Carla Catterall

Land-use intensification reduces functional redundancy and response diversity in plant communities.

Ecosystem resilience depends on functional redundancy (the number of species contributing similarly to an ecosystem function) and response diversity (how functionally similar species respond differently to disturbance). Here, we explore how land-use change impacts these attributes in plant communities, using data from 18 land-use intensity gradients that represent five biomes and > 2800 species. We identify functional groups using multivariate analysis of plant traits which influence ecosystem processes. Functional redundancy is calculated as the species richness within each group, and response diversity as the multivariate within-group dispersion in response trait space, using traits that influence responses to disturbances. Meta-analysis across all datasets showed that land-use intensification significantly reduced both functional redundancy and response diversity, although specific relationships varied considerably among the different land-use gradients. These results indicate that intensified management of ecosystems for resource extraction can increase their vulnerability to future disturbances.

Fates of feathered fruit-eaters in fragmented forests

The editor Dan Lunney and the council supporting members of the Royal Zoological Society of New South Wales are to be congratulated and encouraged for the production of a valuable journal that helps bridge the ever-increasing chasm between the interested public and the enthusiastic scientist. Like most Royal Societies, the emphasis is on rigorous communication of research findings to a broader and often lay audience. Increasingly, ecologists are shouldering their social responsibilities and applying their expertise more widely. The Australian Zoologist will continue to play a key role in this process and will continue to exploit the huge niche successfully and opportunistically in response to the rapid changes in the physical, scientific and social environments in Australia. REFERENCESFruit-eating birds disperse many rainforest seeds, thereby influencing rainforest regeneration. The abundance of these birds may change following forest clearing, causing differences in seed dispersal between extensively-forested and fragmented areas. We assessed the responses of 26 frugivorous bird species to forest fragmentation by comparing their abundance among extensive tracts, remnants and regrowth patches of rainforest (16 replicate sites in each) in subtropical south-east Queensland, Australia. There were five species that were recorded in much lower numbers in remnants and/or regrowth than in extensive forest (“decreasers”), seven that showed higher abundance in remnants and/or regrowth than in extensive forest (“increasers”) and 14 whose abundance did not change substantially between the three habitat types (“tolerant” species). The decreasers included three fruit-specialist rainforest pigeons (the wompoo, rose-crowned and superb fruit-doves Ptilinopus magnificus, P. regina and P. superbus). The increasers were largely bird species with mixed diets, many of which also use non-rainforest habitats. Two decreasers and two tolerant species were substantially more abundant during summer than winter whereas two increaser and two tolerant bird species were more abundant during winter. No effects of altitude on seasonal abundance were apparent. The results of this study show that fragmented remnant and regrowth patches of rainforest do not adequately conserve the full set of frugivorous avifauna. Furthermore, lower abundance of negativelyimpacted birds in fragmented remnant and regrowth sites may lead to reduced regeneration of certain rainforest plant species due to a lack of seed dispersal in these habitats.

Flocking and predator surveillance in house sparrows: Test of an hypothesis

The argument that individuals benefit from foraging in flocks through spending less time in predator surveillance and hence more time foraging and feeding, has been formalized in terms of a mathermatical relationship (Pulliam 1973). We have tested the model using house sparrows (Passer domesticus), and our results support its prediction of an inverse relationship between the time spent in predator surveillance and the flock size. The data did not fit the model exactly, and we attribute this to an unrealistic assumption.

Deforestation, urbanisation and seasonality: Interacting effects on a regional bird assemblage

Abstract We assessed the effects of conversion of eucalypt forests and woodlands (bushland) to cleared or developed land on bird communities in the rapidly urbanising lowlands of south east Queensland, in subtropical Australia. The majority of 56 species analysed showed large and significant density differences between bushland and cleared land: 22 (39%) were classed as ‘bushland species’, 13 (23%) as ‘developed land species’, and 21 (38%) as ‘generalists’ or ‘inconsistent’. ‘Bushland’ species showed a strong correspondence with those identified in other studies as exhibiting regional declines since European settlement, whereas ‘developed land’ species corresponded with those exhibiting regional expansions. Comparisons of summer and winter abundance also showed large differences in many species, mainly because of seasonal migration. Lowland eucalypt forest remnants of this study were characterised by (1) the presence of a suite of distinctive common bird species different from those which occur in cleared and developed areas, and (2) substantially higher total densities in winter than in summer, due mainly to bushland-dependent winter immigrants. The latter are at risk of further declines with ongoing habitat loss. In contrast, bird communities of the developed areas showed few seasonal differences.

Functional variation among frugivorous birds: implications for rainforest seed dispersal in a fragmented subtropical landscape

Seed dispersal plays a critical role in rainforest regeneration patterns, hence loss of avian seed dispersers in fragmented landscapes may disrupt forest regeneration dynamics. To predict whether or not a plant will be dispersed in fragmented forests, it is necessary to have information about frugivorous bird distribution and dietary composition. However, specific dietary information for frugivorous birds is often limited. In such cases, information on the seed-crushing behaviour, gape width and relative dietary dominance by fruit may be used to describe functional groups of bird species with respect to their potential to disperse similar seeds. We used this information to assess differences in the seed dispersal potential of frugivorous bird assemblages in a fragmented rainforest landscape of southeast Queensland, Australia. The relative abundance of frugivorous birds was surveyed in extensive, remnant and regrowth rainforest sites (16 replicates of each). Large-gaped birds with mixed diets and medium-gaped birds with fruit-dominated diets were usually less abundant in remnants and regrowth than in continuous forest. Small-gaped birds with mixed diets and birds with fruit as a minor dietary component were most abundant in regrowth. We recorded a similar number of seed-crushing birds and large-gaped birds with fruit-dominated diets across site types. Bird species that may have the greatest potential to disperse a large volume and wide variety of plants, including large-seeded plants, tended to be less abundant outside of extensive forests, although one species, the figbird Sphecotheres viridis, was much more abundant in these areas. The results suggest that the dispersal of certain plant taxa would be limited in this fragmented landscape, although the potential for the dispersal of large-seeded plants may remain, despite the loss of several large-gaped disperser species.

The use of ants and other soil and litter arthropods as bio-indicators of the impacts of rainforest clearing and subsequent land use

The present study investigated the impacts of rainforest clearance, and associated subsequent land␣use for pasture, on assemblages of soil and litter arthropods in eastern subtropical Australia. We assessed the utility of soil and litter arthropods as potential bio-indicators of cleared and forested habitats. Arthropods were sampled from 24 sites (12 sites each in rainforest and pasture) using two methods (extraction from litter, pitfall traps). Responses of taxa were analysed at various levels of taxonomic resolution, including ‘coarse’ arthropods (all arthropods sorted to Order/Class), ant genera and ant species. Multivariate analyses of arthropod composition indicated that an increase in the level of taxonomic resolution did not provide a commensurate increase in the sensitivity of assemblage response. Indicator values (IndVals), computed for each taxon, showed that a number of arthropod taxa may have potential as bio-indicators of habitat change. However the use of many of these, especially many ant species found in our study, may be unreliable because even after extensive numbers of sites were sampled, most species showed patchy distributions. To overcome this problem, we generated ‘composite indices’, by combining information from sets of indicator taxa. The utility of these composite indices is discussed.

Inter-related age-dependent patterns of ecology and behaviour in a population of silvereyes (Aves: Zosteropidae)

(1) The winter pattern of ecological differences between adults and juveniles was examined in the population of silvereyes (Zosterops lateralis chlorocephala) on Heron Island, Australian Great Barrier Reef. (2) Adults were more likely than juveniles to survive over winter. (3) Adults and juveniles tended to segregate into different habitats. The adults were more likely than juveniles to use the preferred breeding habitat (Pisonia forest) in winter. (4) Adults ranged over smaller areas than did juveniles, and were less likely to join foraging flocks. (5) Adults were socially dominant to juveniles, and were more discriminating in their defence of fig trees and figs, which were common in the clearings and edges of the Pisonia forest.

Integrating plant- and animal- based perspectives for more effective restoration of biodiversity

Ecological restoration of modified and degraded landscapes is an important challenge for the 21st century, with potential for major gains in the recovery of biodiversity. However, there is a general lack of agreement between plant- and animal-based approaches to restoration, both in theory and practice. Here, we review these approaches, identify limitations from failing to effectively integrate their different perspectives, and suggest ways to improve outcomes for biodiversity recovery in agricultural landscapes. We highlight the need to strengthen collaboration between plant and animal ecologists, to overcome disciplinary and cultural differences, and to achieve a more unified approach to restoration ecology. Explicit consideration of key ecosystem functions, the need to plan at multiple spatial and temporal scales, and the importance of plant–animal interactions can provide a bridge between plant- and animal-based methods. A systematic approach to restoration planning is critical to achieving effective biodiversity outcomes while meeting long-term social and economic needs.

Historical changes in the bird fauna at Coomooboolaroo, northeastern Australia, from the early years of pastoral settlement (1873) to 1999

Abstract Across most of northern Australia, the historical record is generally insufficient to serve as a baseline for interpreting the impacts of European settlement on fauna. A notable exception is the pastoral property Coomoobolaroo (454 km2) in central Queensland, where the ornithologist Charles Barnard maintained a detailed record of bird fauna from 1873 to 1933. We re-surveyed the property in 1999, and collated other information on its current avifauna, giving 242 species in total recorded over the period 1873–1999 (of which we had sufficient information to ascribe trends to 200 species). The bird fauna of Coomooboolaroo has undergone substantial change, across both of the periods 1873–1933 and 1934–1999. From 1873 to 1999, 45% of species declined or were lost from the property, compared with 13% of species that either colonised the property or increased. Most of the latter are widespread species or those known to benefit from clearing and land development. This extent of change appears at least as high as that reported for most comparable studies elsewhere in Australia, despite these being conducted at sites that have been subjected to superficially greater environmental degradation. The greatest rates of loss occurred among birds associated with softwood scrub (dry rainforest), grasslands and swamps. Smaller species were more susceptible to decline, but change in status was not significantly associated with foraging style nor different between residents and migrants. Many of the species that have declined at Coomooboolaroo have also declined in many other geographic regions, habitats and land-uses. Change in status at this property can be attributed to diverse factors, including changes in predation pressures; environmental change due to altered fire regimes and/or grazing by livestock; and vegetation clearance at both property and regional scales. The multiplicity and complex interrelationships of such factors renders it difficult to predict assemblage-level change.

Long-distance and frequent movements of the flying-fox Pteropus poliocephalus: implications for management.

Flying-foxes (Pteropodidae) are large bats capable of long-distance flight. Many species are threatened; some are considered pests. Effective conservation and management of flying-foxes are constrained by lack of knowledge of their ecology, especially of movement patterns over large spatial scales. Using satellite telemetry, we quantified long-distance movements of the grey-headed flying-fox Pteropus poliocephalus among roost sites in eastern Australia. Fourteen adult males were tracked for 2–40 weeks (mean 25 weeks). Collectively, these individuals utilised 77 roost sites in an area spanning 1,075 km by 128 km. Movement patterns varied greatly between individuals, with some travelling long distances. Five individuals travelled cumulative distances >1,000 km over the study period. Five individuals showed net displacements >300 km during one month, including one movement of 500 km within 48 hours. Seasonal movements were consistent with facultative latitudinal migration in part of the population. Flying-foxes shifted roost sites frequently: 64% of roost visits lasted <5 consecutive days, although some individuals remained at one roost for several months. Modal 2-day distances between consecutive roosts were 21–50 km (mean 45 km, range 3–166 km). Of 13 individuals tracked for >12 weeks, 10 moved >100 km in one or more weeks. Median cumulative displacement distances over 1, 10 and 30 weeks were 0 km, 260 km and 821 km, respectively. On average, over increasing time-periods, one additional roost site was visited for each additional 100 km travelled. These findings explain why culling and relocation attempts have had limited success in resolving human-bat conflicts in Australia. Flying-foxes are highly mobile between camps and regularly travel long distances. Consequently, local control actions are likely to have only temporary effects on local flying-fox populations. Developing alternative methods to manage these conflicts remains an important challenge that should be informed by a better understanding of the species’ movement patterns.