The Harpy Eagle is not particularly vocal, especially away from the nest. Most calls are given at or near the nest, where adults give a penetrating, weak, melancholy scream, usually in a series of 7-10 notes (Hilty 2003). Retting (1978) described the calls of an incubating male as a "whispy screaming or wailing ... Wheeeeeeeeee-wheeeeeee-wheeeeeeeee." This call would be repeated in a series of five to seven calls in succession, during a period of 30-40 s; the pauses between calling bouts was over 10 s. The female answered the male with calls that were similar, although at different pitch. This female regularly gave similar calls on her own throughout the incubation period.
Calls of a pair of adult birds in captivity can be heard in this recording (recorded in Chiapas, Mexico, by L. Irby Davis; ML 4348).
The incubating female gives a shorter call ('Wheeeeeeee', repeated 9-12 times) after she has fasted for 4-5 days (Rettig 1978).
The male also calls when he approaches the nest when the female is incubating, and after the eaglet hatched. These calls included "rapid chirps, goose-like calls, and occasional sharp screams" (Rettig 1978). The male vocalizes less frequently after the nestling ages (Retting 1978).
Gochfeld et al. (1978) described different calls from an apparent pair of adults that were seen early in the morning, and that were not known to be associated with a nest. The female gave a "yelping note," and the male made a "soft duck-like quacking."
Apparent alarm calls of the hatchling, given during rain or when the hatchling is exposed to the sun, are "Chi-chi-chi ... chi-chi-chi-chi" (Rettig 1978). By the age of 38 days, the nestling has a call that is similar to call of the adult female, but is softer, especially towards the end (Retting 1978). A representative version of is call can be heard in this recording (from Amazonas, Brazil; recording by Curtis Marantz, ML 117258).
Other calls given by nestling or juvenile Harpy Eagles have been described as a croaking call, given when the parent is near (Fowler and Cope 1964); a combination of quacks and whistles, uttered when a human walked under a perched juvenile (Fowler and Cope 1964); and chirps (Rettig 1978).