But first, are you experienced? The consequences of timing, age, and adult condition on reproductive performance in Greater Crested Terns Thalasseus bergii

• Published in: Marine ornithology Vol. 45; no. 2; p. 205
• Main Authors: McLeay, Lachlan J, Page, Brad, Goldsworthy, Simon D
• Format: Journal Article
• Language: English
• Published: Honolulu Pacific Seabird Group 2017
• Subjects: Adults; Age; Animal behavior; Animal reproduction; Availability; Body condition; Breeding seasons; Breeding success; Cattle; Foraging; Growth rate; Hatching; Laridae; Phenotypes; Prey; Primary production; Reproduction; Seabirds; Seasonal variations; Seasons; Success; Survival; Winter
• ISSN: 1018-3337; 2074-1235

Among bird species with defined breeding seasons, rates of reproductive success are higher among individuals that breed earlier in the season and decrease as the season progresses. Seasonal decreases in breeding success have been explained by decreases in prey availability or by variations in parental 'quality,' mediated by age-related experience or phenotype. We examined seasonal patterns of primary production, as an indicator of prey availability, in relation to the breeding phenology of three Greater Crested Tern Thalasseus bergii colonies in gulf waters of South Australia. We then determined the influence of reproductive timing on the reproductive performance (chick growth and survival) of Greater Crested Terns and the role of parental 'quality' in reproductive success by measuring reproductive timing in relation to parental age and body condition. In contrast to expectations, increased primary production was observed in winter months, long after the chick fledging period. High production in winter may benefit newly fledged juvenile terns that have relatively less skill and experience than adults. Chick hatching was synchronised among colonies located 250 km apart, and the timing of breeding had a significant effect on reproductive performance. Chicks reared by older adults hatched earlier in the breeding season than younger adults, and exhibited better growth and body condition (hatch mass, linear growth rate, and asymptotic mass) and higher rates of survival. There was less support for the effects of body condition, measured by a body condition index (BCI), on reproductive timing, and no significant relationship between adult age and body condition. However, individuals less than seven years old had significantly poorer body condition than those that were older. The seasonal patterns in age-related breeding success we observed may be explained by parents' age-related improvements in breeding and foraging proficiency, shaped through their need to provision their chicks with a single prey item that is small enough for the chick to swallow.