Tide Associated Incubation and Foraging Behaviour of Saunders's GullsLarus saundersi

Abstract

Various factors such as food, climate, nest predation, and phylogenetic relationships influence parental behaviour in birds. However, few studies have addressed how the tidal cycle shapes incubation behaviour in seabirds. In the intertidal zone, spatiotemporal limitations in foraging opportunities for the parents are expected to affect breeding behaviour. We studied tide-associated incubation behaviour in Saunders's Gulls Larus saundersi, nesting in a colony on recently reclaimed land and foraging on tidal mudflats, near Incheon in the Republic of Korea. This colony is the last remaining colony in the Republic of Korea. In May 2012, the number of non-foraging adults present in the 200 ha nesting area was monitored; also parental activity at ten nests was videotaped during the daytime, using a car black box recording system. Presence in the colony and parental activity were analysed in relation to the tidal cycle, ambient temperature, time of day, and nesting success. Our results indicated that the number of non-foraging adults staying in the nesting area was higher at high tide than at low tide, and the time that parents incubated eggs increased with higher sea level. The observed pattern was more apparent during ebb tide than during flood tide. No association of time of day, ambient temperature, and nesting success was found. We conclude that the parents regulate incubation in response to the exposure time of their foraging areas and possibly the dietary activity of benthic organisms in the mudflats.