Urbanization alters fear behavior in black-capped chickadees

Urban landscapes contain a multitude of novel sensory stimuli, and urban dwelling animals, such as songbirds living near human dwellings, must quickly learn how to respond to these unfamiliar cues. When exposure reveals that a stimulus is associated with a cost, fearful behavior should increase. Conversely, neophobic fear should decrease when negative outcomes do not regularly follow the stimulus. Because exposure to anthropogenic stimuli is more common in birds that inhabit urbanized landscapes, their fear response patterns should more accurately reflect the risks associated with these stimuli. We conducted a series of feeder and playback experiments to explore whether urbanization altered black-capped chickadees’ (Poecile atricapillus) fear responses to model cats, humans, a novel object, and anthropogenic noise. We predicted that fearful responses to cat models would increase in birds as urbanization increased because negative interactions with cats are more common in the city. However, we expected urban birds to be less fearful of our other stimuli because fitness costs are absent or less severe. As predicted, the fear of cats increased with urbanization, but the fear of noise decreased - as indicated by willingness to visit a feeding station. Other stimuli were not associated with urbanization, which may be related to the use of county and city parks where human presence is relatively common. Nonetheless, our results suggest that plastic fear responses to novel stimuli may facilitate urban success in the black-capped chickadee. More generally, behavioral plasticity may indicate the ability of a species to thrive in the urban environment.     

Effect of noise on behavioural response to simulated territorial intrusion in the Great Kiskadee (Pitangus sulphuratus) (Aves: Tyrannidae)

The urban environment can act as an ecological filter and impose several negative impacts on bird behaviour. Although some species are well adapted to anthropic habitats, others are sensitive to the effects of human disturbance. Here, we addressed whether noise pollution affects the territorial behaviour of the Great Kiskadee, Pitangus sulphuratus. Here we conducted a field experiment on territorial individuals in urban and rural areas. We presented a model decoy along with the playback of the species’ song at 10 m from the focal individual to simulate a territory invasion. We used simulated territory intrusions as a method to stimulate bird territorial behaviour and notedthe time birds took to respond to the stimuli in urban and non-urban areas with different noise levels. The results show that response latency had a positive correlation with noise pollution. We conclude that noise pollution can interfere with intraspecific communication, affecting territorial behaviour.

     

Does traffic noise alter calling time in frogs and toads? A case study of anurans in Eastern Ontario,Canada

In habitats disturbed by anthropogenic noise, acoustically communicating species may develop behavioral responses that help them transmit information and overcome signal masking. We studied four anuran species breeding in wetlands, ponds, and ditches near a highway in eastern Ontario, Canada, to test whether they called more often when traffic noise intensity was lower, and stopped calling when the noise intensity increased (i.e., gap calling behavior). We made call recordings between April and July 2011, and compared the traffic noise intensity (sound pressure level) between times when the anurans were calling and times when they were not calling. We found that the two species with the highest call peak frequency (American toad, gray treefrog) called randomly with regard to traffic noise intensity. In contrast, the two species with the lowest call peak frequency (green frog, bullfrog) called more often when traffic noise intensity was low. The behavioral response in the two latter species likely represents a short-term strategy that enhances their signal-to-noise ratio thereby increasing the chance of effective communication. Our results support predictions derived from the acoustic adaptation hypothesis: low-frequency signals are more prone to be masked by anthropogenic noise and therefore require behavioral adjustments (in this study gap-calling behavior) to ameliorate this effect.     

Urban noise affects song structure and daily patterns of song production in Red-winged Blackbirds (Agelaius phoeniceus)

Traffic noise is becoming a more prominent fixture in urban environments as cities and highways expand to accommodate the growing human population. Birds, in particular, rely heavily on vocal communication and have recently been shown to change the structure of their signals in response to environmental noise. Our objective was to determine the impact of traffic noise on Red-winged Blackbird (Agelaius phoeniceus) song structure and song timing. We recorded bird songs using a directional microphone and installed permanent recording devices to monitor daily song patterns at both high traffic noise sites and low traffic noise sites throughout southern Ontario, Canada. Our results indicate that at sites with high traffic noise, Red-winged Blackbirds sing songs with fewer introductory syllables, which are an important component of individual recognition and repertoire formation. In addition, the typical diurnal singing pattern of birds associated with noisy urban sites is more homogeneous than that of birds associated with quiet rural marshes. In the early morning and evening, singing effort was higher at rural sites than at urban sites, while in the midday singing effort at urban sites was higher than at rural sites. Birds at our noisy urban sites appear to be avoiding acoustic masking by increasing song production during the quiet part of the day and decreasing song production during the noisy rush hour periods. Based on our results, urban noise is impacting communication structure and the daily pattern of song production in a marsh-nesting species. These results have important implications for avian conservation and land use planning for urban development.     

Impacts of traffic noise on anuran and bird communities

Anurans and birds rely on sound for a number of social behaviors. Species that use roadside habitats are exposed to traffic noise that can mask important social signals and directly affect the community diversity and composition. We evaluate the impact of traffic noise on anuran and bird species richness, species occurrence, and composition in Puerto Rico, where there is a high density of highways and cars that generate high levels of noise pollution. We compared paired forest sites near (100 m, n = 20, dB > 60) and far (>300 m, n = 20, dB < 60) from highways, with similar vegetation structure, but different levels of noise. We found that the anuran community was not affected by traffic noise. In contrast, bird species richness and occurrence were significantly lower in sites near the highway, and bird species composition also varied significantly. Bird species with low-frequency songs were only detected in sites far from highways. The differences in the ecology and communication behavior between anurans and birds could explain these results. Anurans mainly call at night, when traffic activity was low. In contrast, bird singing activity occurs during the day and overlaps with the high levels of traffic noise. In addition, in natural habitats, Puerto Rican anurans occur at high densities and form noisy choruses (>80 dB), which may allow them to tolerate high levels of anthropogenic noise.     

Forest bird communities across a gradient of urban development

This study examined native bird communities in forest patches across a gradient of urbanization. We used field data and multivariate statistical techniques to examine the effects of landscape context, roads, traffic noise, and vegetation characteristics on bird community composition in the North Carolina Piedmont (U.S.A.). Landscape-level variables, particularly those related to urbanization, were most important in structuring forest bird communities. Specifically, we found that road density and amount of urban land cover were the best predictors of species composition. We found that urban and rural bird communities were quite distinct from each other. Rural communities had more long-distance migrants and forest interior species but species richness did not differ between the communities. Our results suggest some specific guidelines to target bird species of interest both inside and outside of urban areas. For example, if increasing numbers of migratory species is of primary concern, then conservation areas should be located outside of urban boundaries or in areas with low road density. However, if maximizing species richness is the focus, location of the conservation area may not be as important if the conservation area is surrounded by at least 50 m of forest habitat in all directions.     

Bird diversity in a subtropical South-American City: effects of noise levels,arborisation and human population density

Cities are highly modified environments in which the only areas that resemble natural landscapes are urban parks with low human population density. Attempts are frequently made to maintain high bird diversity in cities for aesthetic or educational reasons. However, it remains unclear whether local site characteristics are important in determining bird assemblage composition or whether simplification of the assemblage is an inevitable consequence of the changes associated with human population density. From May 1998 to December 1999, we undertook bird counts at 521 points in Porto Alegre, Rio Grande do Sul, southern Brazil. Our main goal was to understand the pattern of distribution of the bird species richness and density within the city and determine which variables most affect species assemblages. We recorded 132 species belonging to 43 families that are common in Rio Grande do Sul and obtained quantitative data on 121 species in survey sites. The two most abundant species (House Sparrow, Passer domesticus and Rock dove, Columba livia) were exotics. Analysis based on a reduced subset of 134 points surveyed in spring/early summer suggested that there was a North–south gradient in assemblage structure. Variation in assemblage structure was also affected by the number of trees, urban noise and human population density. However, human population density had a much smaller effect on richness and assemblage structure than variables subject to management, such as tree density and noise levels. These results suggest that complex communities may be maintained in densely populated urban areas of sub-tropical South-America given adequate urban planning.     

Are invasive House Sparrows a nuisance for native avifauna when scarce?

Biological invasions are the second most important cause of species extinction. Aided by processes such as transportation and urbanization, exotic species can establish and spread to new locations, causing changes in the function and structure of ecosystems. The House Sparrow is a widespread and highly abundant landbird associated to human presence. Previous studies performed in urban landscapes have suggested that this species could be acting, in synergy with urbanization, as a potential threat to native urban avian assemblages. In this study we assessed the relationship between House Sparrow density and native bird species richness in a region where the sparrows are scarce and sparsely distributed. We surveyed bird assemblages in and around four small-sized human settlements, considering three conditions in relation to House Sparrow presence: urban invaded, urban non-invaded, and non-urban non-invaded. To assess the potential detrimental role of House Sparrows on native bird species richness, we measured, additionally to sparrow densities, 20 predictor variables that describe vegetation structure and complexity, as well as urban infrastructure and human activities across four seasons of 1 year. Our results show that maximum shrub height was positively related to bird species richness, built cover was negatively associated with it, and House Sparrow invaded sites were related to a significant decrease of bird species richness, with increasing richness loss when more sparrows were present. Thus, we here provide evidence that urban areas can act in synergy with the presence of House Sparrows (even in low densities) in the urban-related species richness decline pattern.

     

Effects of dog leash laws and habitat type on avian and small mammal communities in urban parks

Remnant natural areas within urban settings can act as important refuges for wildlife, substantially increasing local biodiversity. However, habitat suitability for these species is potentially affected by human recreational activities including the presence of free-running dogs. To compare the diversity and abundance of songbird and small mammal communities between areas with bylaws that require, or do not require, dogs to be leashed, point counts and live-trapping surveys were conducted in three habitat types (deciduous, coniferous, and meadow) in the river valley parks of Edmonton, Alberta. Among birds, there was no difference between areas with different leashing bylaws in species diversity for any of the three habitat types. Similarly, there was no difference in bird diversity for a subset of species that were plausibly breeding at these sites. However, higher bird diversity was recorded in deciduous and coniferous sites than in meadow sites, regardless of leash designation, probably as a function of the horticultural practice of mowing meadows. Among both birds and small mammals, there was no difference in the abundance of individuals as a function of leashing bylaws. Our results suggest that off-leash dogs have no effect on the diversity or abundance of birds and small mammals in urban parks, but it is also possible that other factors, such as leash law compliance, reduced or obscured the effects of off-leash dogs in this study.     

Vegetation on and around large-scale buildings positively influences native tropical bird abundance and bird species richness

High population growth in the tropics is driving urbanisation, removing diverse natural ecosystems. This is causing native species to suffer while introduced synanthropes flourish. City planners are developing urban greenspace networks, in part trying to address this issue. Architects contribute to these greenspace networks by designing elevated and ground level green spaces on large-scale buildings. However, little evidence is available on whether building green spaces support native fauna. This is true for birds in tropical Singapore that support important ecosystem services and have existence value. Therefore, in this study, we conducted bird surveys and statistical analyses to determine, if and how vegetation on three building green space types (ground gardens, roof gardens and green walls) have a positive impact on native or introduced bird species. We found that elevated greenery (roof gardens and green walls) on large-scale buildings supported a higher richness of birds and abundance of urban native birds than control roofs and walls without vegetation. Ground gardens supported similar levels of native species as roof gardens but also a larger proportion of generalist synanthropes. However, we found no tropical forest habitat specialists across any space type. Therefore, we recommend roof gardens and ground gardens as a potential space for urban natives outside of a less competitive ground-level urban environment. Our study also found certain building design elements (height of elevated space, presence of specific plants) supported different species groups. Therefore, we suggest that these ecological requirements for different species groups are considered when designing a building’s green space.

     

Peeking into the past to plan the future: Assessing bird species richness in a neotropical city

Urbanization has been considered as a major threat to biodiversity, making its ecology of increasing interest. Many urban ecology studies have been developed in a short time-scale, measuring real-time patterns. However, long-term studies are imperative to understand the responses of some species to the urbanization process. In this study, we aimed to assess the information provided by a recent one-year citywide bird survey when compared to a published ‘historical’ bird list of a neotropical city (Xalapa, Mexico) that compiles information of the past three decades, mainly from urban greenspaces. Specifically, we contrasted species richness values and assessed differences in species composition between both lists. We recorded 51 species in the one-year citywide survey, representing ~15 % of those reported in the historical list. Nonetheless, the upper-bound confidence interval of the citywide survey richness prediction represented ~66 %. Most of the species recorded in the one-year citywide survey are insectivores and granivores, a pattern that agrees with previous findings that underline the importance of insectivores as part of urban bird communities in the Neotropics. Although we used robust methods to compare our one-year citywide bird list and the historical list for the city of Xalapa, we acknowledge the limitations of comparing them. However, our results shed some light on the kind and type of information that one-year citywide surveys can provide and the importance of long-term studies for comprehending the processes involved in biodiversity changes within urban areas over time. Undoubtedly, establishing long-term citywide surveys sampling birds and other biodiversity groups will allow us to better understand the response of biodiversity to urbanization over time.     

Does urbanization affect the seasonal dynamics of bird communities in urban parks?

The environmental factors affecting the spatial dynamics of bird communities in urban parks are well understood, but much less attention has been paid to the seasonal dynamics of bird communities. Since migrant and resident human commensal birds might have contrasting responses to environmental factors of urban parks, we expected different seasonal dynamics among parks. On the other hand, because bird species can have different habitat relationships throughout the year, we also expected different responses of bird richness to environmental variables between breeding and non-breeding seasons. Bird surveys were conducted in 14 small urban parks (1–4 Ha) of Mar del Plata city (Argentina) for one full annual cycle. Bird richness changed between seasons, but bird abundance remained constant. Bird community composition did not vary between seasons, but urban parks near the urban center, with the highest pedestrian traffic and isolation to other green areas had the least seasonal change of composition. During the breeding season, bird richness was negatively affected by the percentage cover of high buildings surrounding the immediate limits of parks, whereas during the non-breeding season bird richness was not related with any environmental variable. Bird composition variation among parks was affected by the distance to the urban center during both seasons. Results showed that urbanization promotes a seasonal homogenization of bird communities in urban parks, probably by affecting the presence of migrant species and promoting the temporal stability of human commensal species.     

Juggling a “junk-food” diet: responses of an urban bird to fluctuating anthropogenic-food availability

Within highly urban systems, anthropogenic activity often fluctuates cyclically, e.g. between weekdays and weekends. Thus, urban species may regularly experience significant changes in human activity and anthropogenic food abundance over very short time scales. Knowledge of how urban birds cope with such fluctuations may improve our understanding of how some species exploit and thrive in urbanised habitats. In this study, we explore the consequences of highly fluctuating anthropogenic food for Red-winged Starlings Onychognathus morio at the University of Cape Town campus, South Africa. Here, high numbers of students (and therefore anthropogenic food resources) are present during weekdays in term time (high human presence “HHP” days). However, students are largely absent and food outlets closed during weekends and vacation periods (“LHP” days). Using focal observations and morning and evening weights of habituated colour-ringed starlings during the non-breeding season, we investigated how diet, behaviour and daily mass gain differed between HHP and LHP days. We hypothesised that anthropogenic food supply is beneficial to this city-dwelling species. We predicted that on HHP days starlings would consume overall more food and a greater proportion of anthropogenic food items, resulting in less time spent foraging and greater daily mass gain compared to LHP days. We found that on HHP days, starlings consumed more anthropogenic food, however overall food intake, and time budgets were similar to LHP days. Additionally, there was an indication that mass gain was greater on HHP days. Thus, starlings appear to cope with potential food shortage on LHP days by including more natural items in their diet.

     

Loud callings limit human tolerance towards invasive parakeets in urban areas

Biological invasions represent today one of the main cause of the global biodiversity crisis, particularly in urban and suburban areas. Research on this topic have traditionally focused on ecological impacts, with poor regards to the social components. The ring-necked parakeet Psittacula krameri is one of the most successful invaders and it is widely appreciated by the general public, being introduced through the pet trade. In this work we assessed whether long-term introduction, total population size and number of loud flight-calls affected social perception of this species in three populations from Italian cities. We used a visual survey (N?=?414 questionnaires), which has been proven to be successful for testing attitudes on ring-necked parakeets. Tolerance towards this invasive species declined sharply with increasing number of loud calls by this species, thus providing support to the hypothesis of involvement of the ring-necked parakeet in noise pollution. Conversely, total population size and years since the first local introduction were not found out to be important variable determining social attitudes. Awareness on invasive species impacts is mostly obtained only when invasive populations are already affecting native biodiversity and human wellness, thus when management becomes challenging. Thus, at early invasion stages, intervention towards invasive species, particularly if charismatic, are often hampered by social public and animal right movements, especially in urban ecosystems. Educational campaigns on ecological and social impact by invasive alien species in urban ecosystems are therefore strongly recommended to implement effective management actions.

     

Relationship of bird richness,abundance and assemblage to the built environment in a small island tropical urban setting: a Suva,Fiji case study

There have been few studies investigating the relationship between the built environment and the status of bird distributions in small island tropical urban areas. We present a study investigating the relationship between bird species richness, abundance and assemblage to the built environment in Suva, Fiji. Field surveys were taken at 54 randomly selected sites throughout the city, stratified by three building density classes and the central business district (CBD). At each site bird counts were recorded, along with environmental data such as average building height, within a 150 m radius. Land-use information was obtained from screen digitized high-resolution satellite imagery within the same radius. Distance to undeveloped patches of land within the urban area was calculated using a GIS. Analysis of the effects of the built environment was carried out for all species, and for exotic and native species separately. Abundance of exotics was significantly higher in the central business district (CBD) than all other urban density classes, and significantly higher than natives in all other density classes. We found a negative relationship between native species richness and distance to undeveloped patches, but no relationship for exotics. Species assemblage was not related to urban density class. We conclude that the status of native and exotic bird species in Suva is similar to what has been found in urban areas in temperate climates, and conservation efforts should focus on minimizing the amount of heavily urbanized “core areas” and protecting undeveloped areas of forested vegetation to improve bird biodiversity in small tropical islands cities.

     

Forest structure and anthropogenic disturbances regulate plant invasion in urban forests

Urban forest ecosystems, the structure, and functions therein are subjected to anthropogenic disturbances. Native and sensitive species from those forests might be lost due to such disturbances. At the same time, supplemented anthropogenic resources might create opportunities for exotic and invasive species. Although invasive species are considered one of the major threats to the urban biodiversity and ecosystems, the research on invasion dynamics in the Himalayas has primarily focused on the impacts of invasion on forest structure and productivity. This study aims to understand the influence of forest structure and anthropogenic factors in invasion success that are poorly covered in the existing literature. We selected 11 urban forest patches for the study considering the presence-absence of selected invasive species and structural attributes. We used Principal Component Analysis (PCA) to reduce co-linearity in the covariates and generalized linear mixed effects model (GLMM) to identify the factors affecting invasion success. We found that forest structural attributes, namely, tree diameter, height and canopy cover, and anthropogenic disturbances regulate invasion success in urban forests. This implies that maintaining urban forest structural attributes, especially the stands with large-sized trees, is essential to control invasion in the context of urbanization.

     

Effects of urbanization on breeding birds in European towns: Impacts of species traits

Urbanization acts as a filter on bird species behavioral traits so that only few species can tolerate urban constraints. We analyzed how behavioral traits (nesting, feeding, and migratory habits) of breeding bird species affect their frequency of occurrence in the urban centers of 38 European towns. We used binary logistic regression analysis to predict the bird species traits belonging to each trait group. A total of 108 species (21% of the European breeding bird species) were found to breed in the European town centers. According to our broad-scale analyses the bird species most frequently breeding in town centers nest in buildings and/or buildings have diverse diets, in trees (40%) and are resident omnivores, or relied on seeds or fruits as their sources of food. However, almost all bird species also fed on arthropods (92%) during the breeding season. Only a few urban bird species bred on the ground. Four out of the studied 108 species were non-native and five species were predators. Our broad-scale results from Europe indicate that bird species with different behavioral traits can respond differently to urbanization. Bird species that nest in cavities/buildings have diverse diets, that benefit a resident way-of-life, may have an advantage in living and settling in European town centers. Our results from Europe may provide insights related to the development of bird assemblages in the urban core areas of the New World.     

Value of an urban habitat for the native Mediterranean avifauna

Mediterranean landscapes resulted from complex land uses that produced a mosaic of extensive crops, grasslands, scrublands and scattered woodlands. During the twentieth century the decrease in traditional agriculture triggered a decrease in open habitats and an increase in forests. In the meantime urban centres grew dramatically. Both spread of forest and urban areas have been suspected to participate in the decline of typical Mediterranean bird species and, in general, to cause faunal loss. However, modern cities offer a variety of landscape types and, in the Mediterranean, their value for native bird species has been little assessed. We compared the bird communities from an urban landscape, including built up and natural or semi natural units within the limits of the city of Montpellier, to the bird communities from non-urban habitats (cropland, grassland and woodland) located nearby but away from direct urban influence. Fifty four percent of the bird species recorded in the non-urban habitats also occurred in the urban landscape. On average, estimated species richness in the urban landscape was similar to values obtained for non-urban habitats. Within the urban landscape species richness was lowest in the dense historical centre and highest in the residential areas. The residential areas and urban woods were suitable habitats for most generalist species but also for several more specialized species recorded in the non-urban habitats. Some species actually reached their highest observation frequency in the urban landscape. Urban landscape was least favourable to the same farmland and open-habitat specialists that have been negatively affected by agricultural abandonment in the region. Finally, five of the species common in the urban landscape had an unfavorable conservation status in 2004 in the EU. This study emphasizes that Mediterranean urban areas have the potential to host a diverse native bird community. Finding ways to improve their carrying capacity for the local avifauna might be a worthwhile objective for animal conservation.     

Relationships between urban parks and bird diversity in the Bangkok metropolitan area,Thailand

An analysis of the birds in Bangkok’s urban parks and landscapes provided guidance in designing healthy urban ecosystems. This research studied the relationships between bird diversity, park size, distance to the nearest main park, and habitat compositions in 10 urban parks in the Bangkok metropolitan area between January and August in 2013. Thirty sampling points per park were used to observe the number and species of birds in each urban park. A total of 50 bird species were found. Phutthamonthon, the largest urban park (400 ha), contained the greatest number of species (39 species), followed by Suan Luang Rama IX (80 ha and 34 species) and Wachirabenchatat (60 ha and 29 species). Moreover, the diversity index (H′) was highest in Phuttamonthon (1.17), followed by Thawiwanarom (1.08), and Wachirabenchatat (1.04). Larger urban parks and parks closer to the largest urban park had higher species richness than smaller parks and parks further from the largest urban park. The large parks contain higher habitat compositions than small parks. These findings can be applied to future urban ecosystem planning to combine the importance of park size (island size, and its proximity to a large park) and its arrangement, including features such as wetland, forest, buildings and grassland; and provide basic advice for future urban park design, as well as re-design of current urban parks.

     

Species richness,phylogenetic and functional structure of bird communities in Chinese university campuses are associated with divergent variables

University campus is an important component of urban landscapes for biodiversity conservation. However, to our knowledge no study has quantitatively assessed the diversity and structure of bird communities in Chinese university campuses, especially from phylogenetic and functional perspectives. Here, for the first time we linked species richness, phylogenetic structure and body mass structure of campus bird communities with contemporary climate, glacial-interglacial climate change, altitudinal range, population density around campus, area and age of campus to test their associations. We found 393 bird species in 38 university campuses (29% of all Chinese bird species, two species are endangered, four species are vulnerable, and 33 species are near threatened). The variables significantly correlated with campus bird species richness, phylogenetic structure and body mass structure were altitudinal range and mean annual precipitation, glacial-interglacial anomaly in temperature, and altitudinal range, respectively. In particular, there were more species in steeper and wetter campuses, more young species clustered in campuses with stable glacial-interglacial climate, and more species with smaller body size in steeper campuses. Our study highlights the importance of considering both phylogenetic and functional information for biodiversity conservation in urban ecosystems.