Slaty Elaenia Elaenia strepera

Highly migratory flycatcher; it nests from about September through March along the east slope of the Andes in Bolivia and northwestern Argentina, then disperses as far as northern South America. It is mostly gray, with a pale belly, faint wingbars, and a broken eyering. Bill is stubby and yellow at the base. Male has a white crown patch that is usually hidden; females and immatures are tinged olive. Inhabits humid forest, and very inconspicuous when not singing. Typical song is an accelerating, toneless rasp, and it remains almost totally silent outside of its breeding range.