Ecology and breeding biology of the Forty-spotted Pardalote and other Pardalotes on North Bruny Island

Abstract

The second largest known colony of the rare Forty-spotted Pardalote Pardalotus quadragintus is on North Bruny Island (Tas). We spent from September to December 1983 at this colony. There were 86 breeding adults on a 55 ha study site (with c. 50 and 22 individuals for the co-existing Striated P. striatus and Spotted P. punctatus Pardalotes respectively). P. punctatus held large (x = 3.4 ha) non-overlapping territories. P. quadragintus held small x = 0.7 ha) territories with little overlap. P. striatus did not defend territories. Both punctatus (males) and quadragintus (males, but also some females) responded vigorously to playbacks of recorded calls of their own species, but there was little evidence of interspecific territoriality. Both quadragintus and striatus had a somewhat clumped dispersion of nests. The choice of nest-site differed between species, with most quadragintus nests (N = 24) in hollous in dead wood (especially cut-off stumps), striatus nests (N = 15) in hollows of living timber or in tunnels on the ground and punctatus nests (N = 5) only in ground tunnels. Most nests were apparently successful. P. striatus started nesting later than the other species. All species had some clutches. Predation of nest contents was rare. P. quadragintus, at least, may show strong nest-site fidelity.

All pardalote species, but particularly quadragintus, foraged disproportionately in Eucalyptus viminalis. Foliage of that species was comparatively rich in arthropods and, more critically, in the exudate, manna. This was a major diet item for all pardalotes (and particularly for quadragintus and punctatus). There was some interspecific aggression associated with foraging, with a distinct dominance hierarchy from Black-headed Honeyeater Melithreptus affinis (weight = 16.4 g) to quadragintus (10.7 g) to striatus (13.6 g) topunctatus (9.2 g). P. quadragintus individuals averaged only c. 5 midday in these interspecific encounters.

The survival of this colony may be jeopardized by habitat modification, through either change in fire regime or further clearing and fragmentation. This would affect not only availability of nest-sites but also potential for local post-breeding dispersal. The latter may be critical because of a presumed winter decline and unpredictability of food resources and because quadragintus has a wing shape which appears to be unsuited for dispersal over long distances.