For the following account on Highland Guan vocalizations, recordings were analyzed using software Raven Pro. Notes were marked in sonograms with the curser and following data were measured: peak frequency (frequency with the highest power), delta time, and center time. All means are given with standard deviation.
Male whistle: The most obvious sounds of Highland Guan are produced by the male. Mainly during the first part of the breeding season (January-April), males utter single, loud and far-carrying whistles which can be heard over more than a kilometer. This call is usually given while perched in the upper forest canopy, midstory, or sometimes on ground (Pullen 1983, González-García et al. 2001; K. Eisermann, personal observations), but it has also been reported during flight (Rowley 1984). A male’s whistle often provokes other males to vocalize (K. Eisermann, personal observations). Often the whistle precedes a wing-rattling which is produced during glides between perches. The whistle has been described as “long whistle, steady in volume but rising in pitch” (Land 1970). Based on recordings and sonograms of 5 individuals in the Guatemalan highlands, whistles ranged in length 2.3-3.1 s (mean: 2.6 ± 0.3, n = 6 calls of 5 individuals; K. Eisermann, personal observations). Peak frequency ranged 2062-2906 Hz (mean: 2469 ± 278, n = 6 calls of 5 individuals; K. Eisermann, personal observations). Sonogram 1 shows a typical whistle. The function of the whistle and combined wing-rattling is thought to be a territorial advertisement and a signal for sexual selection (Pullen 1983, del Hoyo and Motis 2004). Seasons of call activity may change between years. At Montaña Caquipec, Alta Verapaz, Guatemala, there was no call activity from September 1997 to February 1998, but in 1998 guans were calling until October (Eisermann 1999).
Alarm calls: In sight of potential danger, such as humans, male and female Highland Guans utter alarm calls which have been described as “sharp yelp” (Griscom 1932), “pia and noise resembling the neighing of a horse” (Pullen 1978), and “see-uh, may be run into twittering” (Howell and Webb 1995). The short see-uh notes are the low arousal alarm call. Once in a while a see-uh note runs into a twitter. Twitters are given in short intervals in a stage of high arousal. A females with chicks uttered a see-uh note each 0.5-3.0 s (mean interval between center times of see-uh notes: 0.9 ± 0.3 s, n = 266 notes) with twitterings given each 0.9-36.6 s (mean interval between center times of twitters: 15.0 ± 10.9 s, n = 15 twitters; K. Eisermann, personal observations). The length of see-uh notes ranged 0.1-0.4 s (0.22 ± 0.02 s, n = 472 notes of 2 individuals) and peak frequency ranged 375-3750 Hz (1807 ± 772 Hz, n = 472 notes of 2 individuals). The length of twitters, including the introductory see-uh note, ranged 0.5-1.1 s (0.8 ± 0.2 s, n = 21 notes of 3 individuals), and peak frequency ranged 1312-2625 Hz (2158 ± 304 Hz, n = 21 notes of 3 individuals; K. Eisermann, personal observations). Sonogram 2 shows typical see-uh and twitter calls.
Juvenile calls: About two weeks old chicks gave series of soft short whistles wi-wi-wi, while an adult female and an adult male were uttering warning calls (K. Eisermann, personal observations, 13 June 2011).