Ecology of the monsoon-rainforest endemic rainbow pitta, Pitta Iris

  • Udo Zimmermann

    Student thesis: Doctor of Philosophy (PhD) - CDU


    The Rainbow Pitta Pitta iris is endemic to monsoon-rainforests and associated habitats of the Top End of the Northern Territory and the Kimberley of Western Australia. Colour-banding showed that birds were sedentary and mean territory size of pairs varied from 1.6 ha to 3.6 ha. Pittas foraged in the leaf litter, eating mainly ants and beetles during the dry season, and earthworms during the wet season, when they were superabundant. Breeding coincided with the highest abundance of earthworms. Three quarters (74%) of all nests were predated, but predation on eggs was higher in the monsoon-rainforest (60%) than in the eucalypt forest (12%). Experiments with radiotelemetred eggs suggest that nest predators included arboreal snakes and rats. Fledglings remained in their natal territory for a relatively short period (18 days), then apparently dispersed to other forest patches. The species was more abundant in wet than dry monsoon-rainforests. There was no evidence that this species was adversely affected by habitat perturbation by feral animals, weeds or fire.

    The flush of earthworms, which lasted two to three months, but varied annually depending on rainfall, appeared to be a key-factor in the ecology of this species, explaining the brevity and annual variation in the start and length of the breeding season, the relatively high clutch-size (mean = 3.9), weight differences of birds from different populations, and geographical variation in density of birds. The Noisy Pitta P. versicolor in northern Queensland was migratory at some sites, but appeared to be sedentary on Cape York Peninsula, in contrast to the Red-bellied Pitta P. erythrogaster, which visits this region only during the wet season to breed. This difference in migration status may relate to the more specialised diet of the latter species, being more dependent on moisture-requiring invertebrates, which were scarce during the dry season.
    Date of Award1997
    Original languageEnglish
    SupervisorRichard Noske (Supervisor)

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