Landscape influences on avian density in urban remnant vegetation

The management of urban environments is an increasingly important issue on an international scale as humans emigrate from rural areas to cities. Designing cities that can sustain mass human expansion while maintaining biodiversity is becoming an increasingly complex challenge for land managers. This is largely due to the lack of knowledge on how urbanization impacts upon biodiversity. Our previous research has highlighted the importance of urban remnant vegetation for avian diversity, but also suggested that landscape scale influences may have considerable impacts on the ability for a remnant to sustain species. We have since conducted a study examining avian diversity in 38 urban remnants ranging in size from 5ha to 107ha. These sites vary in relation to the quality of vegetation in the patch and their level of isolation from other remnant patches. This talk discusses the relative influences of remnant patch size, vegetation quality and isolation on avian diversity in urban remnant vegetation. We discuss how the findings of this research could be applied to managing avian diversity in the urban landscape.

Determinants of native avian richness in suburban remnant vegetation : implications for conservation planning

While urban areas are increasingly recognized as having potential value for biodiversity conservation, the relationship between biodiversity and the structure and configuration of the urban landscape is poorly understood. In this study we surveyed birds in 39 remnant patches of native vegetation of various sizes (range 1–107 ha) embedded in the suburban matrix in Melbourne, Australia. The total richness of species within remnants was strongly associated with the size of remnants. Remnant-reliant species displayed a much stronger response to remnant area than matrix-tolerant species indicating the importance of large remnants in maintaining representative bird assemblages. Large remnants are important for other ecological groups of species including migratory species, ground foraging birds and canopy foraging birds. Other landscape (e.g. amount of riparian vegetation) and structural components (e.g. shrub cover) of remnants have a lesser role in determining the richness of individual remnants. This research provides conservation managers and planners with a hierarchical process to reserve design and management in order to conserve the highest richness of native species within urban areas. First of all, conservation efforts should preferentially focus on the retention of larger remnants of native vegetation. Second, where possible, riparian vegetation should be included within reserves or, where it is already present, should be carefully managed to ensure its integrity. Third, efforts should be focused at maintaining appropriate habitat and vegetation structure and complexity.

Plasma cholinesterase characteristics in native Australian birds : significance for monitoring avian species for pesticide exposure

Cholinesterase-inhibiting pesticides are applied throughout Australia to control agricultural pests. Blood plasma cholinesterase (ChE) activity is a sensitive indicator of exposure to organophosphorus insecticides in vertebrates. To aid biomonitoring and provide reference data for wildlife pesticide-risk assessment, plasma acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were characterised in nine species of native bird: King Quails (Excalfactoria chinensis), Budgerigars (Melopsittacus undulatus), White-plumed Honeyeaters (Lichenostomas penicillatus), Yellow-throated Miners (Manorina flavigula), Willie Wagtails (Rhipidura leucophrys), Australian Reed-Warblers (Acrocephalus australis), Brown Songlarks (Cincloramphus cruralis), Double-barred Finches (Taeniopygia bichenovii) and Australasian Pipits (Anthus novaeseelandiae). Plasma ChE activities in all species were within the range of most other avian species and all but one contained AChE and BChE; no AChE was present in King Quail, which has not previously been reported for any species. The lowest detectable plasma AChE activity was 0.10 μmol min^–1 mL^–1 in Budgerigars and the highest was 0.86 μmol min^–1 mL^–1 in Australian Reed-Warblers. BChE in the plasma ranged from 0.37 μmol min^–1 mL^–1 in Double-barred Finches to 0.90 μmol min^–1 mL^–1 in White-plumed Honeyeaters and Australian Reed-Warblers. The lowest proportion of AChE was found in Budgerigars (12.8%) and highest in Willie Wagtails (67.8%). No differences were detected in ChE activity at any time of day in Budgerigars and Zebra Finches (Taeniopygia guttata), although there was a significant difference in all ChE activity between seasons in Zebra Finches.

The effect of acute fenitrotion exposure on a variety of physiological indices, including avian aerobic metabolism during exercise and cold exposure

The effect of fenitrothion exposure on birds was examined by measuring aerobic metabolism, blood hemoglobin content, plasma cholinesterases, and body weight for up to 21 d postdose. Peak metabolic rate was measured in a flight chamber in three-dose groups of house sparrows (Passer domesticus; 100 mg/kg = high, 60 mg/kg = medium, 30 mg/kg = low) and one-dose groups of zebra finches (Taeniopygia guttata; 3 mg/kg) and king quails (Coturnix chinensis; 26 mg/kg). Aerobic metabolism was measured during 1 h of exposure to subfreezing thermal conditions in low-dose house sparrows and king quails (26 mg/kg). Fenitrothion had no effect on metabolic rate during cold exposure or on blood hemoglobin at any time. By contrast, aerobic performance during exercise in sparrows was reduced by 58% (high), 18% (medium), and 20% (low), respectively, 2 d postdose. House sparrows (high) had the longest recovery period for peak metabolic rate (21 d) and plasma cholinesterase activity (14 d). House sparrows (high) and treated king quails had significantly lower myoglobin at 48 h postdose, whereas myoglobin was invariant in zebra finches and house sparrows (medium and low). Cholinesterase was maximally inhibited at 6 h postdose, and had recovered within 24 h, in house sparrows (low), king quails, and zebra finches. Exercise peak metabolic rate in zebra finches and king quails was reduced by 23% at 2 d and 3 d, respectively, despite these birds being asymptomatic in both behavior and plasma cholinesterase activities.

Testosterone effects on avian basal metabolic rate and aerobic performance : facts and artefacts

We examined the effects of cage size and testosterone (T) levels on basal and peak metabolic rates (BMR and PMR, respectively) and on pectoral and leg muscle masses of male house sparrows (Passer domesticus). Birds were housed either in small birdcages or in flight aviaries for at least 2 weeks prior to the initial metabolic evaluations. They were then implanted with either empty or T-filled silastic capsules and remeasured 5–6 weeks later. Birds treated with single T implants achieved breeding levels (4–6 ng/mL) and one group given double implants reached 10 ng/mL. There was no effect of T on BMR or PMR in any group studied, but there was an effect of caging. Caged birds showed significant reductions in PMR over the course of captivity, whereas PMR in aviary-housed birds were indistinguishable from their free-living counterparts. Testosterone treatment significantly increased leg muscle mass in caged birds, but had no effect on muscle mass in aviary-housed sparrows. We conclude that testosterone has no direct effect on sparrow metabolic rate or muscle mass, but may interact with cage conditions to produce indirect changes to these variables.

Physiological assessment of avian exposure to fipronil, a new-generation pesticide

Fipronil, a phenyl pyrazole pesticide, is aerially applied in semi-arid and agricultural areas of Australia to control locust outbreaks. Locust populations build to plague proportions when rainfall occurs in late winter and spring, promoting early vegetation growth. These conditions also attract breeding birds. Over 100 species have been observed coincident with locust control operations. Avian exposure to fipronil occurs via direct contact and by ingesting contaminated insects or seeds. Avian toxicity information demonstrates there is high species-specific variability in fipronil sensitivity in the few avian species studied. There is no research, however, explaining this variability, nor is there research regarding physiological or behavioural sub-lethal effects on avian species. This makes it extremely difficult to predict the toxicity of fipronil on unstudied species at high risk of exposure. Our research aims to resolve this lack of essential information in two ways: firstly we examine whether fipronil has identifiable sublethal effects in exposed birds and their offspring that compromise population health, and secondly evaluate avian metabolism of fipronil in selected species to gain insight into the mechanisms underlying variation in species sensitivity. Our results provide critically needed information for evaluating field effects of locust-control spraying in Australia.

Avian retinal oil droplets : dietary manipulation of colour vision?

Avian vision is highly developed, with bird retinas containing rod and double-cone photoreceptors, plus four classes of single cones subserving tetrachromatic colour vision. Cones contain an oil droplet, rich in carotenoid pigments (except VS/ultraviolet-sensitive cones), that acts as a filter, substantially modifying light detected by the photoreceptor. Using dietary manipulations, we tested the effects of carotenoid availability on oil droplet absorbance properties in two species: Platycercus elegans and Taeniopygia guttata. Using microspectrophotometry, we determined whether manipulations affected oil droplet carotenoid concentration and whether changes would alter colour discrimination ability. In both species, increases in carotenoid concentration were found in carotenoid-supplemented birds, but only in the double cones. Magnitudes of effects of manipulations were often dependent on retinal location. The study provides, to our knowledge, the first experimental evidence of dietary intake over a short time period affecting carotenoid concentration of retinal oil droplets. Moreover, the allocation of carotenoids to the retina by both species is such that the change potentially preserves the spectral tuning of colour vision. Our study generates new insights into retinal regulation of carotenoid concentration of oil droplets, an area about which very little is known, with implications for our understanding of trade-offs in carotenoid allocation in birds.

Will Wallace’s Line save Australia from avian influenza?

Australia is separated from the Asian faunal realm by Wallace's Line, across which there is relatively little avian migration. Although this does diminish the risk of high pathogenicity avian influenza of Asian origin arriving with migratory birds, the barrier is not complete. Migratory shorebirds, as well as a few landbirds, move through the region on annual migrations to and from Southeast Asia and destinations further north, although the frequency of infection of avian influenza in these groups is low. Nonetheless,high pathogenicity H5N1 has recently been recorded on the island of New Guinea in West Papua in domestic poultry. This event increases interest in the movements of birds between Wallacea in eastern Indonesia, New Guinea, and Australia, particularly by waterbirds. There are frequent but irregular movements of ducks, geese, and other waterbirds across Torres Strait between New Guinea and Australia, including movements to regions in which H5N1 has occurred in the recent past. Although the likelihood of avian influenza entering Australia via an avian vector is presumed to be low, the nature and extent of bird movements in this region is poorly known. There have been five recorded outbreaks of high pathogenicityavian influenza in Australian poultry flocks, all of the H7 subtype. To date, Australia is the only inhabited continent not to have recorded high pathogenicity avian influenza since 1997, and H5N1 has never been recorded. The ability to map risk from high pathogenicity avian influenza to Australia is hampered by the lack of quantitative data on the extent of bird movements between Australia and its northern neighbors.Recently developed techniques offer the promise to fill this knowledge gap.

The role of wild birds in the transmission of avian influenza for Australia : an ecological perspective

Waterbirds, particularly Anatidae, are natural reservoirs for low-pathogenic avian influenza and have been implicated as the primary source of infection in outbreaks of highly pathogenic avian influenza. An understanding of the movements of birds and the ecology of avian influenza viruses within the wild bird population is essential in assessing the risks to human health and production industries. Marked differences in the movements of Australian birds from those of the Northern Hemisphere emphasises the danger of generalising trends of disease prevalence to Australian conditions. Populations of Anatidae in Australia are not migratory, as they are in the Northern Hemisphere, but rather display typical nomadic traits, sometimes moving large distances across continental Australia in response to flooding or drought. There is little known regular interchange of anatids between Australia and Asia. In contrast, species such as shorebirds and some seabirds are annual migrants to Australia along recognised flyways from breeding grounds in the Northern Hemisphere. Movement into Australia by these species mainly occurs into the north-west and along the east coast over the Pacific Ocean. These species primarily arrive during the Australian spring and form large aggregations along the coastline and on inland wetlands. Other Australian migratory species (passerines, bee-eaters, dollar-birds, cuckoos, doves) regularly move to and from Asia through the Torres Strait Islands. The disease status of these birds is unknown. The movements of some species, particularly anatids and ardeids, which have ranges including Australia and regions where the virus is known to occur, have been poorly studied and there is potential for introduction of avian influenza subtypes via this route. Avian influenza viruses are highly unpredictable and can undergo reassortment to more pathogenic forms. There is insufficient knowledge of the epidemiology and transmission of these viruses in Australia and broad-scale surveillance of wild birds is logistically difficult. Long-term studies of anatids that co-habit with Charadriiformes are recommended. This would provide an indication of the spatial and temporal patterns of subtypes entering Australia and improve our understanding of the ecology of endemic viruses. Until such time as these data become available, Australia's preparedness for avian influenza must focus on biosecurity at the wild bird–poultry interface.

Avian color vision and coloration : multidisciplinary evolutionary biology

A fundamental issue in biology is explaining the diversity of coloration found in nature. Birds provide some of the best-studied examples of the evolution and causes of color variation and some of the most arresting color displays in the natural world. They possess perhaps the most richly endowed visual system of any vertebrate, including UV-A sensitivity and tetrachromatic color vision over the 300-700-nm waveband. Birds provide model systems for the multidisciplinary study of animal coloration and color vision. Recent advances in understanding avian coloration and color vision are due to recognition that birds see colors in a different way than humans do and to the ready availability of small spectrometers. We summarize the state of the current field, recent trends, and likely future directions.

Plumage reflectance and the objective assessment of avian sexual dichromatism

Assessment of color using human vision (or standards based thereon) is central to tests of many evolutionary hypotheses. Yet fundamental differences in color Vision between humans and other animals call this approach into question. Here we use techniques for objectively assessing color patterns that avoid reliance on species-specific (e.g., human) perception. Reflectance spectra are the invariant features that we expect the animal's color cognition to have evolved to extract. We performed multivariate analyses on principal components derived from >2,600 reflectance spectra (300-720 nm) sampled in a stratified random design from different body regions of male and female starlings in breeding plumage. Starlings possess spatially complex plumage patterns and extensive areas of iridescence. Our study revealed previously unnoticed sex differences in plumage coloration and the nature of iridescent and noniridescent sex differences. Sex differences occurred in some body regions bur not others, were more pronounced at some wavelengths (both ultraviolet and human visible), and involved differences in mean reflectance and spectral shape. Discriminant analysis based on principal components were sufficient to sex correctly 100% of our sample. If hidden sexual dichromatism is widespread, then it has important implications for classifications of animals as mono- or dimorphic and for taxonomic and conservation purposes.