Use of nesting resources in an Australian arid-zone landbird community

Abstract

We investigated the use of nesting resources in a landbird community in the arid zone near Peery Lake, northwestern New South Wales. Over a 3.5-year period (1990–1994), which encompassed pre-drought, drought and post-drought conditions, we recorded 504 active nests and 51 breeding species, including open- (45% of all breeding species), hollow- (27%), mud- (8%), ground- (8%) and tunnel-nesters (4%), and species that nested both in the open and in hollows (8%). Almost 90% of observed nests were located in run-on habitats – major creeklines and minor creeklines. Forty-two species nested in, and 24 species nested only in, run-on habitats. Only 23 species nested in the much more extensive surrounding run-off habitats, but the nests of six species were located only in run-off areas. Most nests (90%) were located in plants, all of which were perennials, with 408 nests in live plants and 47 nests in dead plants. The live plants included 20 tree and shrub species ≥0.5 m tall and 4 subshrub and grass species <0.5 m tall. Most (88%) nests in perennial plants were in trees >4 m tall but often low down in the tree (only 47% of all nests in perennial plants were at heights >4 m). Different bird species favoured different plant species. Favoured trees included River Red Gum Eucalyptus camaldulensis for hollow-nesters, and Whitewood Atalaya hemiglauca and Black Box Eucalyptus largiflorens for open- and mud-nesters. Though fewer nests were located in plants <4 m tall, they were in a wider variety of plant species (16 species) than the larger number of nests in plants >4 m tall (14 plant species). Some nomadic species nested in low vegetation which, though perennial, died back and was unavailable in dry times. To support the nesting requirements of all birds, and to retain the diversity of arid-zone birds, the floristic and structural diversity of perennial plants needs to be maintained. This will be difficult to achieve if the current pattern of ongoing, incremental loss of trees and shrubs continues in the arid zone, particularly as the rate of loss is likely to be exacerbated by the impacts of climate change.