Sounds

Development

By 5 d of age, young give beg-ging calls, including weak peeping, and a “harsh note” in response to parents, but calls of young are poorly described. No information on vocal learning or sensitive periods for learning.

Vocal Array

No good recordings available; nearly all descriptions are from observations of courtship and nest behavior only; little is known of vocalizations in nonbreeding season. Vocal repertoire limited, though this species is often described as a “noisy” bird (Oberholser 1974).

Calls. Both sexes give Aaah Call during aggressive encounters (see Rodgers 1977, 1978a). Call during startle reactions. Gives Scaah Calls when approaching nest with food and when in Alert Posture (see Behavior: agonistic behaviors, below). During courtship, males give Unh Calls and groaning sounds; both sexes may give Culh-Culh Calls (Rodgers 1978a).

Phenology

Most vocalizations known only from courtship and nesting period; agonistic and alarm calls (Aaah and Aahrr) are the only ones noted during nonbreeding season.

Daily Pattern

During courtship, vocalizations by both sexes are concentrated during early morning and late afternoon, with midday hiatus (Rodgers 1978a). Begging by young chicks is less frequent during early morning than later in day. No information on nighttime vocalizations.

Places Of Vocalizing

Nearly all vocalizations are described from breeding territory within nesting colonies. The exception is the aggressive Aaah Call, also given during aggressive encounters with conspecifics and heterospecifics at feeding sites. Scaah Call may be given as breeding birds approach nest, sometimes from 5–10 m outside of breeding territory or in flight.

Social Context And Presumed Functions

Aggressive Upright Display (see Behavior: agonistic behavior, below) and many aggressive behaviors often accompanied by Aaah Call; Aaah Call also given when humans approach nest. When parents arrive at nests with well-developed young, Scaah Call often given by adults (Rodgers 1978a); also used during Alert Posture (see Behavior: agonistic behavior, below; Rodgers 1977). Often gives short guttural Aahrr Call as alarm call when flushed. At end of Snap-Stretch Display (see Behavior: sexual behavior, below), males give 1 or more resonant Unh Calls, which vary among males from soft and low to harsh and loud, sometimes audible from 10 m. Male also makes groaning sound toward end of courtship bout (J. S. Huxley in Bent 1926). During Circle Flight Display (see Behavior: sexual behavior, below), male gives long series (5–12/display) of Culh-Culh Calls while moving bill up and down, which movement may continue after landing; females may follow males during Circle Flight Display, and may give these calls, though they give fewer than males give. Also gives Cuhl-Culh Calls during Greeting Ceremony at nest (see Behavior: agonistic behavior, below), mates answering calls from some distance during nest relief (Rodgers 1978a).

Young give begging calls of several kinds, but none described. Because unrelated young are not fed, adults are able to recognize their own young; this recognition is perhaps facilitated by begging sounds of young (Rodgers 1978a). Reciprocal Cuhl-Cuhl Calls between male and female during Greeting Ceremony suggest vocal recognition.

Audible snap of mandibles by males during Snap-Stretch Display (see Behavior: sexual behavior, below), and rattling by mandibles during Bill-Nibbling by both males and females, produced by rapid opening and closing of bill (see Behavior: sexual behavior, below; Rodgers 1977). During Circle Flight (see Behavior: sexual behavior, below), audible and characteristic whomp, whomp made by particularly deep wing thrusts.