Third-last survey for the season took me to Sector 4. This represents the only sector in Toohey Forest not bounded on at least one side by suburban habitat, roads, buildings or any other major anthropogenic disturbance. As a result, the number of species were slightly up on the last couple of surveys. More importantly, the species composition of the sites was also different, with a large number of species that you could categorise as edge-avoiding, interior core-habitat species. Species such as the Rufous Whistler, White-throated Treecreeper and even the Eastern Yellow Robin are more likely to be found within the centre of large patches, and seem to avoid edges. The concept of ‘edge effects’ reflects the different biotic and abiotic attributes associated with ecotone or edge habitat. For example, patch edges with roads or suburban development are typically characterised by increased noise, greater density of weeds, altered microclimate (e.g., windier, sunnier, hotter and thus drier) as well as an increase in ‘edge-tolerant’ and aggressive species such as Noisy Miners, Australian Magpies, Common Mynahs etc. As a result of these altered biotic and abiotic conditions at edges, species such as the Rufous Whistler and Eastern Yellow Robin are excluded from such habitat. Generally therefore, the larger a patch of vegetation, the greater the probability that the patch harbours these ‘edge-sensitive’ species. Back to the survey results……Apart from the species recorded below, I also heard a number of other species just off the survey route, including a Channel-billed Cuckoo, Striated Pardalotes and Olive-backed Orioles. In all therefore, there were a large number of species this morning! I also noted that apart from the number of species, there was a high diversity. By this, I mean, there were an appreciable number of almost all of the species instead of just single records of most species.
Species richness = the number of species in the community
Species diversity = the number and frequency of species in the community
The White-throated Treecreeper is a species that has apparently declined throughout Toohey Forest and is now primarily found on the high ridgelines within the centre of the forest.
As they are specialist bark foragers (with highly developed legs for walking up trees as they feed), they require large mature trees to feed on. The Eastern Yellow Robin is another species that has declined in the forest, for unknown reasons. They are associated with the moister areas of the forest in the gullies. Severe droughts in the last couple of years may have dramatically affected their breeding output and therefore their population persistence. Furthermore, as these species are resident and don’t have strong power of flight and dispersion, it will be hard to see recruits flying in from other patches. The long-term outlook for this species may be bleak, although future research as part of the larger study we are undertaking in the whole Brisbane metropolitan area will determine whether this decline in Toohey Forest is representative of what is happening throughout Brisbane.Date: 16th December 2008
Time: 0545 - 0805
Sector: 4
Number of species seen: 19
Number of birds seen: 123
Australian Magpie (8)Black-faced Cuckoo-shrike (3)
Eastern Whipbird (1)
Eastern Yellow Robin (2)
Grey Shrike-thrush (3)
Laughing Kookaburra (1)
Leaden Flycatcher (2)
Mistletoebird (5)
Pied Butcherbird (2)
Pied Currawong (5)
Rainbow Lorikeet (19)
Rufous Whistler (2)
Sacred Kingfisher (1)
Scaly-breasted Lorikeet (46)
Silvereye (4)
Spangled Drongo (1)
Tawny Frogmouth (1)
White-throated Treecreeper (1)
Yellow-faced Honeyeater (16)
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