Bringing BREEDING Birds Back
Revegetation using native trees and shrubs is known to provide valuable habitat for many woodland birds in agricultural landscapes. Greening Australia's Birdwatch project, conducted in 2000-2001 in ACT and south-east NSW, recorded 110 different bird species using revegetation, even small patches isolated from other suitable habitat. A particularly exciting result of this study was the presence of a number of threatened and declining woodland birds in the young trees and shrubs. However, it is one thing for birds to be observed using revegetation, but a real measure of its success as habitat is evidence of breeding. Occasional observations of breeding had been made during Birdwatch, but a more thorough study was warranted.
In 2003, Suzi Bond from the Australian National University undertook an Honours project to determine whether birds were attempting to breed in patches of revegetation. A supplementary aim of her research was to determine whether the revegetation age bore any influence on the number and type of species that were occupying and attempting to breed within that patch.
During the spring breeding season, 16 revegetated sites and four remnant sites were surveyed for bird species, abundance and for breeding attempts. These sites were located in farming land around Canberra, Boorowa, Binalong, Murrumbateman and Gundaroo. The size of the patches ranged from 0.5 to 10 hectares, with most patches being less than 2 hectares, a size that is often considered to be too small to be useful for birds. Various habitat characteristics were recorded including distance to other habitat patches, tree health, number of tree hollows. All bird species using the sites were identified and categorised as woodland birds (dependent on woodland habitat), non-woodland birds, or whether they required tree hollows for nesting (obligate hollow-nesters).
Again, an impressive number of bird species, 111 in total, were recorded in the revegetated and remnant patches The drought conditions during the 2003 spring-summer meant that some unusual species seeking refuge from the parched inland were recorded in the revegetation. These included Budgerigars and the spectacular Crimson Chat. Eighteen woodland bird species were observed attempting to breed in revegetation, including four declining species and one threatened species - the Diamond Firetail. Other breeders ranged from small insectivorous species such as the Superb Fairy-wren, Weebill and Western Gerygone taking advantage of the shrub cover in which to hide their nests, to the larger Rufous Whistler and White-winged Triller, both considered to be declining species.
The age of the revegetation influenced the number of bird species occupying and attempting to breed in the patch, the older the patch, the more likely to support a greater number of species. The size of the patch was important, more bird species being found in larger patches. Woodland birds were also affected by the connectivity of the patch - whether or not it was close to other suitable habitat. In addition to patch size, age and connectivity, breeding results were found to be affected by tree health, with more breeding attempts in healthy vegetation. Not surprisingly, obligate hollow-nesters were only observed attempting to breed in revegetation which incorporated hollow-bearing remnant trees.
This study has confirmed that woodland birds will attempt to breed within small patches of revegetation. Particularly encouraging were the breeding attempts by locally declining and threatened birds such as the Southern Whiteface and Diamond Firetail, demonstrating once again the importance of revegetation in sustaining our native bird life.