BEHAVIOUR OF BOOBIES SULA SPP.

SUMMARY Some previously undescribed behaviour patterns, mainly of the White Booby and Brown Booby, were observed in the course of 15 months' general study of the species at Ascension. The advertisement display of the male was similar to a posture described as a “taking‐off” one in the Gannet, but was clearly used by unmated male White Boobies to attract a mate; in the Brown Booby the same display was performed (and sometimes in flight) by males of established pairs. Two postures, both involving a turning‐away of the prominent facial features and therefore comparable to “Head‐flagging” in gulls, were similar in the two species, but again were seen frequently among unmated White Boobies but established pairs of Brown Boobies. One of these was similar to “Bill‐hiding”, a posture seen in attacked chicks. Others among the twelve behaviour patterns described are food‐begging of the chick (apparently similar to “Head‐wagging”, a movement seen during combats between adult White Boobies, but not Brown), and a remarkable sunbathing posture. It is suggested that some of the behavioural differences are related to differences in the two species' nesting habits at Ascension.