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Raptors in the city: Site occupancy and abundance of a top predator inhabiting urban green spaces within a megacity
... Thirteen hummingbird species inhabit Mexico City, one of the largest cities in the world (Puga-Caballero et al. 2020, Z uñiga-Vega et al. 2023. This study aims to evaluate how biological factors influence the local distribution of two hummingbird species in a remnant patch of native xerophytic scrubland embedded within the southern part of the city (Zambrano et al. 2016). ...
... These visits took place between 07:00 and 12:00 and between 16:00 and 18:00. At each visit, a group of three to five trained observers used binoculars to visually detect and record the study species during a 15-min period, as performed previously in similar bird studies (Z uñiga- Vega et al. 2023, Z uñiga-Vega et al. 2024. Observations were carried out simultaneously by the observers without communicating with each other to ensure independency of detections. ...
Hummingbirds play an important role as pollinators and are one of the primary examples of animal–plant coevolution. However, factors such as land‐use change, urbanization, exotic species introductions and the disappearance of native plants can negatively affect the persistence of hummingbird populations. Thus, understanding the ecological factors that may favour their presence is essential for their effective conservation in urban areas. We conducted repeated surveys in a native scrubland reserve within Mexico City from 2015 to 2018, and used conditional two‐species occupancy models to estimate a species interaction factor, and to analyse the effect of five native plants ( Agave salmiana , Echeveria gibbiflora , Opuntia lasiacantha , O. tomentosa and Wigandia urens ) and one exotic plant ( Leonotis nepetifolia ) on the occupancy probability of two hummingbirds: the Broad‐billed Hummingbird ( Cynanthus latirostris ) and the Berylline Hummingbird ( Saucerottia beryllina ). Considering that both of the hummingbird species could be competing for similar resources, we also tested the effect of the presence of the Berylline Hummingbird on the occupancy of the Broad‐billed Hummingbird, assuming its dominance based on larger body‐size. We found evidence of positive spatial interactions between plants and hummingbirds, but we did not find these to be consistent throughout the 3 years of monitoring, which could indicate a modification of the original hummingbird–plant interaction networks resulting from urban disturbance. In addition, there were no negative spatial interactions between the two hummingbirds. Instead, we detected an aggregation of both species during two separate seasons, probably owing to one species using the other as a cue for profitable sites. Even though the populations of these two hummingbird species can thrive in an urban ecosystem, changes in spatial interactions might reflect alterations on the structure and functioning of a community. Therefore, we consider it crucial to continue studying their population dynamics and their implications for the conservation of urban hummingbirds.
... Some of these native species can be classified as "urban exploiters" because they can successfully use these anthropogenic resources and because their fitness is likely higher in urban settings than in less disturbed areas (Kark et al. 2007;Jokimäki et al. 2017;Palacio 2020). Numerous studies have documented that native species are actively feeding and successfully breeding in urban settings (Rutz 2008;Møller 2010;Reynolds et al. 2019;Zúñiga-Vega et al. 2023), indicating that they may now depend to some extent on the resources that they can find in the urban environment. However, we still do not know if native urban exploiters have changed their habitat preferences in such a way that they use the urban matrix more frequently than the large green spaces (such as urban ecological reserves) that are available to them within cities. Comparing the rates of occurrence of native species between the urbanized area and urban green spaces can yield insight into the value of urban ecological reserves to preserve the native biodiversity. ...
... This approach, which explicitly estimates detection probabilities (MacKenzie et al. 2018), has been recently implemented to study population trends of species of conservation concern and, in addition, it has allowed identification of environmental features that facilitate the presence of the species of interest (Bled et al. 2013;Louvrier et al. 2018;. However, less than a handful of studies have estimated colonization and local extinction probabilities for native species inhabiting urban green spaces (Cassel et al. 2019;Rudershausen et al. 2021;Zúñiga-Vega et al. 2023). ...
Urban ecological reserves are large green areas immersed within cities where native and exotic species of plants and animals coexist. Here, we examined the environmental features that facilitate the occurrence of nine species of native birds in an urban ecological reserve located within one of the largest cities in the world, Mexico City. We also searched for changes in occupancy rates among the three distinct climatic seasons that occur in central Mexico: warm-dry, rainy, and cold-dry. Using data collected during four years and multi-season occupancy models, we found that most of our study species prefer the urbanized sites that surround the reserve over the core conservation areas. This urban affinity can be explained by the diverse vegetation that prevails in such urban sites, which offers a high habitat heterogeneity that facilitates the presence of bird species with distinct ecological needs. In contrast, the reserve consists of a relatively homogeneous xerophytic scrubland where a few species of shrubs and small trees are dominant. We also detected seasonal changes in five species, with highest occupancy during the warm-dry season of each year, which coincides with both their breeding season and the driest period of the year. This finding indicates that these birds find in the reserve and surrounding urban areas enough food and water during this limiting season as well as safe nesting sites. Our study provides evidence that some native birds can become urban exploiters and that the benefits that they obtain from urban settings are greatest during their breeding season.
... In general, urban parks are dominated by lawns and some trees and shrubs, and vegetation is managed by pruning and irrigation [18]. Some raptor species may thrive in urban parks, due to their supply of nesting sites in trees and food resources such as passerines and doves [19][20][21]. However, other raptor species may be excluded from urban parks because of their specialized diet or habitat use. ...
Urban parks are hot spots of bird diversity in cities. However, their role as urban filters for raptor species has not been assessed yet. This study aimed to compare the functional and phylogenetic traits of raptor assemblages in urban parks with the regional species pool of raptors in east–central Argentina. Diurnal raptors were surveyed in 51 urban parks in six cities during breeding and nonbreeding seasons. The regional species pool was assessed through raptor surveys and published maps surrounding the cities. The observed functional and phylogenetic relatedness of urban raptors was compared with 999 simulated raptor assemblages from the regional species pool. A total of five species were recorded in urban parks. The Chimango Caracara (Milvago chimango) was the numerically dominant species, comprising 95% of the 172 individuals recorded. The regional species pool was composed of 20 diurnal species. The functional and phylogenetic relatedness of urban raptors was higher than expected by chance, suggesting filtering induced by urban parks. Urban raptors were, in general, generalist species with small body sizes. Moreover, species tended to be part of the Falconidae family. Based on the results obtained here and in other published work, a model of raptor assembling in urban parks is proposed. The design of urban parks needs to be more heterogeneous, promoting the occurrence of specialist raptors.
Urbanization has forced animals to respond to novel environments. One of the basic questions in urban ecology is if ecological processes that occur in natural conditions also occur in urban environments. In natural ecosystems, key predators can limit prey abundance and have a widespread effect on trophic levels. Here, we examine a predator-prey interaction in Mexico City, an urban ecosystem where prey can be evaluated in the presence or absence of apex predators. Nearly all original ecosystems in Mexico City have been transformed for human purposes. Many of the green spaces in the city contain populations of the Mexican gray squirrel, a species native to this area. These green spaces are also inhabited by different species of raptors, the most frequent being Harris's hawk, Cooper's hawk, and sharp-shinned hawk. Little is known about the interactions between raptors and squirrels, particularly how different environmental factors influence this ecological relationship. We do know, however, that raptors prey on squirrels. We predicted that in parks where raptors were present, there would be fewer squirrels than in parks where there were no raptors. We studied the relationship between raptors and squirrels using occupancy models, which also allowed us to evaluate environmental factors that affect the presence of both squirrels and raptors. We also tested if the presence of raptors influenced the occupancy probability of squirrels, and vice versa. Lastly, we estimated the abundance of squirrels in parks, both where raptors were present and where they were absent. Contrary to our predictions, in our first two sampling periods we found a positive relationship between the presence of raptors and squirrel abundance, but this relationship was absent during our second two survey periods, which was due to a decline in squirrel abundance in parks where raptors were present. These results suggest that predator-prey interactions occur in urban settings much as they do under natural conditions, but that other factors unique to urbanization can also impact the abundance of raptors and squirrels. Our findings also suggest that raptors might be an effective means of controlling squirrel populations under some conditions.
Urbanization involves changes in landscape terrain, hydrology, and vegetation. These changes allow some wildlife species to thrive in cities while inhibiting others. We analyzed how an urbanization gradient (i.e., percentage of impervious surface) in Xalapa, Mexico, affects raptors habitat associations and at what percentage of impervious surface these effects are the most pronounced. We also characterized the spatial distribution of species along this gradient and quantified seasonal effects. We conducted intensive area searches along an urban-to-conserved gradient inside 20, 500-m radius circular plots. Through direct observations and call-broadcast surveys, we estimated relative abundance, richness, and Shannon diversity index of diurnal and nocturnal raptors. From June 2019–February 2020, we visited each site during three seasons (breeding, fall migration, and winter), during two daily cycle periods, from 07:00–12:00 h and 19:00–00:00 h. We obtained 201 individual records of 14 species. Species abundance ranged from 1–45 individuals from 1–10 species (gradient richness), and the Shannon diversity index varied from 1–7.02 along the urban gradient. As expected, better conserved sites along the gradient held the highest diversity. Our results indicate that the transition from the intermediate to the most urbanized sites (> 70% impervious surface) is where the most abrupt filtering occurs, and we observed only four species in the most urbanized areas. According to Detrended Correspondence Analyses and two-way PERMANOVAs, the spatial distribution of the raptor community in Xalapa is significantly affected by the degree of urbanization, with some resident species using urban areas and migratory species using the intermediate and conserved areas. Our findings expand our understanding on how urbanization influences raptor communities in Neotropical cities. However, more research is needed to determine how urbanization filters raptor assemblages in cities worldwide.
Simple Summary
Restoration of biodiversity in urban green spaces frequently requires eradication or management of invasive species. We aimed to identify fine- and landscape-scale habitat features associated with the presence of five invasive urban mammals (Rattus species, European hedgehogs, mice, and brushtail possums) in three urban green space types (forest fragment, amenity park, residential garden) across three New Zealand cities, and across two seasons, to identify where management effort should be focused. All species were detected in all greenspace types; however, rodents were detected least in residential gardens, possums were detected most often in forest fragments, and hedgehogs least in forest fragments. Proximity of amenity parks to forest patches was positively associated with possum and hedgehog presence and negatively with rats. Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Management of rats should focus on sites with shrub and lower canopy cover and of mice on sites with herb layer cover, while micro-habitat features were not important for hedgehogs and possums. Rats were most likely to be found in residential gardens with compost heaps. The wide distributions of these species suggest that in order to be successful, ecological restoration must be coordinated, target all green space types, and engage urban residents.
Abstract
A barrier to successful ecological restoration of urban green spaces in many cities is invasive mammalian predators. We determined the fine- and landscape-scale habitat characteristics associated with the presence of five urban predators (black and brown rats, European hedgehogs, house mice, and brushtail possums) in three New Zealand cities, in spring and autumn, in three green space types: forest fragments, amenity parks, and residential gardens. Season contributed to variations in detections for all five taxa. Rodents were detected least in residential gardens; mice were detected more often in amenity parks. Hedgehogs were detected least in forest fragments. Possums were detected most often in forest fragments and least often in residential gardens. Some of this variation was explained by our models. Proximity of amenity parks to forest patches was strongly associated with presence of possums (positively), hedgehogs (positively), and rats (negatively). Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Rats were associated with shrub and lower canopy cover and mice with herb layer cover. In residential gardens, rat detection was associated with compost heaps. Successful restoration of biodiversity in these cities needs extensive, coordinated predator control programmes that engage urban residents.
Raptor communities are negatively impacted by urbanization. However, some species can thrive in urban areas. Raptor species traits that favor their presence in urban areas have been scarcely studied. Moreover, phylogenetic relatedness may be a factor promoting raptor occurrence in urban areas. In this study, we use data gathered through citizen science in Argentina to analyze the phylogenetic signal and the drivers that correlate with raptor presence in urban settings. The mean percent urban cover for the records of each species was considered an index of raptor occurrence in urban areas. A total of 55 species were analyzed, which accounted for 90% of the diurnal raptors of Argentina. Harris’s Hawk Parabuteo unicinctus, Pearl Kite Gampsonyx swainsonii and Chimango Caracara Milvago chimango had the highest urban index. Raptor occurrence in urban areas had a marginal phylogenetic signal, indicating a tendency for more closely related species to have similar tolerances to urbanization. The index of raptor occurrence in urban areas was highest for the most common species of the non‐urban areas, and was not related to traits such as body mass, diet, nesting site and migratory behavior. Our results highlight the importance of citizen science projects in data gathering at large geographical scales.
Predator-prey dynamics are fundamental in shaping and regulating wildlife communities; however, these relationships are often altered by urbanization. An urban predation paradox, where predation rates are lower in urban areas despite an increase in predator abundance, has been observed in some predator communities. We looked for evidence of an urban predation paradox in a raptor community in a large urban forest fragment in north Texas, USA. From May–August 2019, we conducted weekly raptor surveys and deployed prey mimics along an urban-to-rural gradient within the forest fragment. We examined relationships between predation rates on mimics, predator abundance, and urbanization intensity using a variety of statistical tests. We detected 161 raptors representing eight species and found that raptor activity was significantly higher in our low urbanization sites. Of the 732 prey mimics deployed, 61 were attacked, and we found no relationship between predation rates and urbanization. Furthermore, we found no relationship between raptor activity and depredation events. Although we failed to find evidence for an urban predation paradox, our results showed a decoupling of the relationship between the abundance of predators and prey in this urban setting. The use of prey mimics is a useful tool for assessing predator-prey dynamics, and more research is necessary to fully understand the impacts of urbanization on this important ecological process.
The Harris's Hawk (Parabuteo unicinctus), a social raptor species, often breeds and hunts cooperatively in groups typically consisting of a dominant breeding pair and one or more auxiliary group members. Why these birds form social groups is not completely understood, but one hypothesis is that the ability to hunt cooperatively may benefit groups with a higher hunting success rate or facilitate the capture of larger prey than an individual hawk could catch on its own. To test the hypothesis that group hunting affects patterns of prey delivery and the types of prey delivered to nests, we recorded videos of prey deliveries in May and June at nests of five breeding groups and five breeding pairs in Cameron County and Willacy County, Texas. In contrast to the diets of Harris's Hawks in New Mexico and Arizona that depend heavily on lagomorphs, we documented mostly avian prey items (39.1% of prey deliveries) and rodent prey items (39.1%), and only 0.7% lagomorphs (n = 284 prey items recorded). Significantly more prey items per day were delivered to nests with more nestlings. Importantly, and contrary to our hypothesis, pairs delivered more prey items per day on average than groups; this pattern was not significant, but this may be attributable in part to a small sample size of nests. These results suggest that the presence of auxiliaries may not necessarily provide direct benefits to offspring during the nest provisioning stage at late spring and summer nests in south Texas.
Globally, but especially in Africa, increasing human populations and anthropogenic land-use change are generally affecting diversity negatively. Urban environments in southern Africa typically comprise a mosaic landscape of anthropogenic infrastructure with some green spaces. These urban cities have a range of fauna that have persisted or increased in population density compared with areas that are more natural. We analysed the occurrence of diurnal and nocturnal raptors using South African Bird Atlas Project (SABAP2) data and reviewed literature. We found 66 raptor species occurred in South African cities. Thirty species had reporting frequencies greater than 10% in at least one of the 11 cities assessed, revealing impressive diversity of the raptor clade in South African cities. Five species were both abundant and widespread, occurring >10% in five or more cities each, of which three belong to the scavenger guild: Black-winged Kite Elanus caeruleus, African Fish Eagle Haliaeetus vocifer, Common Buzzard Buteo buteo vulpinus, Yellow-billed Kite Milvus aegyptius and Black Sparrowhawk Accipiter melanoleucus. However, only a few of these 66 raptors had been extensively studied in urban areas: the Black Sparrowhawk, African Crowned Eagle Stephanoaetus coronatus, Lanner Falcon Falco biarmicus and Peregrine Falcon Falco peregrinus. This lack of research is specifically severe, given that Africa is hosting a unique and diverse range of raptor species and that numbers and diversity of raptors have declined dramatically over the past decades across the continent. In fact, these four extensively studied species occurred in higher densities in urban areas than rural areas, which indicates that urban areas might create valuable opportunities for urban conservation, not least through public engagement.
As natural habitat is progressively transformed, effective wildlife conservation relies on understanding the phenotypic traits that allow select species to persist outside of protected areas. Through behavioural flexibility such species may trade off abundant resources with risks, both real and perceived. As highly adaptable mesocarnivores, caracals (Caracal caracal) provide an opportunity to examine development of successful foraging strategies in high‐risk developed areas. Here we investigated caracal resource selection of both anthropogenic and environmental factors relative to availability at varying levels of urbanization in and around the city of Cape Town, South Africa, using GPS cluster‐located feeding events (n = 326 prey remains, n = 384 scat). We also examined spatial and temporal risk mitigation strategies by assessing behaviours at feeding clusters. We find that, within home ranges, caracals living in the urban‐dominated region (n = 14; 548 feeding events) select for the urban edge, while caracals in the wildland‐dominated region (n = 3; 162 feeding events) avoid it. Adults selected more strongly for foraging at the urban edge than juveniles and may competitively exclude them from resources. By including back‐traced scat feeding event locations, we were able to improve model resolution. We argue that caracals foraging on the edge of a large metropole mitigate risk of detection by remaining cryptic, prolonging handling time, and maintaining high feeding site fidelity where cover was available. Along with the strong functional response to the urban edge, this strategy suggests that carnivores are being drawn into, and stay longer in, areas with potentially increased prey availability despite higher risk. While behavioural plasticity clearly enables carnivore coexistence with humans in urban ecosystems, it can also be maladaptive if it reduces fitness and leads the population into an ecological trap. We provide mitigative recommendations to promote the conservation of this predator in a spatially isolated and rapidly urbanizing landscape.
The red fox is one of the most adaptable carnivores inhabiting cities. The aim of our study was to describe the process of Warsaw colonization by the red fox. We focused on: (1) the fox distribution in Warsaw on the basis of presence-absence data (2005-2012) over a grid of 1 × 1 km 2 , (2) the process of settlement in 29 green areas (study periods 1976-1978, 2004-2012, and 2016-2019) in relation to habitat type, and (3) temporal and spatial patterns of the red fox incidents (1998-2015) reported by Warsaw citizens. We found out that: (1) the red fox penetrated the whole city (i.e. its presence was confirmed in all squares of the grid), (2) 21% of the green areas were colonized in 1976-1978 but 93% in 2016-2019. Forests and riparian habitats were occupied more frequently than parks and cemeteries in 1976-1978 with no difference in the further years; (3) the probability of the fox incidents increased over years, was higher in June-October, on working days, and around noon, and with the share of discontinuous urban fabric in the buffers around incident locations. Nevertheless, the incidents only partially reflect population abundance trends and activity patterns of the species, so should be treated cautiously.
Simple Summary
The process of city colonization by raptors has been documented, if scarcely, in the Northern Hemisphere, whereas this kind of event has been seldom documented in the Southern Hemisphere. Additionally, raptor habitat use in urban areas has been scarcely studied in the Southern Hemisphere. The objectives of this study were: (1) to describe an event of Harris Hawk (Parabuteo unicinctus) arrival in Mar del Plata city, Argentina, and (2) to analyze its green area use in a recently colonized city, Buenos Aires. The Harris Hawk arrival was observed during 2019, mainly in periurban areas of Mar del Plata, and at least three pairs were breeding. In Buenos Aires, the occurrence of the Harris Hawk in green areas was related to the proximity to other large green spaces. The results obtained suggest the importance of green areas for raptor colonization in cities.
Abstract
Urbanization has a negative impact on raptor species diversity and abundance. However, some species can adapt to urban areas, and the process of city colonization by raptors has been documented scarcely in the Northern Hemisphere. Information about city colonization by raptors in the Southern Hemisphere is null, and studies about habitat use by raptors are scarce. The objectives of this study were: (1) to describe an event of Harris Hawk (Parabuteo unicinctus) arrival in Mar del Plata city, Argentina, and (2) to analyze its green area use in a recently colonized city, Buenos Aires. Long-term data collected during 2002–2019, along an urbanization gradient of Mar del Plata, was used to describe the city arrival by the Harris Hawk. Surveys of green areas in Buenos Aires were used to model the Harris Hawk occurrence in relation to green area size and isolation to other green spaces. The Harris Hawk arrival was observed during 2019, mainly in periurban areas of Mar del Plata, and at least three pairs were breeding. In Buenos Aires, the occurrence of the Harris Hawk in green areas was related to the proximity to other large green areas. The results obtained suggest the importance of green areas for raptor colonization in cities.
Urbanisation is rapidly transforming natural landscapes with consequences for biodiversity. Little is documented on the response of African wildlife to urbanisation. We reviewed case studies of vertebrate species’ responses to urbanisation in KwaZulu-Natal, South Africa to determine trends. Connected habitat mosaics of natural and anthropogenic green spaces are critical for urban wildlife persistence. We present a novel modification to the final of three phases of the framework described by Evans et al. (2010), which documents this sequence for vertebrate species persistence, based on the perspective of our research. Species in suburbia exhibit an initial phase where behavioural and ecological flexibility, life-history traits and phenotypic plasticity either contribute to their success, or they stay at low numbers. Where successful, the next phase is a rapid increase in populations and distribution; anthropogenic food resources and alternate breeding sites are effectively exploited. The modified third phase either continues to spread, plateau or decline.
Raptors can be important components of urban ecosystems due to their role as apex predators, the presence of which may bring benefits to people. Urban environments may provide good quality habitats, and the raptors’ ability to utilize resources found here can contribute to their success. However, urban environments are socio-ecological systems and such mechanisms shaping habitats and ecological resources therein are less understood. This paper explores how raptors utilize urban resources, and the socio-ecological processes influencing their quality and availability. It begins with a systematic mapping of the literature to summarize the utility of urban resources by raptors with European distributions. Eighteen species were documented in the literature successfully exploiting novel hunting and/or nesting opportunities in both green and built-up locations of urban areas. We discuss how these may be consequential of human activities, some of which intentionally provided as subsidies, and how their utility by raptors create opportunities for human-raptor interactions further shaping public perception and decisions which potentially affect the raptors. Finally, we demonstrate these concepts by drawing on our experience from an urban peregrine falcon (Falco peregrinus) conservation site in London, UK. The paper concludes with a call for urban raptor conservation and research to consider social and ecological aspects together, appropriately reflecting urban environments as socio-ecological systems.
Eurasian collared-doves (Streptopelia decaocto; hereafter ‘collared-doves’) have spread throughout North America since they first colonized Florida in the early 1980s. Here I test for adverse effects of this introduced species on four confamilial potential competitor dove and pigeon species using data from the breeding season (North American Breeding Bird Survey; BBS) and the winter (Audubon Christmas Bird Count; CBC). Within sites of both sets of surveys, correlations between populations of collared-doves and all four potential competitor species have generally been either nonsignificant or positive, indicating a lack of adverse competitive effects due to collared-doves. Similarly, there were no significant differences in population trends of any of the four species in sites where collared-doves were present compared to those where they were not, and there have been no significant declines in population trends of the four species driven by differences in collared-dove abundance in areas where the latter were present. Overall, analyses revealed no negative effects of collared-doves on populations of these potential competitors. Evidence thus far supports a ‘passenger’ rather than a ‘driver’ role for collared-doves in North America, although future monitoring of potential competitor species is warranted, especially if collared-dove populations continue to increase.
Human socio-cultural factors are recognized as fundamental drivers of urban ecological processes, but their effect on wildlife is still poorly known. In particular, human cultural aspects may differ substantially between the extensively studied urban settings of temperate regions and the poorly studied cities of the tropics, which may offer profoundly different niches for urban wildlife. Here, we report how the population levels of a scavenging raptor which breeds in the megacity of Delhi, the black kite Milvus migrans, depend on spatial variation in human subsidies, mainly in the form of philanthropic offerings of meat given for religious purposes. This tight connection with human culture, which generated the largest raptor concentration in the world, was modulated further by breeding-site availability. The latter constrained the level of resource-tracking by the kites and their potential ecosystem service, and could be used as a density-management tool. Similar ties between animal population densities, key anthropogenic resources and human beliefs may occur in thousands of cities all over the globe and may fit poorly with our current understanding of urban ecosystem functioning. For many urban animals, key resources are inextricably linked with human culture, an aspect that has been largely overlooked.
Coyotes (Canis latrans) are highly adaptable, medium-sized carnivores that now inhabit nearly every large city in the United States and Canada. To help understand how coyotes have adapted to living in urban environments, we compared two ecologically and evolutionarily important behavioral traits (i.e., bold-shy and exploration-avoidance behavior) in two contrasting environments (i.e., rural and urban). Boldness is an individual’s reaction to a risky situation and exploration is an individual’s willingness to explore novel situations. Our results from both tests indicate that urban coyotes are bolder and more exploratory than rural coyotes and that within both populations there are individuals that vary across both spectrums. Bolder behavior in urban coyotes emerged over several decades and we speculate on possible processes (e.g., learning and selection) and site differences that could be playing a role in this behavioral adaptation. We hypothesize that an important factor is how people treat coyotes; in the rural area coyotes were regularly persecuted whereas in the urban area coyotes were rarely persecuted and sometimes positively rewarded to be in close proximity of people. Negative consequences of this behavioral adaptation are coyotes that become bold enough to occasionally prey on pets or attack humans.
Urbanization causes the simplification of natural habitats, resulting in animal communities dominated by exotic species with few top predators. In recent years, however, many predators such as hawks, and in the US coyotes and cougars, have become increasingly common in urban environments. Hawks in the Accipiter genus, especially, are recovering from widespread population declines and are increasingly common in urbanizing landscapes. Our goal was to identify factors that determine the occupancy, colonization and persistence of Accipiter hawks in a major metropolitan area. Through a novel combination of citizen science and advanced remote sensing, we quantified how urban features facilitate the dynamics and long-term establishment of Accipiter hawks. Based on data from Project FeederWatch, we quantified 21 years (1996–2016) of changes in the spatio-temporal dynamics of Accipiter hawks in Chicago, IL, USA. Using a multi-season occupancy model, we estimated Cooper's (Accipiter cooperii) and sharp-shinned (A. striatus) hawk occupancy dynamics as a function of tree canopy cover, impervious surface cover and prey availability. In the late 1990s, hawks occupied 26% of sites around Chicago, but after two decades, their occupancy fluctuated close to 67% of sites and they colonized increasingly urbanized areas. Once established, hawks persisted in areas with high levels of impervious surfaces as long as those areas supported high abundances of prey birds. Urban areas represent increasingly habitable environments for recovering predators, and understanding the precise urban features that drive colonization and persistence is important for wildlife conservation in an urbanizing world.
From Phoenix, Arizona, south to Buenos Aires, Argentina, residents of many cities have Harris’s hawks (Parabuteo unicinctus) as neighbors. This intriguing raptor has adapted to human presence in many urban landscapes, generally without developing conflicts with human residents. Harris’s hawks are often popular among nature enthusiasts due to the species’ accessibility, large size, and easily recognizable plumage. Harris’s hawks have also garnered popularity because of their unique ecology as the proverbial wolves of the air; like a wolf pack, a family group of Harris’s hawks will work together to raise young and will hunt cooperatively.1,2
The world is rapidly urbanizing, and many previously biodiverse areas are now mostly composed of impervious surface. This loss of natural habitat causes local bird communities to become dominated by urban dweller and urban utilizer species and reduces the amount of habitat available for migrating and breeding birds. Green roofs can increase green space in urban landscapes, potentially providing new habitat for wildlife. We surveyed birds and arthropods, an important food source for birds, on green roofs and nearby comparable conventional (non-green) roofs in New York City during spring migration and summer breeding seasons. We predicted that green roofs would have a greater abundance and richness of both birds and arthropods than conventional roofs during both migration and the breeding season for birds. Furthermore, we predicted we would find more urban avoider and urban utilizer bird species on green roofs than conventional roofs. We found that both birds and arthropods were more abundant and rich on green roofs than conventional roofs. In addition, green roofs hosted more urban avoider and utilizer bird species than conventional roofs. Our study shows that birds use green roofs as stopover habitat during migration and as foraging habitat during the breeding season. Establishing green roofs in urban landscapes increases the amount of habitat available for migrating and breeding birds and can partially mitigate the loss of habitat due to increasing urbanization.
Urbanization is one of the most important global trends which causes habitat reduction and alteration which are, in turn, the main reasons for the reduced structural and functional diversity in urbanized environments. Predation is one of the most important ecological functions because of its community-structuring effects. According to previous studies effects of urbanization on predation rates appear inconsistent. Predator species are vulnerable to habitat alteration and loss caused by urbanization, therefore, we hypothesised that predation rate would decrease along the rural-urban gradient. To clarify the impact of urbanization on predation, we performed a meta-analysis on predation rates in rural vs. urban areas using published data of 25 studies. Predation rates on taxa other than birds were underrepresented, preventing an overall evaluation. Reported predation rates on birds were significantly higher in rural than in urban habitats.
Raptors are limited by suitable breeding habitat, and they have specific nest-site requirements. Habitats of high quality presumably have the resources required to sustain relatively high rates of survival and reproduction. High-quality individuals would occupy territories of higher quality and would have greater fitness. Many birds may use their own reproductive success to assess the quality of their territories, and breeding failure would act as a determinant for dispersal, increasing an individual’s propensity to move to a better habitat. Food supply, nest-site availability, weather conditions and bird experience seem to act through the body condition of the female and are known to limit raptor populations. Quality of nesting territories and breeding success vary widely with different factors.
Five raptor species were recorded as breeding in the city of Wrocław (293 km2) during the years 2002-2010: Falco tinnunculus (2.4 pairs per 10 km2), Buteo buteo (4.1 pairs/10 km2 of wooded area), Accipiter gentilis (3.1 pairs/10 km2 of wooded area), Accipiter nisus (1.6 pairs/10 km2 of wooded area), Circus aeruginosus (0.2 pairs per 10 km2). All these species have increased in numbers over the last 20-30 years, both in the inner and outer zone of the city. Falco tinnunculus is a well-established raptor in the inner part of the city, while Accipiter nisus, A. gentilis, Buteo buteo started to infiltrate to the inner zone. In the last 70 years, a few cases of nesting were recorded for four other raptor species in Wrocław: Milvus migrans, Milvus milvus, Pernis apivorus and Falco subbuteo, but none of them was recorded in the inner zone of the city. Abundant and stable food supply (small mammals, columbids, corvids and small passerine birds), and freely available nesting and perching sites may contribute to this success.
Raptors are the most prevalent group of urban apex predators, and the majority of raptor genera in North America have been recorded using urban areas. Prior research assessments along urban-wildland gradients show that urban habitat preference varies by raptor species and that raptor nesting preferences within urban settings may vary. Attempts to understand the intra- and inter-specific nesting patterns along an urban gradient would advance extant knowledge. Here we present the locations of individual nest sites of nine raptor species along an urban gradient in Reno-Sparks, NV. We developed an urban density model based on the number of residents, number of employees, and building footprints and number of floors for built structures within each land parcel at four spatial scales, representing nest site, macrohabitat, average nearest-nest, and landscape scales. Cooper’s Hawks (Accipiter cooperii), Sharp-shinned Hawks (Accipiter striatus), and Red-tailed Hawks (Buteo jamaicensis) nested across the widest range of the urban spectrum and closest to the urban core, whereas Golden Eagles (Aquila chrysaetos) and Swainson’s Hawks (Buteo swainsonii) nested on the urban fringe. Urban density for all nest locations was lowest at the nest-site scale, and the highest at the average nearest-nest and landscape scales. Raptors tended to occupy a wide range of the building-area density spectrum but not the building-height or employee density spectrums indicative of the attractiveness of suburban habitat.
Global urbanisation is rapidly increasing and can have profound impacts on wild flora and fauna. For many species, the impacts are detrimental and irreversible, whereas others are able to colonise and apparently thrive in these novel, human-made environments. Raptors are particularly susceptible to changes in the environment due to their position at the end of the food chain, yet some species are increasingly associated with towns and cities. To explore the impact of urbanisation on raptors, we reviewed the literature and compared breeding performance in urban and rural populations globally. In general, raptors began breeding earlier and had larger brood sizes in urban compared to rural environments. However, some of these raptors also fledged fewer young in urban habitats, apparently caused largely by a lack of prey and, in some cases, increased human disturbance. As such, urban environments may act as ecological traps for some raptor species. Species differed in their response to urbanisation. In particular, specialist bird predators such as Peregrine Falcons (Falco peregrinus) had a higher breeding performance (clutch size, brood size, number to fledge and nest success) and showed a positive response to urbanisation compared to those that predate on small mammals, such as Eurasian Kestrels (F. tinunnculus), which showed a negative response. This suggests that prey availability is one of the most important determinants of the success of urban-nesting raptors. We demonstrate a need for continued research into the breeding performance of urban-living raptors, and stress the importance of focusing on the reasons for any differences in breeding performance between urban and non-urban environments in order to aid conservation and management efforts of this iconic bird group.
We carried out field surveys in order to estimate species richness and composition of the raptor community in Buenos Aires City. We recorded 21 species, most of them belonging to Accipitridae, followed by Strigidae and Falconidae. All of the species were observed using green spaces, indicating a general affinity for natural or semi-natural environments. Some species were also observed using built-up areas and densely built-up areas. Falconidae was the group more tolerant to urbanization. Falco sparverius and Glaucidium brasilianum, which nest in tree hollows and fed on small preys, were frequent in the city and can be considered successful urban species.
Population estimates of birds have a wide range of practical conservation uses, as well as being of enduring interest to many birdwatchers. Following previous reports by the Avian Population Estimates Panel, in 1997 and 2006, we present the third collation of population estimates of birds in Great Britain and the United Kingdom. There are now thought to be about 84 million breeding pairs of birds in the UK. The ten commonest species contribute 57% of this total, with Wren Troglodytes troglodytes alone providing one in ten of our breeding birds. In all, 23 species exceed one million breeding pairs. The individual population estimates come from a wide variety of sources, many from extrapolation of previous estimates by recognised trend measures, others from new surveys and novel analytical approaches developed since the last report. Despite the exceptional level of detail available for some species, many gaps in our knowledge remain. Recommendations are made to allow a continuing improvement in our understanding of the numbers of birds in GB and the UK. There are many opportunities for volunteer and amateur birdwatchers to make a significant contribution.
Urban greenspaces harbor considerable biodiversity. Such areas include spontaneously vegetated spaces such as such as brownfields, street or railway verges and vacant lots. While these spaces may contribute to urban conservation, their informal and liminal nature poses a challenge for reviewing what we know about their value for biodiversity. The relevant literature lacks a common terminology. This paper applied a formal definition and typology of informal urban greenspace (IGS) to identify and systematically review a total of 174 peer- reviewed papers in English (152), German (14) and Japanese (8). We identified three main topics: value for conservation (94 papers), factors influencing diversity (80), and non- indigenous species (37). Additionally, we analyzed this literature for temporal trends, spatial patterns, studied IGS types, taxa, climate zones, human impact types, and key authors. Results show IGS plays an important role for biodiversity. Management practices were identified as the most common and negative impact on diversity, while vegetation, site age, distance to city center, and habitat diversity were positive-influence factors. The number and impact of non-indigenous species varied widely. The analysis of literature patterns reveals: an increase in publications over the last 15 years and a strong geographic bias in publications, as well as towards temperate and humid climate zones. Studies of gap, powerline and microsite IGS were scarce, as were studies of mammals and reptiles. Results suggest different maintenance regimes for IGS may improve its contribution to urban conservation. We therefore propose adapting management to the local context.
Many wildlife species have modified their behaviors in order to thrive within cities. Since the 1980's, Harris's Hawk has become a regular resident species in Mexico City, Mexico. Here, we report on what may be an urban adaptation - two Harris's Hawks hunting bats in urban, southern Mexico City. This represents the first formal record of Harris's Hawk preying on bats, either within anthropogenic or natural ecosystems. Cities might facilitate access to novel food resources for particular sorts of species, including urban adaptable ones such as the Harris's Hawk.
With the extirpation of apex predators from many North American systems, coyotes Canis latrans have become the de facto top predator and are ubiquitous members of most ecosystems. Keystone predators aid in maintaining ecosystem function by regulating the mammal community through direct predation and instilling the landscape of fear, yet the value of coyotes regulating systems to this capacity is understudied and likely variable across environments. Since coyotes are common in the Midwestern United States, we utilized camera traps and occupancy analyses to assess their role in regulating the distribution of mammalian herbivores in a fragmented suburban ecosystem. Forest cover was a strong positive predictor of white-tailed deer Odocoileus virginianus detection, while coyote occurrence had a negative effect. Coyotes exerted a negative effect on squirrel (Sciurus spp.) and eastern cottontail rabbit Sylvilagus floridanus occurrence, while urban cover was a positive predictor for the prey species' occurrence. These results suggest all three species behaviorally avoid coyotes whereby deer seek denser forest cover and squirrels and cottontails mitigate risk by increasing use of urban areas. Although previous studies reveal limited influence of coyote on the rest of the carnivore guild in suburban systems, we suggest coyotes play an important role in regulating the herbivorous mammals and hence may provide similar ecological benefits in urban/suburban forest fragments through trophic cascades. Furthermore, since hunting may not be allowed in urban and suburban habitats, coyotes might also serve as the primary regulator of nuisance species occurring at high abundance such as white-tailed deer and squirrels [Current Zoology 62 (1) : – , 2016 ].
Only 55 of 1117 locations of radio-tagged Haliaeetus leucocephalus (4.9%) occurred in the developed land-cover type ≥4 buildings/4 ha), although 18.2% of potential eagle habitat was developed. Eagle use of the shoreline was inversely related to building density and directly related to the development set-back distance. Few eagles used shoreline segments with boats or pedestrians nearby. Only 360 of 2532 segments (14.2%) had neither human activity nor shoreline development. Eagle flush distances because of approaching boats were greater in winter than in summer (mean 264.9 vs. 175.5 m, respectively), but were similar for adult and immature eagles (203.7 vs. 228.6 m, respectively). Of 2472 km of shoreline on the N Chesapeake, 894 km (36.2%) appears to be too developed to be suitable for eagle use, and an additional 996 km (40.3%) had buildings within 500 m, thereby reducing eagle use. The projected increase in developed land in Maryland (74%) and Virginia (80%) from 1878 to 2020 is likely to determine the future of the bald eagle population in this area. (See also 91L/12673). -from Authors
We measured plasma levels of testosterone (T), estradiol 17β (E), corticosterone, and luteinizing hormone (LH) in adult breeders, adult-plumaged helpers, and juvenal-plumaged helpers of the cooperatively breeding Harris' Hawk (Parabuteo unicinctus) in southeastern Arizona. In the males, both adult breeders and most adult-plumaged helpers had elevated T and LH during February and March, when nest building occurs, whereas most juvenal-plumaged helpers showed no change in LH, T, or E throughout the year. Thus adult-plumaged helpers, usually not related to the breeders, are hormonally ready to breed in the spring. We suggest that these helpers attain breeding readiness because potential benefits they can derive from either occasional successful copulations or possible attainment of the breeding position make reproductive readiness advantageous. In contrast, most juvenal-plumaged helpers are aiding their own parents on their natal territory and are not hormonally ready to breed, and thus they physiologically avoid the potential for inbreeding. An exception to this was a juvenal-plumaged male helper with elevated testosterone levels who was not helping his parents. The female breeders we examined had elevated T, LH, and E during the nest-building period, whereas the helpers (both adult- and juvenal-plumaged) did not show elevations at any time of the year. During the early part of the nesting cycle, the adult-plumaged female helpers weighed significantly less (ca. 10%) than the breeders. It is possible that poor body condition, subordinate status to the breeding females, or both were related to their lack of breeding readiness. In all birds, corticosterone levels increased with handling time, and were higher during the nesting periods than during non-nesting periods, but showed no consistent relation with helper or breeder status. As in other species that are relatively social, maintain long-term pair bonds, or are tropical in distribution, plasma concentrations of LH and sex steroids in Harris' Hawks, even when elevated, were relatively low.
Aim
Predators often have important roles in structuring ecosystems via their effects on each other and on prey populations. However, these effects may be altered in the presence of anthropogenic food resources, fuelling debate about whether the availability of such resources could alter the ecological role of predators. Here, we review the extent to which human‐provided foods are utilised by terrestrial mammalian predators (> 1 kg) across the globe. We also assess whether these resources have a direct impact on the ecology and behaviour of predators and an indirect impact on other co‐occurring species.
Location
Global.
Methods
Data were derived from searches of the published literature. To summarise the data we grouped studies based on the direct and indirect effects of resource subsidies on predators and co‐occurring species. We then compared the types of predators accessing these resources by grouping species taxonomically and into the following categories: (1) domesticated species, (2) mesopredators and (3) top predators.
Results
Human‐provided foods were reported to be utilised by 36 terrestrial predator species in 34 different countries. In the presence of these resources we found that: (1) predator abundance increased, (2) the dietary preferences of predators altered to include the food subsidy, (3) life‐history parameters such as survival, reproduction and sociality shifted to the benefit or detriment of the predator, and (4) predators changed their home ranges, activity and movements. In some instances, these modifications indirectly affected co‐occurring species via increased predation or competition.
Main conclusions
The availability of human‐provided food to predators often results in behavioural or population‐induced changes to predators and trophic cascades. We conclude that there is an urgent need to reduce the access of predators to food subsidies to minimise human–wildlife conflicts and to preserve the integrity of ecosystem functioning in human‐influenced landscapes world‐wide.
Various species of raptors, or birds of prey, have been found living and hunting in all parts of the urban environment, including complexes of business and light industrial facilities, commonly known as business parks. Conservation in business parks is a growing concern due to the amount of land they occupy and their pattern of development of formerly vacant land on the fringes of urban areas. We conducted call-broadcast surveys for raptors at a set of 155 survey points within the business park landscape of the St. Louis area to answer the question of what landscape characteristics of business parks are predictors of presence of raptors. The detection data from these surveys was used to model the occupancy probability of the target species of raptor at each survey site and to determine the effect of landscape variables at each site on occupancy probabilities. We detected nine species of raptors at business parks. The red-tailed hawk (Buteo jamaicensis), the American kestrel (Falco sparverius), and the Cooper’s hawk (Accipiter cooperii) were the most commonly detected species. The probability of raptor occupation was negatively associated with lawn cover. Occupancy probabilities of red-tailed hawks and Cooper’s hawks were positively associated with woodland cover, and American kestrel occupancy probability was positively associated with grassland cover. Based on this study, we would recommend that businesses concerned with the conservation of raptors in and around their properties plan to develop less lawn area, preserve or plant more native grassland, and preserve woodlots.
This practical manual of amphibian ecology and conservation brings together a distinguished, international group of amphibian researchers to provide a state-of-the-art review of the many new and exciting techniques used to study amphibians and to track their conservation status and population trends. The integration of ecology and conservation is a natural outcome of the types of questions posed by these disciplines: how amphibians can and should be sampled, marked, and followed through time; how abundance and population trends are measured; what are the robust statistical methods that can be used in ecology and conservation; what roles do amphibians play in community structure and function; how do animals function in their environment; and what affects the long-term persistence of species assemblages? Although emphasizing field ecology, sections on physiological ecology, genetics, landscape ecology, and disease analysis are also included. The book describes the latest statistical approaches in amphibian field ecology and conservation, as well as the use of models in interpreting field research. Much of this information is scattered in the scientific literature or not readily available, and the intention is to provide an affordable, comprehensive synthesis for use by graduate students, researchers, and practising conservationists worldwide.
Before visiting your local supermarket, do you write your food shopping list in the order you expect to encounter the items as you walk around, aisle by aisle? This way, you minimise your travel distance, saving time and effort. Many other animals do the same. Baboons (Papio ursinus) plan their foraging journeys to out-of-sight resources, moving in an efficient, goal-directed way, and nectar-collecting bumble bees (Bombus impatiens) use efficient travel routes when foraging on familiar resources.
Currently, there are naturalized populations of feral pigeon (Columba livia var. domestica) worldwide with an estimated global population between 165 and 330 million individuals. Feral pigeons are adapted to urban environments, creating problems related to human health, damage to architectural structures, unpleasant soiling, and foul odors. Thus, local governments usually implement measures to reduce feral pigeon populations in cities to a suitable size. We monitored a feral pigeon trapping campaign to investigate the use of cage traps as control method in residential zones. We analyzed efficiency (daily capture rate), effectiveness (defined as the number of feral pigeons captured relative to the total number of potential pigeon captures), animal welfare, selectivity (the proportion of captured feral pigeons in relation to the total number of captured animals), and the effect on feral pigeon abundance. All procedures were conducted in compliance with current European and Spanish legislation. Overall efficiency was 0.25 feral pigeons/trap-day, effectiveness was 22.5%, and selectivity was 99.7%. Over the study period, there was a decreasing trend in abundances. A significant decrease was found in the relative abundances of feral pigeons after 2 months of extractions, and population abundances remained low up to the end of the extraction period. The use of cage traps was a useful and effective method to reduce local feral pigeon populations in isolated urban areas with low building density in which the feral pigeon population has not yet reached high densities.
Occupancy Estimation and Modeling: Inferring Patterns and Dynamics of Species Occurrence, Second Edition, provides a synthesis of model-based approaches for analyzing presence-absence data, allowing for imperfect detection. Beginning from the relatively simple case of estimating the proportion of area or sampling units occupied at the time of surveying, the authors describe a wide variety of extensions that have been developed since the early 2000s. This provides an improved insight about species and community ecology, including, detection heterogeneity; correlated detections; spatial autocorrelation; multiple states or classes of occupancy; changes in occupancy over time; species co-occurrence; community-level modeling, and more. Occupancy Estimation and Modeling: Inferring Patterns and Dynamics of Species Occurrence, Second Edition has been greatly expanded and detail is provided regarding the estimation methods and examples of their application are given. Important study design recommendations are also covered to give a well rounded view of modeling.
Raptors are an unusual success story of wildness thriving in the heart of our cities—they have developed substantial populations around the world in recent decades. But there are deeper issues around how these birds make their urban homes. New research provides insight into the role of raptors as vital members of the urban ecosystem and future opportunities for protection, management, and environmental education.
A cutting-edge synthesis of over two decades of scientific research, Urban Raptors is the first book to offer a complete overview of urban ecosystems in the context of bird-of-prey ecology and conservation. This comprehensive volume examines urban environments, explains why some species adapt to urban areas but others do not, and introduces modern research tools to help in the study of urban raptors. It also delves into climate change adaptation, human-wildlife conflict, and the unique risks birds of prey face in urban areas before concluding with real-world wildlife management case studies and suggestions for future research and conservation efforts.
Boal and Dykstra have compiled the go-to single source of information on urban birds of prey. Among researchers, urban green space planners, wildlife management agencies, birders, and informed citizens alike, Urban Raptors will foster a greater understanding of birds of prey and an increased willingness to accommodate them as important members, not intruders, of our cities.
We live in a world that is experiencing rapid landscape-level changes due to human activities. Indeed, the argument can be made that, from a wildlife perspective, the only form of habitat that is increasing is what we would call “urban habitat.” Despite the negative implications of this, some wildlife species are attracted to, and may even flourish in, urban settings. This is due primarily to urbanization resulting in an altered landscape that, often unintentionally, provides resources that function as components of habitat.¹ This was largely overlooked by biologists until Steve Emlen’s 1974 publication examining bird communities in and near Tucson, Arizona.² Subsequent to Emlen’s work, interest in the phenomenon of urban wildlife grew, and countless articles have since documented ornithological research in urban areas.
If there is a single unifying characteristic of urban/suburban wildlife species, it is likely adaptability. Species that can occupy urban areas are behaviorally flexible,1,2 and this flexibility drives changes in the way they use urban space and cohabit with people. Raptors too exhibit behavioral changes when they move from rural to urban environs.³ Inherent plasticity allows some raptors to adjust their behavior to survive in circumstances that may differ greatly from those of more typical, rural, or natural areas. For example, they may move into urban environments that are suitable for them,4,5 or they may persist by tolerating human activity in a natural area that has been overwhelmed by suburbia. They may perceive human-made objects such as rooftops, utility towers, billboards, and bridges as potential nest sites,3,6,7,8 especially in areas where nest sites in traditional, natural locations are limited. Additionally, they may take advantage of a different prey type that is present, such as rats (Rattus spp.),9,10 or a typical prey type that is more abundant or available (e.g., birds at feeders).5,11
Increasing human populations have accelerated urbanization and altered natural habitats. This process began in the eighteenth century with the industrial revolution when workers began moving to cities leaving agricultural jobs for jobs in manufacturing. Global growth in human populations was accompanied by growth of cities, which has increased the demand of goods and services provided by the exploitation of natural ecosystems. Rapid worldwide urbanization has led to a rampant loss of natural habitats and habitat fragmentation, which alarmed to ecologists and conservationists that have focused their researches in last years to understand the response of wildlife to these new scenes. For birds, the number of published studies on urban effects has increased steadily (Marzluff et al. 2001; Marzluff 2017). However, raptors have been poorly studied during much years, mainly due to several limitations imposed by their natural history (i.e., low densities, large home ranges, variable reproductive behaviors, and inaccessible breeding sites) (Donázar et al. 2016) and the high costs necessary for these studies. Nowadays, research of raptors in urbanized habitats has increased considerably. We will focus on a variety of these aspects.
Urbanization presents a major global issue for the conservation and survival of many different species. With the increasing footprint of cities and intensification of our use of urban areas, wildlife faces extremely difficult challenges to live there. Understanding how species respond to urban processes and how to design urban landscapes that facilitate species’ presences are major emerging research and management priorities. Despite general negative responses to increasing urbanization, some animal taxa, both native and introduced, appear to benefit from urban environments by capitalizing on novel environments and abundant resources.¹ Those that are common in urban systems display particular physical characteristics and ecological traits.2,3,4 They also frequently display a level of behavioral plasticity or tolerance, adjusting their behavior to interact with, and survive in, urban environments.5,6 Termed urban-adaptors,⁷ these species may exhibit altered spatial,8,9,10 foraging,11,12 and breeding behaviors,¹³ as detailed in chapter 2.
Harris's Hawks (Parabuteo unicinctus) are cooperative breeders, and groups of more than a pair have been reported from Arizona (49% to 83%) and New Mexico (51%). However, two studies (Griffin 1976, Brannon 1980) suggested that they breed in groups infrequently in Texas (5% and 13%). During a banding study from 2004-2014, I occasionally captured three or more adults at the same time and place, and I regularly observed groups of three or more adults. I undertook a study to determine sizes of breeding groups in south Texas in 2014 and 2015 in a mix of breeding habitats, primarily thorn scrub forest, but also parks, agriculture with forest and grassy plots, industrial areas, and urban areas. I determined that more than half (56%) of the 73 breeding groups I observed in south Texas were composed of three or more individuals, contrary to the results of the two earlier Texas studies, which may have underestimated group size because of fewer short visits compared to longer visits spent determining group size in this study.
Drivers of wildlife population dynamics are generally numerous and interacting. Some of these drivers may impact demographic processes that are difficult to estimate, such as immigration into the focal population. Populations may furthermore be small and subject to demographic stochasticity. All of these factors contribute to blur the causal relationship between past management action and current population trends. The urban Peregrine Falcon Falco peregrinus population in Cape Town, South Africa, increased from three pairs in 1997 to 18 pairs in 2010. Nestboxes were installed over this period to manage the interface between new urban pairs of Falcons and the human users of colonized buildings, and incidentally to improve breeding success. We used integrated population models (IPMs) formally to combine information from a capture-mark-recapture study, monitoring of reproductive success and counts of population size. As all local demographic processes were directly observed, the IPM approach also allowed us to estimate immigration by difference. The provision of nestboxes, as a possible stimulant of population growth, improved breeding success and accounted for an estimated 3-26% of the population increase. The most important driver of growth, however, was immigration. Despite low sample sizes, the IPM approach allowed us to obtain relatively precise estimates of the population-level impact of nestbox deployment. The goal of conservation interventions is often to increase population size, so the effectiveness of such interventions should ideally be assessed at the population level. IPMs are powerful tools in this context for combining demographic information that may be limited due to small population size or practical constraints on monitoring. Our study quantitatively documented both the immigration process that led to growth of a small population and the effect of a management action that helped the process.
Green roofs are a technology with a long tradition however, today are considered one of the most innovative developments for urban greening and constitute an opportunity for creating additional habitat for birds in the cities. Green roofs provide water and food mainly throughout insects, berries and seeds for feeding birds. Also provide space and cover that protect birds and their nests from predators. However, not all green roofs have the same ecological valueor equally favour the breeding of birds. It depends on the type of green roof, design, selected vegetation and maintenance. This encourages bird presence including of endangered species that permits urban people to obtain benefits such as aesthetic and psychological, ecological and some utilitarian ones. Conversely at the same time birds can damage plants that vegetate on green roofs especially in its establishment phase when the vegetated structure is more fragile or more rarely can act as disease reservoirs or cause accidents, e.g., mthe airport environments. Despite the worldwide increasing wide spread of green roofs in the last decades unhl now little attention has been paid to bird populations in relation to this kind of urban greening and few specific studies have been undertaken. This study carries out a broad review on green roofs as a habitat for birds in the urban environments and proposes a standardised methodology aimed at studying bird population on green roofs.
This paper explores how cougars and humans live together on Vancouver Island, Canada, a region home to what scientists estimate is the densest cougar population in North America and to one quarter of the continent's lethal and nonlethal cougar attacks in the last century. Drawing on biopolitical and spatial theory, I trace how safe space is made, maintained, and unmade and ask what the role of cougars has been in production of spaces and their imagined security. Discussion is informed foremost by stories of cougar human encounters on Vancouver Island and then retold based on newspaper and archival research and semistructured interviews with island residents. The goal of this paper is to demonstrate how nonhumans matter to the material semiotic construction of safety and space. In particular, I examine attempts to discipline cougars in the name of biosecurity, how cougars discipline humans, and how cougars' bodies and behaviors have resisted and shaped spatial configurations. I argue that these contestations and enforcements are biopolitical. My empirical research supports recent theoretical arguments by geographers and actor-network theorists regarding space namely, that space is produced within network formations of which cougars, in this case, are key actors. My analyses suggest that the biothreat cougars and humans pose to each other precludes the formation of ethics through encounter and that conservation strategies must account for cougars' spatial requirements.
The selection of a suitable nest-site is critical for successful reproduction. Species' preferences for nest-sites have presumably evolved in relation to local habitat resources and/or interactions with other species. The importance of these two components in the nest-site selection of the Eurasian Honey Buzzard Pernis apivorus was assessed in two study areas in eastern Austria. There was almost no difference in macro- and micro-habitat features between nest-sites and random plots, suggesting that Honey Buzzards did not base their choice of nest-site on habitat characteristics. However, nests were placed significantly further from nests of Northern Goshawk Accipiter gentilis than would be expected if nest-sites had been chosen at random. Furthermore, in one study area Honey Buzzards appeared to favour areas close to human settlements, perhaps indicating a mechanism to avoid Goshawks, which tend to avoid the proximity of humans. No habitat variable was significantly associated with the loss of Honey Buzzard young, but predation was higher in territories closer to breeding pairs of Goshawks at both study sites. Although Honey Buzzards are restricted to nesting in forests, their choice of nest-site therefore appears to be largely dictated by the distribution of predators. Studies of habitat association may yield misleading results if the effects of predation risk on distribution are not considered.