Urban domestic gardens (IX): Composition and richness of the vascular plant flora, and implications for native biodiversity

Garden floras interact with native biodiversity by providing resources for wildlife and by acting as a source of non-native species. Understanding the composition and richness of garden floras will help evaluate the relationships between these floras and the wider environment. The composition and richness of vascular plant floras were measured in a stratified sample of 61 urban, domestic gardens in Sheffield, UK, based on complete garden inventories. The entire garden flora contained 1166 species, of which 30% were native and 70% alien. Across gardens, aliens showed lower occupancy than natives, comprising 79% of the species recorded only once. The garden flora contained 146 plant families, which included 72% of the native, naturalised or recurrent casual families recorded in the wild in Britain and Ireland. Gardens contained on average 45% natives, irrespective of garden size. Garden area explained 30% of the variation in species richness within individual gardens. Doubling garden size led to an increase in species richness of 25%. The garden flora comprised 10% annuals, 63% biennial/perennials, 18% shrubs and 8% trees; shrubs were disproportionately composed of alien species. The floras of urban domestic gardens probably form the greatest source of potentially invasive alien plants. However, the plants found in domestic gardens have closer affinities with the uncultivated flora than is often perceived, and their role for wildlife in gardens deserves reassessment. Declines in garden size that result from recommendations on the density of new housing are unlikely to have major consequences for plant richness in gardens.     

Urban domestic gardens (XIII): Composition of the bryophyte and lichen floras, and determinants of species richness

Private, residential gardens form a substantial proportion of the undeveloped land in urban areas. Evaluating their role in supporting biodiversity is crucial to (i) predicting which plant and animal species can persist in towns and cities, (ii) understanding the regional impacts of urbanisation, and (iii) guiding sympathetic garden management by owners. To obtain baseline information on a poorly-studied component of garden biodiversity, we measured the size and composition of the cryptogam assemblages in 61 domestic gardens in the city of Sheffield, UK. A total of 67 bryophyte and 77 lichen taxa were recorded. Bryophytes ranged from 3 to 24 species per garden, with a mean richness of 11.3 species; lichens ranged from 2 to 30, with a mean of 14.9 species. Stone substrates supported the highest lichen richness, although minor substrates contributed unique species. Just over one fifth of bryophyte species were recorded in grass lawns, and these were more widespread than those of other habitats. Most cryptogams were scarce, with around one quarter of both bryophytes and lichens occurring in single gardens, and only 10% were found in more than half of the gardens. Garden area - correlated with substrate richness - and garden altitude were the only two factors explaining variation in cryptogam richness (bryophytes 39.1%, lichens 32.4%). Positive correlations existed among bryophyte, lichen and vascular plant richness, and these were only partially mediated by the effect of garden area. Therefore the opportunity remains for garden owners to support cryptogam richness, the most effective action being to enhance substrate diversity.     

Supply of tree-holes limits nest density of cavity-nesting birds in primary and logged subtropical Atlantic forest

Tree cavities are proposed to limit populations and structure communities of cavity-nesting birds. Although the greatest diversity of cavity-nesting birds is found in tropical and subtropical moist forests, little is known about how tropical logging affects the abundance of cavities or cavity-nesting birds. We compared the abundance of cavities and cavity nests between primary and selectively-logged subtropical moist Atlantic forest in Argentina, and conducted the first before-after controlled nest-box addition experiment to determine whether nest sites limit the breeding density of cavity-nesting birds in tropical or subtropical moist forest. Visual inspection of 86 cavities identified through ground-surveys revealed that only 19% were suitable for nesting birds, suggesting that cavity abundance may be overestimated in the literature on tropical forests. Suitable cavities were found in fewer than 1% of 1156 trees <60 cm dbh but 20% of 20 trees >100 cm dbh. Logged forest had half the basal area of primary forest, one third the density of large trees, nine times fewer cavities suitable for nesting birds, and 17 times fewer active nests. When we added nest boxes, nesting density increased on treatment plots but not on control plots in both logged and primary forest, suggesting that cavity supply can limit nest density even in relatively undisturbed forest. This is the first experiment to show how reduced cavity supply in logged tropical forest can limit breeding density of cavity-nesting birds. International initiatives such as forest certification should promote tropical timber management strategies that conserve large live cavity-bearing trees.     

Avifauna homogenisation by urbanisation: Analysis at different European latitudes

We studied the homogenisation effects of urbanisation on avifauna in towns of three countries selected along a latitudinal gradient: Italy, France and Finland. In each town (n = 19), numbers of species were analysed along an urbanisation gradient using two urban sectors (centre and suburban) and one non-urban sector (periurban), representing the regional species pool. Firstly, we compared the avifauna by using species richness and similarity indexes along the urban gradient (S) and latitudinal gradient (L). In Europe, the number of exotic bird species in towns was low. The number of species decreased from the periurban and suburban sectors to the centre sector. Thus, the generally low number of species and few dominant birds indicate that urban bird communities are structurally simple. In addition, many habitat specialists were lacking from urban centres. The centre species represented about 43% of periurban species (similarity S). There was no correlation between town size and species trend in sectors. However, bird community similarity L was lower between town centres than between periurban areas. Latitude explained 89% of the species difference in periurban sector but only 52% in the centre, supporting the homogenisation effect of urbanisation. Secondly, we examined the homogenisation effect through the variability of some specific life-history traits (diets, nest heights, feeding habitats) by using data on Passeriformes. Our results suggested that urbanisation might cause homogenisation by decreasing the abundance of ground nesting bird species and bird species preferring bush-shrub habitats. Urbanisation appeared a cause of taxonomic homogenisation of the avifauna but the effects of latitude and urban habitat diversity may make generalisation difficult.     

Vulnerability of ground-nesting waterbirds to predation by invasive American mink in the Cape Horn Biosphere Reserve, Chile

Biological invasions constitute one of the most important threats to biodiversity. This is especially true for “naïve” birds that have evolved in the absence of terrestrial predators in island ecosystems. The American mink (Mustela vison) has recently established a feral population on Navarino Island (55°S), southern Chile, where it represents a new guild of terrestrial mammal predators. We investigated the impact of mink on ground-nesting coastal waterbirds with the aim of deriving a vulnerability profile for birds as a function of different breeding strategies, habitat, and nest characteristics. We compared rates of nest survival and mink predation on 102 nests of solitary nesting species (Chloephaga picta, Tachyeres pteneres), on 361 nests of colonial birds (Larus dominicanus, Larus scoresbii, Sterna hirundinacea), and on 558 artificial nests. We calculated relative mink and bird densities at all nest sites. Nests of colonial species showed the highest nest survival probabilities (67-84%) and no predation by mink. Nest survival rates for solitary nesting species were lower (5-20%) and mink predation rates higher (10-44%). Discriminant analyses revealed that mink preyed upon artificial nests mainly at shores with rocky outcroppings where mink were abundant. High nest concealment increased the probability for predation by mink. Conservation planning should consider that invasive mink might severely affect the reproduction success of bird species with the following characteristics: solitary nesting, nesting habitat at rocky outcrop shores, and concealed nests. We recommend that work starts immediately to control the mink population with a priority in the nesting habitats of vulnerable endemic waterbirds.     

Does variation in garden characteristics influence the conservation of birds in suburbia?

Can enhancement of garden habitat for native birds have conservation benefits, or are garden bird assemblages determined by landscape and environmental characteristics? The relative roles of vegetation structure, floristics and other garden attributes, and environmental and landscape controls, on the abundance and richness of bird species in 214 back or front gardens in 10 suburbs of Hobart, Tasmania, Australia, are addressed to answer this question. Birds were counted in each garden and the resources they utilized noted. Vascular plant species and other attributes of the garden were noted, along with rainfall, altitude, distance from natural vegetation, distance from the city and garden size. Garden floristics and bird assemblages were ordinated, and garden groups characterized by particular assemblages of birds identified. General linear modelling was used to determine the combinations of independent variables that best predicted the richness of birds and the abundance of individual bird species and groups of species. The models for bird richness, bird species and groups of bird species were highly individualistic. Although native birds showed a preference for native plants, they also utilized many exotic plants. Exotic birds largely utilized exotic plants. Variation in garden characteristics does substantially affect the nature of garden bird assemblages in Hobart, with weaker environmental and landscape influences. The fact that gardens can be designed and managed to favour particular species and species assemblages gives gardeners a potentially substantial role in the conservation of urban native avifauna.     

Density and success of bird nests relative to grazing on western Montana grasslands

Grassland birds are declining at a faster rate than any other group of North American bird species. Livestock grazing is the primary economic use of grasslands in the western United States, but the effects of this use on distribution and productivity of grassland birds are unclear. We examined nest density and success of ground-nesting birds on grazed and ungrazed grasslands in western Montana. In comparison to grazed plots, ungrazed plots had reduced forb cover, increased litter cover, increased litter depth, and increased visual obstruction readings (VOR) of vegetation. Nest density among 10 of 11 common bird species was most strongly correlated with VOR of plots, and greatest nest density for each species occured where mean VOR of the plot was similar to mean VOR at nests. Additionally, all bird species were relatively consistent in their choice of VOR at nests despite substantial differences in VOR among plots. We suggest that birds selected plots based in part on availability of suitable nest sites and that variation in nest density relative to grazing reflected the effect of grazing on availability of nest sites. Nest success was similar between grazed plots and ungrazed plots for two species but was lower for nests on grazed plots than on ungrazed plots for two other species because of increased rates of predation, trampling, or parasitism by brown-headed cowbirds (Molothrus ater). Other species nested almost exclusively on ungrazed plots (six species) or grazed plots (one species), precluding evaluation of the effects of grazing on nest success. We demonstrate that each species in a diverse suite of ground-nesting birds preferentially used certain habitats for nesting and that grazing altered availability of preferred nesting habitats through changes in vegetation structure and plant species composition. We also show that grazing directly or indirectly predisposed some bird species to increased nesting mortality. Management alternatives that avoid intensive grazing during the breeding season would be expected to benefit many grassland bird species.     

Edge effects on nesting success of cavity-nesting birds in fragmented forests

Forest fragmentation leads to the creation of isolated forest patches and habitat edges with subsequent impact on forest-interior bird species. Although the effects of fragmentation and edge on avian nesting success are well documented for open cup-nesting species in eastern deciduous forests in North America, it is unclear whether these effects are common for all birds nesting in predominantly forested landscapes. In particular, edge effects on nesting success of cavity-nesting birds are poorly understood. Using natural cavity nests, we examined nesting success of four species of cavity-nesting birds (two nonexcavators and two excavators), the yellow-rumped flycatcher (Ficedula zanthopygia), the great tit (Parus major), the great spotted woodpecker (Picoides major), and the grey-faced woodpecker (Picus canus) in relation to forest edges in Zuojia Nature Reserve, Jilin province, northeastern China. Our primary objective was to assess whether distance to the edge of agricultural lands was related to nesting success for cavity-nesting birds in fragmented forests. A total of 439 natural cavity nests of the four species were located and monitored during four breeding seasons. Probability of nest success was influenced by distance to forest edge for nonexcavators, but not for excavators. The rate of nesting success of the two nonexcavators, yellow-rumped flycatcher and the great tit, increased with distance from the edges. For all cavity nests, nesting success was 0.43 at 0-100 m, 0.56 at 101-200 m, 0.68 at 201-300 m, 0.61 at 301-400 m, 0.77 at 401-500 m from the edges. Nesting success ranged from 0.57 for the yellow-rumped flycatcher to 0.89 for the Grey-faced Woodpecker. Failed nests were often occupied by nest-site competitors (accounting for 68%). However, predation only accounted for 20% of all nest failures. Our results suggest that negative edge effects do exist for some cavity-nesting birds, especially for nonexcavator species.     

Use of native and exotic garden plants by suburban nectarivorous birds

A lack of food resources is often used as a reason for the decline in native birds in cities. This study investigated the use of exotic and native nectar resources by the nectarivore guild of birds, which often forms a major component of suburban bird communities in Australia. We investigated the food resource (nectar volume, concentration and sugar reward) of two common native and two exotic garden plant genera. We also determined the relative preference of the nectarivorous bird community for native and exotic plants and examined the relationship between nectarivore foraging preferences and particular garden characteristics. Banksias and grevilleas (native genera) produced significantly higher volumes of nectar than camellias and hibiscus (exotic genera) per floral unit, per plant and per cubic metre of foliage. Banksias also produced significantly more concentrated nectar and consequently a higher sugar reward per floral unit than the other three genera. Fourteen bird species were recorded using the study plants, although only three species were commonly observed feeding: the Red Wattlebird (Anthochaera carunculata), Little Wattlebird (Anthochaera chrysoptera) and Noisy Miner (Manorina melanocephala). Banksia and grevillea plants were preferred by all bird species, which spent significantly more time in banksia than in any other genus. Other variables influencing the time birds spent in a plant were the number of floral units per plant and the number of banksia and callistemon plants present in the garden. Overall, the native genera, banksia and grevillea were not only a more valuable source of food than the exotic genera, camellia and hibiscus, but they were also the preferred foraging sites for suburban nectarivorous birds. Whether the surplus of nectar from native shrubs is associated with territories of larger and aggressive honeyeaters competitively excluding small birds from gardens, is an important research agenda for understanding these urban bird communities.     

Landscape-moderated importance of hedges in conserving farmland bird diversity of organic vs. conventional croplands and grasslands

Hedges provide important nesting, feeding and sheltering sites for birds in agricultural areas, while organic farming also enhances farmland birds. However, it is little known how the interaction of these local variables (amount of hedges and organic management) with landscape scale variables affects birds. We selected paired conventional and organic winter wheat fields and meadows in each of 10 landscapes in Germany. Birds were surveyed in the fields and in the adjoining hedges. More bird species occurred in organic than in conventional fields regardless of land-use type (wheat fields and meadows). However, hedge length had a much stronger effect on bird richness than organic farmland management. We found an interaction of landscape complexity and hedge length in that hedge length enhanced bird richness only in case of simple landscapes (<17% semi-natural areas within a 500 m radius around the centre of bird survey plots). In more complex landscapes the local effect of hedge length levelled off because bird richness was high even without local hedges. Therefore, adding hedges or introducing organic farming practices should be primarily promoted in simple landscapes, where it really makes a difference for biodiversity.     

Tallgrass prairie management and bird nest success along roadsides

The attributes of roadside vegetation, an important bird habitat in grassland ecosystems, have been shown to affect bird abundance, distribution composition, and diversity, yet there are relatively few works on reproductive success of birds nesting along roadsides. Because roadsides are linear habitats, management at the landscape scale can affect nest success in roadsides through bottom-up and top-down effects. In northeastern Oklahoma tallgrass prairie is subjected annually to prescribed spring fires. In the short term fires can alter both arthropod abundance and predator access to nests. We explored effects of burning on bird nest success with a five-year study along roads that traversed tallgrass prairie habitat. Using data from ∼1400 nests of 23 species, we generated nest survival curves for groups of altricial species defined by nest substrate (ground, shrub, tree, or culvert). We then determined if these curves were affected by management practice (spring burning), food abundance (arthropod biomass), and habitat attributes (tree density and height). Nest substrate had a large effect on nest success: despite their shorter nest exposure period, ground nests were least successful and culvert nests were most successful. An increase in arthropod biomass following burning was possibly the cause for the increased nest success in burned plots, regardless of substrate, suggesting bottom-up control. Tree height and nest height were correlated positively with nest success, whereas tree density had no effect. Conversely, nest predation rates were correlated negatively with nest success, with ground nests experiencing the highest predation, culvert nests the lowest. Our results suggest that burning may increase nest success through bottom-up processes, but some species may not benefit from the increase in food abundance as a result of a concomitant increase in predation.     

Decline in the distribution and abundance of flesh-footed shearwaters (Puffinus carneipes) on Lord Howe Island, Australia

The flesh-footed shearwater (Puffinus carneipes) is a migratory seabird that ranges widely across the Pacific and Indian Oceans. The principal breeding populations are in Australia and New Zealand. The only breeding site in eastern Australia is on Lord Howe Island. Despite it being afforded a high level of legislative protection, the population on Lord Howe Island has declined substantially during the last few decades. The total extent of nesting habitat in 2002 was 24.3 ha, a reduction of 13.4 ha (35.6%) since 1978. Loss of nesting habitat was associated with increased urbanisation, the adverse impact of which extended beyond the footprint of buildings and gardens. In 2002, overall burrow density was 0.123 per m² and the total number of burrows was estimated to be 29,853 ± 5867, a decline of about 19.0% since 1978. A substantial decline in burrow density was evident in the colony where loss of habitat to urbanisation had been greatest. In 2002, 58% of burrows were occupied by breeding birds, and the total population size was estimated to be 17,462 breeding pairs. Breeding success (the proportion of eggs that produced fledglings) was 50%, but was lowest in the most urbanised colony. To avert further declines in the population of flesh-footed shearwaters on Lord Howe Island major changes in land use practices, enforced through appropriate legislation, are needed, together with reductions in the level of seabird bycatch in fisheries operations and in the amount of plastics that litter the world’s oceans.     

Nesting habitat of the glossy black-cockatoo in central New South Wales

The reliance of cockatoos upon large hollows for nesting makes them vulnerable to any reduction in this resource. Species inhabiting forests managed for timber production are at risk because logging has the capacity to reduce hollow abundance significantly. In this study I identified the factors significantly associated with the selection of nest trees and nest sites by glossy black-cockatoos. Glossy black-cockatoos nested in vertical spouts in large trees. Nests were more likely to be located relatively high in senescent trees or standing dead trees (snags), factors most likely related to hollow suitability. As the density of potential nest hollows increased within a site, so to did the relative probability of it being used for nesting. The number of potential hollows serves as an index for the availability of suitable hollows. The persistence of glossy black-cockatoos within the study area will require careful management of nesting resources. Maximising the available hollow resource within known nesting areas is desirable. This is most efficiently achieved by facilitating the recruitment of large trees. This will require the exclusion of logging from nesting areas. Snags are a critical nesting resource. Information on snag dynamics is required and active intervention, such as the erection of nest boxes, may be necessary if unsustainable snag loss is occurring.     

Protected wading bird species threaten relict centenarian cork oaks in a Mediterranean Biosphere Reserve: A conservation management conflict

Conservation management conflicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Doñana Biological Reserve (SW Spain). A significant increase in the tree mortality rates has been recorded in areas that are yearly influenced by the bird colony.We analysed a cohort of surviving trees using a gradient of nesting bird influence. Tree-nesting history, bird isotopic signature (δ¹⁵N), tree health-related parameters (defoliation, δ¹³C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird influence was related to increased soil salinity. This increase correlated to increased water-use efficiency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves’ surface that was covered by faeces did not improve the fitted SEM model.For the reserve’s managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds.     

Autumn-sowing of cereals reduces breeding bird numbers in a heterogeneous agricultural landscape

The switch from spring-sown to autumn-sown cereals and the loss of habitat heterogeneity are often suggested to be key drivers of breeding bird decline on arable farmland. Yet, both factors are interlinked and it remains uncertain whether autumn-sown cereals reduce breeding bird numbers also in the structurally complex arable farmland of northern Europe. We tested whether autumn-sowing of cereals at both local and landscape scales affected the breeding bird community in a heterogeneous agricultural landscape of south-central Sweden. Rotation between sowing types was used as a semi-experiment based on 34 spring- vs. 41 autumn-sown cereal plots centred on infield non-crop islands of similar structure, size and surroundings. Species richness and territory abundance of ground-foraging species were significantly lower in autumn- than in spring-sown cereal plots both in the crop fields and the infield non-crop islands during the breeding season. No such effect was observed among foliage gleaning birds. Species richness in spring-sown cereal plots was less the more autumn-sown crops in the surrounding landscape within a 500 m radius. Average skylark densities did not differ between autumn- and spring-sown cereal plots because habitat preferences changed; densities declined in autumn-sown cereals during the growing season whereas they increased on spring-sown fields which had shorter swards throughout the breeding season. Our results indicate that negative effects of autumn-sown crops on breeding bird numbers spill over into both neighbouring non-crop and crop habitats. We conclude that agri-environmental schemes should place more emphasis on facilitating the value of the cropped area of fields as a foraging and nesting habitat. The retention of various non-crop habitats alone may not provide sufficient food close to nest sites for farmland birds that rely on crop fields for foraging.     

Do domestic cats impose an unsustainable harvest on urban bird populations?

We assessed the impact of domestic cats on population persistence of native and exotic urban bird populations using a model adjusted for habitat-specific catch rates, cat ownership and hunting activity data. GPS-derived home ranges of 32 cats and resource selection indices demonstrated the degree of penetration and preference for native vegetation fragments. Owners reported on prey brought back by 144 domestic cats in Dunedin, New Zealand, during 12 months. One third of cats never brought back prey, and 21% returned more than one item/month. Cats brought back a mean of 13.4 prey items/year (median = 4), with cats aged <1 year returning more prey than older cats. Birds were the most common prey, followed by rodents. Although cats penetrated adjacent vegetation fragments they did not catch more birds and preferred garden habitat, suggesting that predation pressure may be reduced in fragments. Cat home range size appears to be constrained by cat density while the number of birds caught depends on the density of available prey. Estimates of city-wide catch for six bird species were either more than total urban population size estimates or close to lower confidence intervals. Modelling of three species indicated low likelihood of population persistence with cat predation. The observed persistence of these prey species suggests a meta-population structure with urban populations acting as sinks with source populations located on the city fringe.     

美国市民农园生态植被景观营建及其启示

美国市民农园是一个值得借鉴的兼具生产、生态和生活等多功能的植被景观模式,本研究针对市民农园的生态服务功能,依据市民农园结构模式及经营群体的不同,随机选取了洛杉矶市14个市民农园,采用样地调查、半结构式访谈等方法,基于植被物种功能组合和乡土植物组成,定量化研究了城市植被物种多样性及其分布格局对种植者族裔背景及营建模式等影响因素的响应,进而评析对我国城市绿地建设和休闲农业的启示。本研究共计调查到439种植物,分属90科,242属,分析结果显示:市民农园是城市生态系统中重要的物种库,能维护较为丰富的乡土植物资源;其植物功能以食用植物为主,观赏植物、药用植物次之,这在保护族裔传统文化、区域乡土文化具有重要价值;其植被景观结构和功能受到族裔背景及营建模式等不同程度影响。研究证明,市民农园作为生态多样性和文化多样性的交汇景观,是实现城镇绿色基础建设和休闲农业发展的重要营建模式。以此为经验,我国在进行绿地规划和生态植被建设时要考虑不同利益相关者,尤其是关注外来者的生活习俗和选择偏好;同时也要注意监测外来物种,以防造成物种入侵,这对于建设文化强国背景下开展城镇生态植被建设和发展休闲农业具有启示意义。     

Richness, distribution and conservation status of cavity nesting birds in Mexico

A considerable number of bird species depend on tree cavities availability for nesting in temperate and tropical forests in Mexico. Tree cavity availability is reduced in heavily managed forests, making cavity nesting species particularly vulnerable to the high rates of forest loss and degradation that occur every day in the remaining wilderness areas of the country. We analyzed information about nesting behavior, distribution, and conservation status of resident landbird avifauna from 35 important and protected bird areas of Mexico. The main intention was to determine the proportion of resident bird species that nest in tree cavities and are more sensitive to intensive forest management practices. Our results revealed that 17% (112 species) of the resident landbird avifauna need tree cavities for nesting. Cavity nesters represented a higher proportion of endangered and threatened species than non-cavity nesters. The families Strigidae and Psittacidae represented the highest number of tree cavity nesting species in status. In the 35 avifaunas examined, the mean percentage of cavity nesting species ranged from 17% to 21%. The cloud forest reserve of “El Triunfo” with 43 species, is the area with the highest concentration of cavity nesting species in Mexico.     

Birds and green lanes: Breeding season bird abundance, territories and species richness

This study examines bird occurrence on 20 green lanes (farmland tracks with un-sealed surfaces, bordered on each side by hedgerows) and on 20 paired single hedgerows during the 2002 breeding season in Cheshire, UK. Measures of bird abundance, territories and species richness were all found to be significantly greater on green lanes than on single hedgerows. Significantly more birds were also found to occur on the inside rather than on the outside of green lanes in terms of abundance and species richness. All measures of bird occurrence on green lanes were influenced by hedge width and surrounding land use. Bird abundance on single hedgerows was influenced by the number of trees and amount of hawthorn in the hedge. Seventeen of the 18 most abundant bird species recorded in this study were found to occur in greater numbers on green lanes rather than in single hedgerows; for half of these species the difference was significant. The importance of green lanes for birds, and other wildlife is discussed, as well as their possible future within the UK landscape.     

The search for fragmentation thresholds in a Southern Sydney Suburb

Fragmentation of habitat is recognised as the number one threat to biodiversity and as such has attracted considerable research. However, much of this research has been conducted in forestry and agricultural environments, with little research in urban areas. In this study, field surveys were conducted measuring the impact of fragmentation on bird, frog, plant and fungi species richness, within the fragmented urban landscape of southern Sydney. Of all fragmentation parameters examined, remnant area was the best and most significant predictor of species richness for all taxa studied. Remnant size thresholds, below which biodiversity declined rapidly, were observed at approximately 4 ha for bird and frog species richness and approximately 2 ha for plant and fungal species richness. A further threshold appears to exist at approximately 50 ha for the dominance of forest interior species. Further relationships were also observed for perimeter:area ratio, indicating the influence of various edge effects on all taxa. Isolation effects were observed in the form of an inverse linear relationship between distance to other large reserves and species richness for fungi, birds and frogs. Corridor connectivity also produced an overall positive relationship for birds, frogs and plants. It is concluded that the identification of fragmentation thresholds and relationships provides an important management tool for the design of networks aimed at conserving biodiversity in fragmented urban environments.