Interspecific Aggression for Nest Sites: Model Experiments with Long-Tailed Finches (Poephila Acuticauda) and Endangered Gouldian Finches (Erythrura Gouldiae)

Abstract

ABSTRACT. For cavity-nesting birds, tree cavities often represent a critical, defendable, and limiting resource that is frequently under intense interspecific competition. However, the dynamics of interspecific conflict resolution, especially between species of similar size, are often unclear. We experimentally tested aggression and nest-defense behaviors in Gouldian Finches (Erythrura gouldiae) and Long-tailed Finches (Poephila acuticauda), two sympatric, cavity-nesting estrildid finches that are very similar in size, ecology, and nest-site requirements. Mounted taxidermie models of conspecific and heterospecific nest-site competitors (black and red Gouldian Finch morph and Long-tailed Finch models), as well as a control noncompetitor (Black-chinned Honeyeater [Melithreptus gularis]), were presented to Gouldian and Long-tailed finches. These two competing species differed in their overall responses to simulated intruders and in their relative aggression toward conspecific and heterospecific intruders. Lo...