Scalar effects of vegetation on bird communities in an urbanizing desert ecosystem

We analyzed how urbanization in a desert ecosystem affects avian distribution at two distinct scales. At the regional level, we compared how urban land use configuration, relative to its surrounding agricultural fields and desert, affected the distribution of native and exotic species. While exotic species are isolated to the city; native species actively utilize the entire region, even occurring at higher densities in the city than in some areas of the desert. We also used this approach to compare four foraging guilds of birds: granivores, nectivores, omnivores, and insectivores. Granivores occurred mostly in agricultural fields and in the surrounding urban areas. Nectivores and omnivores occurred throughout the region, but mostly within the city. In contrast, insectivores occurred mostly in the desert. At a more local scale, we tested how the abundance of native species, exotics species and the foraging guilds of birds responded to vegetation cover measured at varying spatial scales (0.1 km–10 km). Bird guilds responded to vegetation at different scales, depending on the association between their life history and vegetation. Granivore abundance was most strongly correlated with vegetation at relatively fine spatial scales, followed by nectivores and omnivores at larger scales; whereas insectivores did not correlate with vegetation at any scale. Exotic and native species showed strikingly opposite trends in their association with vegetation. Native species showed the best fit at the smallest spatial scale and became insignificant at larger scales, whereas the highest correlation of exotic species with vegetation was at moderate to larger scales. While guild relationship with vegetation appears straightforward, the differences between exotic and native birds may indicate a complex response to environmental factors. Possibly, native species are more sensitive than exotics on vegetation abundance for food and shelter, which in the desert is highly variable depending on water availability. In contrast, exotic species, tightly connected to the urban infrastructure, likely respond to the enhanced and homogenized resource abundance characteristic of desert cities. Our results suggest that relationships between birds and vegetation may bear important information that can be revealed when considering smaller class levels than total species diversity.     

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.     

Rainfall events drive foraging choices by an urban coloniser

Using a seven-year data set of visitation of an inner city park by the Australian white ibis, we investigated whether rain events were correlated with ibis abundance in the park. The park is associated with high levels of anthropogenic food, but relatively low levels of natural food sources. For all magnitudes of rainfall tested, ibis abundance significantly decreased after a rainfall event, although stronger responses were associated with higher rainfall, with a 46% decline in ibis abundance following rainfall events of ≥60 mm. Average ibis abundance was higher during the dry, non-breeding period than during the breeding period, and variation associated with rainfall was particularly pronounced in the non-breeding period. However, the rainfall response was still evident in both periods. Results suggest that rainfall influences the ibis distribution in urban centres either by decreasing anthropogenic food supplied to the birds, forcing the birds to relocate to forage, or increasing the amount of natural food available elsewhere, or a combination of the two. Increased rainfall intensified the response by ibis, and our results demonstrate the importance of climatic processes on the behaviour of urban birds.     

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.     

Winter habitat selection of Corvids in an urban ecosystem

Urban Ecosystems - Urban areas attract birds during the winter when cities provide a predictable source of food and relatively stable weather conditions. However, many other factors determine the...     

Birds and the urban environment: the value of green walls

The simplest form of a ‘green wall’ is where self-adhering climbing plants colonise vertical surfaces, an approach that has been used on buildings for millennia (Koehler 2008). Green walls in urban areas are now well-known for their insulation and air cleaning capacities, but little is known of their value as habitats for wildlife. This paper presents preliminary findings of their value for urban birds. The abundance of birds, on 27 green walls and within the area enclosed by a semi-circle of 10 m radius immediately surrounding them, was compared with 27 walls without vegetation (bare walls) and similar surroundings. The study was carried out during the summer and winter of 2010–11 in north Staffordshire (UK). Birds exploited the green walls for various reasons (including nesting, food and shelter) but were never found on bare control walls. The roofs of buildings and the surrounding vegetation were used by birds in both regimes, but birds were more abundant in areas with green walls. The use of green walls by birds depended on the time of day, the season and whether the vegetation was evergreen or deciduous. The birds’ activity was always restricted to the upper half of the wall vegetation. Green walls and the immediate surroundings were used by some species of conservation concern in Great Britain (e.g. Passer domesticus and Sturnus vulgaris). Therefore, encouraging householders and businesses to grow vegetation up walls may be an effective way of providing a range of resources for birds in urban areas without the need for expensive additional land-take.     

Of pelicans and prisoners: avian–human interactions in the Soviet Gulag

The Soviet penal system, commonly referred to by its Stalin-era acronym, Gulag, exposed millions to conditions of imprisonment from 1917 to 1991. Penal institutions were located throughout the Soviet Union, but were concentrated especially in remote and sparsely populated areas such as the Far North, Siberia, and the Kazakh steppe. They were typically camps instead of prisons, with inmates sleeping in communal barracks and performing labour at outdoor work sites. This arrangement brought inmates and their jailers in close contact with the natural world. The richly varied avifauna of the Soviet Union made a particular impression on residents of the Gulag. Administrators employed birds as part of their re-education programs, using them to inculcate in the inmates scientific literacy, but the interactions between inmates and birds were more diverse. Some inmates fed them while others ate them. Some found in birds powerful symbols of springtime, freedom, and home, while others saw them as harbingers of death. Birds were also used by gang members in the Gulag as status symbols tattooed onto their own bodies and the bodies of their victims. Ultimately, birds helped Gulag inmates negotiate and make sense of a world that often seemed devoid of meaning.     

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.     

Palm snags are a critical nesting resource for woodpeckers in an urbanized tropical region

Urban Ecosystems - Critical resources for birds nesting in cities can support populations in spite of the challenges imposed by urbanization, and the identification of such resources can shed light...     

Composition and conservation value of bird assemblages of urban ‘habitat islands’: Do pedestrian traffic and landscape variables exert an influence?

Urban forest fragments can potentially be ‘habitat islands’ for native birds, but pedestrian traffic could influence the composition and conservation value of their bird assemblages by reducing the representation of disturbance-sensitive species. Winter bird assemblages and pedestrian traffic rates were documented in twelve forested parks in suburban Melbourne, Australia. Native birds comprised 87% of sightings, but two exotic species were common. Bird species' distribution among the parks was significantly nested. However, park rank orders for bird assemblage nestedness and mean pedestrian traffic rate were not correlated and only one species' distribution was nested with respect to this variable. The observed correlation between park area and bird assemblage nestedness may have been partly due to passive sampling. Degree of isolation of parks influenced nestedness less than park area. Forested parks provided habitat for species that occur at intermediate to low densities in other suburban habitats and for ecological specialists otherwise rare in suburbia. Larger parks contained more species than, and many of the native species found in, smaller parks. However, smaller parks each had 25% of the native bird species inhabiting the suite of fragments and thus had both aesthetic value and some potential to enhance city-dwellers' awareness about biodiversity conservation.     

Perceptions of Caucasian users about avian resources and beach restoration following hurricane <Emphasis Type="Italic">Sandy</Emphasis>

Hurricane Sandy resulted in massive destruction of many coastal ecological and human communities in the Northeastern United States in 2012. Beach-nesting and migrating birds are vulnerable to loss of essential habitat as a result of storms. In this paper we report the perceptions of beach users about avian use of the beaches, conservation measures to protect birds, and recent restoration efforts at Stone Harbor Point (New Jersey) to provide beach habitat for birds. Nearly all the visitors to the beach were Caucasian (N = 555), and reported their activity as walking (93 %), birding (19 %), biking (7 %), and lounging, boating, fishing or photographing (5 % or less for each). Visitors mainly came to this beach because of aesthetics, exercise, and vacation or to visit friends. Subjects rated protecting endangered species and the environment, restoring the beach, and designating off-limit areas to protect birds the highest. They rated conservation measures for birds the highest, and allowing dogs on the beach and providing more opportunities for jogging the lowest. The results suggest that protecting endangered species and habitat for nesting birds is a slightly higher goal than restoring dunes and marshes for flood control, which provides evidence for public support of restoration projects that protect both ecological and human communities. Providing more space for their own recreational activities was rated much lower, again supporting community good over personal uses. This information supports the restoration efforts following Sandy, and the importance of restoration projects that integrate ecological and human health goals in urban environments.     

Caterpillar phenology predicts differences in timing of mountain chickadee breeding in urban and rural habitats

Urban Ecosystems - To ensure the survival of their offspring, birds need to precisely time their reproduction: when offspring have the highest demand for food, food resources should be most...     

Distribution of neotropical migratory bird species across an urbanizing landscape

Urbanization leads to long-term modification of landscapes by habitat loss, fragmentation, and the creation of new habitats. Species’ distributions respond to these modifications of habitat availability, but the combination of parameters and scale at which habitat alteration most strongly influences species distributions is poorly understood. We evaluated responses of neotropical migratory birds, a group known to be sensitive to habitat modification, across a gradient of urbanization in the southeastern United States. Thirteen Breeding Bird Survey routes, each with 40 to 50 point counts, were used to quantify species richness across the gradient of urbanization extending from downtown areas of Columbus, GA to natural woodlands. Buffers of 100, 200, and 1000 m radii were constructed from remote images around each counting point to quantify land-use with the goal of evaluating land-use parameters and scales that best described spatial variation in migrant bird species richness. Within each buffer we quantified the proportion of each cover type and within the 1000 m buffers we included several configuration parameters. We used an information-theoretic approach to separate models whose predictor variables were land-use parameters. Because measures of landscape configuration were all correlated with urban cover, these variables were entered separately. In 2002, the best model was composed of large-scale urban cover (negative effect) and mid-scale mixed hardwoods (negative and positive effect) and transitional cover (negative and positive effect) as well as the interaction between the latter two terms (positive effect). In 2003, the best model was composed of weighted edge density (negative effect), mid-scale mixed hardwood cover (negative and positive effect) and large scale transitional cover (positive effect) and the interaction between mixed hardwoods and weighted edge density (positive effect). Our results indicate that large scale habitat attributes influence the local species richness of migrant birds more than smaller scales. These results also indicate that urbanization, through increased urban cover or increasing edge contrast, has strong negative effects on species richness. Our findings support the contention that the conservation value of small woodlots in urban settings may be minimal and suggest that conservation of migratory birds will be best achieved by giving higher priority to sites where urban cover is still low and by preserving large areas of “green space” in urbanizing landscapes. The negative influence of urban cover combined with relatively minor effects of non-urban habitats on distributions of neotropical migratory birds indicates that continued urbanization of landscapes is a serious concern for conservation efforts.     

A core on the Atlantic margin of Europe: an urban bird assemblage in Cork City,Ireland

Urban Ecosystems - Urbanization threatens bird populations globally, however many urban habitats present important refugia for wildlife in this rapidly changing landscape. Additionally, birds at...     

Differences in biometry and body condition of the House Sparrow (<Emphasis Type="Italic">Passer domesticus</Emphasis>) in urban and rural population during breeding season

Data collected out of the breeding season suggest that House sparrows (Passer domesticus) from the urban populations are characterized by a smaller body size and poorer body condition compared to birds from rural populations. Considering an urbanized Eurasian Sparrowhawk (Accipiter nisus) and other potential predators, a new predator-prey dependency is developing that can also be a reason for the House sparrow’s poorer condition. This study was aimed at comparing the multivariate biometrical characteristics and few body condition indices of adult birds from urban and rural populations during the breeding season. It was hypothesized that a higher predation risk during the breeding season concerns mainly males, thus affecting their poorer condition. Most of the condition indices of males were significantly lower in the urban population. Males from the urban populations had lower body mass, shorter tarsus, longer alula, greater Kipp’s distance and higher wing pointedness index in comparison to the birds from rural populations, whereas these differences were not found between females. We suggest that the lower body condition and biometric differences in the analyzed birds are a means of adapting to the new predator-prey scheme in accordance to the tradeoff theory between starvation and predation risks. A lower condition of birds in poor foraging urban habitats and higher predation risk may be indicative of a declining population.     

The causal response of avian communities to suburban development: a quasi-experimental,longitudinal study

Correlations between urbanization and biodiversity are well known, but the causes driving such associations are lacking. We used a long-term, quasi-experimental approach to study the responses of avian communities to suburban and exurban development around Seattle, WA, USA. We measured indices of bird abundance, reproduction, and survival for 12 years at many locations, including 5 forest ‘reserves,’ 10 existing ‘developments,’ and 11 ‘changing’ sites where ongoing development converted forests to single-family residential neighborhoods. In the first few years of clearing, building, and occupation of new neighborhoods by humans avian communities shifted from those typical of second-growth forest to those more characteristic of developments. During this time avian diversity increased and numerical dominance by abundant birds declined. Species that adapted and exploited development reproduced more successfully there than did forest-dependent species that avoided development. Adults of species that thrived in developments attained equal annual survival across reserved to developed landscapes, while species that avoided neighborhoods tended to survive poorly outside of reserves. The humans living in our study areas frequently fed birds and provided nest boxes. These actions were positively correlated with increases in secondary cavity nesting and seed eating birds. Humans also maintained outdoor cats and 11 % of humans both fed birds and let their cats outside. These actions were negatively correlated with the abundance of birds regularly using feeders. We suggest that a key management goal in urban ecosystems is the maintenance of avian diversity because a diverse avifauna engages a diversity of humans.     

Island biogeography for an urbanizing world: how extinction and colonization may determine biological diversity in human-dominated landscapes

Urbanization is increasing worldwide with potentially important implications to biological diversity. I show that bird diversity is responsive to the reduction of forest cover associated with urbanization in the Seattle, WA, USA metropolitan area. Bird diversity peaks at intermediate levels of human settlement primarily because of the colonization of intermediately disturbed forests by early successional, native species. Extinction of native forest birds and colonization of settlements by synanthropic birds have lesser effects on the overall pattern of avian diversity with respect to the level of urbanization. However, extinction increases linearly with loss of forest and colonization by synanthropic species decreases curvilinearly with reduction of urbanization. These findings have biological, theoretical, and practical implications. Biologically, intermediate disturbance appears to drive diversity by increasing the heterogeneity of the local land cover. Theoretically, I present a graphical model and use it to derive testable hypotheses about how extinction and colonization are affected by urbanization to determine local diversity. Practically, maintaining high local diversity without reducing regional or global diversity will require planning so that the same landscapes are not promulgated everywhere. This will require cooperation among a diverse group of planners, ecologists, policy makers, home owners, educators, and activists.     

The environmental belief systems of organic and conventional farmers: Evidence from central-southern England

Little comparative work has been conducted on the environmental belief systems and behaviours of conventional and organic farmers, especially in relation to farming culture, the environment and lowland farmland avifauna. Adopting a modified behavioural approach, this paper analyses the ways in which the environmental attitudes and understandings of farmers in central-southern England influence their behaviour. Key stakeholder and farmer interviews and a focus group discussion showed how some organic farmers tend to have small, diverse and untidy farms, ecocentric attitudes and a non-exploitative approach towards farming which includes an appreciation of farmland birds. This often contrasts with the tidy, well-organised conventional farmers with their larger, specialised farms, technocentric attitudes and exploitative view of nature, frequently related to creating pheasant cover and the belief that corvids and birds of prey are vermin and should therefore be eradicated. However, these attitudes and behaviours may not necessarily be representative of any differences between those farmers loosely labelled as ‘organic’ and ‘conventional’.     

Birds of a neotropical green city: an up-to-date review of the avifauna of the city of Xalapa with additional unpublished records

Although urbanization poses severe threats to biodiversity, some wildlife groups manage to thrive within urban areas. Among wildlife, birds are a highly diverse, charismatic and well-known group, establishing complex communities in human settlements around the world, making them suitable bioindicators. However, it is often difficult to have historical species lists that allow understanding current urban ecology trends. In this paper, we compile the available bird records, including unpublished information, for one of the best studied and well vegetated urban areas in México: the city of Xalapa. We gathered records for 329 species, representing ~30 % of the national avifauna in this medium-sized neotropical city. This important avian diversity in the city of Xalapa is mostly due to its environmental heterogeneity, underlining the relevance of its location, and the nature of its surroundings. The information provided in this paper will not only provide an environmental education baseline and represent a starting point for ornithologists, but will represent a reference document on the birds that have been recorded within the limits of Xalapa in the last three decades.     

Dirty Birds,Filthy Immigrants,and the English Sparrow War: Metaphorical Linkage in Constructing Social Problems

The role of metaphor in the construction of social problems has often been neglected. Yet we believe that the use of metaphorical linkage can help explain how social problems become defined. To explore the role of metaphorical linkage, we examine a controversy that shook the American ornithological world of the late 19th century: The Great English Sparrow War. English sparrows were originally imported to the major American cities of the East, in the early 1850s, to control the infestation of trees by dropworms. These birds adapted successfully, and by the mid-1870s they began to be perceived as a menace to the American ecosystem. As a consequence, a vigorous debate began as to their usefulness or harmfulness, which often exceeded the bounds of scientific discourse. We argue that this controversy over the English sparrow was linked to the controversy over “the new immigration.” A post-bellum America faced the task of rebuilding its moral boundaries after the disruption of the Civil War and in the face of millions of immigrants from Southern and Eastern Europe and the Orient. The opponents of the English sparrow drew their imagery from the nativism (anti-foreignism) of the day. They defined the bird as: (1) a foreigner, (2) that competes unfairly with native birds, (3) that has an immoral character, and (4) that needs to be eliminated from the American community of birds. Examining the metaphorical linkages among public concerns of the same period, we suggest, is a fruitful way of examining social problems.