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Wild bird feeding often results in high densities of birds, potentially facilitating transmission of disease. Wild birds are major reservoirs of many zoonotic diseases, and although a number of avian disease outbreaks have been linked to bird feeders, urban bird-feeding and its role in disease systems remains poorly studied. We examined the impacts of typical supplementary feeding practices on the health status of feeder-visiting birds at experimental feeding stations in an urban area of New Zealand. Over an 18-month period, we screened birds captured at feeding and non-feeding properties for three pathogens and four groups of parasites to determine whether feeding altered disease dynamics. We also assessed body condition. All pathogens and parasites were detected in at least one garden bird species. Feeding stations tested positive for Salmonella enterica Typhimurium on ∼7% of occasions, confirming that structures used in feeding are a potential transmission pathway. Feeding influenced some parasite infection parameters; these effects varied among host species. In silvereyes Zosterops lateralis, helminth prevalence and abundance were lower at feeding properties compared to non-feeding properties. In contrast, Eurasian blackbirds Turdus merula at feeding properties had a higher abundance of helminths. House sparrows Passer domesticus at feeding properties had a higher abundance of feather lice. Furthermore, our feeding regime significantly affected body condition in house sparrow and silvereye, though no associations between parasite parameters and body condition indices were found. Our results demonstrate that feeding practices can have varied effects on avian health, including no observable effects for some disease agents in some host species. Disease risks are present, however, thus understanding and reducing these risks should be a key goal for all stakeholders to protect birds that use feeders and other wildlife.

In birds, song divergence often precedes and facilitates divergence of other traits. We assessed the relative roles of cultural drift, innovation, and acoustic adaptation in divergence of island bird dialects, using silvereyes (Zosterops lateralis). In recently colonized populations, syllable diversity was not significantly lower than source populations, shared syllables between populations decreased with increasing number of founder events, and dialect variation displayed contributions from both habitat features and drift. The breadth of multivariate space occupied by recently colonized Z. l. lateralis populations was comparable to evolutionarily old forms that have diverged over thousands to hundreds of thousands of years. In evolutionarily old subspecies, syllable diversity was comparable to the mainland and the amount of variation in syllable composition explained by habitat features increased by two- to threefold compared to recently colonized populations. Together these results suggest that cultural drift influences syllable repertoires in recently colonized populations, but innovation likely counters syllable loss from colonization. In evolutionarily older populations, the influence of acoustic adaptation increases, possibly favoring a high diversity of syllables. These results suggest that the relative importance of cultural drift and acoustic adaptation changes with time since colonization in island bird populations, highlighting the value of considering multiple mechanisms and timescale of divergence when investigating island song divergence.

Understanding the influence of environmental factors on population dynamics is fundamental to many areas in biology. Survival is a key factor of population biology, as it is thought to be the predominant driver of growth in long-lived passerines, which can be influenced by both biotic and abiotic environmental conditions. We used mark-recapture methods and generalized linear mixed models to test the influence of density and climatic variation, measured at a regional and local scale (Southern Oscillation Index [SOI] and rainfall, respectively), on seasonal variation in survival rates of an insular population of Silvereyes (Zosterops lateralis chlorocephalus), during a 15-year study period, off the east coast of Australia. We found overall high survival rates for adults and juveniles (81% and 59%, respectively). Local scale climate (i.e. rainfall) and density were the principal environmental factors influencing their survival, both with a negative relationship. A significant interactive effect of density and rainfall influenced survival as they both increased. However, survival remained low when density was at it highest, independent of the amount of rainfall. Nestling survival was negatively influenced by rainfall and density, positively by SOI, and chicks that hatched later in the breeding season had higher survival rates. The regional scale climate variable (i.e. SOI) did not explain survival rates as strongly as rainfall in any age class. Our results contribute to the understanding of insular avian population dynamics and the differential effects of environmental factors across age classes. Climatic predictions expect El Niño events to increase, meaning dryer conditions in eastern Australia, potentially increasing Silvereye survival across age classes. However, the long-term effect of lower rainfall on food availability is unknown; consequently, the outcome of lower rainfall on Silvereye survival rates is uncertain.

The Tapora Landcare Group, operating on the Okahukura Peninsula, has the long-term goal of making this region predator fenced. The aim of this study was to obtain information on the current status of avian biodiversity and the bird community across the band of coastal wetlands on the Okahukura Peninsula. Bird counts were conducted and playback lures used to detect three cryptic wetland species: fernbirds (Bowdleria punctata); spotless crakes (Porzana tabuensis); and banded rails (Gallirallus philippensis). Fernbirds and banded rails were detected at seven of the eight wetland sites sampled whereas spotless crakes were detected at two sites. The native species with the highest relative abundance across the eight sites were silvereyes (Zosterops lateralis) and South Island pied oystercatchers (Haematopus finschi). Changes in avian biodiversity over time in the region can now be monitored, and comprehensive long-term data on the status of avian biodiversity over time obtained.

Whereas the changes in avian community composition resulting from urban development are well described, the specific factors that allow certain species to thrive in urban areas remain poorly understood. However, the availability of arthropod prey is emerging as a potentially important factor in shaping urban bird communities. Silvereyes (Zosterops lateralis) are common in urban areas and so provide a useful study organism to test the factors that allow some birds to become urban ‘winners’. We here present the results of an observational study on the foraging frequency of Silvereyes and arthropod prey availability in native and exotic urban trees in Dunedin, New Zealand. Silvereyes more frequently used individual trees, native or exotic, that supported the highest level of arthropod abundance. Silvereye foraging also varied greatly on a seasonal scale. Silvereyes were able to adjust their seasonal foraging to incorporate exotic vegetation with high arthropod abundances. We conclude that the flexibility of Silvereyes with regards to foraging and their use of exotic plant species are important factors in their success in surviving urban development.

Differences in song repertoires and characteristics of island and mainland populations of the same avian species are usually explained by dispersal, cultural evolution and/or habitat differences. The influence of morphology is often overlooked, even though island populations are frequently morphologically distinct from mainland populations, and morphology could affect vocalizations. I compared morphological features, songs, contact calls and alarm calls of six isolated island populations of silvereye Zosterops lateralis with those of two mainland populations to examine whether differences between mainland and island vocalizations were consistent across vocalization types, and whether these differences could be linked to morphological differences. Vocalizations were lower in frequency on islands. Island individuals were larger (both in mass and body structure), and body mass was an important predictor of frequency in contact and alarm calls. I argue that this strong association results from the island rule (islands promote larger body sizes) and cascading effects of morphology on vocalization frequency in this species.

Members of the genus Zosterops are known for their colonizing ability and extensive phenotypic differentiation on numerous islands. There have been morphological and biochemical analyses of some Zosterops populations, but little study has been devoted to patterns of vocal communication signals, known to be important pre-mating barriers in many bird species and in possible diversification of taxa. I report on the song system of one subspecies of Zosterops in a mainland population and an island population 15 km distant. I used both a traditional subjective classification of song elements and the multivariate procedure of linear discriminant analyses (LDA) of measured sound features. The syllables constituting songs exhibited a low level of stereotypy, disallowing a lexicon of syllable ‘types’ to be constructed for individuals or a population. New syllables were continuously produced as a bird uttered more and more songs, possibly indicating an extremely large repertoire or an open-ended generation ...

The bioacoustic attributes of vocalisations made by birds in urban environments often differ markedly from those of rural conspecifics. Whether such differences are result from genetic divergence between urban and rural populations, or from plasticity or cultural evolution of song remains poorly understood. Silvereyes (Zosterops lateralis) show evidence of acoustic adaptation to urban noise, modifying both their songs and calls in cities when compared to rural areas. We investigated whether these differences were associated with corresponding morphological and neutral genetic differences. Across six pairs of geographically separate urban and rural populations, all morphological traits measured were similar. Furthermore, genetic analyses of variation at nine microsatellite loci revealed high levels of genetic connectivity between populations, and similar levels of heterozygosity in both habitat types. Consistent directional shifts in song attributes of city birds across large geographic areas thus do not appear to be accompanied by associated morphological or neutral genetic divergence.

The loss of bird species following human colonization of New Zealand has raised concerns about the consequences for crucial ecosystem functions such as pollination. The understorey shrub Alseuosmia macrophylla (Alseuosmiaceae) exhibits characteristics typical of a bird pollination syndrome, but populations still persist in northern North Island forest remnants despite the local extinction of most endemic bird pollinators, leading to the suggestion that moths – rather than birds – may be the primary pollinators. The aim of this study was to quantify the importance of endemic birds as pollinators of A. macrophylla over several years by comparing plants on Little Barrier Island (LBI), where all extant endemic bird pollinators still occur, to plants at sites on the adjacent North Island in the Waitakere Ranges (WTK), where only one of these species remains common. Flowers on LBI were visited by endemic bellbirds (Anthornis melanura) and stitchbirds (Notiomystis cincta), while at WTK sites the most common visitors were the recently arrived silvereye (Zosterops lateralis) and the introduced honeybee (Apis mellifera), both of which acted principally as nectar robbers. Caged flowers on LBI had significantly lower fruit set than open flowers, and plants at WTK were significantly more pollen-limited than plants on LBI. This provides evidence that the loss of endemic pollinating birds is the most likely reason for the high pollen limitation found in some North Island A. macrophylla populations, and the very low seed set of these populations could have serious implications for the long-term persistence of this species.

Predation of eggs and/or chicks is the main cause of nesting failure in birds. Nest predation has been studied in many habitats in New Zealand, but few studies have been conducted in urban ecosystems. Twenty-one nests of four bird species (blackbird [Turdus merula], song thrush [Turdus philomelos], fantail [Rhipidura fuliginosa], and silvereye [Zosterops lateralis]) were monitored over one breeding season in Hamilton using time-lapse recordings. Five predation events were filmed (two by cats [Felis catus], and three by ship rats [Rattus rattus]), 10 nests successfully fledged chicks and 6 nests failed owing to poor weather, desertion, or unknown events. Although the sample size was small, our data suggest that nesting success may be higher in urban Hamilton than in other unmanaged habitats where predation rates can exceed 80%. We recommend that future studies of nesting success in urban birds should also focus on the fates of fledglings, as anecdotal evidence suggested that predation rates may ha...

We compared the feeding behaviour of garden birds in the presence of four heterospecific decoy species at suburban feeding stations to assess the relative importance of body size (large vs. small) and demeanour (high vs. low potential for inter-specific aggression) as cues for threat recognition. We conducted separate trials with live, caged Australian magpie, Cracticus tibicen, and common myna, Acridotheres tristis, large and small species known to chase and harass heterospecifics, and comparably sized species not known for inter-species aggression (i.e. rock dove, Columba livia, and ringneck dove, Streptopelia risoria). Birds of all species arrived at feeding stations sooner and displayed higher-risk activities in the presence of small decoys. The two most common species that visited the feeding stations, silvereye, Zosterops lateralis, and house sparrow, Passer domesticus, were most likely to perform high-risk behaviours (i.e. landing on the stimulus cage and feeding from the station) in the presence of common mynas. The activities were performed least frequently in the presence of Australian magpies. As garden birds likely had the most experience interacting with common mynas, the results suggest that a two-step decision rule, with size and familiarity as important cues, may be used to recognize potential threats.

Secondary metabolites in fruit are compounds that are not directly associated with plant growth; some are directly related to plant reproductive processes, specifically seed protection and dispersion. There is a complex and species-specific interaction between these plant compounds and their avian seed dispersers. To determine whether two important secondary metabolites in wine grapes – tannins and colour pigments – might be important cues to two of the avian species that forage on wine grapes, and how species-specific this interaction might be, comparative field experiments were run with Australasian silvereyes (Zosterops lateralis) and European blackbirds (Turdus merula). Both species were offered a glucose/fructose artificial nectar with increasing concentrations of grape tannins. In a second experiment, they were offered both green and purple artificial grapes where only the colour differed. Both species showed aversion to tannins; silvereyes appeared to have greater tolerance than blackbirds of tannin concentrations above 5%. In summer no preference was shown between green and purple coloured artificial grapes, but in late autumn blackbirds took only purple grapes whereas silvereyes pecked mostly at green. Links between tannin for seed protection and colour signals to birds are discussed. Colour may cue the two species to different species-specific aspects of fruit nutritive value.

Night‐activity patterns of individually‐caged grey‐breasted silvereyes Zosterops lateralis of resident and migrant status were investigated. True migratory restlessness or ‘Zugunruhe’ was exhibited by some individuals, but there was also considerable ‘noise’ in the data caused by cageing and neighbouring disturbance. In general, ‘Zugunruhe’ took place from about 2 h before, to about 4 h after ‘sunrise’, and both the daily timing and annual duration of Zugunruhe were consistent with the migration pattern observed in the field. A total of 42 % of resident birds from Tasmania, 77 % of migrant birds from Tasmania and 90 % of migrant birds from the mainland were considered to have exhibited true ‘Zugunruhe’, while none of the resident birds from Brisbane were considered to have displayed it. A few individuals spontaneously developed ‘Zugunruhe’ in the absence of other birds, but many birds (both residents and migrants) displayed no elevated night unrest when placed in a room on their own, although displaying unrest when placed among birds exhibiting ‘Zugunruhe’. The migration of the silvereye probably has a genetic basis, but whether an individual migrates or not is also influenced by social factors which differ in magnitude between individuals. 1994 Blackwell Verlag GmbH

Incubation can be as energetically costly as rearing chicks(Williams 1991, Tatner & Bryant 1993, Thomson et al.1998a) and might even limit clutch size (Heaney M Thomson et al. 1998b).In Semipalmated Sandpipers Calidris pusilla, anotherbiparental incubator, parents increased incubation by10% when heat loss from eggs was reduced by insulat-ing the nest (Cresswell et al. 2003). These results weresimilar to those for uniparental incubators (Thomsonet al. 1998a, Bryan & Bryant 1999), suggesting biparen-tal incubating species might be as constrained byenergy availability as uniparental incubators. However,few data exist on the incubation strategies of biparen-tal incubating passerines in response to changes in foodavailability.In this study, we assessed the effect of food supple-mentation on incubation behaviour of the biparentalSilvereye Zosterops lateralis. We provided a food supple-ment to free-living Silvereyes and compared the incuba-tion attentiveness of adults before and after they weresupplemented. Many studies show that food supplemen-tation can increase attentiveness (e.g. Nilsson & Smith1988, Eikenaar et al. 2003, Gorman & Nager 2003,Pearse et al. 2004, Chalfoun & Martin 2007, but seeMoreno 1989, Mackintosh & Briskie 2005), but fewhave determined how individual incubation behaviourchanges in response to short-term food supplementation.We used a repeated-measures approach in which incuba-tion behaviour of individual birds was compared beforeand after they received supplementary food. Our resultsshow that Silvereyes increased their attentiveness andother measures of incubation investment in response tofood supplementation.METHODSStudy site and subjectsThe study was conducted during spring 2000 and 2001 atthe Kowhai Bush Reserve (173 36 ¢E, 42 23 S)near Kaikoura, New Zealand. The Silvereye is a small(11–14 g) passerine that ranges throughout Australia andthe South Pacific. The species is insectivorous, but con-sumes nectar and fruit when available. Sexes are similarin size and colouration and both males and females incu-bate, brood and feed nestlings (Heather & Robertson1996). Nests are spaced 10–30 m apart but adults arenon-territorial and only defend an area c. 1 m around thenest. Females alone build a well-concealed cup nest in thelower canopy in which they lay two to four eggs. Incuba-tion begins once the clutch is complete and nestlingshatch about 11 days later (Heather & Robertson 1996).We measured changes in incubation behaviour withfood supplementation at 10 nests. To avoid pseudorepli-cation, we only sampled nests once and did not samplenests of individuals used in previous experiments. Obser-vations of colour-ringed Silvereyes indicate that theyre-nest near previous breeding attempts and thus we didnot use any nest found in the same general area( 50 m) as a previously studied nest.

Winter survival with respect to dominance classes of 932 individually colour‐ringed Silvereyes was examined on Heron Island, Great Barrier Reef, between 1965 and 1969. The dominants (winning two‐thirds or more of aggressive encounters) had significantly better chances of survival between May and August (southern winter) than other birds. The 1967/68 year group was studied in detail; the young born early in the breeding season contained proportionately more dominants than those born later in the season and dominant birds tended to survive better in winter. Adults in the same period showed no dominance dependent survival. The weight of birds in winter differed between first‐year birds and adults in most cases, but winter mortality within each year‐group was not related to the weight of individual birds in May. However, the dominant class had a smaller proportion of birds losing weight through the winter than other classes, and the dominant adults and the intermediate class of first‐year birds tended to be heavier than others in August. The lengths of wing, tail, tarsus and exposed culmen examined for the 1967/68 year group showed no significant trends in either survival or dominance classes. Better survival of dominant birds is considered to be a consequence of their feeding advantages over others, but the intensity of selection for an ability for dominance may fluctuate from year to year in relation to the population density and distribution and abundance of food supply.

Age-related differences in foraging efficiency and behaviour were investigated in a population of colour-ringed Silvereyes Zosterops lateralis. First-year birds were less efficient foragers than older birds with second-year birds being intermediate. First- and second-year birds had lower success rates than older birds overall, and for most capture techniques and substrates. First-year birds never attempted breeding while about half of the second-year birds and all of the older birds did. Both learning and selection effects may have been involved in causing the age-related differences in foraging behaviour. Foraging skills appear to improve during the first 2 years of life and selection could remove the least efficient foragers from the population in winter when food is short. That second-year birds, some of which had already attempted breeding, were not significantly more efficient foragers than first-year birds suggests that reproduction is not delayed until adult levels of foraging efficiency have been attained.

Summary 1. In 1959 and 1960 observations on winter flocks of the White-eye Zosterops lateralis were made at a feeding station and in an aviary at Dunedin, New Zealand. 2. Aggressive behaviour takes different patterns according to the intensity of aggression; ritualized pecking, threat display, incipient attack, combat and chasing are distinguished. Many components of the basic threat posture are similar to those of other passerine species, but “wing fluttering”, presentation of white underwing coverts and the brown colour on the flank, and “beak clattering” seem to be characteristic of the White-eye. “Wing fluttering” is an incipient attack and often develops into an actual attack when stimulated by identical posturing by an opponent. 3. The pecking order found in the captive birds was a peck-right hierarchy, but triangular relations were also observed when mated birds were involved. Prior residence was effective for a short period only and the despot in the prior occupants could be defeated by an aggressive intruder. 4. 710 birds were colour-ringed at the feeding station, 306 returned and 204 were observed in aggressive encounters. The analysis of these encounters showed that in natural flocks dominant birds are engaged in aggressive encounters more frequently than subordinate birds, that dominants fight more often with birds of higher ranks, and that subordinates avoid encounters with aggressive birds. 5. A complex peck-right hierarchy was found among members of different flocks visiting the feeding station. It is suggested that aggressive behaviour serves to establish and maintain the social hierarchy among individuals coming into contact over various objects. In crowded conditions severe fighting frequently takes place and the right of prior residence may be challenged constantly. 6. The importance of ecological implications of flocking and aggressive behaviour in the White-eye population in New Zealand is discussed.

We examined the relationships between food resources, territory density and some breeding parameters (individual reproductive success and parental age) of a Capricorn Silvereye population during two years' detailed study on Heron Island, Great Barrier Reef. The territorial behaviour of the Silvereyes included dawn song. aggression and distinctive vocalizations. During both years, about 85% of pairs occupied territories although the population sizes differed. The dispersion pattern of territories was not regular and was correlated with the density of figs and human food scraps. Nestlings were fed more figs as they grew, and the parents foraged in fig trees outside their territories. However, only about 60%, of territorial pairs fledged young. Pairs which fledged most young were older, fed more insects to their nestlings, and nested in areas containing more fruiting fig trees per territory. We conclude that food resources were in short supply, and that access to fig trees provided breeding birds with a quick energy source while they searched for insect protein for the young. The data are consistent with the predictions of the ‘sufficient resource‘ hypothesis of the adaptive significance of territoriality but not with its assumption that the principal benefit is the food within the territory. Copyright

The 558 prey items brought home by one domestic cat, recorded over its 17‐year lifetime, included 221 mice, 63 rats, 35 rabbits, 4 hares and 2 weasels. The cat hunted up to 600 m from the house, and prey was caught both inside and outside the 0.5 ha garden. Of the 223 birds brought in, 54 were native, including 43 silvereyes (Zosterops lateralis), but those killed were quickly replaced, so there was always a resident population of 1–2 pairs. The other known native birds comprised five fantails (Rhipidura fuliginosa), four warblers (Gerygone igata), a kingfisher (Halcyon sancta), and a shining cuckoo (Chrysococcyx lucidus). Only nine skinks (Cyclodina aenea) and one frog (Litoria raniformis) were brought in. The abundance of birds and reptiles in the garden showed no apparent change over the 17 years compared with the previous 15‐year‐period without a cat. By contrast, the cat exterminated the rabbit population in the garden, and “farmed” surrounding burrows during its whole life; all other prey k...

In this study, we describe and compare the duration and timing of post-breeding moult of primary and secondary wing feathers, tail feathers, wing coverts and body feathers in captive partially migratory and non-migratory Australian silvereyes (Zosterops lateralis). This study allowed us to follow individual birds through the course of their moult and record the progression of moult in two populations. Both groups of birds underwent a conventional (or basic) post-breeding moult. While all birds followed a similar pattern of feather replacement, differences were found in the timing and duration of moult between migratory and non-migratory birds. The migratory birds generally started their moult earlier in the year and completed it before the non-migratory birds. The migratory birds revealed an overall uniformity in the timing and duration of their moult, while the non-migratory birds showed a greater degree of variability between individuals. © Dt. Ornithologen-Gesellschaft e.V. 2006.

Differences between island- and mainland-dwelling forms provide several classic ecological puzzles. Why, for instance, are island-dwelling passerine birds consistently larger than their mainland counterparts? We examine the 'Dominance hypothesis', based on intraspecific competition, which states that large size in island passerines evolves through selection for success in agonistic encounters. We use the Heron Island population of Capricorn silvereyes (Zosterops lateralis chlorocephalus), a large-bodied island-dwelling race of white-eye (Zosteropidae), to test three assumptions of this hypothesis; that (i) large size is positively associated with high fitness, (ii) large size is associated with dominance, and (iii) the relationship between size and dominance is particularly pronounced under extreme intraspecific competition. Our results supported the first two of these assumptions, but provided mixed evidence on the third. On balance, we suggest that the Dominance Hypothesis is a plausible mechanism for the evolution of large size of island passerines, but urge further empirical tests on the role of intraspecific competition on oceanic islands versus that on mainlands.

We examined the cost-benefit patterns of strategies used by Silvereyes initiating aggressive encounters against unfamiliar opponents at a localized food source. We recorded initiator behaviour of individually colour-banded birds at a feeding station on Heron Island, Great Barrier Reef, and found that, in crowded conditions where most fighting occurred indiscriminately, initiators used more threat elements than attack elements and that dominant and lower-ranking birds did not differ in their strategies when initiating encounters. This is in contrast to more attack-oriented initiator behaviour of captive birds fighting against familiar opponents. Between familiar members the initiator would use different strategies according to the rank of the opponent relative to the initiator. Our results indicated that birds fighting unfamiliar opponents would adopt strategies similar to those used against higher ranks by captive silvereyes, supporting the prediction of the cost-benefit hypothesis in agonistic encounters.

Forest fragmentation and agricultural development are important anthropogenic landscape alterations affecting the disease dynamics of malarial parasites (Plasmodium spp.), largely through their effects on vector communities. We compared vector abundance and species composition at two forest edge sites abutting pastureland and two forest interior sites in New Zealand, while simultaneously assessing avian malaria prevalence in silvereyes (Zosterops lateralis). Twenty-two of 240 (9.2%) individual silvereyes captured across all sites tested positive for avian malaria, and Plasmodium prevalence was nearly identical in edge and interior habitats. A total of 580 mosquito specimens were trapped across all sites. These comprised five different species: the introduced Aedes notoscriptus and Culex quinquefasciatus; the native A. antipodeus, C. asteliae and C. pervigilans. The known avian malaria vector C. quinquefasciatus was only recorded in the forest edge (mostly at ground level). In contrast, the probable vector C. pervigilans was abundant and widespread in both edge and interior sites. Although frequently caught in ground traps, more C. pervigilans specimens were captured in the canopy. This study shows that avian malaria prevalence among silvereyes appeared to be unaffected by forest fragmentation, at least at the scale assessed. Introduced mosquito species were almost completely absent from the forest interior, and thus our study provides further circumstantial evidence that native mosquito species (in particular C. pervigilans) play an important role in avian malaria transmission in New Zealand.

Partial migration is a phenomenon in which some individuals of a species are migrants while others are residents. This paper employs the most current information available to provide an overview of the Australian landbird migration system and the occurrence of partial migration. An extensive review of the literature showed that migration occurs in almost 40% of landbird species breeding in Australia, with a large proportion of these containing both migrant and resident populations. Partial migration is found in 44% of 155 non-passerine species and 32% of 317 passerine species examined. Such high proportions of species that are partially migratory are consistent with the suggestion that partial migration is particularly common in austral bird species. The existence of migrant and resident individuals within single populations has not been identified for most species, and the Silvereye, Zosterops lateralis, is the only partially migratory species for which reliable information on percentages of the recaptured population are available. Available evidence suggests that populations with resident and migrant elements are prevalent throughout much of Australia. An understanding of partial migration has important ecological and conservation implications.

We investigated the genetic mating system of a socially monogamous passerine bird, the Capricorn silvereye Zosterops lateralis chlorocephalus, on an island of the Great Barrier Reef. There were no cases of extrapair paternity (EPP) among 122 offspring from 53 broods detectable by minisatellite or microsatellite DNA fingerprinting. Behavioral observations of paired birds showed that this was not a consequence of efficacious paternity guards and that females did not engage in extrapair copulation (EPC). Frequency of intrapair copulations was also low, with only 14 cases observed during 199 hours of observations of the 11 focal pairs in the fertile periods of females, and this was consistent with anatomical features of the cloacal protuberance in males. In this population, young birds form life-time pair bonds soon after gaining independence but females are obviously not attempting EPC possibly to redress this early mate choice. This is despite the fact that they breed in high density with a synchronous start and asynchronous spread of laying in a protracted season and males do not positively exhibit mate guarding behavior when females are fertile. Our results support high fidelity of socially monogamous birds on islands and are consistent with the hypothesis that sexual selection is reduced where genetic variation in fitness is limited.

The diffusion of the environmental weed Bridal Creeper, Asparagus asparagoides, was investigated in south-western Australia. The primary aim was to identify native passerines dispersing the weed and to determine whether the weed’s current density distribution was correlated to the flight patterns of dispersal agents. The secondary aim was to test whether modelling techniques developed for assessing the diffusion of animal pests and diseases were suitable for estimating diffusion of a bird-dispersed environmental weed. Diffusion of A. asparagoides in south-western Australia mostly involved the Silvereye, Zosterops lateralis. Over 60% of weed distribution records with the greatest density were less than 50 m from source infestations. Gut passage rates of Z. lateralis and estimates of its flight speed showed that the maximum potential dispersal distance was approximately 12 km. Modelling showed significant differences between dispersal curves generated from current weed density distribution records (c. 77 m) and those generated from Z. lateralis flight pattern data (c. 90 m). Differences may have resulted from weed distribution/density maps not taking into account dispersal beyond the boundaries of fragmented habitats. The distribution of habitats favoured by Z. lateralis may influence the pattern of diffusion and rate of spread of the weed.

Most Australian birds do not migrate over long distances and therefore have to cope with seasonal changes in weather and food availability. We investigated whether the small (11 g) silvereye Zosterops lateralis changes its thermal tolerance from winter to summer. Body mass and body temperature of silvereyes exhibited little seasonal variability. However, metabolic rates (MR) and thermal conductance showed significant changes. Below the thermoneutral zone (TNZ), winter-acclimatized birds had significantly lower resting MR and thermal conductance than summer-acclimatized birds. Within the TNZ (~ 27.0‐33.68C winter; ~ 25.4‐33.58C summer) basal MR of winter-acclimatized birds (2.30 a 0.29 mL O2 g -1 h -1 ) was significantly lower than that of summer-acclimatized birds (2.88 a 0.43 mL O2 g -1 h -1 ). The average daily MR also differed significantly between summer and winter largely due to a greater reduction of MR at night and the decreased conductance. Our study shows that small passerines such as silvereyes exhibit seasonal variability in physiology and thermal energetics, even when they live in areas with a relatively mild climate, to help overcome seasonal changes in weather conditions and food availability.

The population of silvereyes Zosterops lateralis chlorocephalus, on Heron Island, Great Barrier Reef has been monitored accurately since 1965. Between 1979 and 1993, the breeding success of all birds was determined by monitoring nests. The population fluctuated between 225 and 483 individuals. Four cyclones led to substantial mortality. As this data set is long-term, has little observation error, and is from an effectively closed population, it provides an unusual opportunity to examine density dependence in reproduction or mortality. Using a stochastic logistic model, we found clear evidence of density dependence in adult population size. Logistic regression suggested that fledgling survival decreased with the numbers of birds attempting to breed. There was also some suggestion that adult survival might be density dependent. The fitted stochastic logistic model predicts negligible risks of extinction for this population, in contrast to the predictions of a published population viability analysis. Whilst our statistical model including density dependence may provide better predictions of the usual behaviour of a population than a population viability analysis, we suggest that caution should be exercised when statistically fitted models are used to predict the behaviour of the population at extremes, such as near extinction.

Wild-caught, captive silvereyes (Zosterops lateralis, Zosteropidae) were given choice tests to determine how some traits of fleshy fruits interact to influence fruit selection by this facultative frugivore. When given a choice between red and white fruits of the polymorphic Fragrant saltbush (Rhagodia parabolica, Chenopodiaceae), the silvereyes' preference for the red fruits was enhanced when they were twice as abundant, but reversed when they were only half as abundant, as the white fruits. Given a choice between red and white artificial fruits, silvereyes showed a 2.3-fold preference for the latter when both were equally conspicuous; this preference was significantly enhanced when the white fruits were relatively more conspicuous (greater contrast with the background colour), but eliminated when they were relatively more cryptic (less contrast with the background colour). A third experiment showed that the sugar concentration of artificial fruits influenced the birds' fruit colour preference, enhancing ...

(1) The thermal capabilities of Australian silvereyes ( Zosterops lateralis , 11 g) were investigated both at low and high ambient temperatures ( T a ) during the photophase and scotophase. (2). The peak metabolic rate (PMR) induced by helium–oxygen (79:21 %, He–O 2 ) exposure during the photophase was 15.64±1.55 mL O 2 g −1 h −1 at an effective lower survival limit T a ( T pmr ) of −39.7±6.1°C. (3). Above the thermoneutral zone (TNZ), metabolic rate, body temperature ( T b ), and thermal conductance increased steeply, but they were able to withstand a T a of 39°C. (4). Our study shows that silvereyes are able to tolerate an impressive range of T a from about −42°C to at least +39°C and are able to produce enough heat to maintain a thermal difference between T b and T a of up to 80°C.

We investigated whether the Silvereye, Zosterops lateralis (10-12 g) uses heterothermy to reduce energy expenditure when confronted with adverse environmental conditions. We also determined the thermal physiology and energetics of this species. Z. lateralis entered nocturnal hypothermia over a range of ambient temperatures (T a ) from 3-26°C. Below the thermoneutral zone (TNZ), metabolic rate (MR) decreased by up to 50% and this reduction was more pronounced at high T a than at low T a . The reduction of MR at night was accompanied by a reduction of body temperature (T b ) from 40.3 ± 0.5 to 36.9 ± 0.1°C, a decrease in the difference between T b and T a and a reduction in thermal conductance. Within the TNZ, basal metabolic rate (BMR) was 2.43 ± 0.41 mL O 2 g -1 h -1 , while the corresponding day RMR was significantly elevated at 3.26 ± 0.42 mL O 2 g -1 h -1 . The ability of Silvereyes to reduce daily energy expenditure by employing nocturnal hypothermia may be one reason why this species and its relatives are able to occupy a wide variety of habitats and climates.

Vocal mate recognition was examined in the eastern silvereye using playback experiments and multivariate analysis (canonical discriminant analysis) of measured parameters for three contact calls: the variable, linear and short calls. Fifteen captive pairs from two subspecies were studied: 11 pairs (aviary formed) of Z. l. familiaris (an Australian mainland subspecies) and four breeding pairs of Z. l. chlorocephala (confined to the islands of the southern Great Barrier Reef). Each contact call displayed sufficient individuality in call structure such that individuals could be distinguished statistically. Male and female silvereyes recognized their mates when sequentially presented with three categories of calls: mate, familiar and stranger. This study represents the first evidence of vocal mate recognition in a species that maintains pair bonds within mobile foraging flocks.

This study examined diurnal and nocturnal activity patterns from 40 hours of continuous activity recordings of individually caged resident and migrant Silvereyes Zosterops lateralis. Elevated night activity (= Zugunruhe) was displayed by migrants in autumn and spring but not by residents. Zugunruhe commonly commenced in the dark portion of the morning and continued to about 2-3 h beyond the onset of light. Migrants were more night restless than residents in winter and in the migratory seasons of autumn and spring. They were also more diurnally active in the winter months than residents. The increase in diurnal activity in the latter period is related to winter migratory movements.

The Capricorn silvereye (Zosterops lateralis chlorocephalus) is ideally suited to investigating the genetic basis of body size evolution. We have isolated and characterized a set of microsatellite markers for this species. Seven out of 11 loci were polymorphic. The number of alleles detected ranged from two to five and observed heterozygosities between 0.12 and 0.67. One locus, ZL49, was found to be sex-linked. This moderate level of diversity is consistent with that expected in an isolated, island population.

New Zealand native passerines are hosts to a large variety of gastrointestinal parasites, including coccidia. Coccidian parasites are generally host-specific, obligate intracellular protozoan parasites. In passerine birds, members of the genus Isospora are most common. Under natural conditions, these parasites seldom pose a threat, but stressors such as quarantine for translocation, overcrowding, or habitat changes may cause an infection outbreak that can severely affect wild populations. Although coccidia are important pathogens and have caused mortalities in kiwi (Apteryx spp.) and hihi (Notiomystis cincta), their prevalence, epidemiology, life cycles, and taxonomic relationships are still widely unknown in native New Zealand songbirds. Over a period of 3 years (2007–2009), we examined 330 fecal samples of six native passerine species: tui (Prosthemadera novaeseelandiae), North Island saddleback (Philesturnus carunculatus rufusater), North Island robin (Petroica longipes), silvereye (Zosterops lateralis), and fantail (Rhipidura fuliginosa). The overall prevalence by flotation of coccidian infection in the New Zealand bird species examined was 21–38 %, 21 % in North Island robin, 38 % in tui, and 25 % in saddleback. Similar to prior studies in other countries, preliminary sequencing results suggest that coccidia in passerines in New Zealand are members of the family Eimeriidae, unlike the phenotypically similar genus Cystisospora of mammals. Using molecular methods, we identified at least five new genetically distinct Isospora species in the examined birds (three in tui and one each in saddlebacks and North Island robins).

Reported declines of pollinator populations around the world have led to increasing concerns about the consequences for pollination as a critical ecosystem function and service. Pollination could be maintained through compensation if remaining pollinators increase their contribution or if novel species are recruited as pollinators, but empirical evidence of this compensation is so far lacking. Using a natural experiment in New Zealand where endemic vertebrate pollinators still occur on one offshore island reserve despite their local extinction on the adjacent North Island, we investigated whether compensation could maintain pollination in the face of pollinator extinctions. We show that two recently arrived species in New Zealand, the invasive ship rat ( Rattus rattus ) and the recent colonist silvereye ( Zosterops lateralis ; a passerine bird), at least partly maintain pollination for three forest plant species in northern New Zealand, and without this compensation, these plants would be significantly more pollen-limited. This study provides empirical evidence that widespread non-native species can play an important role in maintaining ecosystem functions, a role that needs to be assessed when planning invasive species control or eradication programmes.

The influences of the temporal change in food supply on the parental feeding effort and breeding success of silvereyes,Zosterops lateralis chlorocephala, was investigated on Heron Island, Australia. Food supply (arthropods and figs) declined as the breeding season progressed. The parental feeding rate and growth of nestlings were lower when food supply was poor. When available, dominant pairs fed their young more figs and fewer arthropods than lower ranking pairs. Dominant pairs raised heavier young than lower ranking pairs when food supply was poor, while there were no significant differences between them when food supply was rich. When food supply was rich, pairs delivering greater amounts of arthropods reared nestlings better, whereas feeding more figs did not improve growth of nestlings. When food supply was poor, pairs spending a longer time at the nest reared nestlings better.

We recorded the locomotor activity of the partially migratory Tasmanian silvereye, Zosterops l. lateralis, and the nonmigratory mainland silvereye, Z. l. familiaris, continuously over 17 and 15 months, respectively, to identify daily and seasonal patterns. While graphing the data showed several trends, statistical analysis did not reveal a significant difference between subspecies, making this study mainly descriptive in nature. The lack of statistical differentiation was possibly due to the low number of study animals and similarities between them. During the first year in captivity, the Tasmanian birds displayed heightened activity during the migratory periods, which was most likely migratory restlessness. The Tasmanian birds did not show any nocturnal activity as in previous laboratory and field studies, rather their activity patterns were similar to those of diurnal migrants, possibly reflecting the temporally variable nature of their migration. Although the Tasmanian birds displayed higher overall activity levels than the mainland birds during the first year in captivity, the activity patterns were similar between the subspecies. Captivity appeared to influence the activity of both subspecies in the second year of the study; following the onset of molt, neither subspecies regained the activity levels of the previous year, nor did activity follow the same pattern. Possible reasons (e.g., prevention of breeding) for this are discussed. This is the most detailed study to date on the daily and seasonal activity patterns of an Australian bird in captivity. © 2010 Japan Ethological Society and Springer.

Removal of the fleshy fruits of Coprosma quadrifida by birds was examined in relation to fruit crop size, neighbouring fruit crop size and time in the season in montane wet sclerophyll forest in south-eastern Australia. On average, 84% of individual fruit crops were removed. Frugivores removed fruit in proportion to its abundance, indicating that they continually assess availability rather than respond to a critical abundance. The size of neighbouring fruit crops did not influence fruit removal rates, suggesting that there is little competition among neighbours for dispersers. The ripe fruits of C. quadrifida were eaten by 14 bird species, comprising 50% of the bird species trapped. Silvereyes (Zosterops lateralis) were the most abundant consumers of fruits. With the exception of the parrot, Platycercus elegans, all birds defecated seeds intact and had no influence on seed viability.

Numerous studies on different taxonomic groups have found that vigilance behavior is negatively correlated with group size, as predicted by several theoretical models. This follows the logical argument that each individual in a larger group can spend less time scanning for predators (and more time feeding), while the group as a whole maintains a high probability of detecting an approaching predator. We investigated the relationship between these variables in the population of silvereyes (Zosterops lateralis chlorocephala) on Heron Island, Great Barrier Reef. The study used procedures of field observation that controlled or measured other variables with which vigilance is often correlated: food density and quality, temperature, time of day, distance from cover, habitat obstructions, observer proximity, breeding status, age, sex, and dominance. There was no relationship between scanning behavior and group size under these conditions. There are several possible explanations, related to the silvereyes' biology, for this lack of covariation. An additional explanation is that Heron Island is a predator-free environment for this species, and covariation between group size and vigilance is not expected in the absence of predators.

Predation of cocooned larvae of codling moth Cydia pomonella by silvereyes Zosterops lateralis was studied in an apple orchard in Nelson, New Zealand. Apple logs with known larval densities were made available to the birds for known periods of time, either in cages or exposed in the apple orchard. The numbers of silvereyes and the natural predation of codling moth were recorded in the same orchard. Predation was density dependent. On caged logs with an initial high density of 32 larvae, 1.1 larvae were consumed per bird‐hour; in contrast, one larva was consumed per 34.5 bird‐hours at three larvae per log. A curvilinear relationship was demonstrated between larval density and the bird‐hours required for predation; this relationship was consistent with the known density dependence of silvereye predation of codling moth. A regression of the total annual winter bird predation of larvae in the orchard on bird numbers was significant. However, the density dependence of predation resulted in declining rates of p...

Pronounced phenotypic shifts in island populations are typically attributed to natural selection, but reconstructing heterogeneity in long-term selective regimes remains a challenge. We examined a scenario of divergence proposed for species colonizing a new environment, involving directional selection with a rapid shift to a new optimum and subsequent stabilization. We provide some of the first empirical evidence for this model of evolution using morphological data from three timescales in an island bird, Zosterops lateralis chlorocephalus. In less than four millennia since separation from its mainland counterpart, a substantial increase in body size has occurred and was probably achieved in fewer than 500 generations after colonization. Over four recent decades, morphological traits have fluctuated in size but showed no significant directional trends, suggesting maintenance of a relatively stable phenotype. Finally, estimates of contemporary selection gradients indicated generally weak directional selection. These results provide a rare description of heterogeneity in long-term natural regimes, and caution that observations of current selection may be of limited value in inferring mechanisms of past adaptation due to a lack of constancy even over short time-frames. © 2008 The Author(s)., Funding was provided by grants from Natural Environment Research Council (UK) and the Australian Research Council

The composition and size of the breeding bird populations of three plots with garden city character in Canberra, Australian Capital Territory, were each estimated for one breeding season between 1978 and 1981 using the modified temtory mapping method. The number of temtories per 10 ha (abundance) were 58.4 (Ainslie). 56.1 (Hackett) and 91.2 (Aranda). Species numbers in the sample areas were 26 (Ainslie, Hackett) and 20 (Aranda). Territories of introduced species, mainly House Sparrow Passer domesticus (44.8-63.5%), Common Starling Sturnus vulgaris (6.8-23.0%) and Blackbird Turdus merula (1.2- 7.6%), comprised between 71-79% of the total number of temtories. The only dominant native bird species was the Silvereye Zosterops lateralis (5.9- 10.3%). 40-69% of all bird species ranked as rare (each < 1% of the total population). The abundances of native bird species, excluding the Silvereye, were 5.9 T/10 ha in Ainslie, 8.5 T/10 ha in Hackett and 18.9 T/10 ha in Aranda, probably reflecting the extent of native trees and shrubs in streets and gardens. In .4inslie, the vegetation was composed largely of exotic species. In Hackett, native trees (eucalypts), were more common but distributed unevenly. In Aranda, native vegetation dominated, many trees had been retained from the original woodland. Aranda supported a significantly higher population of exotic birds (65 T/10 ha) than Ainslie (46.5 T/10 ha) and Hackett (44.2 T/10 ha); many cavities in the original eucalypts provided House Sparrows and Common Starlings with more nest sites than were available in the other plots.

The orientation of two closely related subspecies of Australian silvereye Zosterops lateralis was studied in captivity over 14 months. Migratory silvereyes Z. lateralis lateralis showed significant directional preferences during the spring and autumn migration periods and also displayed orientated behaviour during the breeding period. In contrast, the non-migratory subspecies Z. lateralis familiaris did not display any significant directional preferences at any time. This is the first time that the orientation behaviour of a migratory and non-migratory subspecies has been compared over the duration of an annual cycle, both during and outside the migratory periods. The results suggest that migratory silvereyes possess an endogenous program determining the timing and direction of autumn and spring migration and that this program is unique to the migratory subspecies. This is also the first comparison of this nature on southern hemisphere birds and demonstrates that the migratory behaviour of southern hemisphere migrants may be more similar to that of northern hemisphere migrants than previously thought. © 2006 Springer-Verlag.

The founding of new populations by small numbers of colonists has been considered a potentially important mechanism promoting evolutionary change in island populations. Colonizing species, such as members of the avian species complex Zosterops lateralis, have been used to support this idea. A large amount of background information on recent colonization history is available for one Zosterops subspecies, Z. lateralis lateralis, providing the opportunity to reconstruct the population dynamics of its colonization sequence. We used a Bayesian approach to combine historical and demographic information available on Z. l. lateralis with genotypic data from six microsatellite loci, and a rejection algorithm to make simultaneous inferences on the demographic parameters describing the recent colonization history of this subspecies in four southwest Pacific islands. Demographic models assuming mutation-drift equilibrium or a large number of founders were better supported than models assuming founder events for three of four recently colonized island populations. Posterior distributions of demographic parameters supported (i) a large stable effective population size of several thousands individuals with point estimates around 4000-5000; (ii) a founder event of very low intensity with a large effective number of founders around 150-200 individuals for each island in three of four islands, suggesting the colonization of those islands by one flock of large size or several flocks of average size; and (iii) a founder event of higher intensity on Norfolk Island with an effective number of founders around 20 individuals, suggesting colonization by a single flock of moderate size. Our inferences on demographic parameters, especially those on the number of founders, were relatively insensitive to the precise choice of prior distributions for microsatellite mutation processes and demographic parameters, suggesting that our analysis provides a robust description of the recent colonization history of the subspecies.

The Heron Island population of Silvereyes with a known age distribution was followed through the breeding season. Its breeding cycle is described and the data on the 1969/70 season are used to find out how the dominance status of individual birds in winter affects their breeding performance. Most "floaters" were subordinate first-year birds and among the breeders older birds tended to produce more fledglings than younger birds. Clutch size was nearly constant and variation in brood size was not dependent on age or dominance of parents. The young of the intermediate class of parents had the greatest rate of survival till the winter. The dominant birds tended to nest in food-rich areas in crowded conditions, but the survival rate of their young was not related to the area of their origin. The dominant parents made the greatest contribution and the subordinate parents the least to the number of young surviving till the following breeding season. Thus selection with respect to dominance favoured the dominant birds during the high- density phase of 1969/70. Being dominant in the breeding context means that it enables the individual to establish a nesting territory which offers easy access to concentrated food. Territoriality appears to limit the number of nesting territories in the high-density area. Territorial defence is thought to play an important role in the protection of the nest; this is more effective if parents forage closer to the nesting area.

We examined components of agonistic behavior and dominance in parents and offspring of silvereyes on Heron Island, Great Barrier Reef, to discover their determinants. The data were collected over four years on 1,235 juveniles and their parents. Of four behavioral characters used to compare juveniles and their parents, bill clattering was seen significantly more among young from female parents that exhibited bill clattering. The total absence of submissive behavior and the total absence of aggressive behavior were shown more often than not by young from dominant male parents and subordinate female parents, respectively. Young fledging early in the breeding season tended to be more dominant than those fledging late in the season. The number of brood-mates or the local nest density did not affect the dominance of young. Dominance status appears to be little affected by the performance of parents.

Poxviruses were isolated from skin lesions of eight silvereyes during 1969-71. In all cases, characteristic virus particles were seen in extracts of the lesions and all isolates produced pocks on the chorioallantoic membrane of embryonated chicken eggs. Comparison by immunodiffusion showed that the viruses were antigenically identical, and that they differed from poxviruses recently isolated from domestic fowls, pigeons and a canary.