Landscape-scale conservation of an endangered migrant:the Swift Parrot ( Lathamus discolor) in its winter range

Abstract

The endangered Swift Parrot ( Lathamus discolor) is threatened by disturbance processes in both its breeding and its over-wintering ranges. Here we report on the spatial distribution of Swift Parrots over two successive winters in the box-ironbark system of central Victoria, Australia. The parrots showed little site-fidelity overall, and varied significantly among years in their regional distributions. Moreover, in some years it appears that relatively small remnant patches become significant elements in the landscape for the over-wintering parrots. Logistic-regression analyses suggest that the occurrence of Swift Parrots may be linked to the intensity of flowering by the Golden Wattle ( Acacia pycnantha) and also is associated with the summed density of aggressive, nectarivorous honeyeaters of the box-ironbark system. About 17% (a statistically significant amount) of the variance in the presence of Swift Parrots was explicable by these two variables. On the other hand, densities of Swift Parrots (where present) appeared to be related to densities of other nectarivorous species and of Noisy Miners ( Manorina melanocephala). Although statistically significant, just 5% of the variance in densities of Swift Parrots was explained by these variables. There were no relationships between measures of eucalypt flowering and the occurrence or density of Swift Parrots, nor with densities of potential aerial predators. These statistical patterns were difficult to explain because Swift Parrots seem to depend upon eucalypt nectar, with few feeding observations on racemes of Golden Wattle. Moreover, the positive correlation with the honeyeaters is difficult to reconcile with the lack of correspondence with eucalypt flowering. From a conservation standpoint, inter-annual variation in use of the major areas of the box–ironbark system by Swift Parrots is pronounced so that a very broad perspective needs to be maintained for their management in over-wintering regions. Moreover, remnants as small as 10 ha are utilized in some years by Swift Parrots so that preservation of remnant patches must be encouraged.