Nesting requirements of the endangered Swift Parrot in a variable environment
The Swift Parrot is an obligate migratory species that only breeds in Tasmania. The species nests in tree hollows and forages primarily on flowers of the Tasmanian blue-gum during the breeding season. The study represents the most comprehensive assessment to date of nests and nest site characteristics of the species. Intensive nest surveys were conducted over 3 consecutive breeding seasons. Swift Parrots were found to nest in a highly clumped spatial distribution. Nest aggregations were associated with abundant blue-gum flowering and the presence of large forest patches (>100 ha) with old growth characteristics. Swift Parrot nest trees were characterised as being large eucalypts (mean diameter at breast height = 100 cm, range 33-202 cm) with five or more potential hollows (mean = 8.6, range 2-22) and showing clear signs of senescence or stress. Aggregations of nests at three of the study sites were the largest ever reported, both in extent (c. 50 – 100 ha) and numbers of nests (26-49 nests). Estimated nest densities ranged from 0.7 – 0.8 nests per hectare. The distribution of nesting aggregations was closely related to the distribution of abundant blue-gum flowering. Swift Parrots were generally sparse or absent from an aggregated nesting site if flowering conditions were poor in the surrounding area; however, historical nest records show Swift Parrots regularly return to nesting sites. This study highlights the temporal nature of Swift Parrot breeding habitat and the need for specific management to provide nest hollows for this endangered species with nest tree recruitment considered on a scale of 100’s of years.