Breeding biology and behaviour of the Pacific Baza Aviceda subcristata in subtropical coastal New South Wales

Abstract

The breeding biology and behaviour of predominantly two pairs of Pacific Bazas Aviceda subcristata were studied in subtropical north-eastern New South Wales from 2007 to 2017, with intensive observations in 2010–2012 (442.5 h). Fifteen breeding attempts were documented: eleven from observed nest sites, and four from observations of dependent juveniles. The pre-laying period occupied late August and September, with nest building taking 6–19 days. The mean incubation period was 31 days, usually from early October to early November. Both male and female shared diurnal incubation (Pair 1: male 42%, female 58%, only the female incubated overnight; Pair 2: male 62%, female 38%, sharing overnight incubation). The mean nestling period was 37.5 days, including a brooding period of 9–14 days. Breeding productivity was 1.87–2.0 fledglings/attempt (n = 15) across all sites combined. Fledging generally occurred in December, but on two occasions occurred in mid–late February. The post-fledging dependence period lasted at least 22 days, with juveniles joining flocks of other broods in the area at c. 40 days, and leaving the study area c. 45–60 days after fledging. Delivered prey was predominantly insects, especially cicadas (Hemiptera: Cicadoidea) and phasmatids (Phasmatodea: Phasmatidae) by number, and tree frogs Litoria spp. by biomass. Bazas brought prey at a mean rate of 1.2 items/h/juvenile (nestling and post-fledging periods combined), with juvenile intake estimated at 7.6 g/h/juvenile. Various behaviours – nest building, vocalisations, inter- and intraspecific interactions and their frequencies and contexts, and changes in juvenile morphology through the post-fledging period – are described for the years 2010–2012.