a low, rich, modulated djur and a longer, descending djeeer".

The dawn song of E. a. albiceps is "a series of burry rising-falling-rising djww'awee notes interspersed with an occasional purt trr'cheewee".