Plant-species richness in corridor intersections: is intersection shape influential?

Corridor intersections constitute nodes that can be more mesic than the intersecting corridors themselves. Such microclimatic conditions may lead to an “intersection effect,” in which plant richness is higher in the intersection than in the corridors. We hypothesized that an additional factor contributing to intersection effects is the movement of plants along corridors into intersections by way of bird- and mammal-dispersed seeds. If this hypothesis is correct, one would expect intersection-shape effects, defined herein as differences in intersection section richness associated with the number of possible avenues for plant influx into the intersection. Specifically, richness in intersections should be lowest for L-shape intersections (two avenues), higher for T-shape intersections (three avenues), and highest for X-shape intersections (four avenues). We used data from fencerow networks to test this hypothesis about corridor intersections. During October 1992 and March 1993, we determined woody- and herbaceous-plant richness for 25 intersections and their associated fencerows in central Texas, USA. We compared two measures of intersection richness among the three intersection shapes: richness of plants dispersed primarily by birds and mammals (vertebrate-dispersed plant richness), and richness of plants dispersed primarily by wind, ants or other means (non-vertebrate dispersed plant richness). Vertebrate-dispersed plant richness differed significantly among intersection shapes, but no differences in nonvertebrate dispersed plant richness were evident, which is what one would expect if the number of avenues for vertebrate vectors into an intersection was an important factor influencing intersection richness. The intersection-shape effects we found were not attributable to fencerow features (amount of woody cover, width, pressence of breaks) or intersection characteristics (amount of woody cover, size, distance to nearest connected intersection or patch). Our results from fencerow networks support the hypothesis that intersection effects on plant richness are influenced by intersection shape via the number of intersecting corridors. Understanding patterns and processes that occur in networks is important for conservation biologists because intersections in networks have the potential to function as refugia for plant species that require conditions more mesic than those of the surrounding matrix. Networks also may be valuable asin situ sources of seed for managers attempting to restore plant communities in the matrix.     

Highways and Forest Fragmentation – Effects on Carabid Beetles (Coleoptera,Carabidae)

We conducted two studies on how highways affect their adjacent habitats by sampling carabid beetles (Coleoptera, Carabidae) in patches of formerly continuous forest next to highways. (1) We sampled carabids at 14 highway intersections near Helsinki, Finland. Each intersection (constructed 2–40 years ago) had two forested patches to study: a remnant (0.5–37.4 ha) and, isolated from the remnant by an intersection lane, an islet (size 0.2–1.8 ha). Pitfall trap catch data (2301 carabids, 25 species) showed that remnants hosted higher catches of three carabid species, and slightly higher species richness, than islets (patch-size effect). Time since intersection construction had no apparent effect on carabids. Traffic volume along the intersection lane determined the assemblage structure of carabids in dry patches, and the abundance of a forest carabid Calathus micropterus. Compared to moist patches, drier patches hosted lower catches of four generalist species; they also had different assemblages of carabids (habitat-type effect). An interaction between patch size and habitat type for a forest generalist Pterostichus oblongopunctatus indicated that the patch-size effect was dependent on habitat type. (2) We examined possible dispersal of carabids among forested patches that were separated by highway lanes in Drenthe, the Netherlands. We released 2696 marked individuals of 10 species, and recaptured 376 using dry pitfall traps. We found no evidence for inter-patch movement for nine forest species, but 22 of 225 recaptured individuals of Poecilus versicolor, an eurytopic open-habitat species, had crossed the highway. Catches of seven forest species were also significantly lower in the road verges, compared to the adjacent forests. These two studies suggest that (i) decreasing patch size negatively affects forest-carabid catch and overall species richness, (ii) habitat type can affect the intensity of the patch-size effect, (iii) carabid assemblages of forest fragments vary with traffic volume (which may be linked with urbanization), (iv) forest carabids rarely cross highways, and (v) open habitats associated with road margins are dispersal barriers for forest carabids.     

Vegetation structure moderates the effect of fire on bird assemblages in a heterogeneous landscape

Ecological theory predicting the impact of fire on ecological communities is typically focused on post-disturbance recovery processes or on disturbance-diversity dynamics. Yet the established relationship between vegetation structure and animal diversity could provide a foundation to predict the short-term effects of fire on biodiversity, but has rarely been explored. We tested the hypothesis that fire effects on bird assemblages would be moderated by increasing vegetation structure. We examined bird assemblages in burnt and unburnt sites at 1 and 6 years after a wildfire, and compared richness and composition responses among and within three structurally distinct vegetation types in the same landscape: heath, woodland and forest. We found that short-term changes in bird assemblage composition were largest in simple heath vegetation and smallest in complex forest vegetation. The short-term change in species richness was larger in forest than in heath. We also found that among-site assemblage variability was greater shortly after fire in heath and woodland vegetation compared with forest vegetation. Our results indicate that complexity in vegetation structure, particularly overstorey cover, can act as an important moderator of fire effects on bird assemblages. Mechanisms for this response include a greater loss of structure in vegetation characterised by a single low stratum, and a proportionally greater change in bird species composition despite a smaller absolute change in species richness. We discuss our results in the context of a new conceptual model that predicts contrasting richness and composition responses of bird assemblages following disturbance along a gradient of increasing vegetation structure. This model brings a different perspective to current theories of disturbance, and has implications for understanding and managing the effects of fire on biodiversity in heterogeneous landscapes.     

The distribution of a threatened migratory bird species in a patchy landscape: a multi-scale analysis

Understanding the driving forces behind the distribution of threatened species is critical to set priorities for conservation measures and spatial planning. We examined the distribution of a globally threatened bird, the corncrake (Crex crex), in the lowland floodplains of the Rhine River, which provide an important breeding habitat for the species. We related corncrake distribution to landscape characteristics (area, shape, texture, diversity) at three spatial scales: distinct floodplain units (“floodplain scale”), circular zones around individual observations (“home range scale”), and individual patches (“patch scale”) using logistic regression. Potential intrinsic spatial patterns in the corncrake data were accounted for by including geographic coordinates and an autocovariate as predictors in the regression analysis. The autocovariate was the most important predictor of corncrake occurrence, probably reflecting the strong conspecific attraction that is characteristic of the species. Significant landscape predictors mainly pertained to area characteristics at the patch scale and the home range scale; the probability of corncrake occurrence increased with potential habitat area, patch area, and nature reserve area. The median potential habitat patch size associated with corncrake occurrence was 11.3 ha; 90% of the corncrake records were associated with patches at least 2.2 ha in size. These results indicate that the corncrake is an area-sensitive species, possibly governed by the males’ tendency to reside near other males while maintaining distinct territories. Our results imply that corncrake habitat conservation schemes should focus on the preservation of sufficient potential habitat area and that existing management measures, like delayed mowing, should be implemented in relatively large, preferably contiguous areas.     

Prediction of total and rare plant species richness in agricultural landscapes from satellite images and topographic data

The diversity of future landscapes might depend on our ability to predict their potential species richness. The predictability of patterns of vascular plant species richness in a Finnish agricultural river landscape was studied using generalized linear modeling, floristic records from fifty-three0.25-km grid squares in the “core” study area, and environmental variables derived from Landsat TM images and a digital elevation model. We built multiple regression models for the total number of plant species and the number of rarities, and validated the accuracy of the derived models with a test set of 52 grid squares. We tentatively extrapolated the models from the core study area to the whole study area of 601 km² and produced species richness probability maps using GIS techniques. The results suggest that the local ‘hotspots’ of total flora (grid squares with > 200species) are mainly found in river valleys, where habitat diversity is high and a semi-open agricultural-forest mosaic occurs. The ‘hotspots’ of rare species (grid squares with > 4 rare species) are also found in river valleys, in sites where extensive semi-natural grasslands and herb-rich deciduous forests occur on steep slopes. We conclude that environmental variables derived from satellite images and topographic data can be used as approximate surrogates of plant species diversity in agricultural landscapes. Modeling of biological diversity based on satellite images and GIS can provide useful information needed in land use planning. However, due to the potential pitfalls in processing satellite imagery and model-building procedures, the results of predictive models should be carefully interpreted. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determinants of plant species richness and patterns of nestedness in fragmented landscapes: evidence from land-bridge islands

Land-bridge islands formed by dam construction are considered to be “experimental” systems for studying the effects of habitat loss and fragmentation, offering many distinct advantages over terrestrial fragments. The Thousand Island Lake in Southeast China is one such land-bridge system with more than 1000 islands. Based on a field survey of vascular plant richness on 154 land-bridge islands during 2007–2008, we examined the effects of island and landscape attributes on plant species richness and patterns of species nestedness. We also examined the different responses of plant functional groups (classified according to growth form and shade tolerance) to fragmentation. We found that island area explained the greatest amount of variation in plant species richness. Island area and shape index positively affected species diversity and the degree of nestedness exhibited by plant communities while the perimeter to area ratio of the islands had a negative effect. Shade-tolerant plants were the most sensitive species group to habitat fragmentation. Isolation negatively affected the degree of nestedness in herb and shade-intolerant plants including species with various dispersal abilities in the fragmented landscape. Based on these results, we concluded that the effects of habitat loss and fragmentation on overall species richness depended mostly on the degree of habitat loss, but patterns of nestedness were generated from different ecological mechanisms due to species-specific responses to different characteristics of habitat patches.     

Bird response to disturbance varies with forest productivity in the northwestern United States

Huston’s Dynamic Equilibrium Hypothesis predicts that the response of biodiversity to disturbance varies with productivity. Because disturbance is thought to break competitive advantage of dominant species in productive ecosystems, species richness is predicted to increase with disturbance frequency in productive systems. Recovery of plant biomass following disturbance is also predicted to be faster in productive systems. Here we provide the first test of Huston’s hypothesis in the context of setting harvest rates in managed forests for achieving biodiversity objectives. We examined predictions relating to vegetation and bird response to disturbance and succession in productive and less productive forests in western Oregon and Washington, USA. We found that measurements of understory cover and shrub diversity were higher in young, productive stands than less productive stands of similar age. Later-seral forests in productive environments (mean age = 67 years) had less variable and more complete canopy closure than similar-age forests in less favorable settings. At the stand scale, bird abundance and richness decreased with canopy closure in highly productive forests whereas bird abundance and richness increased with canopy closure in less productive forests. At the landscape scale, bird abundance and richness within stands increased with increasing levels of disturbance in the surrounding landscape within highly productive forests, whereas bird abundance and richness decreased with increasing disturbance in the surrounding landscape within less productive forests. Our results indicate that bird response to disturbance varies across levels of productivity and suggest that bird species abundance and associated species richness will be maximized through relatively more frequent disturbance in highly productive systems.     

Response of snails and slugs to fragmentation of lowland forests in NW Germany

Habitat fragmentation is a major cause for species loss, but its effect on invertebrates with low active dispersal power, like terrestrial gastropods, has rarely been studied. Such species can not cross a hostile habitat matrix, for which the predictions of island theory, such as positive relations between species richness and patch size, should apply. In order to test this prediction, we studied gastropod species diversity by assessing gastropod assemblage characteristics from 35 sites in 19 fragments of deciduous old-growth forests in the Lower Rhine Embayment, Germany. Assemblages differed between larger (≥700 ha) and smaller forests (<400 ha), those of large forests held a higher percentage of forest species. Although α-diversity was similar between the two forest size classes, small forests often comprised matrix species, resulting in a higher β-diversity. Edge effects on the species richness of matrix species were noticeable up to 250 m into the forest. Hierarchical partitioning revealed that distance to disturbances (external edge, internal edges like roads) explained most assemblage variables, whereas forest size and woodland cover within a 1 km radius from the sites explained only a few assemblage variables. Densities of two forest-associated species, Discus rotundatus and Arion fuscus, decreased with forest size. Yet, forest size was positively correlated with richness of typical forest species and densities of Limax cinereoniger. The latter species seems to need forests of >1,000 ha, i.e., well above the size of most fragments. In conclusion, the prediction is valid only for forest species. The response to fragmentation is species specific and seems to depend on habitat specialization and macroclimatic conditions. Jean-Pierre Maelfait: Deceased.     

Experimental evidence of the effects of a changed matrix on conserving biodiversity within patches of native forest in an industrial plantation landscape

We implemented a replicated before-after-control-impact (BACI) experiment to quantify vertebrate response in native forest patches to a major change in the surrounding exotic Radiata Pine (Pinus radiata) plantation. We contrasted vertebrate occupancy of patches of native eucalypt forest where the surrounding stands of exotic Radiata Pine (Pinus radiata) were clearfelled (termed “treatment patches”) with matched “control patches” where surrounding pine stands remained unlogged. Different species of arboreal marsupials varied in their response to our experimental treatments. The Common Ringtail Possum was unaffected by cutting of the surrounding pine stands, whereas all sightings of the Mountain Brushtail Possum were in control patches. For birds, species richness was significantly reduced by 4–9 species in treatment patches. Birds with cup and dome nests were those negatively affected by the cutting of the surrounding pine stands. They may be susceptible to altered microclimatic conditions or increasing levels of nest predation when the surrounding pine matrix is clearfelled. Our study emphasized how the biota inhabiting retained patches of native forest within plantation landscapes can be changed when stands of surrounding Radiata Pine are clearfelled. In the case of birds, more species will be maintained within eucalypt patches if logging is scheduled so that not all the surrounding pine plantation is clearfelled at once.     

Bird assemblages in forest fragments within Mediterranean mosaics created by wild fires

The role of habitat heterogeneity as a key factor in determining species pools in habitat mosaics has been acknowledged, but we still know little on the relative importance of the different ecological processes acting within such complex landscapes. We compared species richness and distribution in forest fragments imbedded in shrub-lands to those in continuous forests or in continuous shrublands. We examined the consistency of our data with the predictions of two hypotheses: 1) the Habitat fragmentation hypothesis which states that fragmentation has negative effects on the species from the original continuous habitat; 2) the Habitat supplementation /complementation hypothesis which stipulates that the presence of a matrix habitat around the fragments will mitigate negative effects on the species from the original habitat (supplementation) or allow the presence of species that depend on the presence of both the fragment and matrix habitats (complementation). We show that: 1) species richness in forest fragments did not differ from species richness in segments of continuous forests of equal area; 2) the bird community of forest fragments got impoverished in some forest species but a higher proportion of species common in continuous forests were not affected by fragmentation; 3) fragment communities had a significant proportion of common species that were scarce in, or absent from both continuous forests and shrublands. While, a few forest species supported predictions from the fragmentation hypothesis, occurrence patterns observed in several other species were consistent with either the supplementation or the complementation hypotheses. Our results suggest that there is no single hypothesis that properly captures the consequences of a shift from continuous forests to a mosaic of forest fragments and shrublands and that different ecological mechanisms act in conjunction to determine species pools in habitat mosaics. Habitat heterogeneity at a local scale appears a key factor in maintaining bird diversity in fire driven Mediterranean landscapes.     

Taxonomic diversity,functional diversity and evolutionary uniqueness in bird communities of Beijing's urban parks: Effects of land use and vegetation structure

The importance of biodiversity conservation is well recognized, and the loss of biodiversity is particularly evident in highly urbanized areas. On the other hand, green spaces inside cities, as parks, can provide a resource for maintaining and increasing biodiversity, especially for bird species. However, only a few studies have addressed the effects of vegetation structure and land use composition on different components of biodiversity.Here, we explored the response of bird community composition to environmental differences related to land use composition and vegetation structure in green spaces in the city of Beijing, China. We compared the values of taxonomic diversity, functional diversity and community evolutionary distinctiveness in breeding bird communities, among ten urban parks of the world's third most populous city. Variation partitioning analysis and generalized linear mixed models were used to explore the unique and shared effects of land use composition and vegetation structure on each biodiversity metric.Park size was not associated with the diversity of bird communities in Beijing. Land use composition was the best predictor of change in bird community composition, followed by vegetation structure at ground level and the intersection between land use and vegetation structure at tree level. Water coverage increased bird species richness, while the presence of large trees increased both taxonomic diversity and bird functional richness in urban parks. Finally, the presence of patches of deciduous trees showed a positive effect on the average score of evolutionary distinctiveness of bird communities. In conclusion, we highlight that different elements of the environment are supporting different components of bird community diversity.     

Factors Associated with Grassland Bird Species Richness: The Relative Roles of Grassland Area, Landscape Structure, and Prey

The factors responsible for widespread declines of grassland birds in the United States are not well understood. This study, conducted in the short-grass prairie of eastern Wyoming, was designed to investigate the relationship between variation in habitat amount, landscape heterogeneity, prey resources, and spatial variation in grassland bird species richness. We estimated bird richness over a 5-year period (1994–1998) from 29 Breeding Bird Survey locations. Estimated bird richness was modeled as a function of landscape structure surrounding survey routes using satellite-based imagery (1996) and grasshopper density and richness, a potentially important prey of grassland birds. Model specification progressed from simple to complex explanations for spatial variation in bird richness. An information-theoretic approach was used to rank and select candidate models. Our best model included measurements of habitat amount, habitat arrangement, landscape matrix, and prey diversity. Grassland bird richness was positively associated with grassland habitat; was negatively associated with habitat dispersion; positively associated with edge habitats; negatively associated with landscape matrix attributes that may restrict movement of grassland bird; and positively related to grasshopper richness. Collectively, 62% of the spatial variation in grassland bird richness was accounted for by the model (adj-R² = 0.514). These results suggest that the distribution of grassland bird species is influenced by a complex mixture of factors that include habitat area affects, landscape pattern and composition, and the availability of prey.     

Spatial,temporal, and life history assumptions influence consistency of landscape effects on species distributions

Models describing relationships between landscape features and species distribution patterns often display inter-study inconsistencies. Identifying factors contributing to these inconsistencies is a vital step in clarifying the ecological importance of landscape features and synthesizing an effective knowledge base for use in conservation contexts. We examined the influence of several spatial, temporal, and life history assumptions on the outcomes of distribution versus landscape models (DLMs) relating wetland bird communities at 29 Massachusetts (USA) sites to independent urbanization, wetland, forest, and agricultural landscape gradients. We considered a bird specialization index as well as obligate and facultative species richness as response variables. Landscape gradients were quantified at 10 landscape extents (0–1000 m in 100 m increments) and three time periods (1971, 1985, 2005). Univariate models indicated that our specialization index showed: (1) the strongest response to landscape gradients at small extents (200 m); (2) a negative, threshold response to urbanization was superior to a linear fit; and (3) no evidence of time-lagged effects of landscape change. Interestingly, the form of our model (i.e. linear versus threshold) influenced the extent at which strongest effects were detected. Multivariate models relating the specialization index as well as obligate and facultative species richness to landscape gradients showed evidence of annual variability (i.e. composition, parameter estimates, and variability explained) that did not depend upon an organism’s degree of specialization. Our results provide evidence that violations of common assumptions (e.g. selection of appropriate extent, lack of time-lagged effects, etc.) can impact the outcome of DLMs, which could lead to inter-study inconsistencies.     

Simple Neural Network Reveals Unexpected Patterns of Bird Species Richness in Forest Fragments

The study of links between bird species richness and forest fragmentation contributes to a better understanding of landscape biodiversity. Difficulties arise from the necessity to deal with multiple non-linear relationships between the involved variables. Neural network models provide an interesting solution thanks to their internal set of non-linear neuron-like components. Their ability is well established for prediction, but their complex structure limits the understanding of underlying processes. To open the ‘black box’ and get a more transparent ‘glass box’ model, we selected a simple neural network (2 inputs, 1 hidden layer with 3 neurons and 1 output neuron), that improves the prediction of birds species richness (lower root mean square error) compared to linear, log-linear and logistic models, and simple enough to analyze its internal components and identify patterns in the data. The first hidden neuron provided a sigmoid relationship related to the forest area, the second was like a Boolean operator separating two groups according to the distance to the nearest source forest larger than 100 ha, and the third acted on the smallest isolated woodlots. We revealed a group of isolated woodlots with a higher species richness than less isolated woodlots for a given forest area. This result, unexpected according to the literature, was not obvious in the raw data, and could be explained by a regional differentiation in fragmentation history. Our neural network showed its ability to improve prediction accuracy in respect to other models, to remain ecologically understandable and to give new insights into data exploration.     

Landscape effects mediate breeding bird abundance in midwestern forests

We examine the influence of both local habitat and landscape variables on avian species abundance at forested study sites situated within fragmented and contiguous landscapes. The study was conducted over a six year period (1991–1996) at 10 study sites equally divided between the heavily forested Missouri Ozarks and forest fragments in central Missouri. We found greater species richness and diversity in the fragments, but there was a higher percentage of Neotropical migrants in the Ozarks. We found significant differences in the mean number of birds detected between the central Missouri fragments and the unfragmented Ozarks for 15 (63%) of 24 focal species. We used stepwise regression to determine which of 12 local vegetation variables and 4 landscape variables (forest cover, core area, edge density, and mean patch size) accounted for the greatest amount of variation in abundance for 24 bird species. Seven species (29%) were most sensitive to local vegetation variables, while 16 species (67%) responded most strongly to one of four landscape variables. Landscape variables are significant predictors of abundance for many bird species; resource managers should consider multiple measures of landscape sensitivity when making bird population management decisions.Order of first two authors decided by coin toss     

Modeling the invasive emerald ash borer risk of spread using a spatially explicit cellular model

The emerald ash borer (EAB, Agrilus planipennis) is decimating native ashes (Fraxinus sp.) throughout midwestern North America, killing millions of trees over the years. With plenty of ash available throughout the continent, the spread of this destructive insect is likely to continue. We estimate that the insect has been moving along a “front” at about 20 km/year since about 1998, but more alarming is its long-range dispersal into new locations facilitated by human activities. We describe a spatially explicit cell-based model used to calculate risk of spread in Ohio, by combining the insect’s flight and short-range dispersal (“insect flight”) with human-facilitated, long-range dispersal (“insect ride”). This hybrid model requires estimates of EAB abundance, ash abundance, major roads and traffic density, campground size and usage, distance from the core infested zone, wood products industry size and type of wood usage, and human population density. With the “insect flight” model, probability of movement is dependent on EAB abundance in the source cells, the quantity of ash in the target cells, and the distances between them. With the “insect-ride” model, we modify the value related to ash abundance based on factors related to potential human-assisted movements of EAB-infested ash wood or just hitchhiking insects. We attempt to show the advantage of our model compared to statistical approaches and to justify its practical value to field managers working with imperfect knowledge. We stress the importance of the road network in distributing insects to new geographically dispersed sites in Ohio, where 84% were within 1 km of a major highway.     

Landscape context affects honeyeater communities and their foraging behaviour in Australia: implications for plant pollination

We investigated the species richness and composition of bird communities in mallee woodland remnants in a highly fragmented landscape, focusing specifically on honeyeaters and their foraging behaviour. We observed birds around flowering Eremophila glabra ssp. glabra plants in three replicated contexts: (1) the interior of large remnants, (2) linear remnants within ~3 km of a large remnant, and (3) linear remnants 5–7 km from a large remnant. We found species richness differed among elements, with an increase in the number of species that tolerate disturbed, open habitat and a decrease in the number of woodland-dependent species in linear elements. Honeyeater assemblages were similar in species richness and abundance among the elements, but differed in composition due to a higher number of large-sized honeyeater species in distant elements. Honeyeater movement patterns into a site and within a site were similar among the elements. Floral visitation varied among honeyeater species and was positively correlated with their abundance in the far element. Our results demonstrate that bird species respond differently to the spatial context of remnants in a fragmented landscape; however, the degree of isolation of linear remnants was not important. Linear remnants appear to be frequently used by honeyeaters, but the changes in community composition among the elements may influence the quality of pollination, which could have implications for plant reproduction.     

Overwintering in a megacity: Urban green areas and migratory birds in Mexico City

Nearctic-Neotropical migratory birds are threatened by land-use change throughout their complex annual cycles. While urbanization is an essential driver of land-use change, it is unclear how it affects migrant birds. Although migratory birds are more diverse in non-urban patches of native vegetation than in urban areas, neotropical cities can host diverse assemblages of overwintering migrant birds. Migratory birds in neotropical cities tend to be closely associated with urban green areas (UGAs). However, how their presence and abundance are affected by the habitat elements of UGAs and the urban matrix of neotropical cities is poorly understood. In this study, we compared the migratory bird species richness and abundances among UGAs and the urban matrix of the southern section of the megacity of Mexico City and native vegetation sites outside the city. Our results show that UGAs in neotropical cities provide habitats capable of maintaining complex overwintering migratory bird assemblages with local trees as critical features. We also assess the role that UGAs' characteristics play in determining migrant bird assemblages. We conducted bird censuses and measured habitat traits to determine how migrant bird assemblages are related to the habitat features of our study sites. We measured local, buffer, and spatial habitat features of each UGA. We found 23 overwintering migrant species in the three habitats, with 22 present within UGAs. Both UGAs and urban matrix sites had higher estimated species richness of migrant birds than non-urban native vegetation sites located outside the city. Only local features of UGAs affected migrant birds. While tree abundance in UGAs was positively associated with migratory bird species richness, the proportion of tree coverage was positively related to bird abundance. Our results show that UGAs in neotropical cities can maintain complex overwintering migratory bird assemblages, with trees being the most critical habitat feature. As a result, UGA management focused on maintaining trees and increasing their numbers can improve habitat conditions for migratory birds overwintering in neotropical cities.     

Matrix Matters: Effects of Surrounding Land Uses on Forest Birds Near Ottawa,Canada

Matrix quality affects probability of persistence in habitat patches in landscape simulation models while empirical studies show that both urban and agricultural land uses affect forest birds. However, due to the fact that forest bird abundance and species richness can be strongly influenced by local habitat factors, it is difficult to analyze matrix effects without confounding effects from such factors. Given this, our objectives were to (1) relate human-dominated land uses to forest bird abundance and species richness without confounding effects from other factors; (2) determine the scale at which forest birds respond to the matrix; and (3) identify whether certain bird migratory strategies or habitat associations vary in richness or abundance as a function of urban and agriculture land uses. Birds were surveyed at a single point count site 100 m from the edge of 23 deciduous forest patches near Ottawa, Ontario. Land uses surrounding each patch were measured within increasingly large circles from 200 to 5000 m radius around the bird survey site. Regression results suggest that effects of urban and agricultural land uses on forest birds (1) are not uniformly positive or negative, (2) can occur at different spatial scales, and (3) differentially affect certain groups of species. In general, agriculture appeared to affect species at a broad spatial scale (within 5 km), while urban land use had an impact at both a narrower spatial scale (within 1.8 km) and at the broad scale. Neotropical and short distance migrant birds seemed to be the most sensitive to land use intensification within the matrix. Limiting urban land use within approximately 200–1800 m of forest patches would be beneficial for Neotropical migrant birds, which are species of growing conservation concern in temperate North America.     

Native oak retention as a key factor for the conservation of winter bird diversity in managed deciduous forests in northern Italy

Birds can serve as useful model organisms to investigate community level consequences of forestry practices. In this study we investigated the relationships between wintering bird communities and habitat and landscape characteristics of lowland managed forests in Northern Italy. This area is characterized by the spread of the black locust, an alien species that has been favored by forestry practices at the expense of natural oak forests. Birds were censused in winter by point counts in randomly selected plots of 50 m radius. We first addressed bird community–habitat relationships by means of habitat structure measurements, then we investigated bird community–landscape relationships by using GIS techniques. We used generalized linear models (GLM) to test for the effects of habitat and landscape variables on bird community parameters (namely bird species richness, diversity and abundance). Bird community parameters were influenced by oak biomass and tree age, and by oak area and core area, while the other forest habitat types showed less influence. In forest management terms, the main conclusion is that the retention of native oaks is the keyfactor for the conservation of winter bird diversity in local deciduous woods. At the habitat level black locust harvesting may be tolerated, provided that old, large, native oaks are retained in all local woodlots to preserve landscape connectivity and foraging resources. At the landscape meso-scale, large native oak patches, should be preserved or, where necessary, restored. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.