Sounds and Vocal Behavior

Development

Information is needed.

Vocal Array

Gill and collaborators (36 Gill, F. B., F. J. Stokes, and C. C. Stokes (1974). Observations on the Horned Screamer. Wilson Bulletin 86(1):43–50. Close ) provide the most detailed descriptions of the vocalizations of the Horned Screamer. The authors distinguished three basic vocalizations: the Moo Co call, honking, and trumpeting.

The Moo Co call ( ) has two syllables with a large decrease in frequency from the first syllable to the second syllable. The calls are usually repeated at 3–10 second intervals, and there are instances where only the first syllable is produced. This call can also form a duet: ha-moo-co. The two birds overlap one bird's second syllable with the other's first. The Moo Co vocalization is used for alarm calls, distance calls, and greetings.

A typical Honking sequence ( ) consists of bisyllabic goose-like calls with two distinct patterns that last about 30 seconds. They are usually performed with head and neck-bobbing, especially if the vocalizing birds are in a group. One of the patterns has seven to eight strongly developed harmonics, spaced at intervals of about 750 Hz over a fundamental frequency of about 450 Hz. The dominant frequency is around 2600 Hz. The Honking sequence sometimes includes Moo Co calls and trumpeting calls. This sequence is used for distance calling and greetings.

The Trumpet call ( ) is a long-distance bisyllabic call consisting of a low introductory note followed by a note with a fundamental frequency of 1000 Hz, four to five harmonics, and with a dominant frequency of 2600 Hz.

Geographic Variation

Information is needed.

Phenology

Information is needed.

Daily Pattern of Vocalizing

Vocalizations are given most frequently in the early morning and sporadically throughout the day (36 Gill, F. B., F. J. Stokes, and C. C. Stokes (1974). Observations on the Horned Screamer. Wilson Bulletin 86(1):43–50. Close 5 Naranjo, L. G. (1986). Aspects of the biology of the Horned Screamer in southwestern Colombia. Wilson Bulletin 98(2):243–256. Close ).

Places of Vocalizing

Most vocalizations are produced while the birds were perched (36 Gill, F. B., F. J. Stokes, and C. C. Stokes (1974). Observations on the Horned Screamer. Wilson Bulletin 86(1):43–50. Close ,5 Naranjo, L. G. (1986). Aspects of the biology of the Horned Screamer in southwestern Colombia. Wilson Bulletin 98(2):243–256. Close ).

Sex Differences

The overall pitch of the call may be related to the sex of the bird calling, as males probably have a deeper-pitched voice than females (36 Gill, F. B., F. J. Stokes, and C. C. Stokes (1974). Observations on the Horned Screamer. Wilson Bulletin 86(1):43–50. Close ,5 Naranjo, L. G. (1986). Aspects of the biology of the Horned Screamer in southwestern Colombia. Wilson Bulletin 98(2):243–256. Close ).

Social Context and Presumed Functions of Vocalizations

When vocalizations are given later in the day, these calls usually accompany the movement of groups or constitute what seems to be communication between groups of Horned Screamers (36 Gill, F. B., F. J. Stokes, and C. C. Stokes (1974). Observations on the Horned Screamer. Wilson Bulletin 86(1):43–50. Close ,5 Naranjo, L. G. (1986). Aspects of the biology of the Horned Screamer in southwestern Colombia. Wilson Bulletin 98(2):243–256. Close ). The more intense calls, Honking and Trumpeting, were performed when other birds landed within or near another’s territory (59 Barrow, J.H., Black, J.M. and Walter, W.B. (1986). Behaviour patterns and their function in the Horned Screamer. Wildfowl 37: 156-162. Close ).

Barrow and collaborators (59 Barrow, J.H., Black, J.M. and Walter, W.B. (1986). Behaviour patterns and their function in the Horned Screamer. Wildfowl 37: 156-162. Close ) described a low-intensity sound associated with pair-bonding and family contact (60 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ) termed the ugh call. During this repetitive "call," the body is held in a horizontal position, with the tail slightly lowered, while feathers in the middle neck region repeatedly become erect and relaxed in concert with a deep ugh sound. The observers hypothesized that the call was produced as air was forced through the subcutaneous air sacs of the neck.