Richard E. Major

Influence of remnant and landscape attributes on Australian woodland bird communities

Abstract This study investigated relationships between the composition of bird communities and remnant and landscape attributes including area, shape, vegetation type and position in the landscape. Vegetation type was the strongest determinant of bird communities. The bird community of river red gum forests was most different from that of white cypress pine woodlands, with the bird communities of other vegetation types intermediate between these two extremes. Honeyeaters and hollow-nesting birds were associated with river red gum forests, whereas small insectivores were associated with white cypress pine woodlands. Bird communities also varied significantly with remnant size. Small insectivores were more likely to be found in remnants larger than 200 ha, whereas noisy miners and grey butcherbirds were more likely to be found in remnants smaller than 100 ha. Vegetation type, remnant area, absence of noisy miners and presence of small insectivores are interrelated. It is likely that the aggressive noisy miner, rather than remnant size per se, determines the presence or absence of small insectivores in remnants. Remnant attributes appeared to be more important than landscape attributes in determining the composition of bird communities, although the widespread occurrence of noisy miners may inhibit the benefits that landscape vegetation might provide. As long as an aggressive edge specialist dominates small remnants and there is a shortage of quality, core patches that might benefit from connectivity, we consider that a focus on landscape connections is a dangerous diversion for efforts directed towards biodiversity conservation. Large, high-quality patches must be established and protected for the conservation of declining birds.

The influence of remnant bushland on the composition of suburban bird assemblages in Australia

A large database collated by bird watchers was analysed to determine whether birds living in the urban habitats of Sydney, Australia could be characterised as a discrete community differing from those occupying a variety of nearby native habitats. Standardised surveys at fixed distances from nine remnants of one native habitat (woodland/scrub on Hawkesbury sandstone) were then conducted to determine whether size of, and distance to, remnants of native habitat influenced the composition of the surrounding suburban bird community. Non-metric multidimensional scaling did not separate the bird community of urban parks and gardens from those occupying residential areas. However, analysis of similarity showed that these communities were significantly different from the bird communities of each of the native habitats. Suburban habitats could be differentiated by the prevalence of exotic species as well as parrots, large honeyeaters, and large birds incorporating vertebrate foods in their diet, and a relative rarity of small insectivores and honeyeaters. Nearby remnant vegetation had little effect on the bird community inhabiting suburban areas. No significant effects of remnant size or remnant proximity were detected for species richness, individual abundance or community composition. These results suggest that there is little overlap in use of urban and remnant habitats by the majority of species and that in order to increase bird diversity, urban habitats must provide a fuller complement of ecological requirements.

Can Nest Predation Explain the Timing of the Breeding Season and the Pattern of Nest Dispersion of New Holland Honeyeaters

We tested the following two predictions of the hypotheses that predation rate may select for nest spacing and winter breeding in New Holland honeyeaters: (a) the level of nest predation should be lower during the breeding season than outside it, and (b) clumped nests should show a higher predation rate than more dispersed nests. Artificial nests, containing budgerigar and artificial eggs, were set out in four different seasons and in two different configurations: clumped and spaced. Clumped nests suffered higher predation than spaced nests but there was no seasonal difference in total predation rates. Birds accounted for 67% of predation events for which the predator was identified

The effect of habitat configuration on arboreal insects in fragmented woodlands of south-eastern Australia

The reduction in area of habitat patches and the concurrent increase in edge habitat associated with fragmentation of native vegetation have been shown to have a marked effect on the persistence of vertebrates in landscapes dominated by agriculture. However, because of the relatively large grain size they can distinguish, the spatial scale at which vertebrates become affected is likely to be different from that for invertebrates. Thus, although the high degree of fragmentation currently present in the sheep/wheat growing areas of Australia has been debilitating for vertebrates, this result cannot be extrapolated to the general state of species diversity. This study investigates the distribution of an arboreal insect fauna across a variety of habitat configurations common in the wheat/sheep belt of New South Wales. The aim was to determine the response of insects to habitat fragmentation at the scale associated with current agricultural practices, and to determine whether an “interior” fauna exists. Insects living on Callitris glaucophylla were sampled in the edge and interior of large state forests, in broad and narrow roadside strips and in small isolated remnants. Forest interiors had a significantly different fauna from the other four habitat configurations, and where differences between configurations occurred, interior sites tended to have fewer species and fewer individuals than the edge habitats. This result implies that the arboreal insects we studied are not adversely affected by this level of habitat fragmentation and the optimum arrangement of habitat for the conservation of insects may be quite different from that for proposed for vertebrates. However, this conclusion must be considered in the light of the dubious prognosis for long-term persistence of small habitat patches, and the possibility that fragmentation-sensitive species have already been lost from this environment.

Do Common Mynas significantly compete with native birds in urban environments

In Australia, the introduced Common Myna (Acridotheres tristis) is commonly believed to aggressively displace native birds and outcompete them for food and nest resources. However, the current paucity of scientific evidence makes it difficult to devise appropriate management strategies for protection of urban bird populations. This study investigates the way in which the Common Myna uses the urban environment and interacts with other species while foraging and nesting in Sydney, Australia. The bird community varied between habitat types along an urbanisation gradient, and the abundance of the Common Myna increased significantly with the degree of habitat modification. Surveys of the frequency of interspecific interactions revealed that the Common Myna did not initiate a significantly greater number of aggressive encounters than did other species. Focal observations of two potential native competitors showed that despite foraging in close proximity, the Common Myna rarely interfered with feeding activity. Assessment of natural tree hollow occupancy found that Common Mynas used significantly fewer tree hollows than did native species. Analysis of nest site selection indicated that Common Mynas chose to nest in more highly modified habitats, and in artificial structures rather than in vegetation. These findings suggest that, in this study area, Common Mynas have little competitive impact on resource use by native bird species in the urban matrix. The logical conclusion of these results is that the substantial efforts currently directed towards culling of Common Mynas in heavily urbanised environments is misdirected, and resources would be better directed to improvement of natural habitat quality in these areas if the purpose of control is to enhance urban bird diversity.ZusammenfassungEs wird allgemein angenommen, dass der nach Australien eingeführte Hirtenmaina die dort einheimischen Vögel aggressiv verdrängt und im Konkurrenzkampf um Nahrung und Nistmöglichkeiten schlägt. Aber der Mangel an wissenschaftlichen Nachweisen hierfür macht es schwierig, angemessene Strategien zum Schutz der in den Städten heimischen Vogelpopulationen auszuarbeiten und einzusetzen. In dieser Studie untersuchen wir die Art und Weise, auf die der Hirtenmaina in Sydney, Australien, das urbane Ökosystem nutzt und mit anderen Spezies bei der Futteraufnahme und den Nistaktivitäten interagiert. Die Vogelgesellschaft variierte zwischen einzelnen Habitat-Typen entlang eines Verstädterungs-Gradienten, und das Auftreten des Hirtenmainas nahm signifikant mit dem Ausmaß der Habitat-Veränderungen zu. Untersuchungen zur Häufigkeit zwischenartlicher Interaktionen ergaben, dass der Hirtenmaina nicht signifikant mehr aggressive Aktionen als andere Arten unternahm. Spezielle Beobachtungen zweier einheimischer, potentieller Konkurrenten zeigten, dass sich trotz Nahrungssuche in unmittelbarer Nähe zueinander der Hirtenmaina nur selten störend in die Nahrungssuche einmischte. Die Überprüfung der Belegung natürlicher Baumhöhlen ergab, dass der Hirtenmaina signifikant weniger Baumhöhlen nutzte als die einheimischen Arten. Eine Analyse der Auswahl von Nistplätzen ließ vermuten, dass der Hirtenmaina bevorzugt in stärker modifizierten Habitaten und eher in künstlichen Strukturen als in Vegetation nistet. All’ diese Ergebnisse legen nahe, dass der Hirtenmaina in dem hier untersuchten Gebiet, einem Stadtbiotop, für die einheimischen Vögel eine nur geringe Konkurrenz um Ressourcen darstellt. Die Schlussfolgerung hieraus ist, dass die derzeitigen substantiellen Bemühungen zur Ausrottung des Hirtenmainas in stark verstädterten Biotopen vergeudet sind und die Ressourcen besser in die Qualitäts-Verbesserung der natürlichen Habitate investiert werden sollten, wenn es darum geht, die Vielfalt der einheimischen urbanen Vögel zu erhöhen.

The pest status of Australian white ibis (Threskiornis molucca) in urban situations and the effectiveness of egg-oil in reproductive control

The Australian white ibis (Threskiornis molucca) is considered to be an urban pest along the east coast of Australia. The non-specific diet and broad habitat requirements of ibis have facilitated their successful exploitation of the urban environment. Ibis are considered a pest because they pose a threat to aircraft safety, scavenge food at waste-management sites, cafes and parks, and compete with other native species for food and habitat. This study assesses a new ibis-management technique, the application of ‘egg-oil’ to suppress hatching. On other species, egg-oiling has been shown to be environmentally safe and socially preferable to culling adult birds. Approximately 5 mL of food-grade canola oil was sprayed upon each egg, and both incubator and field trials were used to investigate the efficacy of this technique on ibis and to determine the optimal application time and frequency of egg-oil. Treatment eggs were given an application of oil during the 23-day incubation period either once per week, or once early ( 18 days) incubation. All four treatments were observed to be 100% effective at preventing ibis eggs from hatching during the laboratory trial and more than 98% effective during the field trial. These results indicate that applying canola oil to ibis eggs once, at any time, during the 23-day incubation period is sufficient to prevent ibis eggs from hatching. The field trial also showed that 30% of ibis, across the four oiling treatments, continued to incubate the unviable eggs for up to 54 days longer than the normal incubation period. Given that ibis are multibrooded, raising up to three successful clutches in a breeding season, the increased time devoted to incubating oil-treated eggs could reduce the opportunity for multiple broods, compared with conventional egg destruction. The egg-oil technique offers an additional tool for land managers to conduct ibis reproduction control, which should reduce the amount of time required to conduct ibis management, consequently reducing the cost to land managers.

What do museum specimens tell us about the impact of urbanisation? A comparison of the recent and historical bird communities of Sydney

Abstract Most research investigating the effect of urbanisation on animals infers temporal change by comparing the species composition of present urban habitats with that of nearby ‘natural’ sites. In regions with a long history of human habitation and large human populations, there are sometimes sizeable museum collections that provide direct evidence of the distribution of animals present before urbanisation. This study identifies changes in the bird community of Sydney associated with urbanisation, by comparing the pre-1900 bird community determined from the ornithological databases of the Australian Museum and Museum Victoria, with the bird community of 1998–99 determined from Birds Australias Atlas database. The major difference in the bird community between the two periods was a shift in body size, with large species comprising a greater proportion of the recent bird community than small birds. The source of this difference was a result of both a relative decline in the small species within bird groupings (e.g. small insectivores) and to a relative increase in groupings dominated by larger species (e.g. parrots and vertebrate feeders). These results are similar to those obtained from comparison of urban areas and nearby natural sites.

Housing shortages in urban regions: aggressive interactions at tree hollows in forest remnants.

Urbanisation typically results in a reduction of hollow-bearing trees and an increase in the density of particularly species, potentially resulting in an increased level of competition as cavity-nesting species compete for a limited resource. To improve understanding of hollow usage between urban cavity-nesting species in Australia, particularly parrots, we investigated how the hollow-using assemblage, visitation rate, diversity and number of interactions varied between hollows within urban remnant forest and continuous forest. Motion-activated video cameras were installed, via roped access to the canopy, and hollow usage was monitored at 61 hollows over a two-year period. Tree hollows within urban remnants had a significantly different assemblage of visitors to those in continuous forest as well as a higher rate of visitation than hollows within continuous forest, with the rainbow lorikeet making significantly more visitations than any other taxa. Hollows within urban remnants were characterised by significantly higher usage rates and significantly more aggressive interactions than hollows within continuous forest, with parrots responsible for almost all interactions. Within urban remnants, high rates of hollow visitation and both interspecific and intraspecific interactions observed at tree hollows suggest the number of available optimal hollows may be limiting. Understanding the usage of urban remnant hollows by wildlife, as well as the role of parrots as a potential flagship for the conservation of tree-hollows, is vital to prevent a decrease in the diversity of urban fauna, particularly as other less competitive species risk being outcompeted by abundant native species.

Population and breeding trends of an urban coloniser: the Australian white ibis

Context. In the Sydney region, the population of Australian white ibis has dramatically increased from rare observations in the 1950s to a breeding season peak of 8900 in 2008, resulting with human–wildlife conflicts. Within natural habitats across the eastern states, the ibis population has declined, yet within urban environments ibis have been lethally managed for over 30 years. However, limited ecological and no regional population data are available for the Sydney region. Aims. The present study of ibis in the Sydney region aims to (1) establish the abundance of the population during the breeding and non-breeding seasons, (2) determine whether the population is increasing, and (3) identify the importance of different foraging and roosting sites. Methods. Across the Sydney region, we surveyed 54 discrete sites for 2.5 years. At each site, we recorded the number of adult, juvenile and nestling ibis as well as the number of active nests. The 54 sites were grouped into 15 areas consisting of five landfills and 10 suburbs, which were assessed with ANOVA. Key results. The ibis population of the Sydney region doubled from a peak of 4200 in 2006 to 8900 in 2008. Seasonal fluctuations saw adults migrating in to the region to breed, and adults and juveniles dispersing following breeding. On average, 44% of the population was located foraging within landfills, whereas 80% of nesting activity occurred within ‘urban-natural’ habitats. Conclusions. Seasonal fluctuations indicated that the ibis population of Sydney is connected with the broader state and national population. Landfills provided an abundant foraging resource that supported extended breeding, including consistent nesting for a 19-month period. Implications. The present study indicated that any localised population management has consequences beyond the immediate or regional population and, consequently, regional management plans or actions need to consider the long-term status of the eastern states’ population. Urban conflicts need to be resolved with human education and a conservation agenda, preferably with the provision of refuge habitat where birds are not disturbed.

Population genetics of wolf spiders of fragmented habitat in the wheat belt of New South Wales.

Possible effects of habitat fragmentation on the population genetics of a species of wolf spider (Lycosidae) from remnant Callitris woodland in the wheat belt of central western New South Wales in Australia are examined. Single‐strand conformational analysis of mitochondrial cytochrome oxidase (subunit 1) was used to characterize the haplotypes of 295 spiders in six blocks each of four woodland sites. DNA sequences were collected from 119 of these spiders to confirm haplotype scoring, allow phylogeny estimation and permit calculation of sequence‐based statistics. Intra‐block tests do not suggest widespread effects of fragmentation. Genetic diversity is high in all blocks, with 25 haplotypes being identified. Nucleotide diversity is relatively low, as all of the haplotypes are closely related. One block had a significantly low value for the Ewens/Watterson test of neutrality and one blocks value was nearly significantly high. Two blocks had nearly significant values of the Harpending Raggedness Index testing for recent population bottlenecks. No other intrablock tests approach significance. Interpopulation comparisons show significant nonhomogeneity of haplotype frequencies globally and in all pairwise comparisons. Relationships between woodland blocks based on haplotype frequencies are discordant with geographical proximity. Haplotype distribution patterns suggest that population structuring existed prior to fragmentation. We develop two measures of genetic distinctiveness to identify subpopulations of interest for conserving evolutionary processes in a species’ regional population. One is based on the sum of pairwise FST values and one on the spatial distribution of genetic variation. High values of the measure suggest a subpopulation might have been recently perturbed and low values that it is relatively undisturbed. The two measures identify different blocks as being of particular interest.