Ecology of eucalypt forest and woodland birds in the Great Western Woodland II: Foraging Guilds

A goal of ecology is to identify and explain structural and functional patterns characteristic of biotic communities. Patterns can be described by identifying how species use their common environment and using similarities and differences among species in the use of resources assign them to guilds. This paper uses foraging behaviour to describe the guilds of birds at four locations in the Great Western Woodland (GWW), Western Australia. Several questions were asked: What guilds characterised each location? What resources defined each guild? Can differences in foraging guilds between locations be attributed to differences in habitat structure and resource availability? Are there consistent similarities and differences in guild structure between bird communities? Five foraging guilds were identified in the GWW: 1. ground foragers; 2. foliage and bark gleaners; 3. bark foragers; 4. aerial foragers; 5. nectar-feeders. All guilds were found at all locations, which differed floristically, but had similar vegetative structure. Guilds at the four locations had similar species composition and there were no differences between locations in foraging behaviours or substrates. Guilds were identified by the foraging substrates used, with smaller clusters of species within guilds separated by prey type and prey-attack behaviour. Because species used a variety of prey-attack behaviours and foraging substrates, many species occurred in two or more guilds. Absent were guilds of fruit-eaters, flycatchers, and wood excavators found globally in forests. Also absent from the GWW were small seed-eaters and large parrots. Forests in the GWW lack an abundance of fruit, small seeds (e.g., grass seed), and large woody seeds of the type fed upon by large parrots elsewhere in Australia. The GWW guilds are the same as reported for eastern Australia and found in forests on other continents. Differences between phylogenetically different and geographically separated forests can be attributed to differences in foraging resources, such as substrates, nectar, fruit, and size of seeds.