Parental care and breeding strategies of the Jacky Winter and its life-history traits compared with other Australasian robins, and northern temperate and tropical songbirds

Abstract

We studied parental care in the Jacky Winter Microeca fascinans at Gluepot Reserve, South Australia, for one breeding season from 16 August to 9 November 2001, supplemented by observations on breeding and social behaviour in September 2012. We monitored ten nests in 2001, nine of which were attended by pairs and one by three adults, and watched three nests for a total of c. 117 hours. Female incubation constancy was 69%, duration of incubation sessions averaged 4.58 minutes and absences from the nest 2.07 minutes. Mean number of nest visits per hour by two pairs during the incubation period was 10.6 and for a group of three adults (two males, one female) was 15.8. Female care included brooding, feeding of nestlings, and nest-hygiene. Male care included delivering food to the sitting female, feeding the nestlings, nest-hygiene, nest-defence, and territoriality. Mean female brooding constancy was 55%. Mean number of feeding trips per hour by male and female combined for the entire nestling period was 14.6. Older young, 12, 13 and 14 days of age, received 21, 20, and 29 feeds/h respectively or one feed about every 2 minutes. Mean number of visits per hour by male and female combined to a nest with two young was 16.5 for Days 1–10 and 20.4 for Days 11–18 of the nestling period. High nest-predation is discussed in relation to nest placement and concealment, high nest visitation during incubation and nestling stages, anti-predator behaviour, nest-defence and types of predators, and re-nesting capacity, and compared with other Australasian robins and northern temperate and tropical songbirds. The small nest, small clutch-size, high nest failure, and anti-predator posture and mottled plumage of nestlings suggest that nest-predation is a strong selective pressure in the Jacky Winter. However, the moderately long nestling period, brood-size reduction, high rates of feeding young and nest visits by both male and female, and short and frequent incubation and brooding bouts on and off the nest relative to other robins are not consistent with nest-predation theory, and suggest behavioural responses to food availability and an ultimate response to food limitation. Incubation behaviour on and off the nest, parental care of young, nest visitation and other life-history traits that influence reproductive effort are discussed to elucidate the breeding strategy compared with other Australasian robins.