Habitat type,food resources,noise and light pollution explain the species composition,abundance and stability of a winter bird assemblage in an urban environment

At present, urban areas cover almost 3% of the Earth’s terrestrial area, and this proportion is constantly increasing. Although urbanization leads to a decline in biodiversity, at the same time it creates extensive habitats that are exploited by an assemblage of organisms, including birds. The species composition and density of birds nesting in towns and cities are determined by the types of buildings, the structure and maturity of urban greenery, and habitat diversity. In contrast, the habitat traits shaping the community of birds wintering in urban areas are not known. The aim of this work was to assess the influence of habitat structure, food resources and the urban effects (pollution, noise, artificial light) on an assemblage of birds overwintering in an urban area. It was carried out in 2014 and 2015 in the city of Kraków (southern Poland), on 56 randomly chosen sample plots, in which the composition, density and interseasonal similarity of bird assemblage were assessed with line transect method. A total of 64 bird species (mean = 17.7 ± 4.9 SD species/plot) was recorded. The mean density was 89.6 ind./km ±63.3 SD. The most numerous species were Great Tit Parus major, Magpie Pica pica, Blackbird Turdus merula, Blue Tit Cyanistes caeruleus, Rook Corvus frugilegus, Fieldfare Turdus pilaris and House Sparrow Passer domesticus. Noise adversely affected species numbers and density, but artificial light acted positively on the density of birds and their interseasonal stability. The species richness and density of birds were also determined by the number of food sources available (e.g. bird-feeders). In addition, the greater the proportion of open areas, the fewer species were recorded. In contrast, the more urban greenery there was, the greater the density of the entire bird assemblage. Urban infrastructure (buildings, roads, refuse tips) had a positive effect on the interseasonal stabilization of the species composition of wintering birds. The results of this work indicate that the urban effect, i.e. noise and light pollution, apart from purely habitat factors, provide a good explanation for the species richness, density and stability of bird assemblage wintering in urban areas.     

Bird and mammal use of vernal pools along an urban development gradient

Vernal pools in the northeastern US are of conservation concern primarily because of their role as habitat for specialized pool-breeding amphibians, but their use by birds and mammals may also be of interest, especially from the perspective of the impact of urbanization. We describe camera-trapped wildlife (CTW) at 38 vernal pools along an urban development gradient in greater Bangor, Maine, USA. We detected 20 mammal and 39 bird taxa (29 contacted pool water; 39 detected at >1 site). Land cover type within 1000 m (%), within-pool vegetation (%), and amphibian egg mass numbers explained a substantial portion of the variance (40.8%) in CTW assemblage composition. Submerged vegetation within pools and cover by water and impervious surfaces within 1000 m of pools were key site characteristics defining assemblages. We scored the urban-affiliation of taxa and modeled the relationship between weighted assemblage scores for each site and impervious cover. Impervious cover within 1000 m of pools was positively (p?<?0.01) related to site urban-affiliation scores. Use probability for red fox increased and snowshoe hare decreased with impervious cover at 1000 m. These results indicate that within-pool vegetation and land cover types at 1000 m influenced bird and mammal assemblages that used study pools and greater impervious cover at 100 and 1000 m was correlated with a shift in assemblages from being dominated by urban-avoider to urban-adapted species. We encourage land use planners and managers to consider the influence of land use practices within 1000 m of vernal pools on birds and mammals, especially near amphibian breeding pools.     

Conservation-priority grassland bird response to urban landcover and habitat fragmentation

As urbanization in the landscape increases, some urban centers are setting aside habitat for wildlife. This habitat may be particularly valuable to declining or conservation-priority species. One group in particular need of conservation actions that may benefit from habitat located in urban areas is grassland birds. Declines of grassland bird species have been particularly severe in the Midwestern U.S., where most grassland cover has been lost, fragmented, and surrounded by unsuitable habitat. Conservation efforts have focused on protecting large grasslands surrounded by minimal amounts of trees and development. Although urban development is considered hostile to grassland birds, this assumption has received little attention. In heavily fragmented landscapes where habitat is limited, urban grasslands may be of significant value to grassland birds. We examined grassland bird response to development and additional landscape and habitat variables in the greater Chicago metropolitan area. In 2012 and 2013, we surveyed bird communities in grassland patches along a gradient of urbanization and patch sizes. Density of Savannah Sparrows (Passerculus sandwichensis) increased with amount of development, while density of Sedge Wrens (Cistothorus platensis) decreased. Development did not appreciably impact Bobolinks (Dolichonyx oryzivorus), Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), Grasshopper Sparrows (Ammodramus savannarum), or Henslow’s Sparrows (Ammodramus henslowii). Patch size had a positive effect on species densities. These results indicate that for many conservation-priority grassland birds, urban landcover surrounding grasslands generally has neutral rather than negative effects on habitat use. Therefore, grasslands in developed landscapes may provide valuable contributions to regional conservation efforts.     

Managing urban wetlands for multiple use: research,restoration, and recreation

Conservation of urban wetland habitat is challenging, because multiple uses must coexist. We use examples from California and Wisconsin to describe potential synergies among recreation, restoration and research activities (the 3 R's). Allowing passive recreation is often essential to garner public support for habitat protection, restoration, and research. In turn, restoration activities can improve the appearance of degraded sites, and designing the work as a research experiment can serve the scientific community. Two projects at Tijuana Estuary support the 3 R's. (1) Oneonta Tidal Linkage is a 0.7-ha tidal channel and salt marsh that was excavated from disturbed upland to bring wetland habitat closer to the Visitor Center (thereby reducing visitor intrusion into natural marsh habitat, where endangered species would be disturbed). It supports an ambitious field experiment that is testing the importance of species diversity in restoration; it also includes a bridge that serves the interpretive program, and it adds 0.7 ha of wetland habitat that helps restore regional biodiversity. (2) A larger excavation (8 ha) of former tidal wetland will soon add wetland habitat, while testing the importance of tidal creek networks in ecosystem functioning and offering views and interpretive opportunities. A third situation, at the 485-ha University of Wisconsin–Madison Arboretum, concerns restored wet prairies, which provide habitat for native species and serve many hikers. Urban stormwater flows into and degrades the Henry Greene Prairie, allowing aggressive plants to invade. Research and restoration efforts are planned to sustain the habitat and recreation functions. These three models suggest that recreation, restoration, and research are compatible uses of urban wetland habitats.     

Cavity nesting birds along an urban-wildland gradient: is human facilitation structuring the bird community?

Urbanization brings dramatic and sudden changes to ecological conditions affecting natural communities. Cavity-nesting birds, both primary and secondary (hereafter PCN and SCN, respectively), may be limited in this novel environment because of reduced abundance of nesting sites (e.g. snags and cavities) and competition for cavities with non-native species. But humans can also directly and indirectly provide nest sites (e.g., nest boxes, crevices on houses), especially for SCN species, potentially partially compensating for negative effects. We investigated whether and how PCNs and humans facilitated the cavity-nesting bird community along a gradient of urbanization. To do so, we estimated the abundance of cavity-nesting species between 1998 and 2010 at 135, 1-km² sites that differed in the degree of urbanization (0–100 % forest cover). Also, we found 367 nests on a subset of 31 sites. PCNs (n = 67 nests) nested mostly on snags (98.5 %), while native SCNs (n = 141) used both natural (71.63 %) and anthropogenic (28.37 %) cavities. Non-native SCNs (n = 159 nests) used mostly anthropogenic cavities (98.11 %). PCN abundance facilitated native SCN abundance on sites with more than 12 % forest cover at 1-km² scale, but not at less forested sites. There, native SCNs nested primarily (59 %) in anthropogenic cavities. Human facilitation allowed native SCNs to successfully use and reproduce where snags were scarce, changing the composition and structure of the cavity-nesting bird community within the most urbanized sites. Flexible nest site selection and human facilitation provide new opportunities for native cavity-nesting birds in a rapidly changing world.     

Perceptions of severe storms,climate change,ecological structures and resiliency three years post-hurricane <Emphasis Type="Italic">Sandy</Emphasis> in New Jersey

Global warming is leading to increased frequency and severity of storms that are associated with flooding, increasing the risk to urban, coastal populations. This study examined perceptions of the relationship between severe storms, sea level rise, climate change and ecological barriers by a vulnerable environmental justice population in New Jersey. Patients using New Jersey’s Federally Qualified Health Centers were interviewed after Hurricane [Superstorm] Sandy because it is essential to understand the perceptions of uninsured, underinsured, and economically challenged people to better develop a resiliency strategy for the most vulnerable people. Patients (N = 355) using 6 centers were interviewed using a structured interview form. Patients were interviewed in the order they entered the reception area, in either English or Spanish. Respondents were asked to rate their agreement with environmental statements. Respondents 1) agreed with experts that “severe storms were due to climate change”, “storms will come more often”, and that “flooding was due to sea level rise”, 2) did not agree as strongly that “climate change was due to human activity”, 3) were neutral for statements that “Sandy damages were due to loss of dunes or salt marshes”. 4) did not differ as a function of ethnic/racial categories, and 5) showed few gender differences. It is imperative that the public understand that climate change and sea level rise are occurring so that they support community programs (and funding) to prepare for increased frequency of storms and coastal flooding. The lack of high ratings for the role of dunes and marshes in preventing flooding indicates a lack of understanding that ecological structures protect coasts, and suggests a lack of support for management actions to restore dunes as part of a coastal preparedness strategy. Perceptions that do not support a public policy of coastal zone management to protect coastlines can lead to increased flooding, extensive property damages, and injuries or loss of life.     

Tritrophic association on dandelion in a European capital city: a pilot quantitative study on the herbivore weevil <Emphasis Type="Italic">Glocianus punctiger</Emphasis> and its parasitoid wasp <Emphasis Type="Italic">Entedon costalis</Emphasis>

This study is a first attempt to estimate the degree of tritrophic association between the common dandelion Taraxacum officinale complex, the herbivorous weevil Glocianus punctiger and its parasitoid Entedon costalis, as an environmental marker in urban ecosystems. The study was conducted on 3926 dandelion flowering stems spread across 24 sample plots situated within the municipal borders of Kyiv (Ukraine). Eighteen plots were infested by the weevils, and 14 plots were infested by E. costalis. Of all the examined dandelion stems, 359 (9.1 %) were infested by weevils, and 21.4 % of these weevil-infested stems were parasitized by E. costalis. Thirty-two incidents of superparasitism were registered in nine sample plots. Seven environmental variables were chosen for characterization of the sample plots and for testing their possible effects on the tritrophic association. The results indicate that the infestation of dandelions by weevils is strongly limited by the grasslands’ mowing. Apart from that, the presence of anthropogenic barriers bounding the study areas negatively affected the parasitism of G. punctiger by E. costalis. This is regarded as an example of the crucial effect of habitat fragmentation on the specialist herbivore and the specialist parasitoid of this tritrophic system. Both the mowing and habitat fragmentation are linked with human land-use regimes on the sample plots.     

Influence of human population size and the built environment on avian assemblages in urban green spaces

While studies of how habitat patch dynamics structures avian communities in urban environments has received some attention, there is considerably less known of how the built environment and human population size may influence the structuring of urban bird communities. We investigated bird populations in Pittsburgh, Pennsylvania (U.S.A.) through replicated point count surveys of breeding birds in 50 parks and cemeteries of varying sizes. We counted 4,435 individual birds in 441 counts. Of the 61 species detected, 27 were rare (detected at <8 points). Migratory species accounted for 46.1 % of all individuals, while 23.2 % of all individuals were of introduced species. Species richness increased significantly with green area size, as did the number of rare species. Species diversity decreased significantly with an increase in the proportion of individuals of introduced species; in particular, cavity nesters were less abundant when introduced species were present. Elements of the built urban environment including commercial development and transportation corridors were associated with significant reductions in park-wide species richness, mean number of species per point, and mean number of individual birds recorded per point. Human population size was positively related to increased numbers of individuals of introduced species, but a lower mean number of species per point. Ours is among the first to identify specific relationships between avian population characteristics and human population size, as few other studies have specifically incorporated human population size into a local, fine grain study design. Our data suggest that human population size is an important parameter that can be measured independently of characteristics of the built environment and the physical characteristics of the park itself as a correlate of avian diversity and abundance. Our study points to a variety of trade-offs needed to manage habitat for birds in urban settings.     

Factors influencing expanded use of urban marine habitats by foraging wading birds

Urban marine habitats are often utilized by wildlife for foraging and other activities despite surrounding anthropogenic impact or disturbance. However little is known of the ecological factors that determine habitat value of these and other remnant natural habitats. We examined the preferential use of urban marine habitats in a northeast US estuary to try to elucidate the factors driving enhanced foraging activity at these sites. Using a bioenergetic model, we compared energy intake to energy expenditure and examined differences in behavior and foraging success of great egrets Ardea alba at three urban and three rural salt marshes in Narragansett Bay, Rhode Island USA. Mean per site available nekton energy averaged 4.44?±?0.97 GJ site^?1 and was significantly higher at urban than at rural sites. While energy expenditure by birds was similar across all sites, mean strike and prey capture rate were significantly greater at urban sites, and 70.1?±?12.2 % of strikes by egrets at urban sites were successful. Egrets foraging at urban sites consumed significantly more energy (23.2?±?6.62 W bird^?1) than those at rural sites. Model results indicated a net energy gain by egrets foraging at urban sites, versus a net energy loss at rural sites. Our results may help explain previously observed increases in the numbers of egrets foraging at urban marine habitats, and help provide input into decisions about the extent to which these areas should be considered for restoration or protection.     

Impacts of urbanisation on the native avifauna of Perth, Western Australia

Urban development either eliminates, or severely fragments, native vegetation, and therefore alters the distribution and abundance of species that depend on it for habitat. We assessed the impact of urban development on bird communities at 121 sites in and around Perth, Western Australia. Based on data from community surveys, at least 83 % of 65 landbirds were found to be dependent, in some way, on the presence of native vegetation. For three groups of species defined by specific patterns of habitat use (bushland birds), there were sufficient data to show that species occurrences declined as the landscape changed from variegated to fragmented to relictual, according to the percentage of vegetation cover remaining. For three other groups (urban birds) species occurrences were either unrelated to the amount of vegetation cover, or increased as vegetation cover declined. In order to maximise the chances of retaining avian diversity when planning for broad-scale changes in land-use (i.e. clearing native vegetation for housing or industrial development), land planners should aim for a mosaic of variegated urban landscapes (>60 % vegetation retention) set amongst the fragmented and relictual urban landscapes (<60 % vegetation retention) that are characteristic of most cities and their suburbs. Management actions for conserving remnant biota within fragmented urban landscapes should concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building awareness among the general public of the conservation value of remnant native vegetation.     

Does education influence wildlife friendly landscaping preferences?

In sprawling metropolitan areas, residential landscaping is a major concern with respect to biodiversity conservation, and it could play a critical role in conserving wildlife habitat. In the United States, residential landscaping typically consists of maintained lawns with specimen plantings of non-native trees and shrubs; such designs provide poor habitat for urban wildlife species. We conducted a case study of Raleigh, North Carolina residents to determine how providing information about the benefits of native plant landscaping to bird species influenced urban residents’ landscaping preferences. We used Wilcoxon Signed Rank tests to determine if respondent preferences for 0, 50, 75 and 100 % native plant landscaping coverages changed after residents were informed about the benefits that native plants provide for birds. Initially, the 50 % native landscaping coverage was most preferred by residents; however, preferences for all four native plant landscaping coverage designs were significantly different after the informational treatment. Neutrality changed to opposition for the 0 % native plant coverage, while opposition changed to support and neutrality for the 75 and 100 % native plant coverage designs, respectively. After the informational treatment, the 50 and 75 % native plant landscaping coverage had the highest mean preference levels, although the 100 % design was ranked first more than any other design. Our findings suggest that residential support for native plant landscaping is higher than is reflected by typical residential landscaping practices, and that dissemination of information regarding the benefits of native plant landscaping to birds could alter public preferences for native plant landscaping.     

Predicting impacts of urbanized stream processes on biota: high flows and river chub (<Emphasis Type="Italic">Nocomis micropogon</Emphasis>) nesting activity

This study quantified the impact of high stream flows on reproductive activities of river chub (Nocomis micropogon). Using observed relationships between flow and reproductive activities, the number of predicted damaging flow events was compared between streams with extant river chub populations and urbanized streams. Monitoring the survivorship of river chub nests during 2013–2014 (N = 101) revealed consistent relationships between interval peak flow measured at flow gauges and the integrity of river chub nests within sites. Flow-mediated disruption of nests was frequent, and interval peak flows were significantly correlated with nest erosion rates. Logistic regression between fate of river chub nests and standardized peak flow (Qs) during monitoring intervals identified thresholds of peak flow corresponding to complete and partial destruction of river chub nests. Observed thresholds were used to predict the frequency of potentially damaging flows in urbanized versus river chub study streams, based on archival flow monitoring data. Repeated measures analysis revealed that the frequency of flows predicted to result in the loss of all nests was significantly higher in urbanized streams (F = 122.2; df = 1; P < 0.001 ). While key life history information needs to be determined to fully understand the impacts of high flows on river chub population dynamics, results indicate the disruption of nests through frequent high flows as a mechanism for the reduction of this important species in urbanized areas. Improved understanding of the interactions between stream processes and biota will aid in the design of specific stream protection and restoration strategies.     

Can I Trust You? Laterality of Facial Trustworthiness in an Economic Game

People tend to turn their left or right cheek to express or conceal emotions, respectively. We examined the lateral posing bias for displaying trustworthiness during a trust game in which participants and their virtual partners cooperated or did not cooperate with their counterparts to earn a monetary reward. Right-handed participants (N = 81) were asked to pose for a photograph and then play the trust game. Participants showed an overall left posing bias (i.e., showing their left cheek to the camera). The left cheek bias was more stable for participants that cooperated very little in the trust game (non-cooperators) than for those that cooperated a lot (cooperators). In the rating experiment (N = 28 and 25), non-cooperators showing their left cheek were rated equally as trustworthy as cooperators. On the other hand, non-cooperators who showed their right cheek were rated as less trustworthy than cooperators. These results suggest that non-cooperators intuitively use the left hemiface to exploit others in social interactions.     

Determinants of species richness within and across taxonomic groups in urban green spaces

Urban green spaces provide habitat for numerous plant and animal species. However, currently we have little knowledge on which determinants drive the species richness within and across taxonomic groups. In this paper we investigate the determinants of total, native, and endangered species richness for vascular plants, birds, and mammals within and across taxonomic groups. We examined a stratified random sample of 32 urban green spaces in Hannover, Germany. Species inventories for plants and birds were generated on the basis of line transect surveys. Mammals were surveyed by means of point counts using camera traps. Using a principal component analysis and multiple regression models, we tested 10 explanatory variables for species-area effects, distance effects, and the effects of habitat structure of green spaces on species richness. When analyzing single explanatory variables, we determined that the species richness of all groups was significantly positively correlated to patch area, number of habitat types, and a short distance to the nearest green space. Testing combined effects of variables showed that patch area in combination with habitat heterogeneity was most important for plants (total, native, and endangered), birds (total and native), and overall species richness. This emphasizes the importance of the species-area effect and the effects of habitat structure on species richness in urban green spaces. We conclude that, in the context of urban planning, it is important to conserve large green spaces that include a high diversity of habitats to maintain high species richness.     

Avian haemosporidian parasites in an urban forest and their relationship to bird size and abundance

Urbanization has been identified as a threat to biodiversity due to landscape modifications. Studies of parasite ecology in urbanized areas lagged behind those made on macro organisms. Here we studied infection prevalence of haemosporidian parasites in an avian community of an urban forest from Germany, and its relationship with bird abundance and body mass. We used PCR to amplify a fragment of the mtDNA cyt b gene to determine the infection status of birds, and bird point counts to determine bird relative abundances. The avifauna was dominated by two small sized insectivore passerines (Parus major, Cyanistes caeruleus), representing ~40 % of the total bird records. The highest haemosporidian prevalence was recorded for Turdus philomelos (100 %) and for Fringilla coelebs (75 %). Bird abundance and body mass were positively associated with infection status for two haemosporidian genera: Plasmodium and Leucocytozoon. Infection rate was lower in juveniles compared to adult birds. We recorded a total of 7 Plasmodium, 26 Haemoproteus, and 10 Leucocytozoon lineages. Avian malaria (P. relictum) was detected infecting 5 individuals of P. major, the most abundant species in the community. These results, together with those of previous studies at the same site, suggest that potentially any of the genetic haemosporidian lineages detected in this urban forest can be transmitted across native and pet bird species, and to species of conservation concern housed at aviaries.     

The pattern of distribution and diversity of avifauna over an urbanizing tropical landscape

An investigation was done to determine the occurrence and composition of avian fauna community in the urbanizing city of Nairobi, Kenya. We conducted bird counts in sample sites randomly distributed over the Nairobi landscape within a two-year period. The proportion of seven different land cover types derived from within a 500 m radius of classified satellite image described the habitat condition of each sample site. Multivariate analysis of the site and species data indicated that savannah vegetation, forest and agriculture land cover types were the main environmental gradients that differentiated the sample sites. Four clusters of sample sites occurred on the ordination plane according to canonical correspondence analysis (CCA). From 50 families of birds observed, species related to bush and scrub habitats occurred at a rate of about 31 %, followed by grassland species at 20 % and forest species at about 16 % rate. Out of CCA, five functional groups of birds were distinguishable. The proportion of sites occupied by birds per functional group and mean count of individual birds declined significantly, p?<?0.0001, as groups of birds changed from being urban-related to savannah and then to forest-related species. One cluster comprised birds marked as having conservation concern status and related mainly to savannah vegetation of scrub and grasslands. In this landscape context, features such as native savannah vegetation and woodland accompanied by a process of controlled land use, could greatly mitigate negative impacts of ecosystem degradation on the sensitive tropical urban bird biodiversity.     

Using housing growth to estimate habitat change: detecting Ovenbird response in a rapidly growing New England State

Numerous measures of human influence on the environment exist, but one that is of particular importance is houses as they can impact the environment from species through the landscape level. Furthermore, because the addition of houses represents an important component of landscape change, housing information could be used to assess ecological responses (e.g., decline in wildlife habitat) to that change. Recently developed housing density data represents a potential source of information to assess landscape and habitat change over long periods of time and at broad spatial extents, which is critically needed for conservation and management. Considering the potential value of housing data, our goal was to demonstrate how changes in the number of houses leads to changes in the amount of habitat across the landscape, and in-turn, how these habitat changes are likely to influence the distribution and abundance for a species of conservation concern, the Ovenbird (Seiurus aurocapillus). Using a relationship between Ovenbird abundance and housing density, we predict suitable habitat in the forests of Massachusetts (USA) from 1970 to 2030. Over this 60-year period, the number of houses was projected to increase from 1.84 to 3.32 million. This magnitude of housing growth translates into a 57 % decline in Ovenbird habitat (6,002 km² to 2,616 km²), a minimum decline of ~850,000 (48 %) Ovenbirds, and an increase in the number of subpopulations across the landscape. Overall, housing data provide important information to robustly measure landscape and habitat change, and hence predict population change of a species. We suggest that time series of housing data linked to ecological responses (e.g., Ovenbird abundance) offers a novel and underutilized approach to estimating long-term and spatially broad predictions of ecosystem response to landscape change, which in turn can inform conservation and management.     

Factors determining the occupancy of Trumpeter Hornbills in urban-forest mosaics of KwaZulu-Natal,South Africa

Understanding the factors determining the occupancy and detection probability of birds in human dominated environments is important for their conservation. In this study we investigated various environmental variables believed to influence the site occupancy and detection probability of Trumpeter Hornbill (Bycanistes bucinator) in urban-forest mosaics of KwaZulu-Natal, South Africa. Presence/absence data were collected from a total of 50 point count stations established between September 2014 and March 2015 in urban-forest mosaics of Durban, Eshowe and Mtunzini. Mean occupancy rate of Trumpeter Hornbill was 0.40 ± 0.09 with a low detection probability of 0.28 ± 0.04. For Trumpeter Hornbills, large trees influenced their occupancy positively (sum AIC weight (ω _i ) = 79%) while relative human abundance negatively influenced their occupancy (ω _i = 91%). Model selection suggested that housing density had a strong negative influence on detection probability of Trumpeter Hornbills (ω _i ?=?82?%?) and availability of fruiting trees influenced their detection positively (ω _i ?=?29%). With continued changing land use in KwaZulu-Natal, these finding are important for conservation of Trumpeter Hornbills as we provide insight into landscape variables or features that influence Trumpeter Hornbill’s occupancy and detection in areas of urban-forest mosaics.     

Connectivity in urbanizing landscapes: The importance of habitat configuration,urban area size,and dispersal

Human activities affect both the amount and configuration of habitat. These changes have important ecological implications that can be measured as changes in landscape connectivity. I investigated how urbanization interacts with the initial amount and aggregation of habitat to change dispersal potential, restoration potential, and the risk of spatially extensive disturbances. I used a factorial set of simulated landscapes and subjected each landscape to habitat loss by overlaying 66 different US urban areas. I used a common connectivity metric, CONNECT, to assess the magnitude and direction of changes for a range of dispersal distances. My results show that the relationship between habitat loss and connectivity loss is non-linear and subject to interactions between the spatial patterns of habitat distribution, urban morphology, and dispersal capabilities. The implications of a given urban form vary widely as a function of habitat distribution and dispersal capabilities. This implies that impact assessments, restoration activities, and conservation planning should consider historical habitat distribution when evaluating observed changes in connectivity. While my results clearly show that more aggregated or continuous habitats are more vulnerable to connectivity loss, this approach can also be used to identify landscapes where restoring connectivity will be particularly effective, for example through placement of stepping stone habitats.     

The effects of scatter-hoarding rodents on Mongolian oak (<Emphasis Type="Italic">Quercus mongolica</Emphasis>) acorn dispersal and seedling distribution in urban woodland

Scatter-hoarding by animals is an effective mechanism for seed dispersal and plant regeneration in natural ecosystems, however, studies on the interaction between hoarding animals and urban forest are insufficient. By methods of acorn placement experiment, cache and seedling survey, the relationship between acorn dispersal and seedlings distribution of Mongolian oak (Quercus mongolica) and scatter hoarding rodents was investigated at the Northeast Forestry University Woodland of Harbin, China. Results indicated that main scatter hoarding rodents of acorns were squirrels (Sciurus vulgaris) and chipmunks (Eutamias sibiricus). Mongolian oak seedlings were distributed primarily in Mongolian Scotch pine, birch and larch parcels (df = 3, χ ² = 1502.77, P < 0.01). Most seedlings were 4 ~ 6 years (df = 3, χ ² = 408.23, P < 0.01) and mainly dispersed within range of 100 m from the parent trees. The activity frequency and cache habitats of squirrels coincided with the distribution pattern of Mongolian oak seedlings, which meant scatter hoarding rodents had important effects on acorn dispersal and seedling establishment of urban Mongolian oaks.