Argentina to eastern Brazil, is fairly similar in appearance to the spectacled but is marked smaller with ochraceous-tawny from the eyebrows down to the belly and dark chestnut eyes. Each of the three currently recognized species also has a distinct song. Vocal activity tends to be most prominent on calm, moonlit nights. The primary sound made by the spectacled owl consists of guttural knocking or tapping sounds with a popping effect: PUP-pup-pup-pup-po, POK pok pok bog bog bog bobobo or BOO Boo boo boo boo. Each progressive note becomes weaker and lower in pitch but faster in pace as the call continues. The male is the primary singer to proclaim a territory, often singing from the upper third of a tall tree. However, females also sing, uttering the same song but with a higher pitch. Duets between pairs have been heard on moonlit nights. Females also make a hawk-like scream with an emphasis on the drawn-out second syllable, ker-WHEEER, which has often been compared to a steam-whistle. Young spectacled owls beg with a harsh, high-pitched call. In Colombia, an author noted that the song is similar to the tapping pattern of the great spotted woodpecker (Dendrocopos major). In Brazil, spectacled owls are known locally as "knocking owls". Subspecies The following subspecies are currently recognized: Pulsatrix perspicillata boliviana (Kelso, 1933)- Distributed in Bolivia. Most similar to P. p. chapmani, with slightly lighter color on mantle than that race and a lighter, more buff underside color. The feathers appear to be relatively long on this race especially on the flanks, probably due to the cooler climates it inhabits. Specimens had wing of and a tail length of Pulsatrix perspicillata chapmani (Griscom, 1932)- Found from eastern Costa Rica to northwestern Ecuador. A relatively dark hued subspecies, sooty black on the back and rich tawny-rufous below. Wing is , tail is , the bill from the cere is . A mean weight of was published. Pulsatrix perspicillata perspicillata (Latham, 1790)- By far the largest distribution of the races, found from northwestern South America to as far south as central Brazil and Bolivia. Nominate as described above. Wing is , tail is from long, and bill from cere is . Pulsatrix perspicillata pulsatrix (Wied-Neuwied, 1820)- Or the "Short-browed Owl"; native to southeastern Brazil from about Bahia south to Rio Grande do Sul in the area of Aparados da Serra National Park and also bordering over