Autumn–winter breeding by the Spotted Harrier Circus assimilis in southern Victoria

The breeding cycle of a pair of Spotted Harriers Circus assimilis was observed in southern Victoria, at 38°S, in autumn–winter 2017 for 42 hours over 22 days from incubation to the post-fledging period. From hatching on 10 June and fledging on 19 July, laying was inferred to have commenced on c. 8 May. Three chicks fledged from an initial brood of four; the nestling period was 38 days for the first-hatched chick. Rodents dominated a small sample of identified prey during a plague of House Mice Mus musculus. The male prey-delivery rate to the incubating female was 0.32 item/h, whereas during the nestling period the male brought 0.71 item/h and the female 0.11 item/h for a combined effective delivery rate of 0.64 item/h to nestlings. The combined parental feeding rate to new fledglings was 0.65 item/h. Parental behaviour is described. Juveniles were dependent for 6 weeks after fledging.