Avian Community Composition Research Articles

Sixty years of change in avian communities of the Pacific Northwest.

Bird communities are influenced by local and regional processes. The degree to which communities are dynamic has implications for projecting responses in community composition as birds track geographic shifts of their habitats. Historic datasets offer a legacy of information that can be used to quantify changes over time in avian community composition. A rare, highly-detailed avian survey of multiple habitat types in the Willamette Valley, Oregon, was conducted in 1952. We resurveyed the same sites in 2013 and evaluated whether observed results agreed with theoretical patterns of community change. We compared alpha, beta, and gamma diversity between survey periods and evaluated shifts in categorical abundances of species. Most patterns of change were consistent with community turnover. Nearly 50% of species were replaced over six decades, with increased species richness and decreased evenness at local and regional spatial extents. Patterns of regional species turnover reflected local turnover. Evidence that local shifts in habitat type drove bird community change were not strongly supported, although historic data on habitats within study plots were limited to macro-level aerial photographs. Thus, regional factors and structural changes likely played important roles determining species composition and abundance.

Tradeoffs among ecosystem services in restored wetlands

Land management decisions frequently involve choices that reflect tradeoffs among ecosystem services. These tradeoffs are not always apparent, and land managers unknowingly may make decisions that diminish the value of some services while enhancing the value of others. Offset policies, such as wetland mitigation in the United States, rely on the assumption that ecosystems can be restored to provide a full suite of services. Wetlands provide many ecosystem services such as water quality maintenance, carbon storage, flood abatement, and biodiversity support. Our objectives were to describe tradeoffs among ecosystem services in mitigation wetlands and identify abiotic and biotic drivers underlying these tradeoffs. We measured denitrification potential, organic matter decomposition, herbaceous biomass, and soil organic content as indicators of nutrient storage and removal services in 30 mitigation wetlands in Illinois, USA. Additionally, we estimated surface-water storage potential, and, since wetlands provide valuable biodiversity support, we determined the species composition of plant, anuran, and avian communities. We found a positive relationship among biodiversity indicators for different taxa. Denitrification potential and surface-water storage potential were positively correlated. However, there was a tradeoff between biodiversity support and nutrient cycling processes; soil organic matter, biomass, decomposition rates, and potential denitrification were greater at less biodiverse sites. Our findings indicate that optimizing restored wetlands for nutrient storage and removal may come at the expense of biodiversity. It is unrealistic to expect all services to be maximized at a restoration site. Therefore, restoration practitioners should prioritize services based on needs and opportunities given local and watershed contexts.

A comparison of point counts with a new acoustic sampling method: a case study of a bird community from the montane forests of Mount Cameroon

Acoustic signals are frequently used for estimating avian species richness, abundance and community composition. However, sampling by traditional methods of bird surveys is often limited by availability of experienced researchers in the field, especially in the tropics. New bioacoustic approaches offer some solutions to such limitations and provide opportunities for more extensive spatial and temporal sampling. In our study, we compared results of traditional point counts with simultaneous acoustic samples obtained by automated soundscape recording units in the montane forest of Mount Cameroon. We showed that the estimates of species richness, abundance and community composition based on point counts and post-hoc laboratory listening to acoustic samples are very similar, especially for a distance limited up to 50 m. Species that were frequently missed during both point counts and listening to acoustic samples were typically those with relatively quiet songs. Abundances were rather underestimated by listening to acoustic samples in the most abundant species, including those occurring in flocks and species with low singing activity. Despite some possible biases, we demonstrated that the method based on listening to acoustic samples is relatively effective and offers a useful alternative approach for surveying Afromontane bird communities.

Supplementary feeding restructures urban bird communities

Food availability is a primary driver of avian population regulation. However, few studies have considered the effects of what is essentially a massive supplementary feeding experiment: the practice of wild bird feeding. Bird feeding has been posited as an important factor influencing the structure of bird communities, especially in urban areas, although experimental evidence to support this is almost entirely lacking. We carried out an 18-mo experimental feeding study at 23 residential properties to investigate the effects of bird feeding on local urban avian assemblages. Our feeding regime was based on predominant urban feeding practices in our region. We used monthly bird surveys to compare avian community composition, species richness, and the densities of local species at feeding and nonfeeding properties. Avian community structure diverged at feeding properties and five of the commonest garden bird species were affected by the experimental feeding regime. Introduced birds particularly benefitted, with dramatic increases observed in the abundances of house sparrow (Passer domesticus) and spotted dove (Streptopelia chinensis) in particular. We also found evidence of a negative effect on the abundance of a native insectivore, the grey warbler (Gerygone igata). Almost all of the observed changes did not persist once feeding had ceased. Our study directly demonstrates that the human pastime of bird feeding substantially contributes to the structure of avian community in urban areas, potentially altering the balance between native and introduced species.

Avian Use of Black-Tailed Prairie Dog Colonies in Shortgrass Prairie

Downward trends in populations of many grassland bird species are of conservation concern. Declines in black-tailed prairie dog ( Cynomys ludovicianus ) populations result in loss of habitat for birds and other species associated with their colonies. We measured abundance, diversity, and species composition of avian communities on prairie dog colonies and noncolony sites in the Texas Panhandle. More resident species ( P < 0.001) occurred on prairie dog colonies than on noncolony areas whereas, more nearctic-neoptropical migrants ( P = 0.003) and nearctic-temperate migrants ( P < 0.001) occurred on noncolony sites. Total avian abundance was greater ( P < 0.001) on noncolony sites than at prairie dog colonies, and differed by season ( P < 0.001). Barn swallows ( Hirundo rustica ), red-winged blackbirds ( Agelaius phoeniceus ), horned larks ( Eremophila alpestris ), and chipping sparrows ( Spizella passerina ) were more abundant on noncolony sites than on prairie dog colonies. Burrowing owl ( Athene cunicularia ), Cassin’s sparrow ( Peucaea cassinnii ), and lark bunting ( Calamospiza melanocorys ) abundances were greater on prairie dog colonies. Vegetative alterations made by prairie dogs may not influence bird populations as much in these shortgrass prairies as has been reported in mixed-grass prairies.

Avian Community Composition in Response to High Explosive Testing Operations at Los Alamos National Laboratory in Northern New Mexico

Breeding bird abundance, species richness, evenness, diversity, composition, productivity, and survivorship were determined near a high-explosive detonation site at Los Alamos National Laboratory, New Mexico, USA, during pre-operation (1997-1999) and operation (2000-2014) periods. The operation periods consisted of detonations ( 0.05) in mean avian abundance and species evenness in any of the operation periods as compared with the pre-operation period. Species richness and diversity were significantly higher (p < 0.05) during the vessel containment period (2007-2014) than the pre-operation period. The time period of this study coincided with a wildfire (2000), a bark beetle infestation (2002), and two periods of drought (Nov 1999-Mar 2004 and Dec 2005-Dec 2014) that affected the study area. Analysis of aerial photos determined that the average percent canopy cover of mature ponderosa pines (Pinus ponderosa) within 100 feet of mist net sites declined from 12% to 3% between 1991 and 2014 and the percent cover of shrubs slightly increased. The percent similarity in presence/abundance between the pre-operation avian community and avian community during the open air, foam containment, and vessel containment periods were 59%, 63% and 68% respectively. Two bird species associated with large trees became less common over the study period (capture rate dropped below 2.0 adults per 600 net-hours relative to the pre-operations period), and four bird species associated

A Cerrado bird community in the northernmost portion of northeastern Brazil - recommendations for conservation

he Cerrado is the largest savanna in South America and it is rich in fauna and flora and considered a biodiversity hotspot. Its contact with the surrounding Amazon, Atlantic Forest and Caatinga is irregular, forming large diffuse ecotones in some regions and disjointed patches in others. The Cerrado patches located in the Amazon are relatively studied, but little is known about those in the Atlantic Forest and Caatinga. This article presents information on the composition of a bird community in a savanna formation on the coast of the northernmost portion of northeast Brazil (5o23'25S / 35o30'25W). This site was visited 17 times between October 2006 and August 2013. The total richness was 87 species distributed into 32 families. The following Cerrado endemics were recorded: Charitospiza eucosma and Porphyrospiza caerulescens. Other species recorded associated mainly with the Cerrado biome were Heliactin bilophus, Cypsnagra hirundinacea and Coryphaspiza melanotis. Some vulnerable and near threatened species were also recorded for the first time in the northernmost portion of northeastern Brazil, with some of these more than 1,000 km from their previously known localities. The results broaden the knowledge on the distribution of various species, in addition to providing information on seasonality and reproduction of others and revealing an overall lack of information on the composition of avian communities in little studied areas of Brazil.

Risks and drivers of wild bird feeding in urban areas of New Zealand

The practice of feeding wild birds is a widespread phenomenon, but there has been little consideration of both human and ecological dimensions of the impacts. We used a comprehensive approach to investigate the practice of bird feeding in the unique avian landscape of New Zealand. We quantified the practice and motivations of bird feeding via a nationwide postal survey, and identified ecological risks from current feeding practices. Our study confirmed that, as in many northern hemisphere countries, bird feeding is a common activity in New Zealand, with an estimated 46.6% of households feeding birds. Increased age and dog ownership were strongly associated with participation. Bread was most commonly provided; we estimated 5.1million loaves/annum across the population of 1.8million in six surveyed cities. The principal potential risk identified was that introduced birds are likely to be the main consumers of supplementary food sources in New Zealand, which may have follow-on effects for avian community composition. Disease transmission risks were also identified, with poor hygiene practices reported by many respondents. However, the social benefits to humans of feeding birds were strongly reflected in the motivations of the respondents. Over half fed birds because it brought them pleasure. As urbanisation increases globally, opportunities for connecting with nature decrease. Therefore, experiences such as bird feeding that increase the interaction between people and wildlife could be a powerful tool for fostering environmental awareness and guardianship. Our study highlights that without information about ecological consequences, humans may inadvertently make harmful choices for wildlife, so we recommend promulgation of appropriate guidelines to minimise the risks.

Avian community composition associated with interactions between local and landscape habitat attributes

As human demand for ecosystem products increases, managers of landscapes used for commodity production require information about effects of management regimes on biological diversity. Landscape attributes, however, may moderate ecological responses to local-scale conservation and management actions. As a result, uniform application of local management prescriptions may yield variable biodiversity responses. We examined how interactions between local habitat structure and landscape forest cover were associated with avian community composition in the Ouachita Mountains, Arkansas, USA, 1995–1998. We used Bayesian hierarchical models to estimate occupancy for 63 breeding bird species, while accounting for variable detection with data collected from 1941 temporally replicated point count stations. Specifically, we estimated how interactions of four local habitat covariates (canopy cover of mature coniferous and hardwood trees, number of snags, and shrub cover) with percentage of mature hardwood forest at the landscape scale were associated with species occupancy and richness. Average predictive comparisons indicated that snag count and shrub cover had the strongest associations with species richness. Estimated associations for each of the four local forest cover variables was similar across all levels of landscape forest cover, suggesting weak or negligible interactions between these local measures and the landscape covariate. We found little support for our main prediction that local/landscape habitat interactions would be strongest at low levels of landscape forest cover (1–20%). Consequently, we suggest that forest managers consider prescriptions that result in a broad spatial distribution of heterogeneous habitat structural conditions (e.g., variation in understory cover and composition), irrespective of landscape context, to maintain a diverse avian breeding assemblage on landscapes in this region.

Birds at the urban fringe: avian community shifts in different peri‐urban ecotones of a megacity

AbstractCities can be regionalized in intra‐urban and peri‐urban areas. The space between urban areas and adjacent systems represents an ecological transition that often acts as a semi‐permeable biological filter. In this study, we assessed changes in avian community species richness, density, and composition at different peri‐urban ecotones (i.e., urban‐croplands, urban‐grasslands, urban‐shrublands) of northeastern Mexico City. Species richness was lower in the urban component of urban‐grassland and urban‐shrubland ecotones, while bird densities were higher in the urban components of the urban‐grassland and urban‐shrubland peri‐urban ecotones, mainly due to the high number of urban exploiter species. However, the urban‐cropland peri‐urban ecotone exhibited a different pattern, with similar low bird species richness and density values between both components (urban and non‐urban). A species composition analysis revealed that urban bird communities were not influenced by adjacent non‐urban habitats, since the urban components of peri‐urban ecotones were more similar among them than in relation to the rest of non‐urban components. In summary, results of this study show that urbanization can represent an important biological filter for birds, often reducing species richness and homogenizing avian communities at local scales. As the environmental variables determining ecological processes related to the semi‐permeable filter effect that urban areas pose to biodiversity might depend on urban habitats, regions, and spatial scales, further studies are needed to fully understand this phenomenon.

Vineyard and riparian habitat, not nest box presence, alter avian community composition

In California, oak woodlands are being converted into vineyards, resulting in a loss of songbird nesting sites. Although many vineyards contain wooded riparian habitat, no previous research has examined the avian species composition in oak-vineyard landscapes. We compared the avian communities associated with vineyard, edge, and riparian habitats and examined to what degree the riparian habitat in vineyard landscapes continues to support birds associated with native oak woodland habitat that spanned the region before agricultural intensification. We further tested whether the presence of nest boxes in vineyard and riparian areas altered avian species composition in the landscape. Mist nets were used to survey the avian community in vineyard, edge, and riparian habitat at four sites during the breeding season. Permutational ANOVAs, using presence-absence data from captures, identified habitat, study sites, and time over the breeding season as highly significant main effects that explained differences in species composition. Establishment of songbird nest boxes did not alter the species composition. Two-thirds of the birds identified as woodland species in prior studies were found in riparian areas adjacent to vineyards, including five watch-list species. Overall the species composition of birds using riparian habitat was greater and significantly different from those found in the vineyard. This highlights the importance of maintaining natural areas like riparian habitat in agricultural landscapes.

Off-road sampling reveals a different grassland bird community than roadside sampling: implications for survey design and estimates to guide conservation

Grassland bird species continue to decline steeply across North America. Road-based surveys such as the North American Breeding Bird Survey (BBS) are often used to estimate trends and population sizes and to build species distribution models for grassland birds, although roadside survey counts may introduce bias in estimates because of differences in habitats along roadsides and in off-road surveys. We tested for differences in land cover composition and in the avian community on 21 roadside-based survey routes and in an equal number of adjacent off-road walking routes in the grasslands of southern Alberta, Canada. Off-road routes (n = 225 point counts) had more native grassland and short shrubs and less fallow land and road area than the roadside routes (n = 225 point counts). Consequently, 17 of the 39 bird species differed between the two route types in frequency of occurrence and relative abundance, measured using an indicator species analysis. Six species, including five obligate grassland species, were more prevalent at off-road sites; they included four species listed under the Canadian federal Species At Risk Act or listed by the Committee on the Status of Endangered Wildlife in Canada: Sprague's Pipit (Anthus spragueii), Baird's Sparrow (Ammodramus bairdii), the Chestnut-collared Longspur (Calcarius ornatus), and McCown's Longspur (Rhynchophanes mccownii). The six species were as much as four times more abundant on off-road sites. Species more prevalent along roadside routes included common species and those typical of farmland and other human-modified habitats, e.g., the European Starling (Sturnus vulgaris), the Black-billed Magpie (Pica hudsonia), and the House Sparrow (Passer domesticus). Differences in avian community composition between roadside and off-road surveys suggest that the use of BBS data when generating population estimates or distribution models may overestimate certain common species and underestimate others of conservation concern. Our results highlight the need to develop appropriate corrections for bias in estimates derived from roadside sampling, and the need to design surveys that sample bird communities across a more representative cross-section of the landscape, both near and far from roads.

Songbird response to wildfire in mixed-conifer forest in south-western Oregon

We used 1 year of pre-fire and 4 years of post-fire data to quantify changes in the occurrence of birds at burned and unburned sites in a southern Oregon watershed after a 2500-ha wildfire. Our objectives were to identify bird species that increased or decreased as a result of this mixed-severity fire. Of the 27 species we investigated, we found evidence for fire-induced changes in the proportion of sites occupied by 13 species. Of these, most (8 species) were species that occurred at fewer sites after the fire than before. These changes were consistent with changes in vegetation composition, which included a decrease in the cover of conifer species and an increase in the cover of broadleaf species. To evaluate the effect of the fire on other ecological conditions, we compared the abundance of nest predators and potential prey items (arthropod biomass) between burned and unburned areas in the 3rd and 4th years after the fire. We found little evidence that the abundance of nest predators differed between burned and unburned areas in either year. There was, however, substantial spatial and temporal variation in arthropod abundance. Hemipteran and coleopteran biomass was greater in burned areas in both the 3rd and 4th year after the fire, and overall arthropod biomass was greater in the 4th year after the fire. The spatial and temporal variability in the bird response to this fire illustrates the importance of before–after–control–impact and multi-year studies for understanding the effects of large-scale disturbances on avian community composition.

Grassland Bird Response to Vegetation Structural Heterogeneity and Clearing of Invasive Bramble

Spatial and temporal patterns of disturbance and the subsequent heterogeneity are critical in maintaining biodiversity within grassland ecosystems. Grassland birds have evolved within this ‘shifting mosaic’ to become reliant on specific habitat characteristics maintained under varying levels of both natural and anthropogenic disturbance. Unfortunately, grasslands in South Africa have been extensively transformed and remain poorly conserved, threatening grassland avifauna. Mistbelt grassland is a threatened vegetation type endemic to the province of KwaZulu-Natal, of which only 0.3% is formally protected. This study investigated seasonal and patch type heterogeneity in a Mistbelt grassland avian community by determining avian community structure and composition in four patch types, i.e. i) untransformed open grassland, ii) burnt grassland, iii) bramble-invaded and, iv) bramble-cleared grassland, during winter and summer. Avian assemblages were significantly different between the different patch types for e...

Grassland bird response to vegetation structural heterogeneity and clearing of invasive bramble

Spatial and temporal patterns of disturbance and the subsequent heterogeneity are critical in maintaining biodiversity within grassland ecosystems. Grassland birds have evolved within this ‘shifting mosaic’ to become reliant on specific habitat characteristics maintained under varying levels of both natural and anthropogenic disturbance. Unfortunately, grasslands in South Africa have been extensively transformed and remain poorly conserved, threatening grassland avifauna. Mistbelt grassland is a threatened vegetation type endemic to the province of KwaZulu-Natal, of which only 0.3% is formally protected. This study investigated seasonal and patch type heterogeneity in a Mistbelt grassland avian community by determining avian community structure and composition in four patch types, i.e. i) untransformed open grassland, ii) burnt grassland, iii) bramble-invaded and, iv) bramble-cleared grassland, during winter and summer. Avian assemblages were significantly different between the different patch types for each season. The bramble patch type negatively affected grassland bird species diversity. Bramble-cleared grassland and untransformed grassland had similar vegetation structure and avian communities in the summer, suggesting that the grassland bird community benefitted soon after the clearing of invasive vegetation. This study provides further evidence that bird diversity is enhanced in structurally heterogeneous grassland landscapes. Furthermore, the protection and appropriate management of privately owned Mistbelt grassland, conserved in the form of rangeland, is an important refuge for threatened and endemic avifauna, such as the globally-threatened blue swallow (Hirundo atrocaerulea) and wattled crane (Bugeranus carunculatus).

Coffee Agroforests Remain Beneficial for Neotropical Bird Community Conservation across Seasons

Coffee agroforestry systems and secondary forests have been shown to support similar bird communities but comparing these habitat types are challenged by potential biases due to differences in detectability between habitats. Furthermore, seasonal dynamics may influence bird communities differently in different habitat types and therefore seasonal effects should be considered in comparisons. To address these issues, we incorporated seasonal effects and factors potentially affecting bird detectability into models to compare avian community composition and dynamics between coffee agroforests and secondary forest fragments. In particular, we modeled community composition and community dynamics of bird functional groups based on habitat type (coffee agroforest vs. secondary forest) and season while accounting for variation in capture probability (i.e. detectability). The models we used estimated capture probability to be similar between habitat types for each dietary guild, but omnivores had a lower capture probability than frugivores and insectivores. Although apparent species richness was higher in coffee agroforest than secondary forest, model results indicated that omnivores and insectivores were more common in secondary forest when accounting for heterogeneity in capture probability. Our results largely support the notion that shade-coffee can serve as a surrogate habitat for secondary forest with respect to avian communities. Small coffee agroforests embedded within the typical tropical countryside matrix of secondary forest patches and small-scale agriculture, therefore, may host avian communities that resemble those of surrounding secondary forest, and may serve as viable corridors linking patches of forest within these landscapes. This information is an important step toward effective landscape-scale conservation in Neotropical agricultural landscapes.

Reduced rainfall explains avian declines in an unfragmented landscape: incremental steps toward an empty forest?

Declines of formerly widespread bird species are being increasingly reported, with habitat loss, agricultural intensification and reduced rainfall frequently implicated. We report on temporal changes in the occurrence of birds over 21 years within continuous forest in the Warrumbungle Mountains to evaluate the influence of rainfall variability on changes in the abundance of birds and species occurence. During this period, six common insectivores declined significantly (Superb Fairy-wren, Malurus cyaneus; White-throated Gerygone, Gerygone albogularis; Grey Shrike-thrush, Colluricincla harmonica; Rufous Whistler, Pachycephala rufiventris; Grey Fantail, Rhipidura albiscapa; Eastern Yellow Robin, Eopsaltria australis). Rainfall significantly predicted the abundance of 13 of the 25 most common species, with the rainfall period of both July-December of the previous year and the combined effects of six years of January-June rainfall correlated with changes in the abundance of birds. Prolonged drought has likely driven food shortages (especially of litterdwelling arthropods), with changes in avian community composition reflecting changes in food availability. Thus, avian declines in southern Australia may reflect the combined effects of habitat fragmentation and other landscape-scale changes in concert with larger-scale ecological processes driven by decreased rainfall. Improved linkages between forested and agricultural landscapes at the regional scale are needed to buffer against local fluctuations in resources.

Invasion of Ligustrum lucidum (Oleaceae) in the southern Yungas: Changes in habitat properties and decline in bird diversity

Ligustrum lucidum is the major exotic tree in NW Argentina montane forests (Yungas). To assess the effects of its expanding invasion on avian communities we (1) measured different habitat properties (vertical forest structure and composition, vegetation cover, light availability, air temperature, air relative humidity and soil litter depth), (2) compared bird species composition and diversity in Ligustrum-dominated and native-dominated secondary forests and (3) analyzed seasonal patterns and changes in these variables between forest types. The study was conducted during 2010–2011 wet and dry seasons, at two altitudinal zones: 500–800 and 1100–1450 masl. Compared with native forests, Ligustrum dominated forests had a more homogeneous vertical forest structure and denser canopy cover (resulting in lower understory solar radiation), significantly lower understory cover and lower litter depth. Air temperature and relative humidity did not differ between forests in either season. Solar radiation was higher in the dry season in both forest types, but litter depth showed opposite patterns between seasons depending on forest type. We recorded 59 bird species in 21 families. Bird species abundance, richness and diversity indexes were significantly lower in Ligustrum-dominated relative to native forests of similar successional age, which had almost twice as many species as the former. Avian communities differed between altitudinal zones, but the difference was stronger between Ligustrum and native-dominated forests. Avian community composition was less variable in time and space in native forests than in Ligustrum-dominated ones. Our results suggest that L. lucidum invasion generates structurally homogeneous and simpler forests that represent a less suitable habitat for a diverse avifauna. This illustrates the wide ecological changes (from habitat properties and ecosystem functioning to vertebrate community composition) that the subtropical mountain forests of Argentina are experiencing with this invasion.

Effects of Management Intervention on Post-Disturbance Community Composition: An Experimental Analysis Using Bayesian Hierarchical Models

As human demand for ecosystem products increases, management intervention may become more frequent after environmental disturbances. Evaluations of ecological responses to cumulative effects of management interventions and natural disturbances provide critical decision-support tools for managers who strive to balance environmental conservation and economic development. We conducted an experiment to evaluate the effects of salvage logging on avian community composition in lodgepole pine (Pinus contorta) forests affected by beetle outbreaks in Oregon, USA, 1996–1998. Treatments consisted of the removal of lodgepole pine snags only, and live trees were not harvested. We used a Bayesian hierarchical model to quantify occupancy dynamics for 27 breeding species, while accounting for variation in the detection process. We examined how magnitude and precision of treatment effects varied when incorporating prior information from a separate intervention study that occurred in a similar ecological system. Regardless of which prior we evaluated, we found no evidence that the harvest treatment had a negative impact on species richness, with an estimated average of 0.2–2.2 more species in harvested stands than unharvested stands. Estimated average similarity between control and treatment stands ranged from 0.82–0.87 (1 indicating complete similarity between a pair of stands) and suggested that treatment stands did not contain novel assemblies of species responding to the harvesting prescription. Estimated treatment effects were positive for twenty-four (90%) of the species, although the credible intervals contained 0 in all cases. These results suggest that, unlike most post-fire salvage logging prescriptions, selective harvesting after beetle outbreaks may meet multiple management objectives, including the maintenance of avian community richness comparable to what is found in unharvested stands. Our results provide managers with prescription alternatives to respond to severe beetle outbreaks that continue to occur across extensive portions of the dry forests of western North America.

Resource availability and foraging of Silvereyes (Zosterops lateralis) in urban trees

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.