Communal Roosts Research Articles

Probing into farmers' perceptions of a globally endangered ecosystem service provider.

Society's perception of ecosystem services is a key issue in conservation, particularly for endangered species providing services linked to human activities. Misperceptions may lead to wildlife-human conflicts with the risk of disappearance of the species involved. We contrasted farmers' perceptions with highly accurate quantitative data of an endangered vulture species, which provide ecosystem services. We combined surveys of 59 farmers with data from 48 GPS-tagged Canarian Egyptian vultures (Neophron percnopterus majorensis endemic to the Spanish Canary Islands) to disentangle factors influencing consistency between farmers' awareness of vulture occurrence on their properties and vulture behavior. Egyptian vultures were perceived as the main providers of scavenging services and the most beneficial avian scavenger. Consistency between farmers' perceptions (surveys) and vulture use of their farms (GPS data) was higher in the morning, in older males, and at farms with lower livestock numbers, located near vulture communal roosts, and visited more frequently by vultures. Our results underline the potential influence of modern livestock husbandry in disconnecting people from ecosystems, and how appreciation could be even lower for scarce or threatened ecosystem service providers.

American Kestrel Nonbreeding Roost Use and Behavior in South Texas

Roost sites are likely an important component of the American Kestrel's (Falco sparverius), kestrel(s) hereafter, nonbreeding habitat, as quality roost structures can provide thermal cover and protection from predators. We studied winter roost-site use by kestrels in an agricultural landscape in South Texas, where the population is composed of a combination of territorial wintering birds and migrating individuals passing through. Through observations of color-marked and unmarked birds, we identified 50 roost sites during September–March, 2014–2017. Kestrels utilized foliated shrubs and trees as roosting sites (n = 24), as well as various human-made structures (n = 26) including buildings, petroleum and farm equipment, and electrical structures for roost sites. Roost sites varied greatly in the level of concealment and exposure, with seven kestrels roosting on electric structures that allowed high levels of exposure to weather and potential avian predators. We observed aggression between kestrels around roost sites, and we documented small communal kestrel roosts. Because we observed roosting in sites exposed to weather and predators, aggression around roost sites, and communal roosting, we speculate that roosting sites suitable for kestrels may be limited or poorly dispersed in this agricultural landscape.

High ambient temperatures induce aggregations of chimney swifts Chaetura pelagica inside a roost

One proposed advantage of communal roosting in birds is a reduction in the costs of thermoregulation. As thermoregulatory benefits are directly linked to the distance between roosting birds, we examined whether temperature is related to inter‐bird spacing in roosting chimney swifts Chaetura pelagica. To test the hypothesis that huddling is used to reduce the costs of thermoregulation, we predicted that swifts would cluster more at colder temperatures. We mounted an all‐weather camera atop a 61 m tall industrial masonry chimney, one of the largest swift roosts in the study region. We deployed temperature loggers inside the chimney and obtained ambient air temperature from a nearby weather station. From 16 May–24 July 2013, we captured hourly images of the positions of roosting swifts at night. We used image analysis software to mark the angular positions of all roosting swifts, and calculated mean angles of orientation (preferred direction) inside the roost and the circular variance (i.e. the concentration of swifts around the mean angle). We used a Gamma regression to relate temperature inside and outside the roost to the clustering of swifts around the mean angle for 3 time periods (pre‐nesting, nesting, and post‐nesting). Converse to our prediction, swifts were closer together when ambient air temperatures were warmer in all periods (pre‐nesting (p < 0.001, n = 168), nesting (p < 0.001, n = 224), and post‐nesting (p < 0.001, n = 135)). Our findings suggest that swifts do not increase clustering intensity in response to colder temperatures, but instead they increase clustering intensity in response to the warmest ambient temperatures. This likely a metabolic response to reduced prey availability at higher temperatures and/or an attempt to reduce evaporative water loss. We suggest clustering may be used by chimney swifts as an energy saving mechanism during periods of lowered food availability.

Overwintering of West Nile virus in a bird community with a communal crow roost

In temperate climates, transmission of West Nile virus (WNV) is detectable rarely during the coldest months (late fall through early spring), yet the virus has reappeared consistently during the next warm season. Several mechanisms may contribute to WNV persistence through winter, including bird-to-bird transmission among highly viremic species. Here we consider whether, under realistic scenarios supported by field and laboratory evidence, a winter bird community could sustain WNV through the winter in the absence of mosquitoes. With this purpose we constructed a deterministic model for a community of susceptible birds consisting of communally roosting crows, raptors and other birds. We simulated WNV introduction and subsequent transmission dynamics during the winter under realistic initial conditions and model parameterizations, including plausible contact rates for roosting crows. Model results were used to determine whether the bird community could yield realistic outbreaks that would result in WNV infectious individuals at the end of the winter, which would set up the potential for onward horizontal transmission into summer. Our findings strongly suggest that winter crow roosts could allow for WNV persistence through the winter, and our model results provide synthesis to explain inconclusive results from field studies on WNV overwintering in crow roosts.

Structure and resilience of bald eagle roost networks

ABSTRACTThe recognition that communal roosts are important elements within the life cycle of bald eagles (Haliaeetus leucocephalus) led to their protection under the “disturb” clause of the Bald and Golden Eagle Protection Act. The regular roost‐switching movements of bald eagles imply that roosts are part of an interactive network where roosts represent nodes linked by birds moving between them. Network analysis holds promise for informing management decisions by assessing the effect of roost removal on the resilience of the broader network. We tracked nonbreeding bald eagles (n = 56) within the upper Chesapeake Bay (2008–2013), USA, to evaluate roost characteristics and network structure. We used midnight locations (n = 14,464) to assess the use of communal roosts (n = 212) and movement of birds among roosts (n = 2,634) on successive roost nights to evaluate the pattern and strength of connections. We performed a sensitivity analysis to assess the response of the roost network to roost loss. Structure of the roost network approximated that of a scale‐free network where the distribution of connections follows a power law of the form P(k) = Ak−γ and γ = 1.1. Unlike random networks, connections within scale‐free networks are concentrated within a few highly connected nodes (hubs). These hub roosts serve as bridges between large numbers of other roosts, have the shortest travel times to other roosts and greatest overall influence on network functioning. The effect of roost removal on overall network function was directly proportional to the connectivity of the roost being removed. The targeted removal of the majority (>90%) of roosts had very little effect on the network. Network sensitivity was high in response to the loss of roosts within the highest 10% of connectivity. This small (n = 18) subset of roosts makes a disproportionate contribution to network function and the protection of these roosts should be a stated management objective with high priority. Network analysis represents a powerful tool with the potential to inform management decisions. © 2018 The Wildlife Society.

Coronaviruses in guano from Pteropus medius bats in Peradeniya, Sri Lanka.

SummaryBats are a unique group of mammals well suited to be hosts for emerging viruses. With current rates of deforestation and urbanization, redistribution of bat habitats to urban and suburban areas may bring bats into closer contact with livestock and humans. Common flying fox, Pteropus medius (previously known as Pteropus giganteus), forms large communal roosts on treetops, often in close proximity to human habitation in Sri Lanka. This report describes the detection of coronavirus RNA in P. medius bat guano collected in Peradeniya, Sri Lanka. These viruses had >97% nucleotide identity with coronaviruses detected in Cynopterus sphinx, Scotophilus heathii and S. kuhlii bats in Thailand. Pteropus medius is widespread in Asia and appears to excrete group D coronaviruses, which are hitherto confined to bats; however, these findings may have public health implications in the future.

How sunrise and weather affect timing of rooks' (Corvus frugilegus) morning departure from the winter communal roost

The pattern of morning departure of rooks (Corvus frugilegus) from large communal roosts in winter is regular though it is affected by several environmental (weather) variables. A total of 151 records of the morning departure of rooks (and associated jackdaws, Corvus monedula) from two large communal roosts in the Czech Republic during the years 1966 to 1974 were analyzed. On average, the birds departed 36 min before local sunrise and 1.5 min after beginning of local civil twilight. Light intensity was the leading factor that explained 60 % of variability of the departure time. Cloud cover 30 min before sunrise, being interrelated with the light intensity at local sunrise, explained 52 % of the variability. Less important but significant factors were several weather variables such as precipitation, relative humidity of the air, horizontal visibility (fog), snow cover, and air temperature. Two best predictive multivariate regression models for timing of the birds' departure involved factors: light intensity (that accelerated the departure) or inter-related cloud cover before sunrise (it delayed the departure), precipitation (delaying the departure), snow cover (accelerating the departure due to increased food demand), and horizontal visibility (fog delayed the departure). The two predictive multivariate models explained together 75 % of variability of the birds' departure in relation to beginning of local civil twilight.

Trophic niche overlap among scavengers in Patagonia supports the condor-vulture competition hypothesis

SummaryAnimals that share resources tend to use different foraging strategies in order to decrease potential competition. Scavenging birds using the same nutritional resources can segregate into different space and time scales. However, it has been suggested that when the species do not co-evolve to achieve such segregation competition may result. Our aim was to study the trophic niche overlap between three species of obligate scavengers, the Andean CondorVultur gryphus, Turkey VultureCathartes auraand American Black VultureCoragyps atratus, which are the main avian consumers of carcasses in north-western Patagonia. Black Vultures arrived in the area relatively recently, have expanded their distribution following human activities, and have been suggested to compete with the threatened condor. We collected pellets in communal roosts of the three species to determine their diet, and to estimate the diversity (Shannon Index) and diet similarity (Pianka overlap index). We found that the Turkey Vulture has greater niche breadth and, apart from domestic livestock, it incorporates smaller items such as fish, reptiles and a great number of birds, carnivores and mice. Although the Black Vulture diet includes arthropods, they feed primarily on introduced ungulates, overlapping more with condor diet when roosting far from urban centres. As these latter two species share the same food resource, human activities that positively affect the abundance of the Black Vulture could increase competition among them, with possible implications for the conservation of the Andean Condor.

Herring Gulls (Larus argentatus) Depredate Chimney Swifts (Chaetura pelagica) at a Migratory Roost

ABSTRACT We describe a new predator-prey relationship between Herring Gulls (Larus argentatus) and Chimney Swifts (Chaetura pelagica) at a communal roost in Sault Ste. Marie, ON, Canada. In a season-long study in 2015, we document 38 instances of predation, an estimate which likely underestimates the extent of total predation pressure. Chimney Swifts were captured on-the-wing by Herring Gulls.

Dynamics in numbers of group-roosting individuals in relation to pair-sleeping occurrence and onset of egg-laying in European Bee-eaters Merops apiaster

Sleeping in the nest at the beginning of the breeding season is common for birds nesting in cavities. Here, we report evidence that European Bee-eaters Merops apiaster sleep in pairs in the nesting burrow. In 3.2% of the nest checks, we found two individuals sleeping together. This behaviour ceased once hatching started. A decrease in the number of birds at a communal roost coincided with the incidences of pair-sleeping and initiation of egg-laying. Thus, checking the burrows of European Bee-eaters at the beginning of the breeding season increases the chance of observing pair-sleeping.

Experimental test of the mechanism underlying sexual segregation at communal roosts of harvestmen (Prionostemma spp.)

AbstractClosely related, ecologically similar species often roost in distinctly different habitats, and roosting patterns also vary within species in relation to sex, age and season. The causes of such variation are not well understood at either a proximate or ultimate level. We studied communal roosting in two congeneric species of Prionostemma harvestmen at a rainforest site in Nicaragua. Previous research showed that Prionostemma sp. 1 forms male‐biased communal roosts in tree‐root cavities, while Prionostemma sp. 2 forms communal roosts of variable but temporally stable sex ratios on spiny palms. Here, we investigate potential mechanisms underlying variation in roosting site choice between and within these syntopic species. First, we present the results of a field experiment designed to probe the mechanism underlying skewed roost sex ratios in Prionostemma sp. 2. Previous studies have suggested that these harvestmen use conspecific scent to locate communal roosts and that new roosts can be established via group translocation. Therefore, to test the hypothesis that skewed roost sex ratios in this species arise from sex differences in scent marks, we translocated single‐sex groups of ca. 30 individuals to each of 20 previously unoccupied spiny palms. Female release sites attracted new recruits of both sexes, while male release sites attracted almost exclusively males. We infer that Prionostemma sp. 2 females preferentially roost in sites scent‐marked by females and that this mechanism is sufficient to explain the skewed roost ratios. Further adding to knowledge of Prionostemma roosting behavior, we show that Prionostemma sp. 1 forms female‐biased communal roosts on spiny palms, that some roosts contain both species, and that the species composition is stable on a time scale of at least 2 weeks. To the best of our knowledge, this study is the first experimental test of mechanisms underlying sexual segregation at communal roosts in any taxon.

Mapping bald eagle activity shadows around communal roosts

ABSTRACTWe assessed diurnal activity patterns associated with communal roosts (n = 26) by tracking nonbreeding bald eagles (Haliaeetus leucocephalus; n = 58) within the upper Chesapeake Bay, USA, 2008–2013. We used daytime locations (n = 54,165) to map activity shadows (using home range analytics, 90% kernel) around communal roosts, to evaluate the spatial structure and to delineate diurnal activity centers. We overlaid a range (100–3,200 m) of buffers around the perimeter of each roost to estimate the benefits of management scenarios in extending protection to daytime activities. Activity shadows around roosts varied from 1.5 km2 to 116 km2 ( = 30.3 ± 5.48 [SE]), reflecting landscape context. Roosts with small (<10 km2) activity shadows tended to have simple shapes with roosts centrally located and positioned along primary shorelines. Roosts supporting large (>50 km2) activity shadows tended to have complex shapes with roosts not centrally located and set back from primary shorelines. Daytime locations were highly concentrated in areas near communal roosts (76% of locations within 2 km of roost perimeters). Diurnal activity centers (n = 38) included areas surrounding roosts and secondary activity centers that were primarily located along prominent shorelines. Communal roosts play a more significant and multi‐faceted role in the eagle life cycle than we previously understood. Many of the roosts positioned along the shoreline provided resting places during the night and day, served as social gathering places during the day, and functioned as feeding locations. Evaluation of management buffers supports current management guidelines that recommend the establishment of 800‐m buffers. Establishment of 800‐m buffers within the study area would enclose 54% of all daytime locations, 66.7% of the area enclosed within activity centers associated with roosts, and 12.1% of the area enclosed in secondary activity centers. © 2017 The Wildlife Society.

Social foraging and individual consistency in following behaviour: testing the information centre hypothesis in free-ranging vultures.

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.

Avian torpor or alternative thermoregulatory strategies for overwintering?

It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (Pomatostomus superciliosus), which has characteristics related to a high probability of torpor use; it is a sedentary, insectivorous, cooperative breeding species, which we studied during winter in a temperate habitat. Wild, free-living babblers maintained normothermy overnight, even at sub-zero ambient temperatures, with a mean minimum body temperature of 38.5±0.04°C that was independent of minimum black bulb temperature. Physiological variables measured in the laboratory revealed that babblers had a low basal metabolic rate and evaporative water loss, but their body temperature and thermal conductance were typical of those of other birds and they had a typical endothermic response to low ambient temperature. Huddling yielded significant energy savings at low temperatures and a roost nest created a microclimate that buffered against low temperatures. Low basal energy requirements, communal roosting and the insulation of a roost nest confer sufficient energetic benefits, allowing babblers to meet energy requirements without resorting to heterothermia, even in their depauperate, low-productivity landscape, suggesting that passerine birds use alternatives to torpor to balance their energy budgets when possible.

Seed dispersal distributions resulting from landscape‐dependent daily movement behaviour of a key vector species,Anas platyrhynchos

SummaryDispersal via animals (zoochory) is a primary mechanism for seed exchange between habitat patches. Recent studies have established that many plant species can survive waterbird gut passage. To quantify the patterns and consequences of waterbird‐mediated dispersal, information on ingestion and gut passage must be combined with bird movement data. Such analysis has recently revealed seed dispersal kernels by migrating waterbirds. However, since many waterbird populations are largely resident, and migrating populations spend only a minor part of the main dispersal season (autumn–winter) on active migration, daily regional‐scale movements probably cause more frequent dispersal.We synthesized high‐resolution empirical data on landscape‐scale movements and seed gut passage times in a key disperser species, the mallard (Anas platyrhynchos), using a spatially explicit, mechanistic model to quantify dispersal distributions resulting from daily autumn–winter movements. We evaluated how landscape composition and seed traits affect these dispersal patterns.The model indicates that mallards generate highly clumped seed deposition patterns, dispersing seeds primarily between core areas used for foraging and resting. Approximately 34% of all dispersed seeds are transported to communal roost areas, which may function as reservoirs for mallard‐dispersed species, and 7% are transported between foraging areas. Landscape‐dependent movement patterns strongly affect the dispersal distributions, resulting in multi‐modal dispersal kernels, with dispersal distances increasing with fragmentation of freshwater foraging habitat. Seed size‐related gut retention times determine the proportion of seeds being dispersed away from the ingestion area, with larger seeds (20 mm3) having a 8–10% higher potential for long‐distance dispersal than smaller seeds (0·2 mm3), if surviving gut passage. However, twice as many small seeds will finally accomplish long‐distance dispersal due to their higher gut passage survival.Synthesis. Firstly, this study reveals how seed dispersal patterns resulting from daily waterfowl movements are shaped by landscape‐dependent differences in movement patterns. Secondly, seed survival appears more important than retention time in determining the scale of long‐distance dispersal by non‐migrating mallards. We conclude that the frequent flights of staging waterbirds result in directed dispersal over distances inversely related to wetland availability, indicating that they maintain landscape connectivity across a range from wet to increasingly dry landscapes.

High warning colour polymorphism inHeliconiushybrid zone roosts

1. Communal roosting behaviour has been documented among a wide range of taxa, particularly among groups of butterflies that display warning colourations. These aggregations of conspecifics and/or other species that share mimetic warning colour patterns can have a large impact on predator learning, and thus the survival of an aposematic form. Yet there has been limited investigation of communal roosting within areas where new and diverse warning colour forms are generated, such as hybrid zones. 2. Here, roosting behaviour was examined in a Heliconius erato hybrid zone in French Guiana between races with divergent warning colourations on their wings. In this hybrid zone, native individuals with nine distinct warning colourations, as well as individuals with altered forms that are not native in the French Guiana population, were marked and observed to determine if divergently coloured individuals participated in communal roosting, and if the proportions of colour pattern forms at roosts differed from the proportions that are found in the population. 3. The results demonstrated that divergently coloured individuals of the same species, including altered, non-native forms, will readily and repeatedly participate in nocturnal communal roosting, often with extreme fidelity to specific perch locations. 4. These findings suggest that roosts composed of polymorphic warning patterns may be common in phenotypic transition zones, which could have major implications on predator training and selection dynamics in hybrid zones.

Energetics of communal roosting in chestnut-crowned babblers: implications for group dynamics and breeding phenology.

For many endotherms, communal roosting saves energy in cold conditions, but how this might affect social dynamics or breeding phenology is not well understood. Using chestnut-crowned babblers (Pomatostomus ruficeps), we studied the effects of nest use and group size on roosting energy costs. These 50 g cooperatively breeding passerine birds of outback Australia breed from late winter to early summer and roost in huddles of up to 20 in single-chambered nests. We measured babbler metabolism at three ecologically relevant temperatures: 5°C (similar to minimum nighttime temperatures during early breeding), 15°C (similar to nighttime temperatures during late breeding) and 28°C (thermal neutrality). Nest use alone had modest effects: even for solitary babblers at 5°C, it reduced nighttime energy expenditures by <15%. However, group-size effects were substantial, with savings of up to 60% in large groups at low temperatures. Babblers roosting in groups of seven or more at 5°C, and five or more at 15°C, did not need to elevate metabolic rates above basal levels. Furthermore, even at 28°C (thermoneutral for solitary babblers), individuals in groups of four or more had 15% lower basal metabolic rate than single birds, hinting that roosting in small groups is stressful. We suggest that the substantial energy savings of communal roosting at low temperatures help explain why early breeding is initiated in large groups and why breeding females, which roost alone and consequently expend 120% more energy overnight than other group members, suffer relatively higher mortality than communally roosting group mates.

Overview of occurrence of the Short-eared Owl Asio flammeus between 1995 and 2015 in Slovenia and its probable breeding in irruptive year 2008

Abstract Between 1995 and 2015 the number of records of Short-eared Owl Asio flammeus in Slovenia increased drastically, especially after 2007, but the species occurred regularly every year since 2002. Before that, the Short-eared Owl was regarded as a very rare migrant in Slovenia. Most of the observations were from wintering and migration periods, and the most important areas for the species in Slovenia were Ljubljansko barje, Lake Cerknica, surroundings of the water reservoir Medvedce and coastal wetlands. In 2008 and 2013 the Short-eared Owl occurred in large numbers, and these years were regarded as irruptive. Flocks of 2 to 8 birds were observed. At Ljubljansko barje, increased numbers of observed Short-eared Owls coincided with a large population of small mammals (species of the genus Apodemus and Microtus) and poor snow cover in 2008, and at least three communal roost sites were found that year. In the irruptive year 2013 there was a greater number of Short-eared Owls observed at the Medvedce water reservoir. On the plain at Lesce near the village of Smokuč an injured second year female was found at the end of March 2008 with a developing brood patch in its initial stage. It is likely that the female attempted to nest, which confirms the status of the species as occasional breeder in Slovenia. The last confirmed breeding in Slovenia was recorded in 1936 at Ljubljansko barje. In addition to local conditions (population of small mammals, snow cover) the frequency of occurrence of the Short-eared Owl in Slovenia is also affected by the population of development in the Boreal region and changes in migratory characteristics of the species in Europe. Therefore, an increase of the number of Short-eared Owls in Slovenia is expected in the future, as well as breeding attempts by this nomadic owl in seasons with high populations of small mammals and green winters, of course, if appropriate meadow habitat is still preserved.

Cold and alone? Roost choice and season affect torpor patterns in lesser short-tailed bats.

Seasonal changes in weather and food availability differentially impact energy budgets of small mammals such as bats. While most thermal physiological research has focused on species that experience extreme seasonal temperature variations, knowledge is lacking from less variable temperate to subtropical climates. We quantified ambient temperature (T a) and skin temperature (T sk) responses by individuals from a population of New Zealand lesser short-tailed bats (Mystacina tuberculata) during summer and winter using temperature telemetry. During summer, communal roosts were more thermally stable than T a. During winter, solitary roosts were warmer than T a indicating significant thermal buffering. Communal roost trees were used on 83% of observation days during summer, and individuals occupying them rarely entered torpor. Solitary roosts were occupied on 93% of observation days during winter, and 100% of individuals occupying them used torpor. During summer and winter, bats employed torpor on 11 and 95% of observation days, respectively. Maximum torpor bout duration was 120.8h and winter torpor bout duration correlated negatively with mean T a. Torpor bout duration did not differ between sexes, although female minimum T sk was significantly lower than males. The summer Heterothermy Index varied, and was also significantly affected by T a. Mean arousal time was correlated with sunset time and arousals occurred most frequently on significantly warmer evenings, which are likely associated with an increased probability of foraging success. We provide the first evidence that torpor is used flexibly throughout the year by M. tuberculata, demonstrating that roost choice and season impact torpor patterns. Our results add to the growing knowledge that even small changes in seasonal climate can have large effects on the energy balance of small mammals.

Communal roosting, thermoregulatory benefits and breeding group size predictability in cooperatively breeding sociable weavers

Extreme temperatures impose energy costs on endotherms through thermoregulation and different adaptations help individuals to cope with these conditions. In social species, communal roosting and huddling are thought to decrease the energetic requirement of thermoregulation under low temperatures. This is likely to represent an important mechanism by which individuals save energy during the coldest parts of the year and hence to represent a non‐breeding benefit of sociality. Here, we investigate the potential thermoregulatory benefits of group living in roosting groups of sociable weavers Philetairus socius, a colonial cooperatively breeding passerine that builds communally a massive nest structure with several independent chambers wherein individuals breed and roost throughout the year. To investigate the benefits of sociality during the non‐breeding season, we studied the thermal environment during roosting in relation to group size. In addition, to understand the link between non‐breeding and breeding sociality in this species we studied group size stability between the pre‐breeding and breeding periods. As expected, we found that the nest chamber's night‐time temperature is strongly related to the number of birds roosting together, especially during cold nights. Specifically, birds in larger groups spent less time below the critical thermal minimum temperature (i.e. the temperature below which energy expenditure increases substantially). They were less exposed to external temperature variations. We also found a positive relationship between the number of birds roosting during winter and the breeding group size, indicating breeding group size predictability. In cooperative breeders such as the sociable weaver, the costs and benefits of sociality are usually studied during the breeding period. This study shows that a better understanding of non‐breeding benefits of group membership and group dynamics between the non‐breeding and breeding periods are necessary for a comprehensive understanding of the benefits of sociality.