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At nesting sites and roosts, produces several deep, guttural calls, like grunts; similar sounds also heard in large fishing flocks, but otherwise generally silent. Seven distinct calls described by van Tets (Van Tets 1959) at breeding colony, mostly prolonged or repeated notes, as follows: before taking-off, t-t-t-t; just before landing, urg-urg-urg; following landing (or hopping), a “roar.” Sexual advertising by male at nest site involves Wing-Waving Display (see Behavior: sexual behavior, below), which is accompanied by synchronized ugh notes; these also described as ok-ok-ok-ok and noted as audible from outside the colony (Palmer 1962a). During individual recognition display (Gape; see Behavior: sexual behavior, below), gives prolonged arr-r-r-r-r-t-t . Threat call is a repeated eh-hr . Before feeding older chicks, gives uhr notes. The only sex-specific call is that associated with Wing-Waving Display by male.
Chicks beg for food and respond to heat stress by chirping, and they hiss in defense.