Scale-dependent habitat relations of birds in riparian corridors in an urbanizing landscape

As the amount of urbanization in the landscape surrounding a riparian zone increases, local riparian vegetation structure and composition change in complex ways. The impact of increasing urbanization on birds in and around riparian zones will depend on their differential sensitivity to local- versus landscape-scale habitat variation. Thus, our principal objective was to determine which spatial scale has a greater association with the distribution of each bird species using riparian corridors in a landscape mosaic comprised of anthropogenic land uses and undeveloped native shrublands in coastal southern California. We surveyed 137 points in riparian vegetation along an urbanization gradient, and used logistic regression and information theory to select best supported models describing the distribution of each of 52 bird species. Models based only on local-scale vegetation variables were best supported for 19 species, whereas landscape-scale (amount of urbanization within a 1000-m radius) models were best supported for 13. Ten species were best described by models combining local- and landscape-scale variables, and 10 had no well-supported models. Within guilds, woodland and riparian-dependent species appeared to respond to local vegetation variables whereas shrubland species appeared more sensitive to landscape context. Likewise, insectivores were more likely to be associated with variation in local-scale variables. In contrast to other studies, Neotropical migrants were not sensitive to increasing urbanization. Provided that local vegetation remains in good condition, our results suggest that riparian bird species may persist even in areas with extensive urbanization.     

How do habitat variability and management regime shape the spatial heterogeneity of birds within a large Mediterranean urban park?

Large urban parks can support a diverse bird community. However, the effects of variability among habitats and of park management on bird assemblages are poorly understood. We studied bird communities within the Yarkon Park, Tel Aviv, the largest urban park in Israel. We examined species richness, abundance and community composition across 20 locations that differ in levels of park management to identify habitat variables responsible for variation in bird richness and composition. Of 91 recorded bird species, 13 were aliens (14%), 4 were urban exploiters (4%), 54 were urban adapters (60%) and 20 were migrants (22%). Management had a significant effect on native bird richness and bird community structure varied among areas with different management regimes. Species richness of all the above species’ groups was lowest in intensively managed areas. Areas with intermediate levels of management had higher or equal richness compared to unmanaged areas. The majority of urban exploiters were found at all locations within the park reaching their highest abundances in intensively managed areas. Species richness of alien birds did not vary across levels of management. Bird species richness was negatively associated with lawn cover and with distance from nearest water source and was positively associated with the number of woody plant species. We suggest that urban parks should be designed such that the heterogeneity of native vegetation is preserved, if we aim to maintain native bird species diversity and minimize urban exploiter and alien species. When lightly managed or unmanaged, urban parks can retain large remnants of sub-natural habitats and can serve as important contributors to the conservation of native biodiversity within a large urban metropolis.     

Living in the big city: Effects of urban land-use on bird community structure, diversity, and composition

Cities represent an important threat to biodiversity at different scales. Nevertheless, little is known on the processes underlying such effects. In this paper we describe bird diversity, structure, and composition patterns in different urban land-use categories. For this, we surveyed resident bird communities in four representative land-use categories of southwestern Mexico City. Our results show that bird communities vary greatly along the different studied urban land-uses, which represent an urbanization development gradient. Bird communities were highly dominated by few generalist species in areas with commercial components, while showed to have higher evenness values in green areas. Bird species richness decreased and bird abundances increased with urbanization intensity. Also, our results indicate that bird species richness and abundance values are sensible to site-specific habitat characteristics. Although we did not find a clear pattern of taxonomic homogenization related to urbanization, our results show that urbanization development entails the functional homogenization of bird communities. Thus, based on our results, we suggest three urban planning and management activities: (1) regulate land-use change related to urbanization; (2) increase the number of green areas within the city; (3) establish bird monitoring programs to identify focal areas that need management and assist with ecological data for urban planning.     

Recommendations for design and management of golf courses and green spaces based on surveys of breeding bird communities in Montreal

It has been suggested that golf courses can serve as wildlife habitat, provided key landscape features are present. Breeding bird communities were characterized on six golf courses and six green spaces in the Montreal area, Quebec, Canada. Landscape variables were measured to see which were the best correlates of avian species richness within and across sites. While there was no difference in the mean number of bird species (golf: 31 ± 2.4 SE; green: 33 ± 4.5 SE), golf courses supported fewer total species (golf: 55; green: 66). However, most of the species contributing to the green spaces’ higher cumulative total were found at one site. Species composition differed between golf courses and green spaces, and was most correlated with site size, housing density surrounding the site, and extent of coniferous tree, grass, and vegetated water cover. Our results support the work of others, and suggest that golf course architects can improve habitat quality by: (1) increasing deciduous and coniferous tree cover; (2) increasing native vegetation within and surrounding all water bodies; (3) reducing the amount of highly managed grass area; (4) ensuring large, undeveloped buffers are maintained to prevent a shift in avian community composition with increasing urban sprawl; and (5) ensuring sites are planned as large as possible.     

Bird communities of the Colorado Rocky Mountains along a gradient of exurban development

Most insights about the effects of residential development on wildlife are based on research from urban and suburban areas. Yet exurban development is an increasingly prevalent form of human settlement in many parts of the world. Moreover because such development often occurs near the periphery of protected areas, it may have a disproportionate influence on native species. We examined bird community patterns in the Rocky Mountains of north-central Colorado across a gradient of exurban development to determine how avifauna responded to this form of settlement. Using fixed-radius point counts, we surveyed the occurrence and abundance of breeding birds in 11 developed sites and in 6 nearby undeveloped sites, all occurring in a forested matrix. We sampled ground-level habitat features at each survey point and derived digital land-cover maps from aerial photographs to characterize and quantify road development and building density. We found little evidence that land-cover varied with development intensity, yet bird abundance increased significantly with building density. Patterns of species richness were equivocal due to a highly influential observation. Principal components analysis (PCA) distinguished two axes that explained nearly 50% of the variation in the bird community and were strongly associated with road and building density. Weighted average analysis showed a marked decline in the abundance and richness of species that were insectivorous or nested in snags, suggesting that reductions in dead wood may have influenced the bird community. However, no conclusions could be drawn because dead wood was confounded with building density. Logistic regression of species occurrence and building density indicated that the incidence of some generalist species increased with building density, whereas the incidence of specialists decreased. Overall, our results suggest that development at low densities can favor habitat generalists. Similar patterns have been observed in more urbanized areas. If exurban development persists as a popular form of settlement in the Rocky Mountains, a regional plan for protecting avian habitat and limiting development dispersion will be necessary to maintain native bird communities.     

Assessing land-use effects on water quality, in-stream habitat, riparian ecosystems and biodiversity in Patagonian northwest streams

Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.     

Effects of urbanization on Neotropical wasp and bee assemblages in a Brazilian metropolis

The rapid growth of cities in many parts of the world has stimulated an increasing number of ecological studies of urban environments. Here, 12 study sites in the city of Belo Horizonte (MG), southeastern Brazil, were compared to analyze the effects of habitat changes related to urbanization on the species richness and abundance of native wasps and bees. Two spatial scales were considered: large portions of the urban landscape (entire sites) and small areas within these sites (public squares). Overall, the abundance of advanced eusocial bees (i.e. stingless bees), which were the dominant species, was directly affected by the loss of vegetation cover and the increase of buildings associated with urbanization. The magnitude of this effect varied according to the nesting habits of each species. The loss of vegetation cover associated with urbanization also had a negative effect on the abundance and species richness of advanced eusocial wasps. Generalist species of bees and wasps, such as Trigona spinipes and Polybia occidentalis, were very abundant and not sensitive to the habitat changes related to urbanization. Advanced eusocial bees also responded to small-scale habitat changes (size and vegetation cover of public squares). No relation was found between the solitary and the primitive eusocial wasps and bees and the habitat changes considered here. Conservation strategies in urban environments need to consider different spatial scales in order to maintain or enhance the local diversity of wasps and bees.     

The avifaunas of some fragmented, periurban, coastal woodlands in south-eastern Australia

Growth of urban centres world-wide has been so dramatic over the past 100–200 years that many natural habitats have been much altered around large cities. A threatened coastal plant community, Moonah Melaleuca lanceolata woodlands, has been largely destroyed and degraded over a long period by the growth of suburbs into the desirable coastal areas on the fringes of the two main cities of Vic., Australia (Melbourne and Geelong). Here, we describe the avifaunas of 19 remnants of coastal Moonah woodland. The largest remnant is about 50 ha and this was used as a site for positioning ‘virtual’ remnants against which we could compare the avifaunas of the more common size-range of real remnants (≤10 ha). Although remnant habitat structure differed consistently between virtual and real remnants, these differences were not sufficient to alter the native avifaunas in constitution or bird densities. However, species richness was higher in 10 ha and in 2 ha remnants than in 1 ha remnants. Of seven landscape-context variables, only one influenced the avifauna: species richness declined as the degree of urbanization increased (measured by roof-counts). Exotic bird species have not colonized the remnants to a great degree (four species [of 38 in total], 8% of total records).     

天津滨海滩涂湿地鸟类丰富度与环境因子的关系研究

由于湿地生态系统的重要性、脆弱性和复杂性,湿地生态系统的保护与修复是当今世界的热点与难点问题之一。本研究选取天津滨海新区的3处湿地生态系统作为参考场地,1处湿地生态系统作为验证场地,通过量化4处场地不同类型栖息地的7个环境因素,综合鸟类对各类型栖息地的使用情况,并采用逐步回归分析,结果表明植被覆盖率、植物水平斑块丰富度及人为干扰程度与鸟类物种丰富度呈显著相关,并建立模型1;植物香农-威纳指数、植物水平斑块丰富度及人为干扰程度与鸟类共位群丰富度呈显著相关关系,并建立模型2。最后,利用验证场地的数据进行模型验证,得出所建立的模型能够较为准确地对栖息地内的鸟类丰富度进行预测。该研究构架了1种利用栖息地类型预测场地鸟类丰富度的方法,以期供相关研究或实际规划设计工作参考。     

Avifaunal Richness and Abundance Along an Urban Rural Gradient with Emphasis on Vegetative and Anthropogenic Attributes in Tiruchirappalli,India

Urban expansion and human migration from rural to urban locations have complex relationships with environmental change. Habitat fragmentation, loss of biodiversity and vegetation changes are some of the most common impacts of urbanisation. In many Indian cities, the urban core is characterised by historical human settlements with narrow lanes and packed commercial establishments, while urbanisation that occurred after 1970s preferred spacing between the dwellings with more greenery or urban forestry. As urbanisation progresses, the urban fringes have more scope for incorporating environmental concerns and conservation. In this study, we measured species richness and abundance of birds within varied urban habitats and landscapes along the urban–rural gradient in Tiruchirappalli, India. We also tried to determine the linkage between bird diversity and landscape attributes including anthropogenic factors. Our observations showed that within urban areas, certain landscapes favoured species richness while many habitats are unfriendly for species but encouraged homogenisation. As we move from urban core towards rural gradient, the species richness increased; however, it is not uniform in all peripheral directions. Interestingly, the urban fringes at certain pockets had richness equivalent to rural locations. Species richness positively correlated with vegetation cover while built cover, noise, vehicular movement and pedestrians had negative impacts. As the urban fringes are in various stages of development, they have more scope for integrating ecological and biodiversity considerations and in this aspect wetlands, riverine farmlands and urban forests may play a crucial role in retaining native birds and also supporting migratory bird species.     

基于鸟类生境修复与营造的湿地 生态设计策略

以天津七里海古潟湖湿地为研究场地,以生活在其中的鸟类及其所需的生境条件为主要研究对象。由于研究中数据有限,因此选择根据有限数据就可得出较为准确结果的Lasso回归算法,分析环境因子与鸟类多样性之间的关系。结果显示人类干扰程度、植物水平斑块丰富度、植物香浓-威纳指数及面积是影响鸟类丰富度的关键环境因子。以此为依据,结合目标鸟类所偏好的生境条件,针对现状斑块类型及斑块内的小生境提出了相应的修复、营建、增加面积及丰富植物群落等设计策略,以期能够以提高研究场地内鸟类丰富度为最终目标,进而达到湿地生态系统修复的目的。     

重庆城市绿地鸟类多样性与影响因素—— 以悦来国际会展城为例

城市绿地能够为城市提供重要的生态系统服务功 能。鸟类作为城市生态系统的重要指示物种,了解影响鸟类群 落多样性的城市绿地特征对于指导城市绿地规划和提升城市生 物多样性有重要意义。然而,多种城市绿地特征如何共同影响 鸟类多样性尚不完全明确。选取重庆市悦来国际会展城为研究 区域,采用样点法调查了49个绿地样地4个季节的鸟类资源数 据,并获取了样地的植被特征、环境特征及人为干扰特征等19 个城市绿地特征。使用广义线性模型、信息论模型选择及差异 性分析方法探析了城市绿地特征对鸟类α多样性的影响,阐述 了研究区鸟类α多样性的基本特征。结果显示：乔木层盖度、 乔木丰富度、灌木层盖度、灌木多度、草本层盖度、草本层多 样性、植被生境类型、环境噪声、距建设用地距离等因素对鸟 类α多样性有显著影响。鸟类α多样性特征在不同植被生境类 型及季节之间存在显著差异。麻竹生境的鸟类多度显著低于其 余多种生境,冬季鸟类α多样性指标偏低。在城市绿地的建设 中,根据显著影响鸟类的各种城市绿地特征,提出增强鸟类α 多样性的针对性建议,如控制乔木盖度,补充灌木层,以乡土 食源树种作为植被生境中的优势种,对冬季休眠植被进行分区 保留管理等。研究结果可以为地区城市生物多样性保护及城市 生态系统优化提供重要参考。     

Investigating alien plant invasion in urban riparian forests in a hot and semi-arid region

In this paper, we examined twelve riparian forests along urban–rural gradients in Austin, TX (USA), on the relationship among watershed urbanization and the invasion of alien woody species. We assessed the degree of biological invasion by measuring relative alien cover (RAC) of the riparian forests. We also measured environmental variables (15 in total) that characterize the study forests, including impervious surface percentage of corresponding watersheds, stream hydrology of adjacent streams, species diversity, canopy gap percentage, and soil nutrient contents of the riparian forests. Stream hydrology was quantified by the transfer function model. The results indicate that impervious surface percentage was related to stream hydrology: the more the impervious surface in a watershed, the faster streamflow recedes after the storm, and the longer dry period the riparian forest experienced (R² = 0.722). Impervious surface percentage was also related to RAC (R² = 0.498). Nonmetric multidimensional scaling (NMDS) grouped the 15 environmental variables into five dimensions. Multiple regression analysis of RAC on the five NMDS dimensions shows that RAC was related only to the dimension related to hydrological drought. Based on these results, we concluded that watershed urbanization facilitates the invasion of alien species in riparian forests by causing hydrologic drought, particularly in hot and semi-arid regions.     

The distribution, abundance and diversity of birds in Manila's last greenspaces

Urban environments are not considered areas with conservation importance. However greenspaces in cities have been previously identified as areas with significant avian biodiversity. We investigated the distribution and diversity of birds in what are increasingly considered as Metropolitan Manila's last greenspaces; the University of the Philippines campus, military cemeteries and two government operated parks. Using species–area analysis, abundance and diversity indices, TWINSPAN ordination and logistic regression to determine important landscape features for species presence, we describe the distribution of bird communities and diversity in Metropolitan Manila. Two major bird community groupings were observed. These are the urban exploiters and the urban adaptable with the former occurring in high abundances and the latter in low abundances in greenspaces. The number of built and natural spatial entities determines abundances. Species area analysis suggests that the greenspaces are distinct habitats that preserve faunal uniqueness whereas urbanization tends to decrease diversity. These observations suggest that greenspaces harbor significant avian biodiversity as well as the presence of endemic and threatened species. As the greenspaces possess remnant wetland and wooded habitat we recommend that they be preserved and maintained by ensuring that these habitats are incorporated in any urban development plan.     

Avian movement across abrupt ecological edges: Differential responses to housing density in an urban matrix

The movements of birds across habitat edges were investigated at the interface between remnant bushland and two densities of suburban housing. Behavioural responses to edges adjoining the two densities of housing matrix differed significantly among feeding guilds. Omnivores and nectarivores were significantly more likely than insectivores to penetrate edges adjoining high-density housing. Analysis of individual species revealed several consistent trends. Nectarivorous species appeared more likely to cross at edges of high-density housing, while insectivores were more likely to cross at edges of low-density housing. Regression models suggest these trends may be influenced by characteristics within the matrix, principally the proportion of housing and variables associated with shrub and canopy vegetation. These trends corresponded well with the known distribution of the guilds in remnant vegetation of the suburban landscape. Importantly, by crossing at these habitat edges, many species demonstrate that with appropriate management of the housing matrix they have the potential for dispersal necessary for the maintenance of meta-populations.     

Factors influencing species diversity of ferns and fern allies in fragmented forest patches in the Kyoto city area

We investigated the relationship between species diversity of pteridophytes and the environmental factors of 39 fragmented forest patches in the Kyoto city area. There was a significant correlation between the number of species and the micro-landform diversity, artificial habitat diversity, and logarithm of the area of the forest patch. When we performed a multiple regression analysis to identify the best-fit model so as to optimize the amount of variation in species diversity explained by using stepwise selection, three species diversity indices (species richness or Shannon’s diversity index, logarithm of inverse Simpson index) had significant positive partial correlations with the logarithm of area of the forest patch, and negative correlations with the logarithm of isolation distance from mountain forest. Therefore, we conclude that pteridophyte species diversity depends on patch size and isolation distance from mountain forests. Comparison of the woody plant species–area curve with the pteridophyte species–area curve showed that the rate of increase of species number (inclination) with area was the same, but the Y-intercept of the pteridophyte species–area curve was lower than that of the woody plant curve. Therefore, the minimum conservation area required for ferns and fern allies is greater than that for woody plant species.     

A tool for tracking floodplain age land surface patterns on a large meandering river with applications for ecological planning and restoration design

An alluvial river channel typically meanders by eroding its outer banks and depositing sediments on the inside of bends, producing new land surfaces. Over time the landscape pattern created by these processes is important to the understanding of riparian plant ecology and the spatial structure of riparian forest development for restoration planning and design as well as other purposes. The middle sector of the Sacramento River is an actively meandering channel that deposits sediments in discrete new areas from fluvial geomorphic events creating a land age gradient. Newly formed land undergoes a primary succession by woody species such as willow and cottonwood communities that provide habitat for important conservation target species in California. Conservation and restoration of primary and secondary successional processes is an important management goal on the Sacramento River. The objectives of this paper were: (1) to develop and codify new methods to track the surficial chronological patterns of floodplain land age in a meandering river system, and (2) to analyze land production and the spatial distributions of gravel bars, riparian vegetation communities, and forest structure in relation to the land age gradient. Results from the ecological analysis indicate 71% of extant riparian vegetation was located within the 101-year meander zone; willow (18%) and cottonwood (31–43%) had the highest proportional canopy cover on lands aged 1–9 and 10–44 years, respectively. Potential applications of this approach for conservation and restoration planning and design of alluvial river floodplains are discussed.     

Nature reserve selection on forest fragments in a suburban landscape (Rome, Central Italy): indications from a set of avian species

A set of avian forest species, known from the literature as fragmentation-sensitive, was considered as the target in nature reserve planning following a conceptual framework. Their abundance was investigated in an 'archipelago' of oak woodland fragments embedded in a suburban landscape matrix of central Italy. None of the four species were found in any wood fragment smaller than 10 ha. The presence/absence analysis of woodland fragments studied showed that the study species were present, however, in larger fragments, highlighting the strategic role of habitat size and isolation for the persistence of these species at local scale. Species numbers and their total abundance were significantly and directly correlated to overall species richness of each fragment: in this landscape context our study species shows characteristics of serving as focus and surrogate species of bird richness. The selected species are area-sensitive and poor dispersers: however, they are still relatively widespread, at a regional scale. Although the abundance of individual species may be affected by stochastic factors, total abundance of this forest bird guild may constitute a useful dependent variable that can provide rapid quantitative data needed for planning strategies at local scales.     

Biotic homogenization and alien bird species along an urban gradient in South Africa

Similar to the process seen in invasion biology, urbanized environments lead to biotic homogenization with a few species, often alien, dominating the urban habitat. We investigated avian communities across an urban gradient in Pretoria (South Africa). We defined three urbanization zones: urban, suburban and semi-natural, based on land-cover. We conducted point counts of all species at each of 13 sites in these zones over a 4-month period. We found significantly more species in the semi-natural zone than the urban zone but abundance was significantly lower in semi-natural than urban. The increase in abundance was mainly as a result of alien species with the three most abundant species in the urban zone being all alien. Semi-natural contained fewer alien species than urban and significantly fewer than suburban. The Common Myna Acridotheres tristis was the only alien species that was observed in all three urbanization zones and was the second most abundant species in the suburban and urban zones. Our study supports the process of biotic homogenization, where an increase in alien species occurs in the urban compared to semi-natural zone. Although the suburban zone made an important contribution towards native bird abundance in a larger city environment, this environment was also an important environment for alien species, especially for the Common Myna.