Competition and aggression for nest cavities between Striated Pardalotes and endangered Forty-spotted Pardalotes

Abstract

ABSTRACT The Forty-spotted Pardalote (Pardalotus quadragintus) is an endangered songbird with specialized habitat requirements, including Eucalyptus viminalis trees for foraging and tree cavities for nesting. The species was originally distributed throughout eastern Tasmania, Australia, but habitat loss and fragmentation resulted in the contraction of its range to just 3 islands and several remnant mainland patches, primarily in the southeast of the state. The species' remaining habitat is exclusively second-growth forest, with reduced nest-cavity availability, and it competes for cavities with a common generalist, the Striated Pardalote (Pardalotus substriatus). This study documents the frequency of cavity takeover across the major populations of Forty-spotted Pardalotes on Maria Island, Bruny Island, and mainland Tasmania. Additionally, the intensity of interspecific aggression by pardalotes toward conspecific and heterospecific competitors at nest sites was assessed using a model presentation experimen...