Responses to fire of Slender-billed Thornbills, Acanthiza iredalei hedleyi, in Ngarkat Conservation Park, South Australia. II. Foraging behaviour

Abstract

The foraging behaviour of the Slender-billed Thornbill, Acanthiza iredalei hedleyi, and associated habitat structure and composition was studied in burnt, regenerating and mature heath (3, 10 and 22 years since fire, respectively) in Ngarkat Conservation Park, South Australia. In total, 80% of all behavioural observations were of Slender-billed Thornbills foraging, primarily gleaning insects from the foliage (71% of all foraging moves). The height and degree of senescence of shrubs was greatest in the mature heath followed by the regenerating heath, where Banksia ornata and Allocasuarina pusilla were the most dominant shrubs. The recently burnt heath was dominated by Leptospermum myrsinoides and L. coriaceum, which regenerate from underground lignotubers after fire, and a diversity of plants and shrubs that germinate from seed.

Slender-billed Thornbills used all available habitat structures in each habitat type, although there were differences in foraging behaviour between different post-fire successional stages. In the burnt heath, birds foraged more often on the ground and between 0 and 50 cm and made more perch changes per minute (46) than in the regenerating (37) and mature (41) heath. Furthermore, in the recently burnt heath, Slender-billed Thornbills foraged on a diverse range of shrubs that germinate after fire. In the regenerating and mature heath birds foraged more often between 50 cm and 100 cm, and in the mature heath birds foraged primarily on Leptospermum and B. ornata. Slender-billed Thornbills therefore are able to adapt to the changes that occur in habitat structure and composition between a recently burnt and a mature heath.