Impacts of bushfire on the Glossy Black-Cockatoo Calyptorhynchus lathami and its single food source in eastern Victoria

Abstract

The Glossy Black-Cockatoo Calyptorhynchus lathami eats only unripened seeds extracted from green cones of Allocasuarina and Casuarina trees. This specialised feeding habit results in Glossy Black-Cockatoos leaving unique evidence of having fed in a tree (i.e. feeding sign). The frequency of feeding sign beneath Black Sheoak Allocasuarina littoralis trees in East Gippsland, Victoria, was used as an index of the presence of Glossy Black-Cockatoos before and after intense and widespread bushfires during the summer of 2019–2020. Species distribution models for the cockatoo and its major food tree in the region were used to define 175 survey points in forested parts of East Gippsland. Survey points were visited in mid 2019, to score the presence or absence of Black Sheoak and Glossy Black-Cockatoo feeding sign. Following the 2019–2020 bushfires, all sites where Black Sheoak was present pre-fire were revisited twice within the following 28 months to search for feeding sign and score the extent of regeneration of Black Sheoak. Across all sites, the frequency of sites with feeding sign effectively halved between the pre-fire survey and first post-fire survey, then halved again between the first and second post-fire surveys, an overall decline of 76%. After 25–28 months, regeneration of Black Sheoak, in the form of either basal sprouting of established trees or seed germination, was observed at 80.6% of burnt sites, with a tendency for highest rates of regeneration at lower-fire- severity sites and for suckering to be more common than seedlings at higher-fire-severity sites. These results highlight the vulnerability of the Glossy Black-Cockatoo to reductions in the availability of its specialised food. The greatest threat to food security stems from increased frequency and intensity of fire, as predicted for the region by climate change models.