Ecology of birds in wet sclerophyll forests of tropical Queensland

Abstract

This is the first study to present detailed quantitative data on bird species utilising wetnsclerophyll forests of northeast Queensland. The resident and non-resident birdncommunity dependent upon this unique forest within the Wet tropics World Heritage Areanis described. Also examined in detail were the effects of two processes, rainforest invasionnand fire, operating in this unique tropical forest. This information contributes to both thentheoretical understanding of habitat selection in birds and in developing a soundnmanagement policy for wet sclerophyll forest.One hundred bird species was recorded in wet sclerophyll forests throughout the study,nrepresenting 35 families and 76 genera. One third are either endemic or are recognised as anseparate subspecies within northeast Queensland and includes six species which are listednas 'Near Threatened' and two species listed as 'Conservation Dependent'. The birdnpopulation in wet sclerophyll forest is composed of small insectivores (58%), followed bynhoneyeaters (21%), frugivores, which also take some insects (11%), granivores (5%) andnnectarivores (5%). Wet sclerophyll forest is rich in insects and nectar, but relativelyndepauperate in finit and seeds.There was a great deal of variation in density of birds. Of the resident species 78% showednsignificant differences in density between sites, 13% showed significant differencesnbetween years and 26% showed significant differences between months, or the interactionnbetween months and years. Reasons for these differences include (a) local and longndistance movement of species to track food resources, (b) altitudinal preferences and (c)nmicrohabitat preferences.The most common species to make a long-distance movement into wet sclerophyll forestnin summer was the Spangled Drongo, Dicrurus bracteatus. Other summer visitorsnincluded Leaden Flycatcher Myiagra rubecula, Satin Flycatcher Myiagra cyanoleuca,nCicadabird Coracina tenuirostris and Black-faced Monarch Monarcha melanopsis. Sevennspecies of birds showed correlation between density and elevation.Changes in fire regime have been identified as the cause of the loss of approximately 50%nof wet sclerophyll forest in north Queensland in the last 50 years. In the absence of fire, rainforest invades and eventually eliminates the endemic wet sclerophyll forest biota. Birdnpopulations and foraging behaviour were monitored in areas selected to encompass bothnrecent and advanced rainforest invasion. Foraging guilds are discussed in relation tonincreasing rainforest biomass. Some species, such as the Pale Yellow Robin, Tregallasiancapito nana were advantaged by the expansion of rainforest. Other species, such as thenGolden Whistler, Pachycephala pectoralis showed no significant response, whereas thenendemic subspecies of the Eastern Yellow Robin, Eopsaltria australis magnirostris wasnclearly disadvantaged. The latter species is of particular concern because in north-eastnQueensland it is dependent upon wet areas adjacent to rainforest and requires open groundnin which to forage. Over the longer term the northern race of the White-cheekednHoneyeater Phylidonyris nigra and the White-naped Honeyeater Melithreptus lunatus arenthreatened by habitat loss. These honeyeaters favour the wetter areas adjacent to thenrainforest which are gradually being lost to the invasive process. In addition, the endemicnNear Threatened, Bridled Honeyeater Lichenostomas frenatus also moves into wetnsclerophyll forest for food during the dry season.n n n n