High urban population density of birds reflects their timing of urbanization

Living organisms generally occur at the highest population density in the most suitable habitat. Therefore, invasion of and adaptation to novel habitats imply a gradual increase in population density, from that at or below what was found in the ancestral habitat to a density that may reach higher levels in the novel habitat following adaptation to that habitat. We tested this prediction of invasion biology by analyzing data on population density of breeding birds in their ancestral rural habitats and in matched nearby urban habitats that have been colonized recently across a continental latitudinal gradient. We estimated population density in the two types of habitats using extensive point census bird counts, and we obtained information on the year of urbanization when population density in urban habitats reached levels higher than that of the ancestral rural habitat from published records and estimates by experienced ornithologists. Both the difference in population density between urban and rural habitats and the year of urbanization were significantly repeatable when analyzing multiple populations of the same species across Europe. Population density was on average 30 % higher in urban than in rural habitats, although density reached as much as 100-fold higher in urban habitats in some species. Invasive urban bird species that colonized urban environments over a long period achieved the largest increases in population density compared to their ancestral rural habitats. This was independent of whether species were anciently or recently urbanized, providing a unique cross-validation of timing of urban invasions. These results suggest that successful invasion of urban habitats was associated with gradual adaptation to these habitats as shown by a significant increase in population density in urban habitats over time.     

Constraints on home range behaviour affect nutritional condition in urban house sparrows (Passer domesticus)

In human‐dominated landscapes (semi)natural habitats are typically embedded in tracts of unsuitable habitat. Under such conditions, habitat characteristics and grain size of the surrounding landscape may affect how much food, and at what cost, is available for sedentary species with low home‐range plasticity. Here we combine behavioural radio‐tracking, feather ptilochronology, and landscape analysis to test how nutritional condition varies with home range size in 13 house sparrow [Passer domesticus (Linnaeus, 1758)] populations along an urban gradient. Urban individuals occupied smaller home ranges than conspecifics from rural areas, most distinctly if key cover was highly scattered. In urban plots, patch connectivity, home range sizes, and activity areas were positively correlated, indicating that individual ranging behaviour was related to the spatial distribution of suitable habitat. Urban House sparrows also showed the smallest feather growth bars, which were positively related to home range size at plot level. In contrast, growth bar widths and home range sizes were negatively related in rural populations, whereas in suburban populations, both variables varied independently. We conclude that individuals from progressively more built‐up areas show a restricted ability to adjust their daily ranging behaviour to the scattered distribution of critical resources. This may complement other putative causes of the widespread population decline of urban house sparrows. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 41–50.     

Urban badger setts: characteristics, patterns of use and management implications

Damage caused by badger setts is an important source of human–carnivore conflict in urban areas of the UK, yet little is known about the spatial distribution of urban badger setts or their pattern of occupation. We compared the density, spatial distribution and size of setts in four urban and two rural study areas in the UK and assessed the applicability to urban systems of distinguishing between 'main' and 'outlier' setts. In addition, we used radio-telemetry to investigate diurnal patterns of sett use in one urban area (Brighton). It was possible to distinguish between main and outlier setts in urban environments, and local sett densities were comparable in urban and rural areas. However, urban badgers used substantially fewer setts than did a nearby rural population, and they spent a smaller proportion of days in outlier setts. Social groups with larger ranges had more setts available to them and, within groups, individuals with larger ranges used more setts. Outliers appeared to serve multiple functions, including allowing efficient and safe travel to important parts of the home range. We conclude that sett densities can be high in urban habitats, suggesting significant potential for sett-related problems to arise. The fact that urban main setts can be distinguished from outliers enables management actions to be tailored accordingly. In particular, because main setts seem to represent a particularly valuable resource to urban badgers, alternatives to the closure of problem main setts need to be considered.     

Effect of acute stressor on reproductive behavior differs between urban and rural birds

The life‐history trade‐off between self‐maintenance and reproduction posits that investment in one function decreases investment in the other. Manipulating the costs and benefits of functions involved in a trade‐off may alter this interaction. Here we ask whether investment in self‐maintenance during a stress response alters territorial behavior in wild Dark‐eyed Juncos and whether rural and urban birds, which are known to differ in the magnitude of the stress response (greater in rural), also differ in the degree to which stress reduces territorial behavior. In rural and urban habitats, we measured territorial behavior using song playback, followed by either an acute stressor (capture and collection of a blood sample) or a nonstressful control situation. The following day, we again measured territorial behavior, predicting greater reduction in territorial behavior in individuals exposed to the stressor but a lesser reduction in territorial behavior in the urban as compared to the rural environment. We further assessed individual and population differences in response to stressors by measuring flight initiation distance, breath rate, and corticosterone levels in the blood. The rural population had a higher physiological and behavioral stress response than the urban population, and acute capture stress had a lasting (24 h) negative effect on territorial behavior, but only in the rural habitat. However, individual‐level differences in measures of the stress response did not explain variation in the impact of stress on territorial behavior. Our findings show that stressors can have a negative effect on territorial behavior, but that this effect may differ between populations that vary in their stress ecology.     

Home range and habitat selection by the Nutcracker Nucifraga caryocatactes during autumn in the Alps

In the Mont Avic Natural Park (NW Italian Alps), the Nutcracker Nucifraga caryocatactes occurred in coniferous forests where Arolla Pines Pinus cembra, its preferred habitat, were absent. A radiotelemetric study carried out during autumn 1992 and 1993 showed that, from September, Nutcrackers concentrated in the few Hazel Corylus avellana hedges of the rural zones of the park to collect nuts, which were eaten or stored. Individual home ranges overlapped to a high degree until October, when birds started to abandon the Hazel areas. From October onward, individual home ranges significantly expanded and their degree of overlap diminished compared to September. The home range analysis and the observations in the field suggested that the population of Nutcrackers in the park during autumn was made up of at least three different categories of birds, which displayed different ranging behaviour patterns. A few untagged birds probably stored nuts in their breeding territories, whereas all the radio-tagged birds ( n = 15) gave no indication of territorial use, since from October they either stored nuts in the coniferous woods near the Hazel hedges or abandoned the park to fly to other Hazel areas. Hence, during autumn the ranging behaviour of the Nutcrackers seems to be largely independent of their reproductive territorial system. Habitat selection analysis and transect counts revealed that birds positively selected Hazels, especially in the coniferous woods around Hazel hedges, and avoided the other coniferous forests. Nevertheless, from October some individuals reversed their habitat choices and positively selected coniferous forests (especially Mountain Pine Pinus uncinata woods) while avoiding Hazel.     

Low genetic variability, female-biased dispersal and high movement rates in an urban population of Eurasian badgers Meles meles

1. Urban and rural populations of animals can differ in their behaviour, both in order to meet their ecological requirements and due to the constraints imposed by different environments. The study of urban populations can therefore offer useful insights into the behavioural flexibility of a species as a whole, as well as indicating how the species in question adapts to a specifically urban environment. 2. The genetic structure of a population can provide information about social structure and movement patterns that is difficult to obtain by other means. Using non-invasively collected hair samples, we estimated the population size of Eurasian badgers Meles meles in the city of Brighton, England, and calculated population-specific parameters of genetic variability and sex-specific rates of outbreeding and dispersal. 3. Population density was high in the context of badger densities reported throughout their range. This was due to a high density of social groups rather than large numbers of individuals per group. 4. The allelic richness of the population was low compared with other British populations. However, the rate of extra-group paternity and the relatively frequent (mainly temporary) intergroup movements suggest that, on a local scale, the population was outbred. Although members of both sexes visited other groups, there was a trend for more females to make intergroup movements. 5. The results reveal that urban badgers can achieve high densities and suggest that while some population parameters are similar between urban and rural populations, the frequency of intergroup movements is higher among urban badgers. In a wider context, these results demonstrate the ability of non-invasive genetic sampling to provide information about the population density, social structure and behaviour of urban wildlife.     

Use of space and habitat selection by roe deer Capreolus capreolus in a Mediterranean coastal area: how does woods landscape affect home range?

The home-range dynamics and habitat selection of nine roe deer were studied from March 1994 to August 1994 in the Maremma Natural Park along the Tyrrhenian coast of Italy. The habitat was highly fragmented, with open agricultural fields prevailing in the study area (57%); the climate was Mediterranean. Data on spatial behaviour were collected by radio-tracking techniques. Habitat selection and structure were investigated by compositional and landscape analysis, both within the study area and within the home ranges. Animals of our sample showed spatial-use patterns varying from stationary to roaming. Stationary individuals used small home ranges while roaming ones moved, especially during the reproductive period in July and August. The percentage and structure of woodlands influenced the size of home ranges and the behaviour of males: stationary males used large amounts of woodlands within their home ranges and showed a territorial behaviour whereas males that used a high percentage of fields showed wider home ranges even during the territorial period. Females seemed to be less influenced by the presence and patch-structure of woodland within their home range. Landscape structure and habitat composition seemed to be important factors influencing the spatial behaviour of this roe deer population.     

Habitat use and ranging behaviour of the red fox (Vulpes vulpes) in a Mediterranean rural area: is shelter availability a key factor?

Factors affecting activity, habitat use, and home-range size of the red fox were analysed in a highly heterogeneous rural environment. Individual differences in behaviour were used to test our hypotheses. Food habits tended to depend on food availability, which, in turn, was mainly influenced by temperature. Diet was highly heterogeneous. Insects, e.g. grasshoppers and beetles, and cultivated fruits were the staple of the diet, but no diet component stood out clearly from all others. For an opportunistic species such as the fox, habitat heterogeneity may be the main factor underlying a wide trophic niche. All foxes selected the vineyard as part of their home ranges, whereas they preferred for activity the abandoned olive-yard among the habitats of their home ranges. Human intolerance of foxes affects their pattern of activity, habitat selection, and ranging behaviour. Foxes were strongly nocturnal. Cover-rich habitats were preferred for resting and for movements in daylight. Areas under human management were mainly used at night. Selectivity was higher for resting than for activity sites. Variation in home-range size and shape can be influenced not only by the dispersion of the main food patches, but also by the location of shelters     

Factors affecting hedgehog (<Emphasis Type="Italic">Erinaceus europaeus</Emphasis>) attraction to rural villages in arable landscapes

Although residential areas are often unfavourable for wildlife, some species can take advantage of the available shelter and anthropogenic sources of food such as supplementary feeding. The European hedgehog (Erinaceus europaeus) is increasingly associated with gardens and villages and less so with arable farmland. Suggested drivers for this include the following: hedgehogs’ attraction to higher food densities, including natural prey and anthropogenic sources, a greater range of day nest sites and warmer microclimates in rural villages, coupled with decreased risk of predation by badgers (Meles meles). We investigated the contribution of these drivers by radio-tracking hedgehogs on four arable sites, two with badgers present. Seventy-eight hedgehogs were tracked, 32 yielding enough data to calculate home range sizes. At the home range and landscape scales, gardens and buildings were the highest ranked habitats compared with their availability. Woodland and arable land were the lowest ranked compared with their availability. Villages were the most selected habitat for nesting. When hedgehogs were found closer to buildings, their ranges were smaller and we speculate this is due to increased food availability in villages. Where badgers were present hedgehogs remained closer to cover and their home ranges were on average 12.2 ha smaller. On badger-occupied sites, 50% fewer radio-tracking fixes were on arable land. We conclude that resource availability coupled with nest site selection and badger presence drives hedgehogs’ selection of rural villages. We found no effect of ambient temperature on habitat use. We recommend focusing conservation efforts on maintaining hedgehog populations in rural villages.     

Associations of garden birds with gradients in garden habitat and local habitat

Habitat associations of 40 bird species were analysed using data from a survey of 12892 garden sites throughout the United Kingdom between 1995 and 2002. Gradients in 20 garden habitat variables and 25 variables describing the surrounding local habitat were derived from Detrended Correspondence Analysis. The main garden axis explained 13.3% of variation in the data and described a gradient from sites containing and bounded by high levels of vegetation cover to open sites bounded by walls and fences. The main local axis explained 29.9% of variation in the data and described a gradient from rural to urban habitats. Higher probability of occurrence was detected in larger sites in 25 species and in smaller sites in four (urban-associated) species. Many species (22 out of 40) were significantly associated with the local gradient: seven species showed the highest probability of occurrence in sites within more urbanised habitats. Other species were most likely to occur in sites within rural or suburban habitats. Only five species showed a significant association with garden habitat gradient, four of these being most likely to occur in sites with highest vegetation cover. These associations were similar when controlling for garden size and for food provision in gardens. The results imply that the likelihood of many species occurring in gardens is dependent on the surrounding local habitat rather than the garden habitat. However, survey participants were likely to have "bird-friendly" gardens which may have reduced the variation in garden habitat across the sample. An assessment of the representativeness of survey sites is needed to further understand habitat associations of garden birds.     

Distribution of badger latrines in a high-density population: habitat selection and implications for the transmission of bovine tuberculosis to cattle

Eurasian badgers Meles meles habitually deposit droppings and other scent marks at latrines, which may be associated with territorial defence, and communicate information related to group and individual identity and status, and food resources. Understanding patterns of latrine distribution contributes to our understanding of badger social behaviour, and may be relevant to managing the risks of transmission of bovine tuberculosis from badgers to cattle. We investigated the distribution of badger latrines relative to habitat composition in a high-density badger population occupying a 7 km² area of diverse landscape in south-west England. Results indicated that the frequency and density of badger latrines varied according to land use, with woodland and linear landscape features (particularly hedges and stone walls) being positively selected. The number of latrines decreased significantly with distance from linear features. Grassland was negatively selected given its availability, but contained the highest number of latrines. The tendency for latrines to be associated with particular habitat types covaried spatially across the study area. We present a habitat selection probability function, based on the output of our analyses, to allow comparison of observed versus expected latrine counts per habitat type at different sites. Habitat manipulation on farmland may offer opportunities to manage exposure of cattle to badger latrines. However, our analyses indicate that other factors (perhaps demographic or environmental) may also exert a substantial local influence on latrine location.     

The effect of urban and rural habitats and resource type on activity budgets of commensal rhesus macaques (Macaca mulatta) in Bangladesh

Macaques are characterized by their wide distribution and ability to adapt to a variety of habitats. Activity budgets are affected by habitat type, season, and food availability in relation to differing age–sex class and individual requirements. We conducted a comparative study on two commensal rhesus groups, one living in a rural village and the other in the center of urban Dhaka, Bangladesh. The study was conducted in three different seasons between 2007 and 2009 in order to evaluate how habitat type and season affects their behavioral activities. Differences in food type and its availability between these two habitats were mainly responsible for the variations in activity budgets between groups. Feeding time in the rural group was significantly longer than that in the urban group. In contrast, grooming and object manipulation/play were significantly greater in the urban than the rural group. Seasonal variations in all major behaviors were significantly affected by group, with more time spent feeding in summer than in winter/dry season, and more time spent grooming and moving in winter/dry season than summer in the rural group. In contrast, time spent resting was greater in the monsoon and summer seasons than the winter/dry season in the urban group. Grooming time was greater in the winter/dry season than the monsoon and summer seasons. In both groups, immature of both sexes spent significantly more time on feeding and object manipulation/playing and less time resting than adults. Adult females spent more time grooming than males and immatures, of both sexes, in both groups. Moreover, the rural group spent most of their time feeding on garden/crop produce and wild plant food resources, while the urban group spent more time feeding on provisioned foods. These results showed that differences in the activity budgets of rural and urban dwelling macaques were due largely to the differences in available food resources. Commensal rhesus macaques show a high degree of behavioral flexibility in response to habitat and resource variability, and knowledge of these differences is important for the conservation and management of highly commensal primates.     

A comparison of infestation patterns by Ixodes ticks in urban and rural populations of the Common Blackbird Turdus merula

Although spatial variation in the patterns of parasite infestations among host populations may have important ecological and epidemiological consequences, the causes underlying such variation are poorly known. In the context of a long-term study on the population biology of Common Blackbirds Turdus merula , we examined the prevalence and intensity of infestation by Ixodes ticks between birds living in rural vs. urban habitats. The overall prevalence of tick infestations was significantly higher in the rural habitat where 74% of individuals ( n  = 130) were infested. This result contrasted markedly with the situation in the urban habitat where less than 2% of individuals ( n  = 360) carried ticks. There was no significant effect of the sex of the host on the intensity or prevalence of tick infestations. There was a significant effect of the age of the host on tick infestations essentially due to the absence of ticks on nestlings. Possible mechanisms responsible for the differences between habitats could include differences in tick survival and/or host resistance towards ticks. Previous studies have shown higher population densities and suggested longer survival for Blackbirds in urban than in rural habitats. Given that ixodid ticks are known to transmit pathogens like Borrelia spp. to wild birds, and that Blackbirds can act as reservoirs for these pathogens, the infection patterns observed in our study area provide a suitable situation to study the interrelations between ticks, Blackbirds and pathogens.     

Socio-spatial organization of urban stone martens

Stone martens Martes foina are common occupants of urban environments across continental Europe. We predicted that like other 'urban adapters', urban stone martens should exhibit smaller home ranges, more extensive home-range overlap and higher population densities than their rural counterparts. We radio-tracked 13 stone martens (10 females, three males) in two towns in southern Luxembourg during a 2-year period, in order to investigate nocturnal ranging behaviour. All martens maintained stable, year-round territories almost wholly within the urban perimeter of the respective study towns. Socio-spatial organization was based on intra-sexual territoriality. Territories (100% minimum convex polygon) were small in size (males: 112.6±24.8 ha; females: 37.0±22.2 ha) and population densities moderately high (4.7–5.8 adults km⁻²) by comparison with previous studies of rural populations. We conclude that although stone martens are clearly well adapted to urban conditions, urbanization has surprisingly little impact on their socio-spatial organization by comparison with its effects on other mesocarnivores. This apparent inflexibility in the spacing patterns of stone martens lends support to the view that spacing in martens ( Martes spp.) is a predominantly phylogenetic trait that is under limited environmental influence.     

Habitat specialization and adaptive phenotypic divergence of anuran populations

We tested for adaptive population structure in the frog Rana temporaria by rearing tadpoles from 23 populations in a common garden experiment, with and without larval dragonfly predators. The goal was to compare tadpole phenotypes with the habitats of their source ponds. The choice of traits and habitat variables was guided by prior information about phenotypic function. There were large differences among populations in life history, behaviour, morphological shape, and the predator-induced plasticities in most of these. Body size and behaviour were correlated with predation risk in the source pond, in agreement with adaptive population divergence. Tadpoles from large sunny ponds were morphologically distinct from those inhabiting small woodland ponds, although here an adaptive explanation was unclear. There was no evidence that plasticity evolves in populations exposed to more variable environments. Much among-population variation in phenotype and plasticity was not associated with habitat, perhaps reflecting rapid changes in wetland habitats.     

Song Post Height in Relation to Predator Diversity and Urbanization

Birds may sing from positions in the vegetation (song posts) to allow efficient transmission of sexual and territorial vocal displays while simultaneously minimizing the risk of predation because of avian and mammalian predators. Because urban areas are deficient in specialized avian predators, but have many cats while the opposite is the case for nearby rural areas, urban birds should display higher in the vegetation. In a comparison of the abundance of predators in three cities (Oslo, Brønderslev, Orsay), I show that avian predators are more common in rural areas, while mammalian predators are more common in urban areas. Singing birds sang from higher positions in the vegetation of urban than nearby rural areas. Differences in song post heights between urban and rural areas were consistent among cities, suggesting inherent specific difference in microhabitat choice. Bird species that have become urbanized recently had similar song post heights in urban and rural habitats, while species that have been urbanized for a long time sang from relatively higher song posts in urban areas. These findings suggest that urban and rural birds differ in habitat use when singing. These differences in song post choice between urban and rural habitats may have a number of consequences for vocal displays in the two different habitats.     

Ranging behaviour of huemul in relation to habitat and landscape

The huemul Hippocamelus bisulcus is an endangered species of deer occupying temperate woodland habitats in the Andes of southern Chile and Argentina. Continuing declines due to a combination of hunting and habitat loss have created a need for more conservation measures. However, current information on ranging behaviour, dispersal and seasonal movements is very limited. Three sites were therefore selected in Aysén, Chilean Patagonia, to study the movements and habitat associations of huemul. Although seasonal migrations in elevation had been reported previously for the species, we found the extent of seasonal movement limited, much less than that reported for other deer species in mountainous environments. Huemul selected mid-slope elevations, and the winter ranges of most animals overlapped summer ranges. The extent of the seasonal movements that were undertaken were, however, the greatest at the highest site and insignificant at the lowest site. Previously published information shows that habitats used by huemul follow a latitudinal gradient in elevation (reducing c . 100 m °S⁻¹ in latitude), and our results suggest that seasonal movements are likely to be greater in sites above this line. The mean range size differed between sites, ranging from 357 to 656 ha (mean 444 ha; median 506 ha). These estimates excluded long-distance (>5 km) movements, which were infrequent.     

Spillover of trap-nesting bees and wasps in an urban–rural interface

A mismatch of resource availability in certain periods can lead to spillover of insects between habitats, resulting in temporal differences in insect diversity. Urban gardens are important anthropogenic habitats but it is unknown whether, when and why spillover of beneficial insects occurs between gardens and agricultural habitats. We used trap nests for Hymenoptera to monthly monitor bee and wasp abundance and species richness in 12 gardens and 12 rapeseed fields. Half of the gardens and rapeseed fields were located in the urban–rural interface and bordered each other (a garden paired with a rapeseed field) and the other half were isolated in the rural landscape (isolated rapeseed fields) and in the urban city centre (isolated gardens). In general, gardens in the urban–rural interface comprised the highest richness of bees and wasps. The abundance of bees but not of wasps was highest in paired habitats and peaked at full rapeseed blooming, indicating that mass-flowering rapeseed offers foraging resources for bees nesting in adjacent gardens. Thus, bees nest and increase their populations in both areas, benefiting from the mass-flowering resource in the agricultural habitat as well as the nesting resources from gardens, suggesting spillover of bees but not of wasps between paired gardens and rapeseed fields. Our study highlights the value of gardens in the urban–rural interface for the biodiversity of functionally important insects. Implementing urban gardening and small-scale agriculture in cities and suburban habitats can promote local pollinator populations and benefit adjacent croplands.     

Behavioural Syndromes in Urban and Rural Populations of Song Sparrows

Animals in urban habitats are often noticeably bold in the presence of humans. Such boldness may arise due to habituation, as urban animals learn, through repeated exposure, that passing humans do not represent a threat. However, there is growing research suggesting that: (1) inherent traits, as opposed to learned behaviour, influence which species invade urban habitats, and (2) individuals exhibit individual personality traits that limit behavioural flexibility, with the possible result that not all individuals would be able to demonstrate an appropriate level of boldness in urban environments. As a result, perhaps only birds with inherently bold personalities could successfully settle in an area of high human disturbance, and further, we might also expect to see the existence of behavioural syndromes, where boldness is correlated with variation in other behavioural traits such as aggression. In this study, we examined boldness and territorial aggression in urban and rural populations of song sparrows. We found that urban birds were bolder towards humans and that urban birds also showed higher levels of territorial aggression. We also found an overall correlation between boldness and territorial aggression, suggesting that urban boldness may be part of a behavioural syndrome. However, we see no correlation between boldness and aggression in the urban population, and thus, more work is needed to determine the mechanisms accounting for high levels of boldness and aggression urban song sparrows.     

Habitat use and behaviour of European hedgehogErinaceus europaeus in a Danish rural area

HedgehogsErinaceus europaeus Linnaeus, 1758 were radio-tagged and monitored during the summer of 2001 in a Danish rural area with the objective of quantifying home ranges, nightly distances travelled, habitat use, activity patterns, day-nesting habits, and body-weight changes of the five males and five females being recorded. Males had larger home-range sizes and travelled longer nightly distances than females. The two most common habitat types within the home ranges of the hedgehogs were deciduous forest and arable land, whereas the two most frequently used habitat types were deciduous forest and grassland. No differences between the sexes were found in the proportions of different habitat types within the home ranges or in habitat use. Non-random habitat use was found; forested areas and edge habitats seemed preferred to open areas. The most frequently used day-nesting habitat was deciduous forest. Foraging was by far the most time-consuming nightly activity for both sexes. Males lost weight during the study period (May–July), whereas females gained weight. A peak in the frequency of sexual behaviour was found from late-June to mid-July. The high level of male ranging activity and the weight loss of males are interpreted as a consequence of the promiscuous mating system of hedgehogs.