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Communal roosting is a well-known phenomenon among numerous species of corvid (family Corvidae) worldwide. Surprisingly, in Australia this behaviour occurs only in certain urban populations of two species, and is unknown in any of the five native corvid species living away from urban areas. We studied the communal roosting behaviour of Torresian crows (Corvus orru) in the suburbs of Brisbane, Queensland, Australia, by following six radio-tagged birds and by observing in detail the activities of crows as they departed and arrived at focal roosting trees. Several hundred birds were found to use the roosts on most nights, although there was clear seasonal variation; highest numbers were noted during the autumn and lowest were in spring. Radio-tagged adult birds tended to use the same roost regularly, while juveniles were far less faithful to a particular tree. Roosting behaviour was significantly influenced by cloud cover and temperature and the location of suitable pre-roost gathering sites. We were unable to determine why urban Torresian crows formed large roosting groups but our data did not support the information centre hypothesis.

Aerial vertebrate foragers, e.g. insectivorous bats, martins and swallows, often show gregarious behavior such as colonial breeding, communal roosting and aggregating behavior during foraging. Studies of gregariousness in aerial foragers have mostly focused on colonial breeding or communal roosting, and only a few intensive studies have dealt with gregariousness during foraging. Here, we report on large and stable aggregations of barn swallows, Hirundo rustica, observed during daytime after the breeding season in Japan. Relatively large aggregations of 20 or more birds were located around poultry, pig and cattle farms and mounds of manure. The aggregations were stable in size both within-days and between-days. Their activities consisted only of repeated cycles of foraging and resting around the farms where their prey, the large black soldier fly Hermetia illuceus (>10 mm) and other medium (5–10 mm) flies, was dense. Distributions of swallows around the farms overlapped with the distributions of prey, and the size of the aggregations significantly correlated with the abundance of prey.

Between 1975 and 2000, 4,525 sightings of wintering bald eagles (Haliaeetus leucocephalus) were recorded at Mormon Lake in northern Arizona. Numbers of wintering eagles fluctuated little in the 20 years from 1975 through 1994 (5.5 ± 3.0 mean sightings per day). However, during the winters of 1995 through 1997 local record highs of 59 to 118 eagles increased mean sightings per day to 22.4 ± 9.6. This dramatic population increase led to a major change in social behavior favoring consistent communal roosting; maximum roost counts of 2 to 8 eagles scattered among 11 roosts in prior years shifted to maximums of 33 to 45 eagles regularly using 2 roosts during 1996 and 1997. Winter population averaged 58% adults and 42% immatures, but during 5 recent years of greatest numbers (≥40 eagles in 1989, 1995 through 1997, and 2000), the proportion of immatures increased to 58%. Local increases in the wintering eagle population at Mormon Lake were largely attributable to this greater proportion of immature bald...

The debate over whether communal nests and roosts function primarily as information centers (they facilitate the sharing of foraging information) remains unresolved. Here I use evolutionary game theory to investigate the relative importance of this influential hypothesis and an alternative: that roosts, in particular, function as recruitment centers (they facilitate aggregation at food patches). Basing my model on juvenile common raven (Corvus corax) behavior, I assume there is no net cost to being at food patches in groups, and foragers roost communally. Moreover, one strategic outcome is the observed raven behavior: individuals search independently and recruit from the roost once a patch is found (they play Search-and-Recruit, or SR). I investigate the stability of this in two scenarios that differ in the magnitude of the lost opportunity costs to mutants playing SR in populations of other strategies. When these costs only involve a chance of not being in a group at a located carcass, SR is the only evolutionarily stable strategy under all conditions. However, when these costs also include missing opportunities to be socially dominant, SR no longer enjoys exclusive dominance in the strategy set. Nevertheless, in both cases, there are conditions where group foraging benefits have no effect on the evolutionary stability of SR. Thus, contrary to assertions in the literature, the opportunity to share foraging information can be sufficient to drive the evolution and maintenance of recruitment to food from communal roosts. However, I conclude that both information and grouping benefits are likely to underlie communal roosting behavior in my focal system. Copyright 2002.

Communal roosting in birds may function to enhance foraging efficiency as explained by the information centre hypothesis, which predicts that successful foragers return from the roost to the rewarding food patch and that birds ignorant of this food follow knowledgeable roost-mates. We tested these predictions by exposing 34 radio-tagged, free-ranging, flock-living hooded crows (Corvus corone cornix) to a novel experimental set-up mimicking a superfluous food patch with maximum temporal and spatial unpredictability Each replicate lasted two days and was located on a new site. Data were collected during ten replicates over three years. First, a crow was more likely to visit the experimental food patch on the second day when it had been there on the first day. Second, when a crow had not been at this food patch on the first day, it was more likely to visit it on the second day if it had roosted together with a crow that had been there on the first day, but only if this knowledgeable roost-mate returned to the food patch on the second day. Our results support the information centre hypothesis and suggest that communal roosting might function to enhance foraging efficiency in hooded crows.

Communal roosting has been studied extensively in birds, but the mechanisms and functions of this taxonomically widespread behaviour pattern remain poorly understood. We studied the roosting behaviour of rubyspot damselflies, Hetaerina americana, in relation to sex and territorial status, and conducted field experiments to test for specific mechanisms of roost formation and maintenance. Both sexes tended to return close to their previous night's roost, but only males were significantly more roost site faithful than chance expectations based on individual day ranges. Males were more roost site faithful when they held mating territories. After acquiring a territory, males usually began roosting closer to the territory after a delay of a few days. Roosts were not located at sites that reduced the daily commuting distance between hunting areas and territories; males generally hunted closer to their territories than to their roosts. In field experiments, sites 'seeded' with synthetic models of male rubyspots attracted more recruits than vacant control sites and control sites seeded with nonrubyspot (clear-winged) damselfly models. Sites seeded repeatedly with rubyspot models often remained popular for roosting after the models were removed, suggesting that the models established new traditional roosts. These results indicate that conspecific attraction and individual spatial memory together may be sufficient to explain, at a proximate level, the traditional night roost aggregations of this species. We discuss these results in relation to functional hypotheses for roost site choice and fidelity. Copyright 2000 The Association for the Study of Animal Behaviour.

Three main benefits are thought to underlie communal roosting in birds: a reduction in thermoregulation demands, a decrease in predation risk, and an increase in foraging efficiency. I investigated interspecific variation in communal roosting tendencies across categories of several ecological factors to examine the relevance of each functional hypothesis in the evolutionary transition to communal roosting and the secondary reversal to solitary roosting habits. The study phylogenetic tree included 30 families and 437 species. Evolutionary transitions to communal roosting occurred more often on branches with flocking species and with larger species but were not associated with diet, territoriality, geographical area, or time of day. The association with flocking activities suggests that increased foraging efficiency, a factor thought to operate through the formation of flocks, may have been a key factor in the origin of avian communal roosting. However, several transitions to communal roosting occurred on branches with nonflocking species, indicating that foraging efficiency may not be the only factor involved in the evolution of communal roosting. Secondary losses of communal roosting habits occurred on several branches, with a concomitant loss of flocking behavior and a tendency to exhibit territorial behavior and nocturnal foraging. Secondary losses suggest that communal roosting is costly to perform and maintain and may be lost when an asocial selection regime operates. The large number of exceptions to the above patterns may force a reevaluation of current functional hypotheses about communal roosting in birds.

In field tests of the information-center hypothesis (ICH) in south Texas with black vultures (Coragyps atratus) and turkey vultures (Cathartes aura), large carcasses were provided and kept under continuous observation. The use vultures made of these bait sites and their patterns of arrival were recorded to evaluate predictions derived from the ICH. Turkey vultures discovered most bait sites (30 of 31) first, but frequently were displaced from the food by later-arriving black vultures. This competitive exclusion by black vultures limited subsequent feeding opportunities for turkey vultures sufficiently that few (27%) returned on subsequent days to bait sites they had previously visited. I found no evidence that those turkey vultures that did return to bait sites acted as leaders for groups of naive birds and led them to bait sites – knowledgeable and naive turkey vultures did not arrive at bait sites together, and groups arriving at bait sites were not larger on subsequent days than on the first days carcasses were available. In contrast, a significantly larger percentage (47%) of knowledgeable black vultures returned to bait sites they had visited on previous days, and the first groups of black vultures arriving at bait sites on subsequent days were significantly larger than the equivalent groups on first days. Nine flocks of black vultures that arrived on subsequent days at bait sites before sunrise (which suggests the birds had commuted directly from a roost) contained knowledgeable birds, and two of these flocks contained both knowledgeable and naive individuals. Overall, 10 of 54 naive tagged black vultures (18.5%) arrived at bait sites under circumstances that suggested they had followed conspecifics to the food from a roost. However, most black vultures apparently found carcasses through independent search or by using local enhancement. Therefore, I conclude that while following from roosts to food sites is a strategy used by black vultures, at this study site it is one they use relatively infrequently.

Cooperative groups of American Crows (Corvus brachyrhynchos) maintain group territories year-round while often traveling long distances to roost communally at night. Our goal was to discover how territorial crows resolve the conflict between the cohesive nature of group behavior with requirements of dispersal to roost communally. We color-marked crows to study group composition over two years, and radio-tagged crows to study movement among roosts, territories, and feeding areas. Most crows showed diurnal fidelity to the group territory throughout the year. Yet, most birds frequently left territories during the day to forage up to 4 km away. At night, crows roosted either on their territory or 18 km away at a large roost adjacent to a landfill. Crows roosted on territories more often in spring (87%) than in winter (42%). Group cohesion was high on territories, yet we found no evidence for group behavior away from territories. Crows arrived singly both to territories in the morning and to the communal roost in the afternoon. Group cohesion for territorial crows appears to be based on decisions of individuals to return to territories from distant roosting and foraging sites. Group cohesion on territories is tied to retention of breeding sites, whereas dispersal for communal roosting likely is linked to benefits derived from foraging away from territories, particularly in winter when physiological stress is greatest and territorial food supplies are lowest. Received 10 May 1996, accepted 9 April 1997. COOPERATIVE BREEDING AND COMMUNAL ROOSTING in large aggregations have attracted considerable recent attention (e.g. Allen and Young 1982, Brown 1987, Caccamise 1993). Cooperative breeding and communal roosting are forms of group behavior, yet we know of no studies that have simultaneously examined relationships between these behaviors. Occurrence of both behaviors in a single species apparently is uncommon and may explain the lack of attention from researchers. American Crows (Corvus brachyrhynchos) offer the opportunity to examine relationships between cooperative breeding (Chamberlain-Auger et al. 1990) and communal roosting (Stouffer and Caccamise 1991a) because crows frequently travel to large communal roosts, yet they live in stable groups that breed cooperatively and defend year-round territories. In the northeastern United States, large com1 E-mail: caccamis@rci.rutgers.edu 2 Present address: Department of Vertebrate Ecology, Institute of Ecology, Polish Academy of Science, 05-092 Lomianki, n. Warsaw, Dziekanow Lesny, Poland. 3Present address: Department of Biological Sciences, Southeastern Louisiana University, Hammond, Louisiana 70402, USA. munal roosts of American Crows form each evening from late summer through early spring. The largest aggregations develop in winter (Goodwin 1976). Cooperative breeding and communal roosting have what appear to be conflicting requirements in that group territorial behavior requires group cohesion on territories, whereas communal roosting requires travel to distant sites with long absences from territories. It is not known how stable groups occupying territories during the day are related to large assemblages that form communal roosts at night. Nor is it known why individual crows that belong to stable groups abandon territories to join distant aggregations at communal roosts. Our goal was to understand how crows resolve apparent conflicts between the group cohesion required for cooperative breeding and territory defense with the temporary abandonment of territories necessary to join communal roosts. We used color-marking to study group composition and radiotelemetry to study movements of individuals among roosts, territories, and feeding areas.

IN recent winters mass deaths of flocking wild birds, popularly termed ‘aflockalypses’, usually caused by adverse weather or in-flight trauma, have made the news. With winter commencing, the time when passerine flocking and communal roosting usually occurs, it seems appropriate to mention a flock mass mortality incident in the UK, which caused some public concern and was potentially dangerous to drivers. This was investigated by the AHVLA Diseases of Wildlife Scheme, a national programme set up by Defra in 1998 to investigate disease and mortality in wildlife. In the incident, in February 2011, 88 starlings ( Sturnus vulgaris ) were submitted from a busy trunk road …

Many birds use communal roosts, but how they use them is generally poorly known. For conservation purposes, and to better understand communal roosting behaviour, it is important to know which factors produce variability in group sizes at roosts. I studied the effect of age-class, abundance of individuals and roost site selection on the patterns of variability in group size in the Andean condor (Vultur gryphus). I fitted a variance-mean relationship known as Taylorâ??s Power Law (TPL) to the number of individuals that roosted daily in seven communal roosts, and made temporal (in each roost) and spatial (among roosts) comparisons of the relationship. The abundance of individuals in a roost fitted well to TPL both temporally and spatially. The variability in the abundance of individuals was significantly influenced by the roost selected, independent of the effect of the mean number of individuals. Moreover, the effect of the roost site on the variability of abundance of individuals was stronger than the effect of age-class. Accordingly, I highlight the importance of the roost site in modulating group size variability of communally roosting individuals. This understanding of the patterns of variability in communal roosts could aid in prioritizing sites for the conservation of a species. Fil: Lambertucci, Sergio Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina

The quality and availability of resources influence the geographical distribution of species. Social species need safe places to rest, meet, exchange information and obtain thermoregulatory benefits, but those places may also serve other important functions that have been overlooked in research. We use a large soaring bird that roosts communally in cliffs, the Andean condor (Vultur gryphus), as a model species to elucidate whether roost locations serve as a refuge from adverse weather conditions (climatic refuge hypothesis, CRH), and/or from predators or anthropogenic disturbances (threats refuge hypothesis, TRH). The CRH predicts that communal roosts will face in the opposite direction from where storms originate, and will be located in climatically stable, low precipitation areas. The TRH predicts that communal roosts will be large, poorly accessible cliffs, located far from human-made constructions. We surveyed cliffs used as communal roosts by condors in northwestern Patagonia, and compared them with alternative non-roosting cliffs to test these predictions at local and regional scales. We conclude that communal roosting places provide refuge against climate and disturbances such as, for instance, the threats of predators (including humans). Thus, it is not only the benefits gained from being aggregated per se, but the characteristics of the place selected for roosting that may both be essential for the survival of the species. This should be considered in management and conservation plans given the current scenario of global climate change and the increase in environmental disturbances.

Milvago chimango (Falconidae, Caracarinae) es una rapaz común con una extensa área de distribución geográfica en América del Sur. Esta especie se caracteriza por un comportamiento gregario y se puede observar en grupos mientras forrajea y descansa. Observamos dormideros de M. chimango en un humedal en la provincia de Buenos Aires, Argentina. En este sitio realizamos conteos mensuales de M. chimango durante tres años. Se utilizó un análisis de varianza (ANAVA) para explorar las variaciones estacionales y anuales en el dormidero, y se exploró la relación entre la abundancia de aves y la precipitación mensual. Se registró un promedio mensual de 1.004 ± 689 individuos de M. chimango en el dormidero. Se encontraron diferencias en la abundancia entre el invierno y el verano, el invierno y la primavera, y el otoño y el verano, y no se observó asociación entre la abundancia de aves y la precipitación mensual. La variación en el número podría reflejar variaciones en los comportamientos de alimentación de cada temporada, que están vinculados a las prácticas agrícolas y su dieta. Estas actividades agrícolas se llevan a cabo principalmente durante el invierno, cuando varias especies de aves se congregan. La disminución durante el verano podría estar asociada con el inicio del período reproductivo de la especie, y no con el régimen de precipitación. Este sitio dormidero también podría funcionar como un “centro de información,” donde jóvenes y adultos de M. chimango adquieren información sobre buenos sitios de alimentación o aprenden habilidades de forrajeo. Sin embargo, se necesitan más estudios para comprender la combinación de factores físicos y biológicos en la conducta de descanso comunal en esta especie. Fil: Josens, Maria Laura. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pretelli, Matías Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Escalante, Alicia Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

I investigated foraging behavior and competition for food between Turkey Vultures (Cathartes aura) and Black Vultures (Coragyps atratus) in southern Texas. Turkey Vultures usually located carcasses first, but often were displaced by later-arriving Black Vultures, which used local enhancement to locate the carcasses. Turkey Vultures occurred equally frequently at carcasses of all sizes, but Black Vultures were more likely to visit large carcasses (>5 kg) than small ones. In addition, at very large carcasses (> 100 kg), Black Vultures outnumbered Turkey Vultures. Turkey Vultures apparently depend primarily on small items, which they can consume quickly before Black Vultures usurp them. Both vulture species roost communally and it has been suggested that their roosts may function as information centers. However, because recent research indicates that the information-center hypothesis is unlikely to be a sufficient explanation for communal roosting in vultures, I explored other possible foraging benefits of communal roosting. Specifically, I incorporated field data col- lected on the foraging behavior of vultures into two simulation models designed to evaluate the possibility that communal roosting facilitates the use of local enhancement by roost members, either by promoting the formation of foraging groups (the assembly-point hy- pothesis) or by concentrating birds in space (the spatial-concentration hypothesis). I conclude that birds depending on spatial-concentration effects occasionally may forage more success- fully than noncommunally roosting individuals, but those that form foraging groups do best. Thus, communal roosting may be advantageous because it facilitates the formation of foraging groups. Received 29 September 1995, accepted 10 December 1995.

Black vultures, Coragyps atratus , spend each night in a communal roost, and individuals sleep at several different roosts over time. They feed in large aggregations at carcasses and engage in apparently cooperative behaviour within coalitions of individuals that co-occur predictably at both roosts and carcasses. Roost census data and DNA fingerprinting results were used to investigate whether black vultures tend to roost in the company of genetic relatives. Restricting the analysis to dyads of breeding adults that were the heads of known lineages and were not mated to one another, a positive correlation emerged between indices of the genetic similarity of individuals and their tendency to use the same roost on the same night. The results provide evidence of long-term associations between some closely related breeding adults, associations that appear not to be simply a consequence of natal philopatry but reflect the daily reassembly of coalitions at communal roosting sites. This social organization could facilitate the evolutionary stability of cooperation among communally roosting black vultures.

‘Tradition’ has been invoked to explain instances in which animals aggregate repeatedly in the same locations for no apparent reason, but alternative explanations, such as cryptic habitat selection, are difficult to rule out. Distinguishing among these hypotheses requires field experiments. We studied a species of harvestman (Prionostemma sp.) that forages solitarily at night and forms roosting aggregations in spiny palms by dawn. Aggregations have formed repeatedly in the same sites for over a decade, and yet the aggregation sites do not appear to differ from unused sites in tree characteristics or microclimate. Previous research suggested that the harvestmen find aggregation sites by detecting chemicals left behind by conspecifics. If so, it should be possible to establish new aggregation sites simply by moving harvestmen to new locations. We carried out such an experiment and, as predicted, release sites attracted harvestmen at much higher rates than did matched control sites. Most individuals that came to release sites were new recruits, and one site continued to attract several harvestmen for at least 7 days, suggesting that a new roosting tradition was established. We also revisited the question of whether any other factors, besides past usage, predict site use. Among sites used by the harvestmen, the size of the aggregations was strongly predicted by microclimate and spiny palm characteristics. Together these findings support the hypothesis that attraction to conspecific cues is the primary mechanism responsible for the long-term stability of aggregation sites, while also suggesting that site characteristics play a previously unrecognized role. Understanding how site traditions develop may have direct applications in conservation.

Aposematic passion-vine butterflies from the genusHeliconiusform 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-indiscriminableHeliconius eratomodels 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 maintainingHeliconiuscommunal roosting behaviour.

We examined the thermal consequences, energy benefits and patterns of nighttime communal roosting in Acorn Woodpeckers (Melanerpesformicivorus) during the nonbreeding season, the period when they are most reliant on nutrient-poor acorn stores. Because the oak limbs (Quercus) in which Acorn Woodpeckers excavate roost cavities cool more slowly than the surrounding air, the nighttime temperature inside unoccupied woodpecker roost cavities averaged 4.3*C higher than the outside ambient temperature, when the latter was approximately 0*C. The temperature of occupied roosts was further augmented in proportion to the number of birds sharing the roost. A single woodpecker increased the cavity temperature an additional 1.20C, whereas four birds increased it an additional 6.0*C. Acorn Woodpeckers did not huddle together at low air temperatures when placed in a simulated roost-cavity metabolism chamber. Consequently their nighttime, fasted oxygen consumption was independent of group size (one, two, or four birds) and was described by the relation: ml O0/(g hr) = 3.33-0.055 Ta. From this relation and our cavity temperature measurements, we estimate that at an outside temperature of 0?C a single cavity-roosting woodpecker would reduce its heat loss by at least 9%, whereas four birds would reduce their heat loss by at least 17%, and even more in the presence of wind. This energy savings may contribute to the higher winter survival noted for male Acorn Woodpeckers that live in larger groups.

The evolutionary pathway to obligate scavenging in Gyps vultures remains unclear. We propose that communal roosting plays a central role in setting up the information transfer network critical for obligate scavengers in ephemeral environments and that the formation of a flotilla-like foraging group is a likely strategy for foraging Gyps vultures. Using a spatial, individual-based, optimisation model we find that the communal roost is critical for establishing the information network that enables information transfer owing to the spatial-concentration of foragers close to the roost. There is also strong selection pressure for grouping behaviour owing to the importance of maintaining network integrity and hence information transfer during foraging. We present a simple mechanism for grouping, common in many animal species, which has the added implication that it negates the requirement for roost-centric information transfer. The formation of a flotilla-like foraging group also improves foraging efficiency through the reduction of overlapping search paths. Finally, we highlight the importance of consideration of information transfer mechanisms in order to maximise the success of vulture reintroduction programmes.

Although the White-tailed Kite (Elanus leucurus) is widely distributed throughout the Americas, winter communal roosting has been recorded only in the Nearctic portion of its range. As a result, data on the food habits of the White-tailed Kite in South America during the nonbreeding season are scarce and, when available, limited to pellets from solitary individuals. Here, we report the communal roosting behavior and the winter diet of White-tailed Kites in an agricultural habitat on the Argentine pampas based on information gathered over three consecutive years (20062008). From May to July of each year, we observed an average of 11 (±SD 2.8) kites roosting in a grove of Eucalyptus viminalis. Prior to roosting, kites gathered in a tall, dead, and leafless Eucalyptus tree before flying to more densely foliated trees where they spent the night. The diet of kites during winter was composed almost entirely of small mammals, mainly Calomys sp. and Akodon azarae. Because agricultural intensification in the Argentine pampas is ongoing, further studies are needed to gain a complete knowledge of White-tailed Kites in this habitat and of the effects of land-use changes on their foraging and other behavior. © 2010 The Raptor Research Foundation, Inc. Fil: Sarasola, José Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencia Exactas y Naturales. Departamento de Recursos Naturales. Centro para el Estudio y Conservación de Aves Rapaces; Argentina Fil: Solaro, Claudina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencia Exactas y Naturales. Departamento de Recursos Naturales. Centro para el Estudio y Conservación de Aves Rapaces; Argentina Fil: Santillán, Miguel Ángel. Universidad Nacional de La Pampa. Facultad de Ciencia Exactas y Naturales. Departamento de Recursos Naturales. Centro para el Estudio y Conservación de Aves Rapaces; Argentina Fil: Galmes, Maximiliano Adrian. Universidad Nacional de La Pampa. Facultad de Ciencia Exactas y Naturales. Departamento de Recursos Naturales. Centro para el Estudio y Conservación de Aves Rapaces; Argentina. The Peregrine Fund; Estados Unidos

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.

We studied roosting behavior of Dunlins (Calidris alpina) during late summer along the coast of the Yukon-Kuskokwim Delta, Alaska, in relation to tidal cycle, time of day, time of season, and occurrence of predators. Within Angyoyaravak Bay, peak populations of 70,000-100,000 Dunlins occur each year. The major diurnal roost sites were adjacent to intertidal feeding areas, provided an unobstructed view of predators, and were close to shallow waters used for bathing. At one site studied intensively, roosting flocks formed at high water consistently during the day but rarely at night. On about 75% of the days, Dunlins also came to the roost at dawn and dusk when the tide was low. The size of the roosting flock, the length of time birds spent at the roost site, and behavior at the roost site were highly variable throughout the season and significantly affected by both tide level and time of day. Roosting behavior changed significantly between early and late August, as Dunlins underwent heavy wing and body molt, and began premigratory fattening. The reaction of Dunlins to potential predators, the formation of roosting flocks in response to light cues, and seasonal changes in social behavior at the roost site suggested that communal roosting behavior may be related not only to the risk of predation but also to behavior during migration. Received 9 July 1990, accepted 5 August 1991. FEW investigators have examined the roosting behavior of shorebirds in light of either the physical factors that govern it or the benefits that might accrue (for review, see Myers 1984, Hockey 1985). Postbreeding Dunlins (Calidris alpina) roost in large flocks and feed on expansive intertidal mudflats of the Yukon-Kuskokwim Delta, Alaska, from July until early October (Holmes 1971, Gill and Handel 1990). At this time they are in transition from the breeding period, during which they defend dispersed nesting and feeding territories (Holmes 1966a, b, 1970, Pitelka et al. 1974), to the wintering period, during which they are highly social, and most commonly feed and roost in flocks along the coast (Storer 1951, Page 1974, Page and Whitacre 1975, O'Connor 1981, Brennan et al. 1985, Ruiz et al. 1989). While on the Yukon-Kuskokwim Delta, Dunlins complete prebasic molt (Holmes 1971) and prepare for a transoceanic migration to wintering areas in southeastern Asia and California (Gill and Handel 1990, in prep.). We expected that their feeding and roosting schedule would be dictated primarily by physical factors, such as the tidal cycle, that affect the profitability of foraging (Heppleston 1971, Prater 1972, Burger et al. 1977, Hartwick and Blaylock 1979, Kelly and Cogswell 1979, O'Connor 1981, Zwarts et al. 1990). We examined the patterns of formation and dispersal of roosting, premigratory Dunlin flocks to determine what factors might influence roosting behavior during this important part of their annual cycle.

Communal roosting has been proposed as a mechanism for facilitating thermoregulation in bats. We examined the effects of cluster size on body temperature $(T_{b})$ and metabolism (measured as O₂ consumption, $\dot{V}o_{2}$) in Noctilio albiventris, a colonial insectivorous Neotropical bat with an adult body mass of 33-45 g. Measurements were made for group sizes of one, two, three, four, eight, and sixteen individuals at ambient temperatures $(T_{a})$ of 10°, 20°, and 30° C. At 30° C, $\dot{V}o_{2}$ is minimal (0.016 mL/[g · min]) and is not significantly affected by group size. At 10° and 20° C, $\dot{V}o_{2}$ is considerably higher than at 30° C, but it declines rapidly as group size increases from one to four. Increasing the group size beyond four individuals has little additional effect on $\dot{V}o_{2}$. By switching from solitary roosting to a cluster offour or more, individual bats can reduce their $\dot{V}o_{2}$ from 0.082 to 0.051 mL/(g min) at a $T_{a}$ of 10°C (a 38% savings) and from 0.048 to ...

A survey of Hen Harrier winter roosts traced 202 sites in Britain to the end of 1985/86 winter, and 12 in Ireland. Communal roosting had been recorded at more than 90% of sites, and 43% were known to be used every winter. Of reported sites 39% were in E England, where coverage was undoubtedly more comprehensive. The majority of sites in England were reported to have been discovered since the mid 1970s. Hen Harriers almost invariably roosted amongst rank ground vegetation, in a variety of open habitats, and 28% of sites were on d rtl ground. Most sites were at low altitudes, but some had been found up to 427 m above sea level. Co-ordinated counts at roosts recorded maximum overall numbers at mid-winter in both 1983/84 and 1984/85, although the pattern of occupancy varied between regions. No estimate could be made of the sizes of the winter populations in Scotland, Ireland and Wales, but extrapolation of counts to estimate the numbers wintering in England indicated populations which peaked at about 400 bird...

While communal roosting is fairly common in animals, the costs, benefits, and proximal factors influencing this behavior are poorly understood. Moreover, many species with communal roosting that have been studied to date have a strong association with humans; however, there have been few formal tests of how human activity might influence roosting behaviors. We studied roosting activity in the Northwestern Crow (Corvus caurinus) within a highly urbanized setting. Specifically, we were interested in whether variation in anthropogenic noise influenced departure times of crows from their roosts. We tested this by comparing roosting activity between days that differed in the extent and timing of automobile noise. We also tested whether other environmental factors (i.e., sunrise time and precipitation) might also influence roost departure times. We found that morning departure was later on rainy mornings and was largely correlated with sunrise time, consistent with previous studies of other species. We...

Aim The Argentine Pampas was extensively and abruptly altered by European colonization. Between 1880 and 1885 the indigenous human inhabitants were completely displaced, and native grasslands were replaced by exotic pasture plants and crops. One of the most important ecological changes in the Pampas landscape, the introduction of tall exotic tree species, has received little attention, and its effect on wildlife has never been assessed. We have made an intensive survey of habitat use of Swainson’s hawk, Buteo swainsoni in its most important non-breeding quarters, the Pampas of Argentina, aiming to characterize the sites used by hawks for communal roosting.

Information transfer among group members is believed to play an important part in the evolution of coloniality in both birds and bats. Although information transfer has received much scientific interest, field studies using experiments to test the underlying hypotheses are rare. We used a field experiment to test if communally breeding female Bechstein's bats (Myotis bechsteinii) exchange information regarding novel roosts. We supplied a wild colony, comprising 17 adult females of known relatedness, with pairs of suitable and unsuitable roosts and monitored the arrival of individuals marked with transponders (PIT-tags) over 2 years. As expected with information transfer, significantly more naive females were recruited towards suitable than towards unsuitable roosts. We conclude that information transfer about roosts has two functions: (i) it generates communal knowledge of a large set of roosts; and (ii) it aids avoidance of colony fission during roost switching. Both functions seem important in Bechstein's bats, in which colonies depend on many day roosts and where colony members live together for many years.

We studied communal roosting in the Common Myna (Acridotheres tristis) in the light of the recruitment centre hypothesis and predation at the roost. The number and sizes of flocks departing from and arriving at focal roosts were recorded over a two year period. We also recorded the sizes and behaviour of foraging flocks. We found that flock sizes of birds departing from roosts at sunrise were larger than those at the feeding site, suggesting that there was no recruitment from the roosts. Flocks entering the roosts during sunset were larger on average than those leaving the following sunrise, suggesting no consolidation of flocks in the morning. Flocks entering the roosts at sunset were also larger on average than those that had left that sunrise, although there was no recruitment at the feeding site. There was no effect of group size on the proportion of time spent feeding. Contrary to expectation, single birds showed lower apparent vigilance than birds that foraged in pairs or groups, possibly due to scrounging tactics being used in the presence of feeding companions. Thus, the recruitment centre hypothesis did not hold in our study population of mynas. Predation at dawn and dusk were also not important to communal roosting: predators near the roosts did not result in larger flocks, and resulted in larger durations of arrival/departure contrary to expectation. Since flock sizes were smallest at the feeding site and larger in the evening than in the morning, but did not coincide with predator activity, information transfer unrelated to food (such as breeding opportunities) may possibly give rise to the evening aggregations.

To explain coloniality in birds and bats, communal roosts have been hypothesized to serve as information centers where colony members transfer knowledge about their habitat. If information is exchanged about food, individuals with low hunting success benefit by following successful foragers to their profitable feeding sites. Colony members should therefore forage together regularly and move in pairs or groups among different feeding places. In 1996 and 1997, we used radio-telemetry to study the nightly habitat use of ten adult female Bechstein's bats (Myotis bechsteinii) living in one maternity colony. Over several nights, each bat revisited its own foraging area, although females regularly switched day-roosts at the same time. Most individual foraging areas showed no, or only little, overlap with each other. Distances between individual activity centers were negatively and significantly correlated with the degree of individual day-roost association. Genetic similarity among colony members, determined using seven nuclear microsatellites, was significantly positively correlated with the degree of overlap among individual areas. Five females were repeatedly radio-tracked at different seasons, months apart. Even between years, all bats maintained their individual hunting areas. Because females are very loyal to their individual foraging areas and these areas are typically substantial distances from each other, information transfer about feeding sites is unlikely to be the crucial factor promoting coloniality. Therefore, other benefits of sociality like cooperative breeding may cause communal roosting. Strong fidelity to individual foraging areas suggests the importance of familiarity with the local habitat, and profound site knowledge could be a crucial "resource", promoting female philopatry in Bechstein's bats.

We assessed the value of communal roosting for mating and territory acquisition in nonbreeding red-billed choughs, Pyrrhocorax pyrrhocorax. Between 1991 and 1996 we surveyed all communal roosts, breeding territories and vacant nest sites in an area of 250 km2in Los Monegros (northeast Spain), as well as other communal roosts in the surrounding 500 km2from 1987 to 1996. Main roosts were used traditionally and throughout the year and gathered more choughs than subroosts, which were used only during the nonbreeding season. Nonbreeding choughs were socially segregated in these roosts according to their age and breeding prospects. Compared with random potential roost sites, main roosts included more first-year birds and were in areas of higher breeding density. Subroosts were mainly joined by choughs of breeding age (at least 2 years old) whose morphology (males) and body condition (females) were similar to those of established breeders, and were in areas with breeding densities as high as around main roosts but with more available nest sites. Nonbreeding choughs that used main roosts later used subroosts, while the converse was rare. More choughs joining subroosts acquired mates than those joining main roosts. Choughs mostly paired with roostmates but also with widowed territorial breeders. Finally, choughs from subroosts acquired territories closer to the roost than those who mated in main roosts, supporting the hypothesis that subroosts reduce the costs of mating and territory acquisition. Copyright 1999 The Association for the Study of Animal Behaviour.

Background Extensive work has shown that vectors almost never feed at random. Often, a subset of individual hosts and host species are fed on much more frequently than expected from their abundance and this can amplify pathogen transmission. However, the drivers of variation in contact patterns between vectors and their hosts are not well understood, even in relatively well-studied systems such as West Nile virus (WNV). Methods We compared roosting height and roost aggregation size of seven avian host species of WNV with patterns of host-seeking mosquito (Culex pipiens) abundance at communal and non-communal roost sites. Results First, host-seeking mosquito abundance increased with height and paralleled increased mosquito feeding preferences on species roosting higher in the tree canopy. Second, there were several hundred-fold fewer mosquitoes per bird trapped at American robin (Turdus migratorius) communal roosts compared to non-communal roost sites, which could reduce transmission from and to this key amplifying host species. Third, seasonal changes in communal roost formation may partly explain observed seasonal changes in mosquito feeding patterns, including a decrease in feeding on communal roosting robins. Conclusions These results illustrate how variation in habitat use by hosts and vectors and social aggregation by hosts influence vector-host interactions and link the behavioral ecology of birds and the transmission of vector-borne diseases to humans.

Sleeping cluster composition and distribution were studied in a semi-free-ranging population of 174 Barbary macaques (Macaca sylvanus) in Rocamadour/France. Over a period of 2 months 341 sleeping clusters comprising 754 animals were recorded as animals left the sleeping trees. To control for nocturnal activities five observation periods were conducted, each of which covered a complete night. Sleeping partners were selected from a particular set of individuals. From night to night there was considerable fluctuation among the individuals, which finally formed a sleeping cluster. Preferred size of sleeping clusters was two and three individuals per cluster. The majority of females spent the nights in body contact to infants or female juveniles; whereas males either slept alone or with older male juveniles. Adult males and females never shared a sleeping cluster. During the night the animals showed hardly any locomotive and vocal activity. Sleeping clusters remained stable until dissociation the next morning. © 1992 Wiley-Liss, Inc.

Rates of infestation by the scaley leg mite (Knemidokoptes jamaicensis) were examined on two overwintering Nearctic-Neotropical migrants, Palm Warbler (Dendroica palmarum) and Prairie Warbler (D. discolor), in low-elevation desert thorn scrub and high-elevation pine forest in the Dominican Republic. Ectoparasites were common on birds in the dry thorn scrub where birds roosted communally, but were never found on birds in the moister pine forest where communal roosting was not detected. Prevalence of ectoparasites varied between years and generally increased in prevalence within winters, with mean rates of infestation reaching as high as 25% among Palm Warblers in late-winter. Parasitized Palm Warblers showed significant decreases in mean pectoral muscle mass scores indicating a negative effect on body condition and physiological stress. Infestation had a significant effect on overwinter site persistence and annual return rates; no infected individuals ever returned the following year. Results of a path analysis indicated that mite infestation was more important than general physiological condition (as represented by pectoral muscle score) in determining annual return. Data suggest that environmental variables and host behavior may affect parasite infestation rates, and further attention should be given to the potential contribution of parasite infestation to winter limitation of avian populations.

to parametric statistics? Ecology 74:1617-1628. SPARLING, D. W., AND G. L. KRAPU. 1994. Communal roosting and foraging behavior of staging sandhill cranes. Wilson Bulletin 106:62-77. STUTZENBAKER, C. D., AND M. W. WELLER. 1989. The Texas Coast. In: Smith, L. M., R. L. Pederson, and R. M. Kaminski, editors. Habitat management for migrating and wintering waterfowl in North America. Texas Tech University Press, Lubbock. Pp. 385-405. TACHA, T. C., S. A. NESBITT, AND P. A. VOHS. 1992. Sandhill crane. In: Poole, A., P. Stettenheim, and F. Gill, editors. The birds of North America, Number 31. American Ornithologists' Union, Philadelphia, Pennsylvania, and Academy of Natural Sciences, Washington, D.C. Pp. 1-24. TACHA, T. C., S. A. NESBITT, AND P. A. VOHS. 1994. Sandhill crane. In: Tacha, T. C., and C. E. Braun, editors. Migratory shore and upland game bird management in North America. International Association of Fish and Wildlife Agencies, Washington, D.C. Pp. 77-94. WALKER, D. L., AND S. D. SCHEMNITZ. 1987. Food habits of sandhill cranes in relation to agriculture in central and southwestern New Mexico. In: Lewis, J. C., editor. Proceedings 1985 International Crane Workshop. United States Fish and Wildlife Service, Grand Island, Nebraska. Pp. 201-212.

The Gray-breasted Woodpecker (Melanerpes hypopolius) is a relatively common species in southwestern Mexico (Guerrero, Mexico, Morelos, Puebla), especially where large columnar cacti are found. However, almost nothing is known about the behavior of this woodpecker species (Short 1982). Here, we describe Gray-breasted Woodpecker communal roosting and winter social behavior and speculate on the possibility of cooperative breeding by this species. Our observations were made between 27 December

ing on mistletoe in their winter range (Walsberg 1975), the much larger gizzards of Phainopeplas collected in their summer range (August and September samples) all held multiple fruits. This method of fruit processing is similar to that of nonmistletoe-specializing frugivores that typically use the gizzard to mechanically reduce multiple fruits at a time (Walsberg, unpubl. data). This presumably is associated with the easier handling characteristics of fruit without the adhesive qualities of mistletoes. Major restructuring of body components is characteristic of the annual cycle of many bird species. This restructuring can include alteration in plumage, fat reserves, and locomotor muscles (King and Murphy 1985). The alteration in gizzard size observed in the Phainopepla reinforces the view that the avian digestive tract also can exhibit substantial seasonal restructuring (e.g., Davis 1961, Ankney 1977, Al-Dabbagh et al. 1987). Although digestive efficiency and rate during summer months have not been measured, the altered gizzard morphology does suggest that adaptations for seasonal dietary specialization may not entail substantial reduction in the effectiveness of food processing at other times of the year.

Summary Hockey P. A. R. 1985. Observations on the communal roosting of African Black Oystercatchers. Ostrich 56: 52–57. There are currently three main hypotheses for the adaptive significance of avian communal roosts: physiological advantages, predator avoidance and information centres. The African Black Oystercatcher Haematopus moquini is territorial throughout the year and forms communal roosts during the nonbreeding season, but does not breed communally. Roosts generally are small, and site fidelity is high. Roosts are normally sited on a rocky promontory with adjacent offshore rocks (west coast), or in flat areas with extensive all-round visibility. The main predators of African Black Oystercatchers are nocturnal terrestrial mammals and nocturnal communal roosts are larger and more tightly packed than daytime roosts. Breeding birds do not roost communally during the breeding season and at this time of year mortality due to mammal predators at a study site in Saldanha Bay was greatest (X2 = 9.46; p

Why does MagpiesPica pica roost communally rather than solitarily in winter? Most roosts were situated in deciduous trees near water, and they held relatively small numbers of birds. All Magpies roosted communally in winter. Strong winds reduced the height of roost perches, and roosting in leeward conditions increased. Less time was spent at the roost before and following roosting in winter when compared with the autumn and the spring situations. Magpies from high quality territories arrived late in the evening and left early in the morning. Foraging activity increased at the roost as day-length decreased, whereas flying remained constant. Sexual and aggressive behaviour were common in spring. Juveniles were sub-ordinate at the roost. Communal gathering was common at the roost. Several activities occurred frequently either at the pre-roost or at the roost, but aggressive and sexual behaviour had a spatial distribution as expected from the number of birdhours spent in the two sites. Roosting ceased following initiation of nesting activity, but early nesters attended the roost longer than late nesters following start of nest building. Start of breeding was not synchronized within roosts. Predation was rare at the roost and elsewhere in the study area. Roosting seems not to be due to information centre effects, predator avoidance, favourable micro-climate, lack of roost sites, or synchronization of breeding activities. Magpies may monitor the quality of their neighbours including their mating status at the roost. Communal roosting of corvid species seems to be related primarily to the distribution and the abundance of food, species with an unpredictable food supply roosting communally.

Observations of marked individuals in a partially marked population of Black Vultures (Coragyps atratus) show that immediate family members maintain close contact throughout the year. Associations between mates and between parents and offspring are primarily responsible for this. Mutual allopreening, feedings, and intercessions in fights occur almost exclusively within families. Adults known to breed within the study area (neighbors) associate more strongly than nonneighbors, although not as strongly as mates. Certain families associate preferentially with certain other families. Strength of interfamily associations is not related to distance between nest sites within the study area. I argue, therefore, that birds actively seek particular individuals as associates. Further knowledge of breeding dispersal of young of known parentage will provide clues to relatedness of highly associated neighbors. Strong associations among related individuals can help explain the use of avian communal roosts as information centers. Received 27 April 1984, accepted 10 June 1985. COMMUNAL roosts and breeding colonies could serve as "information centers" to which unsuccessful foragers return and follow successful individuals to a known food source (Ward and Zahavi 1973). Explaining the apparent aid-giving of successful foragers remains a difficulty of this hypothesis. Some workers emphasize the probability of high levels of relatedness within colonies (e.g. Erwin 1978, Waltz 1982) to help explain why successful foragers might tolerate any costs of being followed. By sharing food with closely related individuals, successful foragers could increase their inclusive fitness (Hamilton 1964). If mechanisms exist that allow preferential sharing with close relatives, inclusive fitness gains could outweigh costs of sharing. Black Vultures (Coragyps atratus) form large communal roosts each night throughout the year, although they nest in pairs in isolated, well-protected locations. Indirect evidence suggests that Black Vulture roosts may serve as food-finding information centers. For instance, morning roost departures are significantly clumped both in time and in direction, and these clumped departures cannot be explained by weather conditions (Rabenold 1983). A successful forager might return to the roost to recruit particular individuals with whom to I Present address: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907 USA. share or cooperatively defend its find. If these associations of individuals are stable over time, it should be possible to detect relative differences in the strengths of associations between different individuals in communal roosting and feeding situations. There is evidence suggesting that parent-offspring ties persist for several months past fledging in Black Vultures (Jackson 1975, McHargue 1977, this study). This behavior would help explain the use of roosts as information centers. Preferential association and preferential behavioral interactions among individuals in a population could structure the distribution of benefits accruing from shared information at communal roosts. The maintenance of family associations outside the breeding season is the subject of this paper. To examine associations of individuals within Black Vulture communal groups, I ask specifically (1) whether mated pairs and individuals of known relatedness (parents and offspring or siblings) are seen together more often than predicted by chance; (2) whether these intrafamilial associations differ from associations of the same individuals with birds not known to be related (extrafamilial associations); (3) whether pairs nesting in an area associate more than expected by chance with other pairs nesting in the same area, and whether these neighborhood associations differ in degree from associations within families or between nonneighbors; and (4) whether strength of associations between neighbors is dependent on the distance between their nest sites. 32 The Auk 103: 32-41. January 1986 This content downloaded from 207.46.13.75 on Sat, 03 Sep 2016 04:08:06 UTC All use subject to http://about.jstor.org/terms January 1986] Black Vulture Family Associations 33

In this synthesis we have attempted to survey and reanalyse the current literature concerning bird sleep. This was achieved by first reviewing present theory describing functions of sleep. Two general models surfaced which encompass many of the specific sleep theories, namely homeostatic and ecological theories. The terminology used to describe sleep and other associated behaviour was organized into an operational hierarchy. We defined loafing behaviour as a general state of immobility. This functional heterogenous group may include comfort behaviour, feeding, social interaction, wariness, staring down and inactive behaviour. Sleep and associated behaviour are considered inactive behaviour. We next described the common sleeping postures as follows: 1. Bill on back or under scapulars; the classical sleep posture. 2. Bill forward or rest-sleep posture. 3. Head on ground. Specific sleep characteristics were also identified as: 1. Quality of sleep based on duration and frequency of eyelid closure. 2. Length of sleep, called sleep session time which is based on the summation of sleep bouts. A sleep bout is defined as the time elapsed during eye closure and opening. 3. Temporal patterning of sleep sessions which are suggested to be dependent on timing of other higher priority behaviours. 4. The resilience (flexibility) of sleep session time. An original analysis was conducted on these sleep characteristics and other environmental, constitutional, behavioural and predation factors. The results indicated that birds experiencing longer daylength slept less each day. Further, birds slept less if (1) overall dangers were greater and (2) they were more communal sleepers. Longer sleep session times were associated with greater exposure while sleeping (i.e. on a lake or mud flat). Several possible functions of sleep were then suggested. Protection theories encompass choice of a safe sleep site while addressing the significance of communal roosting. Recuperation theories were not adequately supported by quantitative studies. Energy conservation theories imply that birds sleep when doing other behaviour might be non-productive. We suggest a model based on eyelid blinking which allows for a degree of vigilance during sleep but which is also compatible with minimizing energy expenditure.

Summary Short, L.L. & Horne, J. F. M. 1980, Vocal and other behaviour of the Green Barbet in Kenya. Ostrich 51:219–229. Brief field studies of the Green Barbet Stactolaema olivacea in coastal Kenya, with emphasis on vocalizations, document its social behaviour, including communal roosting of four birds in a cavity. Green Barbets are aggressive, interacting strongly with a number of species. Erecting of the crown feathers, cocking of the tail, and woodpeckerlike swinging movements characterize displays. Wing Flutters and audible Bill Wiping are visual-auditory displays. Vocalizations include the Grating Call, Kek Call, Chuk Call and Chowp Call. These are agonistic and agonistic-reproductive in function. The Chowp Call comprises the song, used in simultaneous singing and duetting.