Roost Site Selection Research Articles

Bat Community and Roost Site Selection of Tree-Dwelling Bats in a Well-Preserved European Lowland Forest

Worldwide species density of bats is highest in forests ecosystems. European primeval forests are now reduced to a few small and isolated patches because almost all forests are subject to management. Therefore, knowledge about bats in ancient and near-natural forests in Europe is scarce. In the well-preserved forest stands of the Belovezhskaya Pushcha National Park in Belarus we studied the bat community (1), the presence of maternity colonies and their preference in tree roost selection (2) and parameters of roosts used by forest dwelling bats (3). By mist-netting surveys, we identified 13 bat species and acoustic data suggested the presence of another three species. We detected 15 maternity colonies of seven bat species by radio-tracking reproductive females and 40 tree roosts within the forest. Roosts of Barbastella barbastellus, Pipistrellus pygmaeus and Plecotus auritus were almost exclusively behind the loose tree bark of decaying trees, or within narrow crevices. Myotis nattereri and Nyctalus leisleri showed a preference towards hollows (e.g., woodpecker-made cavities) within oak trees (Quercus robur). Our study shows that all tree-dwelling bat species are highly dependent on natural processes within forests that allow the formation of roost sites. Therefore, we strongly support that the natural aging process of trees, as well as the consequences of natural disturbance (e.g. through weather), should be permitted. This should extend beyond the protected zones of National Parks. In contrast, sanitary cuttings decrease the habitat's suitability for forest-dwelling bats. Finally, our results indicate that the forest complex of Belovezhskaya Pushcha and Białowieża is one of the most important bat areas in Europe.

Diurnal space use and nocturnal roost-site selection by male Cerulean Warblers during the breeding season

Diurnal space use and nocturnal roost-site selection by male Cerulean Warblers during the breeding season

Roost site selection of western long‐eared myotis in a western juniper woodland

ABSTRACTSeveral bat species occur in piñon (Pinus monophylla) and juniper (Juniperus ssp.) woodlands across the western United States, yet factors influencing roost site selection in these vegetation communities are poorly understood. Piñon‐juniper woodlands have expanded beyond their historical geographic range in the western United States since European settlement. Many former stands of widely spaced old‐growth juniper are now crowded with younger trees. Currently, federal and state land management agencies and private landowners are removing juniper trees to restore shrub‐steppe for greater sage‐grouse (Centrocercus urophasianus) across its geographic range, with little understanding of the treatment effects on roost site selection by bats. We used radio‐telemetry to examine roost site selection of western long‐eared myotis (Myotis evotis) at 3 spatial scales (roost, plot, and home range) during the breeding season. We attached radio‐transmitters to 32 individuals and located 92 day roost sites for 25 different individuals. Lactating females selected rock crevices as roosts more frequently than tree cavities, whereas males used tree roosts and rock roosts more evenly. The majority of tree roosts were in pre‐settlement trees that had at least 1 cavity. The odds that a tree was selected as a roost site increased with the number of available tree roosts within 17.8 m of the roost site. Preference by lactating females for rock roost sites increased with the number of available rock roosts within 5 m of the roost site and decreased with distance from water. Preference by males for rock roosts decreased if the roost was a single rock compared to an aggregate of rocks, increased with the number of available roosts within 5 m of the roost site, decreased with distance from water, and increased with area of pre‐settlement juniper woodland within 1 km of the roost site. These results provide support for protecting pre‐settlement juniper trees and rock formations near water sources in juniper woodlands to conserve existing populations of western long‐eared myotis during the breeding season. © 2018 The Wildlife Society.

Diel changes in habitat use by dragonflies: Nocturnal roosting site selection by the threatened dragonfly Sympetrum depressiusculum (Odonata: Libellulidae)

AbstractAlthough it is well recognized that insects' habitat use and requirements may change during the season, very little attention has been devoted to diel habitat changes in most insects. In this study, we compared habitat utilization patterns of Sympetrum depressiusculum (Selys, 1841) adult dragonflies between daytime activities and nocturnal roosting. During daytime, we captured and marked adult individuals with fluorescent paint in different habitats. At night, we searched, using UV light, for marked individuals that remained on the habitats. We found that habitat selection for daytime activities and that for nocturnal roosting differed significantly. Adults clearly avoided ponds and their immediate surroundings for nocturnal roosting, whereas this habitat type was frequently utilized for daytime activities. We suggest that nocturnal avoidance of the riparian area is associated with lower temperatures, which adversely affect thermoregulation, and that selection of specific habitats for nocturnal roosting is closely associated with vegetation structure providing stability during windy nights and serving as a suitable shelter. Such habitat properties are found especially on fallow land, a habitat type whose representation in agricultural areas has been gradually decreasing in recent decades.

Offal dumping sites influence the relative abundance and roosting site selection of Black Kites (Milvus migrans govinda) in urban landscape: a study from Kolkata metropolis, India.

Although Black Kites (Milvus migrans govinda) serve as major scavenging raptor in most of the urban areas, scientific studies on this important ecosystem service provider are almost non-existent in Indian context. The present study was carried out in a metropolis in eastern India to find out the factors influencing relative abundance and roosting site selection of Black Kites. Separate generalized linear models (GLMs) were performed considering encounter rate and roosting Black Kite abundance as response variables. The study conclusively indicated that encounter rates of Black Kites were significantly influenced by the presence of garbage dumps in its vicinity. Numbers of Black Kites were also higher in the roosting sites situated closer to garbage dumps and open spaces. In addition, expected counts of Black Kites significantly increased in roosting sites situated away from buildings and water bodies. However, built-up area and tree cover around the roosting sites had no influence on the abundance of Black Kites therein. With rapid urbanization and changing offal disposal patterns, our findings would be useful to ensure continued availability of food and roosting sites of Black Kites in urban areas.

Roost site selection and colony size of the common Japanese pipistrelle (Pipistrellus abramus) in Fuchu, Tokyo

Roost site selection and colony size of the common Japanese pipistrelle (Pipistrellus abramus) in Fuchu, Tokyo

Sandhill crane roost selection, human disturbance, and forage resources

ABSTRACTSites used for roosting represent a key habitat requirement for many species of birds because availability and quality of roost sites can influence individual fitness. Birds select roost sites based on numerous factors, requirements, and motivations, and selection of roosts can be dynamic in time and space because of various ecological and environmental influences. For sandhill cranes (Antigone canadensis) at their main spring‐staging area along the Platte River in south‐central Nebraska, USA, past investigations of roosting cranes focused on physical channel characteristics related to perceived security as motivating roost distribution. We used 6,310 roost sites selected by 313 sandhill cranes over 5 spring migration seasons (2003–2007) to quantify resource selection functions of roost sites on the central Platte River using a discrete choice analysis. Sandhill cranes generally showed stronger selection for wider channels with shorter bank vegetation situated farther from potential human disturbance features such as roads, bridges, and dwellings. Furthermore, selection for roost sites with preferable physical characteristics (wide channels with short bank vegetation) was more resilient to nearby disturbance features than more narrow channels with taller bank vegetation. The amount of cornfields surrounding sandhill crane roost sites positively influenced relative probability of use but only for more narrow channels <100 m and those with shorter bank vegetation. We confirmed key resource features that sandhill cranes selected at river channels along the Platte River, and after incorporating spatial variation due to human disturbance, our understanding of roost site selection was more robust, providing insights on how disturbance may interact with physical habitat features. Managers can use information on roost‐site selection when developing plans to increase probability of crane use at existing roost sites and to identify new areas for potential use if existing sites become limited. © 2016 The Wildlife Society.

Vegetation and Thermal Chracteristics of Bobwhite Nocturnal Roost Sites in Native Warm-Season Grass

Native warm-season grass (NWSG) has been widely promoted as wildlife habitat, but little empirical evidence is available to support its value for most wildlife species. One justification for a conversion to NWSG is the high thermal quality of cover resulting from the height and structure of the vegetation. Because vegetation cover is an important factor contributing to bobwhite winter survival, we predicted that they should select roost sites with superior thermal characteristics during winter when energy requirements for thermoregulation are greatest. In this 3-year study we used data derived from roost sites (n 166) obtained from radio-marked quail to compare the relative use of NWSG and 5 other habitat types, and the micro-habitat characteristics of winter roost and random sites on an area intensively managed for quail in Missouri. Of the 6 habitats used for roosting, most locations (51.2%) were in old-field habitats. NWSG ranked third with 17% of the locations. Our findings indicated that roost site selection may be influenced to a greater extent by the micro-habitat characteristics of a site rather than by habitat type. Two micro-habitat features that were of particular importance in habitats used most by quail were litter cover and canopy cover. These habitat features are valuable in reducing conductive and convective heat loss.

Roosting records in tree cavities by a forest-dwelling bat species (Histiotus magellanicus) in Andean temperate ecosystems of southern Chile

Tree cavities can provide critical roosting sites for cavity-using vertebrates. These sites can directly affect productivity and survival of bats. Histiotus magellanicus, one of the bat species with the southernmost distribution in the world, is suspected to use tree cavities, under bark, caves and human buildings for roosting. We document the first records of this bat roosting in tree cavities created by both cavity-facilitators (i.e., excavators) and tree-decay processes on standing dead and large decaying trees in Andean temperate forests, southern Chile. Our records contribute to improve current knowledge of roosting habitat of H. magellanicus. We discuss these natural history records on roosting site selection and the potential importance of tree cavities for this species in southern temperate ecosystems.

Winter Cover Height and Heat Loss: Is Taller Better? (Oral Abstract)

Previous studies have demonstrated that roost site selection affects energy requirements for thermoregulation in several avian species; however, the influence of microhabitat characteristics on heat loss has not been evaluated for northern bobwhites (Colinus virginianus). One frequently measured microhabitat feature that is commonly thought to influence the thermal characteristics of avian ground roost sites is cover height. We simultaneously measured thermoregulatory energy expenditure of bobwhites across a range of low ambient temperatures (-24 to 14 C) in 3 cover heights (0 cm, 46 cm, 124 cm) using 3 heated taxidermic mounts. Predicted metabolic rates (PMR) were derived on the basis of power consumption of the taxidermic mounts. Predicted metabolic rate for each vegetation height was linearly related to ambient temperature, and decreased significantly (P < 0.05) as temperature increased. Contrary to our predictions, PMR did not differ (P = 0.769) among the 3 vegetation heights across a range of environmental conditions. These findings suggest that under the conditions occurring during our field measurements, thermoregulatory energy requirements of bobwhites are essentially independent of vegetation height at the roost, and primarily are a function of conductive rather than convective heat loss.

Different responses of attic-dwelling bat species to landscape naturalness

Although the general role of bats and the tolerance of many species to urbanized areas is well known, the relationship between urban roosts and their surrounding landscapes having different degrees of naturalness still requires our attention, mainly in species that are the most adapted to human-made structures. We used extensive data from attic-dwelling bat surveillance conducted throughout Slovakia to assess species responses to the degree of naturalness of the landscape surrounding their anthropogenic roosts. Using generalized linear mixed-effects modelling, we found that some bats established their nursery colonies in either a habitat with a higher proportion of forests mostly at sub-mountain/mountain altitudes (R. hipposideros, P. auritus, M. emarginatus), or they preferred lowlands with a predominance of arable land (E. serotinus, P. austriacus). Furthermore, higher habitat heterogeneity and the proportion of grassland were positively associated with the occurrence of P. auritus; however, negative associations with these habitat variables were found in E. serotinus. The predicted suitability of an area for bats to establish nursery colonies suggests the existence of two regions with different bat species composition in the study area: a region of the Pannonian Lowlands and a less urbanized mountain region of the Carpathian Mountains. Our study thus showed that landscape naturalness is a determining factor for roost-site selection by bats preferring anthropogenic roosts; however, some bat species did not express specific preferences according to the tested environmental variables, and other ecological traits in the evaluated species should be considered.

Patterns of roost site selection and use by Southern Ground-Hornbills in north-eastern South Africa

Different habitats may be used for the needs of various aspects of an animal’s life. Southern Ground-Hornbill Bucorvus leadbeateri groups announce their presence within year-round territories by calling at dawn from their overnight roost sites. Knowledge on ground-hornbill roosting habits is limited. Groups roost in large trees, apparently close to where they end up after daily foraging. We investigated patterns of roost site selection and use for four Southern Ground-Hornbill groups in the Associated Private Nature Reserves, north-eastern South Africa, based on data from GPS-satellite transmitters. The number of roost sites used per month averaged 15.4 ± 4.7 across all groups, indicating little evidence of strong preferences for specific sites. This number was least when groups were breeding, decreasing throughout the early wet season (October–December) and was lowest during the late wet season (January–March) when actively breeding groups frequently roosted close to the nest (54–83% of roosts <1 000 m of the nest). As might be expected, the mean monthly number of nights per roost peaked during the breeding season (December–January). Riparian habitats were preferred for roosting during the breeding season, whereas disturbed areas, as well as Combretumand mopane-dominated habitats were preferred during the dry non-breeding season. Adequate large trees not only for nesting, but also for roosting, particularly in riparian habitats, may therefore be an important and potentially limiting factor for the successful reproduction of Southern Ground-Hornbills.

Seeing the Forest through the Trees: Considering Roost-Site Selection at Multiple Spatial Scales.

Conservation of bat species is one of the most daunting wildlife conservation challenges in North America, requiring detailed knowledge about their ecology to guide conservation efforts. Outside of the hibernating season, bats in temperate forest environments spend their diurnal time in day-roosts. In addition to simple shelter, summer roost availability is as critical as maternity sites and maintaining social group contact. To date, a major focus of bat conservation has concentrated on conserving individual roost sites, with comparatively less focus on the role that broader habitat conditions contribute towards roost-site selection. We evaluated roost-site selection by a northern population of federally-endangered Indiana bats (Myotis sodalis) at Fort Drum Military Installation in New York, USA at three different spatial scales: landscape, forest stand, and individual tree level. During 2007–2011, we radiotracked 33 Indiana bats (10 males, 23 females) and located 348 roosting events in 116 unique roost trees. At the landscape scale, bat roost-site selection was positively associated with northern mixed forest, increased slope, and greater distance from human development. At the stand scale, we observed subtle differences in roost site selection based on sex and season, but roost selection was generally positively associated with larger stands with a higher basal area, larger tree diameter, and a greater sugar maple (Acer saccharum) component. We observed no distinct trends of roosts being near high-quality foraging areas of water and forest edges. At the tree scale, roosts were typically in American elm (Ulmus americana) or sugar maple of large diameter (>30 cm) of moderate decay with loose bark. Collectively, our results highlight the importance of considering day roost needs simultaneously across multiple spatial scales. Size and decay class of individual roosts are key ecological attributes for the Indiana bat, however, larger-scale stand structural components that are products of past and current land use interacting with environmental aspects such as landform also are important factors influencing roost-tree selection patterns.

Roost site selection by ring‐billed and herring gulls

ABSTRACTGulls (Larus spp.) commonly roost in large numbers on inland and coastal waters, yet there is little information on how or where gulls choose sites for roosting. Roost site selection can lead to water quality degradation or aviation hazards when roosts are formed on water supply reservoirs or are close to airports. Harassment programs are frequently initiated to move or relocate roosting gulls but often have mixed results because gulls are reluctant to leave or keep returning. As such, knowledge of gull roost site selection and roosting ecology has applied and ecological importance. We used satellite telemetry and an information‐theoretic approach to model seasonal roost selection of ring‐billed (L. delawarensis) and herring gulls (L. argentatus) in Massachusetts, USA. Our results indicated that ring‐billed gulls preferred freshwater roosts and will use a variety of rivers, lakes, and reservoirs. Herring gulls regularly roosted on fresh water but used salt water roosts more often than ring‐billed gulls and also roosted on a variety of land habitats. Roost modeling showed that herring and ring‐billed gulls selected inland fresh water roosts based on size of the water body and proximity to their last daytime location; they selected the largest roost closest to where they ended the day. Management strategies to reduce or eliminate roosting gulls could identify and try to eliminate other habitat variables (e.g., close‐by foraging sites) that are attracting gulls before attempting to relocate or redistribute (e.g., through hazing programs) roosting birds. © 2016 The Wildlife Society.

Roost Site Selection of the Common Crane in Its Largest European Stop-Over Site

Along several migratory corridors in Europe, the Common Crane Grus grus exhibits a variety of migratory and roost site selection strategies. In this study we determined which environmental factors explained roost-site usage of Common Cranes in 64 fishponds and 25 marshes suitable for Crane roosting inside the Hortobagy National Park (HNP, Hungary) between 1995 and 2007. HNP has become the largest stop-over site of Cranes in Europe. Despite the relatively high number of potential roost sites, Cranes chose only 44% of suitable wetlands for roosting. Roost site selection of Common Cranes was primarily governed by conservation management measures, wetland type and size, as well as disturbance-related characteristics of the roost-site. Artificially flooded marshes, as well as large fishponds, actively managed through drainage, far from human settlements, are of critical importance for staging Common Cranes. The timing of controlled floods in marshes as well as the matching of drainage for fish-farming to migra...

Roost site selection by tree‐dwelling bats across biogeographical regions: an updated meta‐analysis with meta‐regression

Abstract Bats roosting in tree cavities, under loose bark or just on branches in foliage, so‐called tree‐dwelling bats, are a very diverse and abundant group of species. Although they can be very different species with locally distinct needs, radical exploitation of forest habitats and global changes have meant that many of them are regionally endangered and survive today only in small populations. To help develop appropriate conservation policies and management plans, much research in recent decades has been focussed on inferring habitat selection by tree‐dwelling bats. However, large variability in the reported selection patterns makes it difficult to suggest some more‐or‐less universal and easily applicable management recommendations, also for regions in which nature conservation awareness is low. We created a meta‐analytic model to explore selection patterns at a global scale. Phylogenetic relationships among species and additional variables were included to explain discrepancies between studies. A meta‐analytic model showed that bats are selecting trees with trunk diameters that are larger than those of randomly selected trees, and this pattern is consistent within each biogeographical region. However, meta‐regression revealed that the detectability of the selection depends strongly on the structural variability within the study environment (size of randomly selected or surrounding trees in forest stands, forest fragmentation, habitat disturbance) and on the methodological approach that has been applied (the length of the study). We found stronger selection for larger trees in non‐fragmented and less disturbed forests than in fragmented forests with high habitat disturbance, and, strikingly, short‐term studies yielded results with stronger selection than long‐term studies. Our results suggest that patterns of roosting habitat selection by bats may be overestimated in some studies. In conclusion, we propose that further research should be conducted in all types of forest ecosystem (data from the tropics are currently missing). Future studies should include at least three years of data collection, in order to avoid estimation bias in habitat selection patterns.

Patterns of occurrence and abundance of roosting geese: the role of spatial scale for site selection and consequences for conservation

AbstractRoosting site selection by geese is a key factor for survival during migration and wintering. Birds should select sites that minimize thermoregulation demands and predation risk, and maximize foraging efficiency. We used data on the spatial location of geese roosting sites in Poland to compare landscape features and the conservation status of roosting and non‐roosting sites at different scales ranging from 5 to 50 km. Logistic regression revealed that the sites selected by geese had larger waterbody size than non‐selected sites, and surrounded by a smaller coverage of woodland at the scale of 50 km. They also were more often Natura 2000 sites. The most important factors positively affecting the abundance of geese were the size of waterbody and low coverage of artificial area (mostly urban) within a 50 km radius. Several further factors also influenced the roosting site selection. Regardless to the scale a large coverage of farmland (mostly rapeseed) positively affected roosting geese whereas forest coverage had a negative effect. Spatial hierarchical clustering analysis showed that the roosting sites were densely located in regions characterized by the most intensive agriculture. Farming intensity therefore seems to increase the abundance of geese, and consequently, to increase a possible conflict between goose conservation and food production. To alleviate the conflicts we delineated areas that may be most affected and where the conservation measures should be implemented first. As geese respond to environmental factors at different spatial scales this scale‐dependency should be included in the conservation and management of goose populations.

Roost Site Selection in Pregnant and Lactating Soprano Pipistrelles (Pipistrellus pygmaeusLeach, 1825) at the Species Northern Extreme: The Importance of Warm and Safe Roosts

In summer reproducing female bats prefer roosts with temperatures in their thermo neutral zone, but in northern Europe, such roosts may be difficult to find. In this study, summer roost site selection of pregnant and lactating soprano pipistrelles were investigated using radio telemetry (2004–2006) in a fiord landscape with complex topography at the species northern extreme. The soprano pipistrelles' common roost sites were in hollow trees (n = 14), but they also used crevices in rock walls (n = 2) and the attic of one building. The bats exclusively sought out roosts on the north side of the fiord with the slope facing south, where solar irradiation yielded the warmest micro climate. From 2005 to 2014, bat boxes were erected at three sites in the study area. From 2012 to 2014 we only found maternity roosts in such structures, thus there was a clear shift in roost site selection by the soprano pipistrelle in the study area. Man-made structures, such as buildings and bat boxes, provided the warmest cavities, whereas natural cavities did not differ significantly from air temperatures. The bats did not find thermo neutral roosts most of the time, and this should affect the energy budgets, and thus the bats' behaviour. Direct observation of predation at roosts in build-up areas suggests that living close to humans could be costly to bats emerging in daylight conditions. No predation attempts were recorded at roosts in woodland habitats.

The Common Myna (Sturnus tristis) in urban, rural and semi-rural areas in Greater Sydney and its surrounds

Common Myna (Sturnus tristis, formerly Acridotheres tristis) is one of Australia's most readily identified pest species and have been implicated in the reduction of native fauna. This study aimed to determine the distribution, habitat use and roost site selection of Mynas on the urban fringes of Sydney, New South Wales, Australia, as well as the avian species composition of areas in which Mynas occurred. The information was gathered with a view to estimating the impact of this invasive species on native avifauna. In total 3661 birds were counted in 1349 km of survey transects in western Sydney. Mynas were the most abundant bird recorded in the surveys, and exotic species accounted for 41% of all birds counted, but only 20% of the total number of species. Comparison of distribution data across habitat types suggests that Mynas do not extend far beyond urban habitats, and Mynas were primarily observed in suburban-industrial areas, small suburban reserves or sporting grounds and roadsides in semi-rural areas. Differences in sex-specific size distribution of Mynas occurred in semi-rural and urban areas. Urban areas also contained higher densities of preferred roosting trees with dense canopies, suggesting Myna populations have been aided by historical urban planning and landscaping. Together these data suggest that Mynas are likely to affect urban-dwelling native avifauna and that careful urban planning may reduce their distribution and potentially their impact.

Using thermal imaging cameras with radiotelemetry to locate roost sites of male wild turkeys

Thermal imagery is a relatively new technology to the wildlife field. Researchers have begun testing whether this tool can be used to increase detection rates for various wildlife species. Little research has been conducted on roost-site selection of eastern wild turkeys (Meleagris gallopavo silvestris), partially because locating roosting birds and viewing them in forested environments is impractical. We evaluated the efficacy of ground-based thermal imaging combined with radiotelemetry to locate roosting male turkeys in southwestern Georgia, USA, 2011–2013. Using radiotelemetry and thermal imaging, we successfully collected data on 74 of 79 attempts (93.7%) to locate roosting male turkeys and identify the roost tree the bird was using. Compared with other methods of viewing roosting turkeys using thermal imagery, our methods were more successful. We recommend that researchers consider using ground-based thermal imaging to conduct more detailed studies on roost ecology of wild turkeys. © 2014 The Wildlife Society.