Foraging ecology of the Swift Parrot Lathamus discolor in the box-ironbark forests and woodlands of Victoria

Abstract

The foraging ecology of the Swift Parrot Lathamus discolor in the box-ironbark forests and woodlands of Victoria was investigated over three years. We sought to identify features that characterized Swift Parrot foraging habitats. A total of 159 foraging sites was found, mainly in box-ironbark forests or nearby woodlands, and were located at a disproportionately high frequency on drainage lines, and a correspondingly low frequency on ridges. The species was observed foraging on 12 eucalypt and one Acacia species, but more than 90% of observations were of birds using Red Ironbark Eucalyptus tricarpa, Mugga Ironbark E. sideroxylon, Yellow Gum E. leucoxylon or Grey Box E. microcarpa. Nectar, lerp and other food from eucalypt foliage were frequent dietary items. Foraging and random sites were broadly similar in tree size-class structure. However, Swift Parrots selected trees in larger size classes for foraging more often than expected given the relative abundance of such trees. Larger trees flowered more reliably across the study area in all years. The habitat of the Swift Parrot in the study area is extensively fragmented and degraded, and management to increase the density of larger trees is recommended. We found considerable between-year variation in regional distribution and relative use of prinCipal tree species. The five identified regions within the study area all supported a significant percentage of the population in at least one of the three years. As a result, recovery measures will need to target important sites across the geographical extent of the study area.