Brian G. Collins

Seasonal variations in the energetics of an Australian nectarivorous bird, Lichmera indistincta

1. Seasonal variations in unit perching costs, flying costs and energy budgets for Lichmera indistincta were investigated. 2. Unit perching and flying costs were greatest in winter and least in summer. Variations in perching costs occurred principally because of changes in conductance. Flying cost variations may have been due to changes in wing disc loading and/or the integrity of wing feathers. 3. Rates of net energy intake were greatest in winter and least in summer. Variations in these rates were such that they offset changes in the rates of total energy expenditure to provide diurnal energy balance. 4. Regardless of the season, net daytime energy storage proceeded at a uniform rate and resulted in the storage of sufficient energy to offset overnight expenditure.

Nocturnal energy expenditure by honeyeaters experiencing food shortage and low environmental temperatures

Abstract 1. 1. Honeyeaters exhibit diurnal variations in body temperature and metabolic rate, with lowest values consistently occurring at night. 2. 2. Deprivation of nectar prior to dusk results in increased nocturnal hypothermia and decreased metabolic rates. 3. 3. Regardless of whether nectar deprivation occurs or not, total nocturnal energy expenditure closely approximates the amount of energy stored as lipid during each preceding day. 4. 4. Under the experimental conditions imposed, birds do not increase total diurnal energy storage significantly in anticipation that nectar availability will be curtailed.

Floral development and breeding systems of Dryandra sessilis and Grevillea wilsonii (Proteaceae)

Dryandra sessilis (Knight) Domin. and Grevillea wilsonii A.Cunn. co-occur on lateritic soils in the jarrah forest of Western Australia, with their flowering seasons overlapping for several months during winter and spring. Both species are protandrous, with pollen presentation occurring 1–2 days before the stigmas of individual flowers become receptive. Peak receptivity, as indicated by maximum peroxidase secretion, coincides with the maximum opening of stigmatic grooves for D. sessilis or maximum elevation of the stigmatic papillae in G. wilsonii. Pollinators such as western wattlebirds, New Holland honeyeaters and western spinebills almost exclusively visit flowers or inflorescences at times when large amounts of nectar are present, and when self-pollen is available for transfer or stigmas are receptive to the deposition of pollen. By foraging in this manner, yet still moving frequently between plants and inflorescences, honeyeaters that visit D. sessilis should guarantee an effective spread of pollen. The overall level of fruiting success achieved by this species is considerably higher than that for G. wilsonii, a species whose flowers are visited much less often than those of D. sessilis. Allozyme analysis, artificial pollination experiments and the calculation of pollen : ovule ratios indicate that D. sessilis is essentially an obligate outcrosser, at least in locations where plant densities are high, whereas G. wilsonii has a mixed mating system that allows it to set fruits as a consequence of either selfing or outcrossing. Potential fruit-set is low for both species, with post-zygotic incompatibility mechanisms mediated by the availability of nutritional resources thought to be at least partly responsible for the even lower levels of final fruit-set. Total fruit and seed production by individual plants is much greater for D. sessilis than for G. wilsonii, and possibly a reflection of differences in the regeneration requirements of the two species after environmental disturbance such as fire.

PREFERENTIAL FORAGING BY HONEYEATERS IN THE JARRAH FOREST OF WESTERN AUSTRALIA

Summary Collins, B.G. & Grey, J. 1988. Preferential foraging by honeyeaters in the jarrah forest of Western Australia. Ostrich suppl. 14:39-47. Individual Dryandra sessilis plants are patchily distributed in jarrah forest habitats, sometimes occurring in dense clumps but often widely spaced. These plants can differ considerably in terms of their canopy volumes and the number of nectar-producing inflorescences that they bear. Honeyeaters forage preferentially at D. sessilis inflorescences, selecting those that are youngest and produce the most nectar. The frequency with which honeyeaters visit particular plants is significantly and positively correlated with the number of productive inflorescences present, birds visiting more inflorescences, spending more time foraging for nectar and making a greater number of probes per inflorescence at plants with greater numbers of inflorescences. By behaving in this manner, birds enhance their foraging efficiencies. Birds identify appropriate plants and inflorescences ...