First Record of Breeding Behaviour of Brewster's Brown Booby Sula leucogaster brewsteri in Japan

Abstract

The Brown Booby Sula leucogaster is divided into four subspecies and is distributed throughout the tropical and subtropical seas of the world. This species was believed to show little movement and low or no gene flow among populations, however, there exist several records of dispersal and breeding across the East Pacific Basin, both by S. l. plotus and S. l. brewsteri inhabiting the western and eastern sides, respectively. We observed a male of S. l. brewsteri visiting Nakanokamishima, Japan, which is one of the breeding sites of S. l. plotus in the West Pacific. Presumably, it was this same individual that was observed intermittently until 2014 and bred and produced offspring with a S. l. plotus female, adapting to the breeding schedule of the Nakanokamishima population from 2012 to 2014. Another male having a white head and neck was recorded at another location on the island since 2011. Although this male often courted a female, they have not yet formed a pair. These are the first records of S. l. brewsteri breeding behaviour in Japan and provide important ecological information regarding the process of pair formation and breeding at the breeding sites of other S. leucogaster subspecies.