During the dawn chorus in lowland terra firme forest at Caxiuanã, Pará, Brazil one morning in 1997, Andrew Whittaker recorded the vocalizations of a forest-falcon that he could not immediately place into any known species. After playback of the recording, he coaxed a small forest-falcon into the open. It looked almost exactly like the common Lined Forest-Falcon (Micrastur gilvicollis), yet in addition to its distinctive vocalizations, there were also subtle plumage differences. After examining museum specimens and an exhaustive analysis of forest-falcon recordings, Whittaker described this distinctive form as a new species, the Cryptic Forest-Falcon. It is a testament to how poorly known forest-falcons are that such a large bird that is widespread in southeastern Amazonia - ranging south of the Amazon, east of the Rio Madeira and west and south to the southern edge of humid lowland forest - could have remained unrecognized for so long.