The Rufous Whistler (Pachycephala rufiventris), a small insectivorous passerine, was studied in two areas of native dry sclerophyll forest and two exotic pine plantations in south-east Queensland. The pine plantations were approximately 30 and 45 years old respectively, and the younger was more intensively managed than the older.
Whistlers devoted more time to searching for food than any other activity, in all areas and seasons. Time budgets varied with sex and season, but there was little variation with area or forest type - with the exception of time spent in agonistic behaviour, which increased in the older plantation. Time spent at different foliage heights and in different tree species was, however, strongly dependent on forest type. In pine plantations, Whistlers used higher foliage and spent more time in pine trees. This is seen as an energetically efficient strategy since food supply is likely to be homogeneously distributed in the pine canopy, even if average supply per "patch" is low. Time and energy devoted to travelling between patches are minimised thereby.
Some native tree species found within pine plantations were actively "selected" when available, and preference shifted noticeably towards these species in autumn. Whistlers were rarely recorded in plantations in winter. Time devoted to food searching rose in winter to a recorded maximum of 66% in native forest, and most Whistlers were evidently unable to satisfy their food requirements efficiently in pine forest in winter in the maximum allowable time.
Habitat quality of the older plantation seemed comparable to that of the native forest areas, but the younger and more intensively managed plantation was of much lower quality. Average visit time per tree and average foraging time between flights were both shortest in this area, and availability of preferred food types seemed to be lower.
When foraging. Whistlers used snatching, hovering and pecking manoeuvres, with some aerial chases. Prey was mostly taken from foliage while the bird itself was in the air. More caterpillars were taken than any other food type. There was little variation in foraging strategy with area or forest type, except in the younger plantation where caterpillar intake was substantially lower, with more aerial chases after large flying insects. Capture attempts were more often unsuccessful in this area.
Whistlers showed a preference for wetter, more structurally complex portions of plantations. Driest sites with least structural complexity were generally avoided. Overall bird species richness showed similar trends.
Rufous Whistlers appeared to be flexible strategists, and underwent shifts along several niche dimensions on colonising pine forests. Males and females exhibited some differences in ecological strategy, but overlapped strongly on all niche dimensions and appeared equally successful in colonising plantations. Time budget is considered as a quantifiable dimension of a bird's niche. For the Rufous Whistler, it appears to be a relatively inflexible dimension. Ecological strategy is adjusted in new environments by variation along other more flexible niche dimensions to accomodate the limits imposed by energetic requirements (expressed in the time budget). When the critical limits of time budgeting cannot be adhered to. the species cannot remain within the new environment.
More intensive modern silvicultural practice (which includes draining and mounding of wetter areas and more frequent thinning and hazard-reduction burning) is likely to decrease the chances of successful plantation colonisation by Whistlers and other bird species.