Birds and Nectar in a Monsoonal Woodland: Correlations at Three Spatio-temporal Scales

Abstract

The relationship between avian nectarivores and the availability of nectar was explored at three spatio-temporal scales over 23 weeks in tropical woodland near Darwin, Australia. Nectar was available in the study area throughout this period but its distribution varied spatially as the study progressed, and total availability was estimated to fluctuate 60-fold, being superabundant from mid-June to mid-August. The nectarivore community comprised 11 specialist nectarivores (two lorikeet and nine honeyeater species) and a variety of opportunists. The abundance and biomass of specialist nectarivores fluctuated five-fold and were positively correlated with nectar availability, but most of the fluctuation was due to just one species, the Little Friarbird, and at least six species were present in the area throughout the study period. Within the study area, the spatial distribution of all specialists combined was always positively correlated with nectar availability, but the correlation was weak and non-significant when nectar was most abundant. Correlations suggest that the Rainbow Lorikeet and Little Friarbird tracked nectar availability, but did so at different spatial scales. Evidence is presented that opportunists occupied niches left available by specialist nectarivores during the period of nectar abundance. The ‘failure’ of the specialist nectarivores to fully exploit the period of abundance may be related to the widespread availability of nectar in northern Australia during the middle of the dry season.