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I recorded information on pre-roost habitats of Western Marsh Harriers (Circus aeruginosus) near communal roost sites located in and around Keoladeo National Park (KNP), India, during three winters from 1997 to 2000. Harriers pre-roosted in different habitats in KNP compared to the surrounding areas (25-km radius). Harriers used trees as their main pre-roosting perches in KNP, but mainly used open fields in the surrounding areas. All nine tree species present near roost sites in KNP were used for pre-roosting. Among tree species used for pre-roosting, harriers preferred sacred fig (Ficus religiosa), a tall tree with a wide canopy. Babul (Vachellia nilotica) trees, though not preferred, were more utilized for pre-roosting, probably because of their abundance. The lack of suitable open areas near the primary roost site in KNP may help explain why harriers used trees as pre-roosting perches there. At other roost sites outside KNP where trees were sparse, harriers mainly pre-roosted on the ground. By perching on trees, harriers may be conspicuous to other arriving harriers, which likely helps the birds gather into a large roosting flock. Such large roosts may benefit harriers by providing protection from predators and a site where birds may obtain information on food resources. Although trees were used as pre-roosting sites at KNP, I did not observe any harriers roosting on trees overnight during the 3-yr study. [ABSTRACT FROM AUTHOR]

Social relationships among animals emerge from interactions in multiple ecological and social situations. However, we seldom ask how each situation contributes to the global structure of a population, and whether different situations contribute different information about social relationships and the position of individuals within the social fabric. Griffon vultures (Gyps fulvus) interact socially in multiple situations, including communal roosting, joint flights, and co-feeding. These social interactions can influence population-level outcomes, such as disease transmission and information sharing that determine survival and response to changes. We examined the unique contribution of each social and ecological situation to the social structure of the population and individuals' positions within the overall social network using high-resolution GPS tracking. We found that the number of individuals each vulture interacted with (degree) was best predicted by diurnal interactions-both during flights and on the ground (such as when feeding). However, the strength of social bonds, that is, the number of interactions an individual had (strength), was best predicted by interactions on the ground-both during the day (e.g., while feeding) and at night (e.g., while roosting) but not by interactions while flying. Thus, social situations differ in their impact on the relationships that individuals form. By incorporating the ecological situations in which social interactions occur we gain a more complete view of how social relationships are formed and which situations are important for different types of interactions.

In various animal species conspecifics aggregate at sleeping sites. Such aggregations can act as information centres where individuals acquire up‐to‐date knowledge about their environment. In some species, communal sleeping sites comprise individuals from multiple groups, where each group maintains stable membership over time.We used GPS tracking to simultaneously record group movement in a population of wild vulturine guineafowl (Acryllium vulturinum) to investigate whether communal sleeping sites can facilitate the transfer of information among individuals across distinct groups. These birds live in large and stable groups that move both together and apart, often forming communal roosts containing up to five groups.We first test whether roosts provide the opportunity for individuals to acquire information from members of other groups by examining the spatial organization at roosts. The GPS data reveal that groups intermix, thereby providing an opportunity for individuals to acquire out‐group information.We next conduct a field experiment to test whether naïve groups can locate novel food patches when co‐roosting with knowledgeable groups. We find that co‐roosting substantially increases the chances for the members of a naïve group to discover a patch known to individuals from other groups at the shared roost. Further, we find that the discovery of food patches by naïve groups subsequently shapes their space use and inter‐group associations. We also draw on our long‐term tracking to provide examples that demonstrate natural cases where communal roosting has preceded large‐scale multi‐group collective movements that extend into areas beyond the groups' normal ranges.Our findings support the extension of the information centre hypothesis to communal sleeping sites that consist of distinct social groups. [ABSTRACT FROM AUTHOR]

The nesting habits of Baya Weaver Ploceus philippinus with nesting site (e.g., power and television cables), source of nest materials, various developmental stages of nests, abnormal nests, number of individuals and their association with other bird species, and threats to their nests were studied between March and September 2021 in the agrarian landscapes of 42 villages in Kallakurichi District, Tamil Nadu. A total of 155 nest colonies containing 1,725 nests of various developmental stages and 1,993 adult birds were counted on power/television cables. The number of nests per colony found varied from one to 57. The average number of nests per colony was eleven. Baya Weaver had preferred power/television cables as nesting sites in the study area in spite of availability of potential nest-supporting trees, such as Cocos nucifera and Borassus flabellifer within 500 m radii from cables bearing nests. Birds used fibres of sugarcane leaves (Saccharum officinarum) for the construction of nests. Out of 778 helmet stage nests observed, 90% (n = 716) helmet stage nests had clay deposits on their inner walls and no clay deposits were found in the remaining 10% (n = 62) helmet stage nests. Eleven types of abnormal nests constituted 17% (n = 286) of the total nests. Sixteen other bird species (e.g., birds of order: Passeriformes, Coraciiformes, Piciformes, Cuculiformes and Columbiformes) were found associated with the individuals of Baya Weaver. These bird species strictly shared similar roosting and foraging grounds. The avian predators such as House Crow Corvus splendens, Large-billed Crow Corvus macrorhynchos, Black Drongo Dicrurus macrocercus, Rufous Treepie Dendrocitta vagabunda, Coucal Centropus senegalensis, and Shikra Accipiter badius had damaged the nests, eggs and chicks. The study revealed that about 1.1% nests (n = 197) were probably damaged by these avian predators. Power cables in the study sites had provided suitable nesting sites for Baya Weavers. The causes for utilization of power cables as nesting sites in larger geographical areas require further studies. [ABSTRACT FROM AUTHOR]

BIRDS THAT SPEND the winter in a harsh and cold climate face a suite of challenges that require optimization of energy expenditure and energy intake. Some birds roost communally, which can increase energy savings during cold winter nights. However, this behaviour is almost completely absent in chickadees, tits, and titmice (Paridae) as there are very few accounts in the literature of parids roosting together. Here I review these accounts and describe an observation where two Eurasian Blue Tits Cyanistes caeruleus were found roosting together in a nest-box on multiple winter nights in January 2021. [ABSTRACT FROM AUTHOR]

The Red Kite (Milvus milvus) is a common raptor in suitable areas of Austria, the Czech Republic, and Slovakia during the nonbreeding season. However, the exact number of birds wintering in these countries remains unknown. Through an integrated approach using satellite telemetry, direct field surveys at nocturnal roosts, and citizen science databases, we estimated the wintering population of Red Kites in this area during the winter of 2020/2021. Based on three surveys taking place at the beginning (28 November 2020), middle (9 January 2021), and end (5 February 2021) of winter, respectively, we counted 566, 558, and 536 Red Kites. The observations from online citizen science databases mostly appeared to correspond with the area of communal roost sites. Using our combined approach, the estimates of wintering Red Kites were determined as minimum numbers in the study area. A comparison of historical data (from the second half of the 20th and beginning of the 21st centuries, respectively) and our own results suggests that the wintering population of Red Kites in the study area has increased substantially. This dynamic could be caused by changes in climatic conditions, a shift of the birds' breeding range in Europe, changes in migration behavior and/or food availability, and/or conservation efforts. Milvus milvus es un rapaz común en áreas adecuadas de Austria, la República Checa y Eslovaquia durante la estación no reproductiva. Sin embargo, el número exacto de aves que pasan el invierno en estos países sigue siendo desconocido. A través de un enfoque integrado utilizando telemetría satelital, censos de campo directos en refugios nocturnos y bases de datos de ciencia ciudadana, estimamos la población invernante de M. milvus en esta área durante el invierno de 2020/2021. Basados en tres censos realizados al inicio (28 de noviembre de 2020), a la mitad (9 de enero de 2021) y al final (5 de febrero de 2021) del invierno, contamos 566, 558 y 536 individuos de M. milvus, respectivamente. Las observaciones de las bases de datos de ciencia ciudadana en línea parecieron corresponder principalmente con el área de los dormideros comunales. Usando nuestro enfoque combinado, las estimaciones de individuos invernantes de M. milvus se determinaron como números mínimos en el área de estudio. Una comparación de los datos históricos (de la segunda mitad del siglo XX y del inicio del siglo XXI, respectivamente) y nuestros propios resultados sugiere que la población invernante de M. milvus en el área de estudio ha aumentado sustancialmente. Esta dinámica podría estar causada por cambios en las condiciones climáticas, un cambio en el área de cría de las aves en Europa, cambios en el comportamiento migratorio y/o en la disponibilidad de alimentos, y/o los esfuerzos de conservación. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

Abstract Background Mixed-species groups in animals have been shown to confer antipredator, foraging and other benefits to their members that may provide selective advantages. In most cases, however, it is unclear whether functional benefits are a principal driver of heterospecific groups, or whether groups simply result from simultaneous exploitation of common resources. Mixed-species groups that form independently of environmental conditions may, however, evidence direct benefits of species associations. Bats are among the most gregarious mammals, with sometimes thousands of individuals of various species roosting communally. Despite numerous potential functional benefits of such mixed-species roosting groups, interspecific attraction has never been shown. To explore alternative explanations for mixed-species roosting, we studied roost selection in a speciose neotropical understory bat community in lowland rainforest in Costa Rica. Long term roost data were recorded over 10 years in a total of 133 roosts comprising both natural roosts and structurally uniform artificial roosts. We modelled bat roost occupancy and abundance in each roost type and in forest and pasture habitats to quantify the effects of roost- and environmental variability. Results We found that bat species presence in natural roosts is predictable from habitat and structural roost parameters, but that the presence and abundance of other bat species further modifies roost choice. One third of the 12 study species were found to actively associate with selected other bat species in roosts (e.g. Glossophaga commissarisi with Carollia sowelli). Other species did not engage in communal roosting, which in some cases indicates a role for negative interspecific interactions, such as roost competition. Conclusions Mixed-species roosting may provide thermoregulatory benefits, reduce intraspecific competition and promote interspecific information transfer, and hence some heterospecific associations may be selected for in bats. Overall, our study contributes to an improved understanding of the array of factors that shape diverse tropical bat communities and drive the dynamics of heterospecific grouping in mammals more generally.

Uncertainties regarding food location and quality are among the greatest challenges faced by foragers and communal roosting may facilitate success through social foraging. The information centre hypothesis (ICH) suggests that uninformed individuals at shared roosts benefit from following informed individuals to previously visited resources. We tested several key prerequisites of the ICH in a social obligate scavenger, the Eurasian griffon vulture (Gyps fulvus), by tracking movements and behaviour of sympatric individuals over extended periods and across relatively large spatial scales, thereby precluding alternative explanations such as local enhancement. In agreement with the ICH, we found that 'informed' individuals returning to previously visited carcasses were followed by 'uninformed' vultures that consequently got access to these resources. When a dyad (two individuals that depart from the same roost within 2 min of each other) included an informed individual, they spent a higher proportion of the flight time close to each other at a shorter distance between them than otherwise. Although all individuals occasionally profited from following others, they differed in their tendencies to be informed or uninformed. This study provides evidence for 'following behaviour' in natural conditions and demonstrates differential roles and information states among foragers within a population. Moreover, demonstrating the possible reliance of vultures on following behaviour emphasizes that individuals in declining populations may suffer from reduced foraging efficiency.

Abstract Background Communal roosting is a common avian social behaviour, which potentially provides foraging benefits, predation avoidance or thermoregulation in birds. To identify the crucial environmental factors associated with roost site selection, most studies have focused on the comparison of physical characteristics between roosts and non-roosts. However, the differences among roosts have usually been neglected and the causes of roost switching have seldom been investigated. Methods To explore the variations among roost sites and assess the most influential environmental factors related to seasonal roost switching, we conducted a 105-day observation on an introduced population of critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) in an urban environment in Hong Kong from 2014 to 2016. We identified seven roost sites that were occupied in different seasons and then measured their microhabitat characteristics in terms of land use types, human disturbance and microclimate temperature. To quantify these differences, we used Pearson’s chi-squared test, partial least squares determinant analysis (PLS-DA) and one-way repeated measures ANOVA, respectively. Results Our results distinguished roost sites occupied in three seasons, i.e. spring, summer and winter roosts, using several microhabitat characteristics. The land use types were significantly associated with roosts, where spring roosts were usually located in tree-dominated areas, which are the major feeding grounds. The discriminant analysis on human disturbance variables indicated that summer roosts were positively associated with night illumination. The microhabitat temperatures of winter roosts were significantly higher than those of most other roosts on cold nights. Conclusions The results highlighted significant variations among roosts, and seasonal roost switching was likely driven by specific microhabitat characteristics of each roost site, such as microclimate. It also helps us understand the behavioural adaptation of birds to urban environments.

Movement patterns and habitat selection of animals have important implications for ecology and evolution. Darwin's finches are a classic model system for ecological and evolutionary studies, yet their spatial ecology remains poorly studied. We tagged and radio‐tracked five (three females, two males) medium ground finches (Geospiza fortis) to examine the feasibility of telemetry for understanding their movement and habitat use. Based on 143 locations collected during a 3‐week period, we analyzed for the first time home‐range size and habitat selection patterns of finches at El Garrapatero, an arid coastal ecosystem on Santa Cruz Island (Galápagos). The average 95% home range and 50% core area for G. fortis in the breeding season was 20.54 ha ± 4.04 ha SE and 4.03 ha ± 1.11 ha SE, respectively. For most of the finches, their home range covered a diverse set of habitats. Three finches positively selected the dry‐forest habitat, while the other habitats seemed to be either negatively selected or simply neglected by the finches. In addition, we noted a communal roosting behavior in an area close to the ocean, where the vegetation is greener and denser than the more inland dry‐forest vegetation. We show that telemetry on Darwin's finches provides valuable data to understand the movement ecology of the species. Based on our results, we propose a series of questions about the ecology and evolution of Darwin's finches that can be addressed using telemetry. [ABSTRACT FROM AUTHOR]

Background: Mixed-species groups in animals have been shown to confer antipredator, foraging and other benefits to their members that may provide selective advantages. In most cases, however, it is unclear whether functional benefits are a principal driver of heterospecific groups, or whether groups simply result from simultaneous exploitation of common resources. Mixed-species groups that form independently of environmental conditions may, however, evidence direct benefits of species associations. Bats are among the most gregarious mammals, with sometimes thousands of individuals of various species roosting communally. Despite numerous potential functional benefits of such mixed-species roosting groups, interspecific attraction has never been shown. To explore alternative explanations for mixed-species roosting, we studied roost selection in a speciose neotropical understory bat community in lowland rainforest in Costa Rica. Long term roost data were recorded over 10 years in a total of 133 roosts comprising both natural roosts and structurally uniform artificial roosts. We modelled bat roost occupancy and abundance in each roost type and in forest and pasture habitats to quantify the effects of roost- and environmental variability. Results: We found that bat species presence in natural roosts is predictable from habitat and structural roost parameters, but that the presence and abundance of other bat species further modifies roost choice. One third of the 12 study species were found to actively associate with selected other bat species in roosts (e.g. Glossophaga commissarisi with Carollia sowelli). Other species did not engage in communal roosting, which in some cases indicates a role for negative interspecific interactions, such as roost competition. Conclusions: Mixed-species roosting may provide thermoregulatory benefits, reduce intraspecific competition and promote interspecific information transfer, and hence some heterospecific associations may be selected for in bats. Overall, our study contributes to an improved understanding of the array of factors that shape diverse tropical bat communities and drive the dynamics of heterospecific grouping in mammals more generally. [ABSTRACT FROM AUTHOR]

Predator behaviour and population numbers can be determined by many factors such as prey availability, individual and habitat characteristics, and intraspecific or interspecific factors. Using satellite telemetry, we measured home range size in 3 individuals of Red Kites (Milvus milvus) in three consecutive winters to document the pattern of spatial responses to increasing availability of its dominant prey, the Common Vole (Microtus arvalis), in the Břeclav District, Czech Republic. Starting with winter 2017/2018, we found that the home range sizes decreased in winter 2018/2019 when the index of vole population density increased from 678 burrow entrances in autumn 2017 to 1414 burrow entrances per hectare in autumn 2018. Home range sizes did not change in winter 2019/2020 in spite of the further increase in vole population density up to 6673 entrances per hectare in autumn 2019. Based on censuses at 5 communal roosts in January 2018, 2019, and 2020, we documented the pattern of numerical responses to increasing availability of voles. Numbers of wintering Red Kites did not respond to growing vole densities until they reached the highest level in autumn 2019, suggesting that the response of wintering numbers was delayed by 1 year compared to that in home range. Our study thus provides empirical support for the spatial and numerical responses of Red Kites to prey availability and suggest that these responses may differ in sensitivity to increases in vole density, being triggered at different periods of the vole population cycle. [ABSTRACT FROM AUTHOR]

Background: Communal roosting is a common avian social behaviour, which potentially provides foraging benefits, predation avoidance or thermoregulation in birds. To identify the crucial environmental factors associated with roost site selection, most studies have focused on the comparison of physical characteristics between roosts and non-roosts. However, the differences among roosts have usually been neglected and the causes of roost switching have seldom been investigated. Methods: To explore the variations among roost sites and assess the most influential environmental factors related to seasonal roost switching, we conducted a 105-day observation on an introduced population of critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) in an urban environment in Hong Kong from 2014 to 2016. We identified seven roost sites that were occupied in different seasons and then measured their microhabitat characteristics in terms of land use types, human disturbance and microclimate temperature. To quantify these differences, we used Pearson's chi-squared test, partial least squares determinant analysis (PLS-DA) and one-way repeated measures ANOVA, respectively. Results: Our results distinguished roost sites occupied in three seasons, i.e. spring, summer and winter roosts, using several microhabitat characteristics. The land use types were significantly associated with roosts, where spring roosts were usually located in tree-dominated areas, which are the major feeding grounds. The discriminant analysis on human disturbance variables indicated that summer roosts were positively associated with night illumination. The microhabitat temperatures of winter roosts were significantly higher than those of most other roosts on cold nights. Conclusions: The results highlighted significant variations among roosts, and seasonal roost switching was likely driven by specific microhabitat characteristics of each roost site, such as microclimate. It also helps us understand the behavioural adaptation of birds to urban environments. [ABSTRACT FROM AUTHOR]

Present paper describes the communal roosting of the widely inhabiting four passerine species in Faisalabad. It is regular among birds' and provides significant vision to the evolution, conservation, thermoregulation, enhanced foraging and vigilance against predation. Observations were consecutively conducted in the four closely located roosts in the selected agro-ecosystem of Faisalabad for the 20-minutes time intervals for four hours in the morning. Occurrence of trees as Salmalia malabarica (DC), Dalbergia sissoo (Roxb) Ficus bengalensis (Linn.), Terminalia arjuna (Roxb.), Eugenea cumini (Linn.) Cedrella toona (MR) and Eucalyptus (LH) species served as main roosts for four passerines. For roost one, in all 39 (±0.37) different trees, 188 (±1.89) total number of cavities, 108 (±1.80) productive nests and 20.19 (±0.39) nests per tree were recorded. Concurrently, from three other roosts, similar numerical counts were also made. Roost behaviour of all four birds was also determined. All of the birds depicted varying numbers of short flights, the calls, mobbing, roost exits and returns and breeding scuffles. Seemingly, the short flights and roost exits were apparent regarding the early intervals. Overall, roosting habits were important for all the birds' in their diurnal activities and for achieving the improved sustainability and endurance in the agro-ecosystems. [ABSTRACT FROM AUTHOR]

MASS CONCENTRATIONS of birds, or the lack thereof, is a phenomenon of great ecological and domestic significance. Apart from being and indicator of, e.g., food availability, ecological change, and population size, it is also a source of conflict between humans and birds. By attracting the attention of the public--either as a spectacular phenomenon or as an unwelcome pest--they also form the public perception of birds and their abundance. In the context of the mass concentration of Bramblings Fringilla montifringilla in Sweden during the winter 2019-2020, this work reviews the literature on this striking phenomenon. I found that winter roosts amount to about one million birds per hectare of roost area, but the variation between reports is significant. There is support for roosts of up to around 15 million Bramblings, but much larger numbers are frequently cited in the literature. I discuss difficulties related to the assessment of mass concentrations, and argue that reports of very large numbers should always be carefully scrutinized. [ABSTRACT FROM AUTHOR]

The behaviour of birds to settle or rest at a place at specific times of day and night is called roosting. Some birds prefer solitary roosting while others roost communally. The Communal roosting behaviour of Egyptian vulture was studied in five districts (Sambhal, Lakhimpur Kheri, Aligarh, Bareilly and Faizabad) of Uttar Pradesh, India from January 2014- December 2017. Total count was conducted at roosting sites in all the seasons (summer, winter and monsoon). The maximum number of individuals counted at the roost site was in Sambhal followed by Lakhimpur Kheri, Aligarh, Bareilly, Faizabad. Four different roost substrates were identified: Ground, tree, building, and electric pylon. A maximum (63%) of Egyptian vultures were observed roosting on the ground, followed by electric pylon (19%), tree (10%) and minimum on building (8%). The present study confirmed that Egyptian vultures are communal roosters and a number of roosting individuals most probably depended on the availability of food of the area. Egyptian vultures are globally endangered species and so far no work has been done on their roosting behaviour in India; therefore the present study will prove beneficial to plan for their conservation strategies. [ABSTRACT FROM AUTHOR]

We investigated the ontogenetic changes of two call types, the inquiry call and the response call, which comprise an interactive communication system in Spix's disc-winged bats, Thyroptera tricolor. We documented structural changes on both inquiry and response calls during ontogeny by recording single individual vocalizations in a flight cage and triggering response calls with playbacks of adult inquiry calls. Most ontogenetic changes in response calls were sex dependent. In addition, individuality was high for both call types across age categories. Despite the observed changes during development, both call types resembled the structure of adult calls from early ontogenetic stages, suggesting little influence of social learning in call development. Finally, we found sex dependent ontogenetic changes and high levels of individuality of calls early in life, which may indicate additional functionality in sex and pup recognition. Overall, the findings bring novel insight into the complex developmental process of the call types comprising the communication systems of Spix's disc-winged bats, and contribute to a better understanding of signal development in complex social communication systems. • Both inquiry and response calls showed ontogenetic changes during maturation. • Calls seemed to be functional since early stages. • Most ontogenetic changes in response calls were sex dependent. • Calls show high levels of individuality early in life. [ABSTRACT FROM AUTHOR]

The article presents the discussion on long-eared owls (Asio otus) frequently inhabiting human altered landscapes including residential areas in cities. Topics include pellet analyses usually documenting a very low proportion and occasional rather than regular occurrence of birds in the owls' diet; and owls wintering in cities usually hunting outside the settlements in grasslands, agricultural areas, or shrubby habitats.

This study describes the relationship between Helmeted Guineafowl Numida meleagris and invasive alien trees on livestock and maize farms south-east of Johannesburg, Gauteng province, South Africa. The dependence of the birds on alien trees affects strategies for the removal of these trees. During June to December 2014, Helmeted Guineafowl were recorded weekly on maps along a 42 km transect. Since Helmeted Guineafowl live in cohesive social groups of 15-20 birds, they roost communally in one or two trees during winter rather than spreading across an entire tree grove. The distribution of alien trees across the landscape in patches has enabled Helmeted Guineafowl flocks to reach new feeding patches near to roosting trees, as old feeding patches are depleted. One Helmeted Guineafowl flock of 15-20 birds requires ∼0.09 ha covered with mature alien trees for roosting. Suggestions are presented relating to the reduction of alien trees in compliance with the Conservation of Agricultural Resources Act 43 of 1983 and conservation of Helmeted Guineafowl. [ABSTRACT FROM AUTHOR]

Presentamos las tendencias y las características de un dormidero comunal pre-migratorio de Falco naumanni en la ciudad de Ioannina (Noroeste de Grecia), así como las zonas de campeo que usa la especie en este período. Durante los 15 años que duró el estudio, se registró un número máximo de 3500 individuos, concretamente en los años 2003 y 2004. Los dormideros se encuentran exclusivamente en ejemplares maduros de Platanus orientalis ubicados a orillas del lago Pamvotida, mientras que las zonas de campeo están en praderas alpinas a más de 34 km de los dormideros. En base al uso de un modelo de regresión logisitica binaria se puede predecir la presencia o ausencia de la especie en relación con la abundancia de ortópteros en la zona. Es vital la protección de los dormideros comunales y de las zonas de campeo durante la época de pre-migración para la conservación de la especie. [Traducción de Victoria Saravia editada] [ABSTRACT FROM AUTHOR]

Thermal benefits from clustering during the reproductive period are assumed to explain the almost ubiquitous group living behaviour in female temperate zone bats. While there is evidence for such benefits in adult female bats in the field, to our knowledge no studies have quantified the thermal benefits of clustering in juvenile, non-volant bats. Using thermography, we assessed in the field (1) whether juvenile Bechstein's bats thermally benefitted from clustering during the absence of adult females at night; and (2) whether the regular nightly visits of adult females led to an increase in juveniles’ skin temperatures. We show that the juveniles did indeed thermally benefit from clustering when their mothers were absent. With increasing age, clustering juveniles experienced lower heat loss during the absence of adult females. Also the influence of roost temperatures on the juveniles’ skin temperature decreased when they became older, indicating improved thermoregulation abilities. We also observed a small, although significant increase in the juveniles’ surface skin temperature after visits by adult females. In conclusion, our study provides evidence that clustering at night is advantageous for non-volant juvenile bats, because it improves their thermoregulation at times when mothers are not present in the communal roost. [ABSTRACT FROM AUTHOR]

Intensive dairy farming has changed the agricultural grassland areas of The Netherlands profoundly, with negative impacts on the reproduction of the shorebirds breeding there. This modern agricultural landscape also forms a staging site for migrating shorebirds, where they moult and replenish fuel stores, but staging performance in these areas has received much less attention. We studied northbound migrating Ruffs Philomachus pugnax staging in the grasslands of southwest Friesland over a ten year period, during which peak numbers declined from 20,000 in 2003 to 3500 birds in 2009 and then stabilized. On the basis of resighting locations of individually marked birds, we describe changes in their day-time foraging distribution from spring 2006 to spring 2013. Ruffs progressively retreated to the centre of the c. 10,000 ha study area, where, among intensive grasslands, established and newly created inland wetlands occurred that served as feeding and/or roosting sites. To quantify the spatial changes, in 2013 we repeated a transect survey of meadow use carried out earlier in 2003. Using similar characteristics of individual meadows in terms of herb richness (a measure of agricultural intensity) and landscape characteristics (distance to the roost, soil type), we show that, during spring 2013, as in 2003, Ruffs foraged preferentially on meadows close to roosting areas. The survey also highlights the preference of Ruffs for the Workumerwaard, a particularly large and open polder with a sandy soil and short vegetation bordered by a traditional roosting area on the shoreline. This study provides some evidence that inland wetlands may increase the attractiveness for migrating Ruffs of landscapes dominated by modern grasslands. [ABSTRACT FROM AUTHOR]

Artificial aquatic habitats are ubiquitous in anthropogenic landscapes and highly susceptible to colonization by invasive plant species. Recent research into the ecology of infectious diseases indicates that the establishment of invasive plant species can trigger ecological cascades which alter the transmission dynamics of vector-borne pathogens that imperil human health. Here, we examined whether the presence or management of two invasive, emergent plants, cattails ( Typha spp.) and phragmites ( Phragmites australis), in stormwater dry detention basins (DDBs) alter the local distribution of vectors, avian hosts, or West Nile virus (WNV) transmission risk in an urban residential setting. Mosquitoes and birds were surveyed at 14 DDBs and paired adjacent residential sites. During the study period, emergent vegetation was mowed by site managers in three DDBs. In the absence of vegetation management, the overall abundance and species composition of both adult vectors and avian hosts differed between residential and DDB habitats; however, WNV entomological risk indices were equivalent. Communal bird roosts composed primarily of three species, European Starlings ( Sturnus vulgaris), Red-winged Blackbirds ( Agelaius phoeniceus), and Common Grackles ( Quiscalus quiscula), representing a broad range of WNV reservoir competence, were observed at half (three out of six) of the DDBs containing unmanaged stands of phragmites; however, their presence was associated with a lower seasonal increase in vector infection rate. Conversely, mowing of emergent vegetation resulted in a significant and sustained increase in the abundance of WNV-infected vectors in DDBs and the increase in risk extended to adjacent residential sites. These findings indicate that management of invasive plants in DDBs during the growing season can increase, while presence of communal bird roosts can decrease, WNV transmission risk. [ABSTRACT FROM AUTHOR]

Studies on the use of aggregation sites, or communal roosts, found that these roosts have high stability but that individuals will migrate to other sites when the original site is disturbed or otherwise no longer suitable. In this study, the aggregation dynamics of groups of Periplaneta americana were examined without interruption for 5 days and 4 nights. Our results showed that groups inside an undisturbed aggregation site presented stable group personalities and choice in aggregation site. The individuals that were aggregated in a site that was repeatedly disturbed by a lighting stimulus during their resting period not only exhibited stability in their group personalities but also a resistance to the disturbance, which allowed the initial aggregation site to remain the site of choice for a few days. Regarding the group personalities, we showed that the groups had distinct personalities with respect to the total amount of time spent outside of aggregation sites and at the sources during their active period and the time spent sheltered during their resting period. For the reaction to the disturbances, we found that the groups showed distinct personalities between the fraction that fled and the fraction that migrated to the undisturbed site. Our study also showed that although the disturbances were strong enough to trigger fleeing behaviour and induce migration to an undisturbed shelter site, the disturbance did not influence the group's global activity rhythm. [ABSTRACT FROM AUTHOR]

Rainbow lorikeets ( Trichoglossus haematodus) have successfully adapted to urban environments and are today abundant in many Australian cities. Here they often form noisy communal roosts and may damage infrastructure. While extensive studies on problem birds (mainly passeriforms) and their roosts have been conducted in other parts of the world, no detailed studies exist in Australia, where non-passeriform birds (e.g. parrots) can cause problems. This study investigates the roosting preferences of rainbow lorikeets in Sydney (Australia) and establishes the site characteristics that typify these roosts. Lorikeets preferred three exotic tree species, namely the plane tree ( Platanus spp. including Platanus x hybrida), Canary Island palm ( Phoenix canariensis) and Norfolk Island pine ( Araucaria heterophylla). They were also common in brush boxes ( Lophostemon confertus), a tree native to Queensland, Australia. Rainbow lorikeets commonly roosted in tall trees with thick trunks and medium density foliage and the trees next to their roost trees were of the same species. Roosting trees were often in areas of high anthropogenic disturbance and close to streetlights. [ABSTRACT FROM AUTHOR]

The benefits of communal roosting are unlikely to be acquired equally by all roosting birds, and it has been suggested that individual ordering during roost formation can be determined by factors such as social status. However, to date there have been no published data on this issue among precocial, cooperative breeders. We examined social ordering of roosting by buff-throated partridgesTetraophasis szechenyii, a typical cooperative breeding Galliform species newly found where group members roost in a linear huddle. We revealed that the breeding male was normally the first to enter roosting trees and a helper entered last, regardless of whether groups had young or not (n = 50 observations from seven groups). In a linear huddle, a helper frequently occupied the outermost position, especially in groups with young, and young birds were often squeezed into the center (n = 48 observations from seven groups). For buff-throated partridges, we suggest that while structuring of communal roosts confers the greatest energy benefits and protection from predators to young birds, helpers, rather than the breeding male, may face higher costs in terms of lookout and thermoregulation. To further understand social ordering of roosting by buff-throated partridges, future studies need to examine quantitatively the relative value of predation risk and/or thermoregulatory costs among roosting members placed in certain ordering, and determine the relatedness indices among group members. [ABSTRACT FROM AUTHOR]

Aposematic passion-vine butterflies from the genus Heliconius form communal roosts on a nightly basis. This behaviour has been hypothesized to be beneficial in terms of information sharing and/or anti-predator defence. To better understand the adaptive value of communal roosting, we tested these two hypotheses in field studies. The information-sharing hypothesis was addressed by examining following behaviour of butterflies departing from natural roosts. We found no evidence of roost mates following one another to resources, thus providing no support for this hypothesis. The anti-predator defence hypothesis was tested using avian-indiscriminable Heliconius erato models placed singly and in aggregations at field sites. A significantly higher number of predation attempts were observed on solitary models versus aggregations of models. This relationship between aggregation size and attack rate suggests that communally roosting butterflies enjoy the benefits of both overall decreased attack frequency as well as a prey dilution effect. Communal roosts probably deter predators through collective aposematism in which aggregations of conspicuous, unpalatable prey communicate a more effective repel signal to predators. On the basis of our results, we propose that predation by birds is a key selective pressure maintaining Heliconius communal roosting behaviour. [ABSTRACT FROM AUTHOR]

The article presents a study on the White-tailed Kite's (Elanus leucurus) winter diet and communal roosting behavior in an agricultural habitat on the Argentine pampas from 2006-2008. Conducted during austral winters from May to July, the study observed an average of 11 kites gathered in a tall, dead and leafless Eucalyptus viminalis before roosting in to more densely foliated trees. Their diet consisted of small mammals, mainly Calomys sp. and Akodon azarae. Further studies are suggested to improve knowledge on their feeding behavior during winter.

Several Heliconius L. butterflies species form nocturnal aggregations in sites with a particular architecture. Roosts are usually formed under relatively dense vegetation mats where dry vines or branches provide a perch for the night. These sites may last for months. To understand the importance of factors related to the expression of Heliconius roosting, data on light, temperature, relative humidity, wind, and use of wing color cues were recorded at H. erato and H. sara roost sites in Costa Rica and Panama in 2008 and 2009. The results show that roost sites offer reduced light conditions at dusk, provide a drier environment compared with its vicinity, and offer protection from wind and rain. Moreover, individuals use wing color recognition under reduced light conditions at dusk to successfully assemble aggregations. These findings provide key information for future experiments to study the use of landmarks, hygrosensitivity, and dim-light eye adaptations in Heliconius navigation to find roost sites. [ABSTRACT FROM AUTHOR]

Avian time–activity budgets are known to be affected by many environmental factors. The aim of this study was to examine whether roosting times of common ravens Corvus corax are affected by inclement weather conditions in response to increased energy demands. The study was conducted at a communal roost of ravens in Thuringia, Germany, from August 2003 to January 2005. The number of roosting ravens fluctuated substantially, ranging from zero individuals in summer to 574 in winter. During the entire study period, a composting facility served as the main feeding ground for roosting ravens. There, the feeding-to-resting ratio did not depend on flock size, indicating the ravens were not food limited. Ravens arrived at the preroost and the roost later relative to sunset on cloudless evenings and on days with shorter length of daylight. Weather conditions measured as ambient temperature, wind speed, and cumulative daily precipitation had no effect on arrival times at the preroost and the roost. Likewise, moonlight did not affect roosting times. Apparently, flexible time–activity budgets resulting from a superabundant food supply may have enabled ravens to moderate the effects of environmental conditions on arrival times at the preroost and the roost. [ABSTRACT FROM AUTHOR]

Mousebirds (Coliiformes) exhibit well-developed communal roosting behaviour as well as a pronounced capacity for facultative hypothermic responses. We recorded body temperature (Tb) in speckled mousebirds (Colius striatus) under semi-natural conditions in outdoor aviaries, and examined interactions between behavioural and metabolic thermoregulation by experimentally manipulating food availability and communal roosting behaviour. When food was available ad libitum, mousebirds roosting in a cluster maintained approximately constant rest-phase Tb, with 32°C < Tb < 42°C. By contrast, rest-phase Tb in single mousebirds decreased at 0.5°C/hr and minimum rest-phase Tb was significantly lower than when clustering. When food availability was restricted, the mousebirds exhibited facultative hypothermic responses that were less pronounced in clustering groups (minimum rest-phase Tb = 33.3°C, circadian amplitude of Tb = 9.5°C) compared to single birds (minimum rest-phase Tb = 30.7°C, circadian amplitude of Tb = 11.8°C). When clustering, rest-phase Tb was highly synchronized among individuals. Our data reveal that communal roosting has profound consequences for rest-phase thermoregulation in C. striatus, and provide further insights into the potential role of physiological constraints in the evolution of avian sodality. [ABSTRACT FROM AUTHOR]

The function of the conspicuous pre-roost gathering in communally roosting birds is poorly known. We studied movement and social cohesion of radio-tagged hooded crows ( Corvus corone cornix) from their daytime location via pre-roost to roost in autumn and winter. With increasing snowfall the previous 24 h, the crows attended pre-roosts farther from the territory, and moved longer from pre-roost to roost. The crows became more likely to roost communally as distance to their territory increased. Attending a pre-roost on average almost doubled the travel distance to a communal roost. Crows were much more likely to join the same roost when they had attended the same pre-roost than otherwise. Breeding mates were more likely to keep together from pre-roost to roost than were other assigned pairs of a territorial male and female. For assigned pairs of non-mates, cohesion from pre-roost to roost decreased with increasing distance to roost, and was higher when both crows roosted communally compared to when at least one of them roosted in its territory. When both roosted communally, cohesion decreased with increasing snowfall and increasing number of crows attending the pre-roost, increased with increasing snow depth, and became higher among two females, compared to other combinations of two crows, with increasing number of crows attending the pre-roost. These patterns may be interpreted as supporting several of the current hypotheses on the function of pre-roost gathering. [ABSTRACT FROM AUTHOR]