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The "paradox of the great speciators" has puzzled evolutionary biologists for over half a century. A great speciator requires excellent dispersal propensity to explain its occurrence on multiple islands, but reduced dispersal ability to explain its high number of subspecies. A rapid reduction in dispersal ability is often invoked to solve this apparent paradox, but a proximate mechanism has not been identified yet. Here, we explored the role of six genes linked to migration and animal personality differences (CREB1, CLOCK, ADCYAP1, NPAS2, DRD4, and SERT) in 20 South Pacific populations of silvereye (Zosterops lateralis) that range from highly sedentary to partially migratory, to determine if genetic variation is associated with dispersal propensity and migration. We detected genetic associations in three of the six genes: (i) in a partial migrant population, migrant individuals had longer microsatellite alleles at the CLOCK gene compared to resident individuals from the same population; (ii) CREB1 displayed longer average microsatellite allele lengths in recently colonized island populations (<200 years), compared to evolutionarily older populations. Bayesian broken stick regression models supported a reduction in CREB1 length with time since colonization; and (iii) like CREB1, DRD4 showed differences in polymorphisms between recent and old colonizations but a larger sample is needed to confirm. ADCYAP1, SERT, and NPAS2 were variable but that variation was not associated with dispersal propensity. The association of genetic variants at three genes with migration and dispersal ability in silvereyes provides the impetus for further exploration of genetic mechanisms underlying dispersal shifts, and the prospect of resolving a long‐running evolutionary paradox through a genetic lens. [ABSTRACT FROM AUTHOR]

The rate at which avian offspring grow can have consequences for survival and reproductive output as an adult and is known to vary widely among and within species. This variation is thought to be an adaptive response to cope with environmental variation. The principal environmental factors affecting growth are food availability and predation risk, predominantly acting as constraints on parental care. Islands pose an interesting system to explore growth rate dynamics, because the characteristic insular features of high population densities and depauperate predator diversity translate into a potentially food limited environment with low predation risk. Insular environments typically produce populations with slower life history strategies and larger body size in small-bodied species, features that are likely to be mediated by growth rate. We describe the nestling growth of an insular population of Silvereyes and how it relates to parental size and parental care. Neither parental size nor parental care explained insular nestling growth rate, even though food acquisition is thought to underpin avian growth rates. This could be due to a mismatch between acquisition and allocation of resources by nestlings. Compared to a small number of mainland nestlings, the island growth curve asymptotes were significantly larger and inflection points much later, but insular growth rates were only marginally slower. This is in line with proposed insular adaptations required to produce larger body size on islands, however understanding the mechanism underlying this pattern will require data on the relationship between food quality and acquisition, and physiological allocation of resources within individuals. [ABSTRACT FROM AUTHOR]

The most significant damage inflicted by birds in Australia is to germinating cereal and to ripening sunflower and fruit crops. The main pests are several native psittacine and corvid species, silvereyes (Zosterops lateralis) and European starlings (Sturnus vulgaris). The economic cost of damage is largely unquantified. While losses to industries as a whole are often low, losses to individual growers may be severe, and losses are distributed patchily in space and time. Shooting is the most widely practiced and most ineffective bird control technique used in Australia. Despite the high numbers of birds killed, damage persists, and disturbance caused by shooting and scare devices may actually increase damage. Trapping and export of native birds is frequently suggested as a solution but would be ineffective for damage control. Illegal poisoning is thought to have caused significant reductions in some parrot populations, but has not prevented crop damage. Decoy feeding shows promise for damage control in winter cereals. One site attracted 4,000 cockatoos for most of the seeding and germination phase. For sunflower, the main problem is rendering the main crop less attractive than the decoy. Netting is cost-effective even at moderate to low levels of bird damage for intensive growing systems with new varieties of high-yielding stonefruit. Research is needed on techniques to assess the cost of damage. The cost-effectiveness of damage control techniques can then be assessed. There is also a need for more studies on the biology of pest birds, in relation to the potential mitigation of crop damage by habitat modification or changes in crop growing practices.

Aim Colonization and extinction are important drivers of island biogeography, but they are difficult to study. We used a long-term dataset to determine the mechanisms that contribute to colonization and persistence for vector-borne blood parasites in an island population of birds that regularly receives infected vagrant conspecifics and wind-assisted potential vectors from the mainland. Location Heron Island (Australia) and the Australian mainland. Methods We determined the prevalence, temporal stability and host-specificity of Haemoproteus and Plasmodium parasites in resident and mainland-vagrant silvereyes ( Zosterops lateralis) on Heron Island over seven years (1999-2003 and 2012-2013). We carried out simulations using mainland infection data and vagrant arrival scenarios to test whether transmission from vagrants influences infection patterns in island residents. We tested whether variation in island parasite prevalence was predicted by abiotic factors associated with vector breeding and dispersal. Results Parasite prevalence and composition on the island varied considerably across years. Host-specialist Haemoproteus species exhibited lower prevalence than expected and frequent absence despite a high probability of arriving via vagrants. In contrast, host-generalist Plasmodium species exhibited a low probability of arriving via vagrants but were temporally persistent in island silvereyes. Increases in prevalence and diversity of Plasmodium species were associated with episodes of offshore winds. Main conclusions This study shows that parasites that are abundant in source populations do not necessarily exhibit increased colonization success via vagrant host movement. Vagrant silvereyes are not likely to shape infection patterns in island-resident silvereyes. Instead, indirect evidence of associations between weather patterns and parasite dynamics suggests that the insular parasite community may be limited by vector establishment. Our results support the hypothesis that host-specificity is important in determining a parasite's ability to persist on islands, with host-specialists at greater risk of failing to establish after their initial arrival. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Many passerines adjust song attributes to avoid potential masking by anthropogenic noise. The costs of masking should be particularly high for vocalizations important for survival (e.g. alarm calls), but few studies have investigated how such calls are affected. We compared urban and rural silvereye, Zosterops lateralis , alarm calls across southeastern Australia, and found that urban calls had lower average, peak and maximum frequencies than rural calls. The average, peak and maximum frequency of alarm calls also decreased linearly with increasing background noise. The direction of this frequency shift runs contrary to expectations and previous findings of higher-pitched avian vocal signals in urban habitats, including higher-pitched song and contact calls in urban silvereyes. However, assuming no change in call amplitude, acoustic modelling indicates that the observed frequency shift would lead to a 20% increase in the predicted active space of alarm calls (i.e. the distance over which the calls can be detected by a conspecific bird) in urban noise, and therefore may be potentially adaptive. Our findings highlight the importance of considering behavioural and ecological contexts in urban acoustic-adaptation studies. [ABSTRACT FROM AUTHOR]

Succession from anthropogenic grassland to secondary woody plant communities in New Zealand's eastern South Island dryland zone has potential to alter animal communities. We compared indigenous and exotic birds, terrestrial invertebrates and ground-dwelling lizards in 100-ha blocks representing vegetation at three woodiness levels (grassland, mixed grassland-shrubland, and shrubland) at three sites in Central Otago. We predicted that shrublands would support invertebrate taxa and indigenous bird species complementary (additional) to those in grasslands, thus increasing the diversity of taxa present in the landscape, and that shrublands would have higher indigenous dominance of bird composition than grassland. We also expected that vegetation woodiness would affect the taxonomic composition of assemblages of indigenous and exotic birds and of ground-dwelling invertebrates. We predicted shrubland would have little net effect on indigenous dryland ground-dwelling lizards, which we expected to be regulated by other microhabitat characteristics. To test our predictions we used rarefaction-based analyses of faunal complementarity, and canonical correspondence analysis (CCA) and generalised mixed models of animal response variables in relation to vegetation and environmental predictors. Our results showed that shrubland blocks supported ground-dwelling invertebrate orders and indigenous forest bird species complementary to those present in grasslands. Block-level woodiness was a primary predictor of indigenous, but not exotic, bird assemblages. At smaller scales of transects within blocks, the indigenous dominance of bird species assemblages in shrubland blocks was not significantly higher than elsewhere, but was related to plant-community-specific variations in more numerous and diverse exotic birds. Terrestrial beetle-family assemblages within plots varied significantly with local woodiness, but invertebrateorder assemblages did not. Shrubland development had little effect on common ground-dwelling lizards, which showed strong microhabitat preferences and favoured habitats dominated by indigenous plant species. We conclude that sizeable (i.e. >1 km2) areas of shrubland vegetation enhanced the diversity of indigenous birds and of ground invertebrate orders present at a landscape scale. Both grassland and shrubland habitat patches in drylands supported indigenous ground-dwelling lizards, but lizards may be vulnerable to habitat modifications that reduce indigenous plant dominance. [ABSTRACT FROM AUTHOR]

The article discusses the first evidence of avian malaria in capricorn silvereyes, Zosterops lateralis chlorocephalus, on Heron Island in Queensland. Topics covered include a high prevalance of haemosporidian blood parasites exhibited by Silvereyes on the Australian mainland, the extraction of DNA from the birds using standard ammonium acetate/ethanol precipitation and an explanation of why positive infections were found.

Birds have a number of ways of adjusting communication patterns in noisy environments in order to be heard. Using a captive experiment, we show that silvereyes increase the volume of their contact calls during noisy periods, and can shift the pitch of their calls depending on the pitch of the masking noise. This may be how some birds cope with urban noise, explaining why behavioral ecologists have recorded higher vocalizations in urban areas.Many birds raise the pitch of their vocalizations in urban environments, a shift generally attributed to avoidance of low frequencies vulnerable to masking by anthropogenic noise (acoustic adaptation hypothesis [AAH]). However, high frequencies could just be an incidental byproduct of singing more loudly (Lombard hypothesis). If birds cope with background noise by singing more loudly and increases in frequency are byproducts of increased amplitudes, they should respond with louder songs (and increased pitch) to either high- (HFN) or low-frequency noise (LFN) of similar amplitude. However, if birds adaptively adjust frequency to minimize interference, they should increase frequency in response to LFN but decrease it in response to HFN. We exposed silvereyes (Zosterops lateralis), which use higher songs and calls in urban areas, to high- and low-frequency background noise of standardized amplitude. Silvereyes from both rural and urban areas exposed to HFN responded by lowering the minimum frequencies of their calls, and this shift was independent of call amplitude, which increased in all noise treatments. These findings support the AAH. Calls during HFN treatments were also longer than those made during quiet treatments. Our results suggest that silvereyes are capable of flexible adjustments of call frequency, amplitude, and duration to maximize signal-to-noise ratio in noisy environments. [ABSTRACT FROM PUBLISHER]

Nectar-feeding birds generally demonstrate preference for hex-ose solutions at low sugar concentrations, switching to sucrose/ no preference at higher concentrations. Species vary in the concentration at which the switch from hexose preference occurs; this could reflect physiological constraints that would also influence nectar selection when foraging. We recorded concentration-dependent sugar type preferences in three opportunis-tic/generalist Australian nectarivorous species: Dicaeum hirundinaceum, Zosterops lateralis, and Lichenostomus virescens. All three preferred hexoses up to sugar concentrations of 0.25 mol L-1 and switched to sucrose/no preference for higher concentrations. Using these and literature records, we investigated physiological mechanisms that may explain the concentration dependence of sugar type preferences and compared diet preference data with foraging records. We measured sucrase activity in Z. lateralis and L. virescens as well as three specialized nectarivorous species (Anthochaera carunculata, Phylidonyris no-vaehollandiae, and Trichoglossus haematodus) for comparison with published concentration-dependent sugar preference data. Sucrase activity varied between these species (P = 0.006). The minimum diet concentration at which birds show no sugar preference was significantly correlated with sucrase activity for the 11 species analyzed (P = 0.005). Birds with the lowest sucrase activity showed hexose preference at higher diet concentrations, and birds with the greatest sucrase activity showed either no hexose preference or hexose preference on only the most dilute diets. Foraging data compiled from the literature also support the laboratory analyses; for example, T. haematodus (preference for hexose over a wide range of diet concentrations, low sucrase activity) also feed primarily on hexose nectars in the wild. Intestinal sucrase activity is likely to contribute to diet selectivity in nectarivorous bird species. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Geographic relocations of migratory passerines have shown that adults can compensate for physical displacements; juveniles on their first migration, however, use an innate clock-and-compass strategy and are unable to compensate for displacement. We examined the effects of changes in magnetic inclination and intensity on orientation of adult and juvenile Australian Silvereyes (Zosterops l. lateralis) to learn if geomagnetic cues are used by a migratory passerine for geographic positioning. Silvereyes, captured in breeding areas in Tasmania, were physically transported to a location along their migratory route and assessed for orientation during autumn migration. Adults and juveniles exhibited seasonally appropriate, northeasterly orientation (19° and 23° east of magnetic North, respectively) when tested under the natural geomagnetic field. Birds were then exposed to changes in the magnetic field that simulated either southern (SimS) or northern (SimN) locations near the beginning and end, respectively, of their migratory route. Inexperienced juveniles continued to show seasonally appropriate orientation (3° and 358°, respectively) in both SimS and SimN magnetic fields. Adults, in contrast, exhibited changes in orientation but only when the experimental magnetic field was consistent with a geographical displacement that should require compensatory orientation (i.e., SimN). Adults exposed to a SimS magnetic field continued to show seasonally-appropriate orientation to the North (0°). However, adults exposed to magnetic fields simulating locations beyond their wintering areas (SimN) altered their orientation significantly, orienting bimodally and perpendicular (123°--303°) to their seasonally appropriate migratory direction. These results are consistent with the presence of an age- or experience-dependent magnetic geographic position sense in migratory Australian Silvereyes. [ABSTRACT FROM AUTHOR]

Recent studies in the Northern Hemisphere have shown that songbirds living in noisy urban environments sing at higher frequencies than their rural counterparts. However, several aspects of this phenomenon remain poorly understood. These include the geographical scale over which such patterns occur (most studies have compared local populations), and whether they involve phenotypic plasticity or microevolutionary change. We conducted a field study of silvereye (Zosterops lateralis) vocalizations over more than 1 million km² of urban and rural south-eastern Australia, and compared possible effects of urban noise on songs (which are learned) and contact calls (which are innate). Across 14 paired urban and rural populations, silvereyes consistently sang both songs and contact calls at higher frequencies in urban environments. Syllable rate (syllables per second) decreased in urban environments, consistent with the hypothesis that reflective structures degrade song and encourage longer intervals between syllables. This comprehensive study is, to our knowledge, the first to demonstrate varied adaptations of urban bird vocalizations over a vast geographical area, and to provide insight into the mechanism responsible for these changes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The author describes the Zosterops photographed by the author at Sawtell, New South Wales on February 22, 2009. A range of opinions have been offered by amateur and professional ornithologists regarding the possible nature of the bird. It is noted by the author, that the appearance of the bird matches the appearance of Z. luteus, except from the colour of the bill and legs. He says another possibility is that the bird is an uncommon colour variant of Z. lateralis because of its pale bill and legs. The author concludes that the bird is either a vagrant Z. luteus or an unreported colour variant of Z. lateralis.

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. [ABSTRACT FROM AUTHOR]

To assess the relative importance of celestial and magnetic cues for orientation at dusk, Australian silvereyes, Zosterops l. lateralis, were subjected to artificial magnetic fields under the natural evening sky, beginning 30 min before sunset. Control birds tested in the local geomagnetic field preferred their normal south-southwesterly migratory direction. Birds tested in a magnetic field with north deflected counterclockwise to 240°WSW showed northeasterly tendencies from the first test onward. Birds subjected to a corresponding clockwise deflection to 120°ESE, in contrast, first showed southerly directions, but from the 7th test onward shifted towards the northwest. Hence, both experimental groups followed the shift in magnetic north, one immediately, the other after a delay. When the birds were later tested in a vertical magnetic field without directional information, the two experimental groups continued in the direction they had preferred in the artificial magnetic fields, presumably by celestial cues alone. This indicates that they had not simply ignored celestial cues, but had recalibrated them according to the altered magnetic fields. The reasons for the initial difference between the two experimental groups remain unclear. Delayed responses to deflections of magnetic north have also been observed in previous studies. They appear to be the main reason why studies that expose birds only once to a cue-conflict situation often seem to indicate a dominance of celestial cues, whereas studies exposing the birds repeatedly usually indicate a dominance of magnetic cues. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Recent studies have revealed differences between urban and rural vocalizations of numerous bird species. These differences include frequency shifts, amplitude shifts, altered song speed, and selective meme use. If particular memes sung by urban populations are adapted to the urban soundscape, "urban-typical" calls, memes, or repertoires should be consistently used in multiple urban populations of the same species, regardless of geographic location. We tested whether songs or contact calls of silvereyes (Zosterops lateralis) might be subject to such convergent cultural evolution by comparing syllable repertoires of geographically dispersed urban and rural population pairs throughout southeastern Australia. Despite frequency and tempo differences between urban and rural calls, call repertoires were similar between habitat types. However, certain song syllables were used more frequently by birds from urban than rural populations. Partial redundancy analysis revealed that both geographic location and habitat characteristics were important predictors of syllable repertoire composition. These findings suggest convergent cultural evolution: urban populations modify both song and call syllables from their local repertoire in response to noise.