Harry F. Recher

Why have birds in the woodlands of Southern Australia declined

This paper reviews the reasons why so many species of birds have declined in the eucalypt woodlands and associated habitats across the agricultural zone of southern Australia. The extent of habitat lost, over 90% in some regions, has led to the local extinction of some bird species, simply through random sampling effects. Habitat specialists and those that move sequentially among several habitats, are especially at risk, as some habitats have been lost disproportionally. Fragmentation introduces additional problems by subdividing populations into small, isolated sub-populations. Whereas some of the remaining species of birds appear able to move through highly fragmented landscapes, it is possible that they suffer high mortality while doing so. Some species that have been lost regionally may have had difficulty dispersing, but there have been few detailed studies of the demography of Australian birds in fragmented landscapes. Such studies are necessary before we can assess the value of corridors, or other means, to assist dispersal of birds. Fragmentation also leads to edge effects, which, when compounded by habitat degradation, may alter the intensity of a number of ecological processes. There is circumstantial evidence suggesting that loss of nest sites and increased predation on nests and free-living birds have contributed to the decline of woodland birds. Increased interspecific competition, for instance with noisy miners Manorina melanocephala, may also have a major impact on smaller insectivores and honeyeaters. Effects of parasites and disease have barely been studied in Australia, though brood parasitism could account for local losses. Dieback of eucalypts and loss of understorey are common in fragmented and degraded landscapes and are associated with a greatly reduced diversity of birds. The effect of fragmentation and degradation on food has received minimal attention. We propose further research that tests the importance of some of these ecological processes in causing the decline and loss of bird species in agricultural woodlands. Although management should proceed immediately, including a cessation of any further clearing of native vegetation, it should be conducted in conjunction with research. We suggest how the findings of research can inform managers, which will make management more effective in achieving conservation of regional avifaunas.

Conservation of woodland birds in a fragmented rural landscape

Increasingly, conservation efforts are being extended towards agricultural and pastoral areas outside large reserves. This indicates a change from the view of the landscape as islands of native habitat in a hostile matrix, to one in which the landscape is regarded as a patchwork of differing levels of disturbance. This latter view considers the whole of the landscape as the biological resource. These trends are discussed in relation to land bird species near Armidale on the New England Tablelands, north-east New South Wales, Australia. We assess the conservation status of 137 species of land birds. Of these, six species are locally extinct, 18 are thought to be declining and 35 are vulnerable due to their dependence on healthy woodland. Only 33 species are abundant and widely distributed on the Tablelands. The remaining 45 species tend to be habitat specialists that are marginal to the Armidale Plateau, and may never have been common in the study area. Most of the species that are dependent on large areas of continuous woodland (>400 ha) are in this last group, and it is demonstrated that an emphasis on these species may result in a conservation strategy that is inappropriate for most of the land birds in the region. Indeed, this could result in the extinction of species that at present are secure. An alternative strategy, specific to areas outside large reserves, is proposed that aims to maintain local species richness. In this management plan, priority is given to core species that are tolerant of intermediate levels of habitat fragmentation.

Major conservation policy issues for biodiversity in oceania

Oceania is a diverse region encompassing Australia, Melanesia, Micronesia, New Zealand, and Polynesia, and it contains six of the worlds 39 hotspots of diversity. It has a poor record for extinctions, particularly for birds on islands and mammals. Major causes include habitat loss and degradation, invasive species, and overexploitation. We identified six major threatening processes (habitat loss and degradation, invasive species, climate change, overexploitation, pollution, and disease) based on a comprehensive review of the literature and for each developed a set of conservation policies. Many policies reflect the urgent need to deal with the effects of burgeoning human populations (expected to increase significantly in the region) on biodiversity. There is considerable difference in resources for conservation, including people and available scientific information, which are heavily biased toward more developed countries in Oceania. Most scientific publications analyzed for four threats (habitat loss, invasive species, overexploitation, and pollution) are from developed countries: 88.6% of Web of Science publications were from Australia (53.7%), New Zealand (24.3%), and Hawaiian Islands (10.5%). Many island states have limited resources or expertise. Even countries that do (e.g., Australia, New Zealand) have ongoing and emerging significant challenges, particularly with the interactive effects of climate change. Oceania will require the implementation of effective policies for conservation if the regions poor record on extinctions is not to continue.

Comparative foraging efficiency of adult and immature little blue herons (Florida caerulea)

Juvenile little blue herons (Florida caerulea) miss prey more frequently and capture less food per minute foraging than do adults. The inefficiency of juveniles in capturing prey is an adequate explanation for the deferment of reproduction beyond the time when the birds might first be expected to breed.

The role of connectivity in Australian conservation

The existing system of nature reserves in Australia is inadequate for the long-term conservation and restoration of native biological diversity because it fails to accommodate, among other elements, large scale and long-term ecological processes and change, including physical and biotic transport in the landscape. This paper is an overview of the connectivity elements that inform a scientific framework for significantly improving the prospects for the long-term conservation of Australias biodiversity. The framework forms the basis for the WildCountry programme. This programme has identified connectivity at landscape, regional and continental scales as a critical component of an effective conservation system. Seven categories of ecological phenomena are reviewed that require landscape permeability and that must be considered when planning for the maintenance of biological diversity and ecological resilience in Australia: (1) trophic relations at regional scales; (2) animal migration, dispersal, and other large scale movements of individuals and propagules; (3) fire and other forms of disturbance at regional scales; (4) climate variability in space and time and human forced rapid climate change; (5) hydroecological relations and flows at all scales; (6) coastal zone fluxes of organisms, matter, and energy; and, (7) spatially-dependent evolutionary processes at all scales. Finally, we mention eight cross-cutting themes that further illuminate the interactions and implications of the seven connectivity-related phenomena for conservation assessment, planning, research, and management, and we suggest how the results might be applied by analysts, planners, scientists, and community conservationists.

Eucalypts, arthropods and birds: on the relation between foliar nutrients and species richness

Using chemical knockdown procedures, canopy arthropod communities on eucalypts (Eucalyptus spp.) were found to be extraordinarily rich in species. Four seasonal samples from four species of eucalypts, two in eastern Australia and two in Western Australia, yielded 976 species of canopy arthropods from the eastern site and 683 species from the west. The richest and most abundant faunas occurred on the site with the greatest soil fertility and on the tree species with highest levels of foliage nutrients (i.e. nitrogen and phosphorous). High nutrient concentrations are taken as a measure of overall productivity. Seasonal and annual differences in arthropod abundances, biomass, and species richness are correlated with temporal changes in rainfall affecting tree phenological events (e.g. growth of new leaves) and productivity. Species of insectivorous birds that are dependent on energy-rich source carbohydrates (e.g. lerp, manna) select between plant species as foraging substrates on the basis of the kinds of arthropods available and their abundance on each kind of plant. On the basis of our results from studies of avian and canopy arthropod communities, we propose a general model to explain patterns of species richness in eucalypt forest communities. In eucalypt forests, site productivity appears to shape faunal richness in two ways. First, productive forests tend to be structurally and floristically complex. This provides opportunities for a high degree of specialisation among animal species. Secondly, these levels of specialisation are possible only where there are high levels of productivity and resources that are abundant and equitable in their temporal distribution. The richness of eucalypt communities, the rarity of many arthropod species, and the association of the richest communities with temperate, moist forests on the most productive soils suggests that eucalypt forest biodiversity will be sensitive to changes in forest structure, floristic composition, and changed levels of productivity associated with logging and broad area fuel reduction fires.

Ecology of co-existing White-cheeked and New Holland Honeyeaters

The ecology and breeding biology of White-cheeked Phylidonyris nigra and New Holland P. novaehollandiae Honeyeaters has been studied since 1967 in the Brisbane Waters National Park north of Sydney, NSW. This is an area where the ranges of the two birds overlap and in one study plot, a heath, both nest close to each other. Only the White-cheeked occurs in a second plot, a dry sclerophyll woodland, near the heath. Breeding bird censuses have revealed that during most years similar numbers of honeyeaters nest during the autumn and spring but there can be considerable variation in numbers between years. The number of nesting pairs may be related to weather and to long-term changes in vegetation but there is no consistent pattern and numbers may be determined by environmental factors outside the study area. Both species forage in similar ways and take insects and nectar from the same places. It is suggested that the presence of both on the heath for part of the year is related to the abundance of nectar. In other places where the species overlap they are separated by habitat. Data on clutch size, nest sites and breeding success are presented and discussed.

Small mammal populations in a eucalypt forest affected by fire and drought. I. Long-term patterns in an era of climate change

This paper reports a study of ground-dwelling, small mammals in coastal eucalypt forest in south-eastern Australia from 1970 through 2005. During this time, the study area burnt in an intense fire in December 1972 and was partially burnt in November 1980. Both fires were associated with prolonged drought. The mammals studied comprised two dasyurid marsupials, Antechinus agilis and A. swainsonii, two native murid rodents, Rattus fuscipes and R. lutreolus, and the introduced house mouse Mus musculus. After intensive sampling throughout the year from 1970 through 1972 to establish basic ecological and population parameters of the small mammal community, populations were sampled annually during late autumn and early winter before the onset of breeding. There were marked differences in the annual (autumn/winter) abundances of all species; numbers of A. agilis ranged from 4 to 142 individuals; A. swainsonii 0 to 43; R. fuscipes 4 to 54; R. lutreolus 0 to 11; M. musculus 0 to 23. Following the 1972 fire, numbers fell to the lowest level recorded during the study and each population subsequently disappeared from the plot between the 1973 and 1974 winter censuses. The less intense 1980 fire did not lead to extirpation, but numbers of A. agilis, A. swainsonii and R. fuscipes declined as drought conditions persisted through 1983. R. lutreolus occurred consistently only following the fires, when a grassy ground vegetation favoured by this species developed. Similarly, M. musculus colonised within two years of the fires and persisted on the plot for 3–4 years before disappearing. Following the fires, populations of the omnivorous R. fuscipes recovered first followed by the scansorial, insectivorous A. agilis and last by the fossorial, insectivorous A. swainsonii. Two primary conclusions emerged from this study. First, the intense fire of 1972 did not kill all the animals immediately, but led to the disappearance of each species from the plot over 18 months. Thus, intense fire had a delayed but catastrophic impact on small ground-dwelling mammals. The fluctuations in population levels, covering more than an order of magnitude, demonstrate that factors other than fire, such as rainfall and drought, drive the population dynamics of these small mammals. As stability and recovery are not features of local populations, long-term studies of benchmark populations are necessary to manage forest biodiversity.

The biota of the Hawkesbury-Nepean catchment: reconstruction and restoration

Despite 200 years of European settlement, the Hawkesbury-Nepean catchment sustains a rich and diverse fauna. This is a consequence of extensive sandstone environments largely unsuited for development that escaped the extensive habitat modifications affecting the fauna of the grassy woodlands on the Cumberland Plain and Southern Tablelands. The most significant impacts followed the clearing and fragmentation of the vegetation for agriculture. Changed fire regimes, the naturalization of exotic plants and animals, and disease were also factors in the decline of native birds and mammals. Data on frogs and reptiles are limited, but some reptiles have declined in abundance in association with the loss of habitats. Not all native species have been adversely affected by European settlement and a number of birds have increased in abundance and extended their range within the catchment. Agricultural clearing and urban development have also affected aquatic ecosystems. The pre-European environment was apparently characterized by creek and river systems subjected to periodic floods, but with clear water, low nutrient levels, and clean sandly or rocky substrates. Increased nutrient levels, turbidity and siltation associated with urban and rural effluents, land clearing, foreshore erosion and river bed mining has reduced the extent of seagrass communities in the lower Hawkesbury and changed the substrate of rivers and the estuary. Mangrove communities have expanded. Other impacts on aquatic environments include the removal of riparian vegetation and the draining of wetlands, changes of flow regimes, dredging of channels, pollution of water from domestic, industrial and agricultural sources, changes in salinity, eutrophication of wetlands and the over-exploitation of the aquatic fauna. In freshwater creeks and rivers the native fauna has declined in abundance, while introduced species have spread throughout the catchment. In estuarine and marine environments, the fauna associated with clear water, low siltation rates, and seagrass beds has declined and species that were formerly abundant are now scarce. The native terrestrial and aquatic fauna in the catchment will continue to decline with urban expansion and better management of human activities within the catchment is urgently required. Further clearing within the catchment is unwise and existing vegetation remnants (including freshwater wetlands) should be protected from development. This is particularly important on the Cumberland Plain and Southern Tablelands where as distinctive fauna is associated with vegetation remnants and the reserve system is inadequate. Similarly provision needs to be made for minimum freshwater flows into the Hawkesbury-Nepean estuary. Nutrient removal from sewage, control of stormwater runoff, and better management of agricultural chemicals, fertilizers and mining within the catchment is necessary to restore water quality. Foreshoes should be revegetated. Most importantly, urban expansion and population growth within the catchment should be restricted.

Determinants of guild structure in forest bird communities: an intercontinental comparison

We examined the patterns of food resource utilization (guild structure) of 41 species of birds that breed in eucalypt forests and woodlands in south temperate Australia, and compared them to the results of a similar study in a north temperate, broad-leaved forest in North America (Holmes et al. 1979). Both studies used the same field methods and analytical techniques. The Australian community was more complex as inferred from the greater number of guilds (9 vs. 4) and from the results of principal components and factor analyses of the foraging data. These multivariate methods showed that guilds at the Australian site were separated first by differences in foraging height and bird weight, and second by foraging methods and food substrates. Use of specific foraging substrates (e.g., exfoliating bark) and food resources (e.g., nectar and other carbohydrates) were important at finer scales of separation. The results support the hypothesis that vegetation structure and food availability, which vary with plant species and vertical strata, produce particular sets of foraging opportunities for birds. These in turn influence which species can obtain food successfully, and thus can be considered primary determinants of guild structure. This comparison of food utilization patterns of birds in contrasting habitats provides insight into the factors determining bird community organization.