A RARE CASE: HABITAT SPECIALISATION AND COOPERATIVE BREEDING FACILITATES THE PERSISTENCE OF AN UNDERSTORY INSECTIVORE IN RAINFOREST FRAGMENTS
Habitat loss and degradation are among the greatest threats to biodiversity. Within rainforest communities, understory insectivores are disproportionately impacted. Consequently, populations are declining globally. The Pale-yellow Robin (PYR) Tregellasia capito is a territorial, understory insectivore known to inhabit small forest fragments where other species have been lost. The literature provides two possible explanations. The most likely being that while not immediately detrimental, a post-fragmentation crowding effect will ultimately lead to extinction. However, fragmentation is not negative for all species. Traits that confer protective or competitive advantages can facilitate persistence. PYR populations in complex notophyll vine forest fragments (n = 16) on the Atherton Tablelands were studied. No significant changes in territory characteristics or defence behaviour due to a reduction in overall fragment size were found. Group size (n = 65) showed cooperative breeding was employed throughout fragments of all sizes, with no increase in incidence as size decreased. Habitat surveys (n = 112) revealed stem density and ‘wait-a-while’ – both abundant features of disturbed habitat – were significantly related to presence / absence. Contrary to the literature, my results showed PYRs to be a disturbed habitat specialist, with the ability to utilise a cooperative breeding strategy to maximise use of preferred habitat.
Thesis submitted by Renée Cassels in partial fulfilment of the requirements for the degree of Bachelor of Science with Honours in the College of Science & Engineering of James Cook University.