Communal Roosts Research Articles

The Hen HarrierCircus cyaneusWinter Roost Survey in Britain and Ireland

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...

Comparison of Roost Use by Three Species of Communal Roostmates

Our previous studies of communally roosting European Starlings (Sturnus vulgaris) revealed that each bird fed daily for months on its own diurnal activity center (DAC) and commuted to a variety of nearby and distant roosts. Since these observations contrast sharply with the predictions of most foraging explanations for communal roosting, we wanted to determine if this DAC-centered roosting pattern occurred in other communally roosting species. In this study we used radiotelemetry to monitor feeding and roosting sites used by starlings, Common Grackles (Quiscalus quiscula), and American Robins (Turdus migratorious), three species that share communal roosts in central New Jersey. Our goals were to determine (a) whether avian species that roost together use the roosts in similar ways, and (b) when and why individuals change roosts. Foraging patterns were similar in all three species; individuals fed daily on their DACs for many weeks. Roosting patterns were similar for grackles and starlings; individuals switched among nearby and distant roosts. In contrast, robins always roosted near their DACs, changing both roosts and DACs at the end of the breeding season. Predation rates at roosts were extremely low and did not explain the use patterns of large and small roosts. We argue that (a) DACs and DAC-centered roosting are probably widespread among communally roosting species, and (b) DAC-based individuals select roosts primarily on the basis of their proximity to good sources of food.

Habitat Use by Nonbreeding Bald Eagles in North Carolina

We examined nocturnal roosting and diurnal perching habitat used by nonbreeding bald eagles (Haliaeetus leucocephalus) in North Carolina during 1986 and 1987. Eagles used roost areas that were less dense, had less canopy cover, were closer to forest edges, and had larger trees than randomly selected areas, and they used trees that were larger than random trees for roosting and perching. Suitable perch trees were the most important attribute of perching habitat. Eagles used loblolly pines (Pinus taeda) and trees with leafless crowns, probably because these crowns were most accessible for perching. Eagles perched in the bottom of tree crowns during summer, but they perched in tree tops during fall and winter. Eagle did not use perches that were different from forest stand characteristics within 20 m of perch trees, forest cover types in 1-ha blocks surrounding perches, or habitat disturbances. Roosting habitat should receive primary management emphasis because of its apparent low occurrence in central North Carolina. Perch trees were plentiful, but long-term management is desirable. J. WILDL. MANAGE. 54(2):223-234 Bald eagles are listed as endangered or threatened throughout much of North America (50CFR ? 17.11), but populations have stabilized or increased in recent years (Nickerson 1989, Bohall Wood et al. In Press). Shooting, trapping, electrocution, poisoning by pesticides and lead shot, and habitat loss to human encroachment through cutting of nest trees, perch trees, and roost sites remain a serious concern for management of eagles (Stalmaster 1976, Stalmaster and Newman 1979, Hansen et al. 1980, Nash et al. 1980). Since summer 1985, relatively large numbers (>30) of bald eagles have been observed on B. Everett Jordan and Falls lakes in central North Carolina, apparently representing a substantial increase in the state bald eagle population (W. Adams, U.S. Army Corps Eng., pers. commun.). The Jordan and Falls lakes populations primarily represent a transient summer assemblage of mostly immature, nonbreeding eagles. Little has been published about communal summer roosts and postnesting summer habitat use of bald eagles. Research emphasis has been on communal winter roosting and nesting habitat use (e.g., McEwan and Hirth 1979, Hansen et al. 1980, Anthony et al. 1982, Keister and Anthony 1983). Identification of summer postnesting habitat requirements is necessary for management of bald eagles during part of the nonbreeding period. Our objectives were to describe the vegetative characteristics of roost and perch sites in relation to overall habitat characteristics and to develop management guides for eagle habitat on reservoirs in North Carolina. Funding was provided by the U.S. Army Corps of Engineers, Wilmington District. M. T. Gaudette and A. K. DeLong provided field assistance. A. R. Davidson, K. K. Stout, and G. N. Hirsh assisted with data input. Thanks to J. Rich and C. Adams of the North Carolina Wildlife Resources Commission, and M. Tippett of AeroServices, Inc. for pilot services. L. G. Jervis provided information on forestry practices at the Mason Point roost and allowed access to North Carolina State University property. R. C. Duckson, S. Brown, and B. Adams provided information and cooperation throughout the study. 1 Present address: Box 2434, Cordova, AK 99574. 2 Present address: 778 Palmer Avenue, Falmouth, MA 02540. 3 Present address: Wildlife Division, Department of Natural Resources, 2455 N. Williams Lake R ad, Pontiac, MI 48054.

On Communal Roosting and Associated Winter Social Behavior of Gray-Breasted Woodpeckers

Journal Article On Communal Roosting and Associated Winter Social Behavior of Gray-Breasted Woodpeckers Get access Paul Hendricks, Paul Hendricks Department of Zoology, Washington State University, Pullman, WA 99164 Search for other works by this author on: Oxford Academic Google Scholar Joseph R. McAuliffe, Joseph R. McAuliffe Department of Biological Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154 Search for other works by this author on: Oxford Academic Google Scholar Alfonso Valiente-Banuet Alfonso Valiente-Banuet Centro de Ecologfa, Universidad Nacional Aut6noma de Mexico, Apartado Postal 70-275, Mexico, Coyoacan, D.F. C.P. 04510 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 92, Issue 1, 1 February 1990, Pages 254–255, https://doi.org/10.2307/1368413 Published: 01 February 1990 Article history Received: 12 June 1989 Accepted: 18 October 1989 Published: 01 February 1990

Winter Use and Habitat Characteristics of Vulture Communal Roosts

We examined winter use and characteristics of 16 communal roosts used by black (Coragyps atratus) and turkey (Cathartes aura) vultures during 1986 and 1987 in southern Pennsylvania, northern Maryland, and northeastern Virginia. Eight roosts were classified as primary and 8 as secondary based on numbers of vultures per roost and on frequency of use in both winters. Roosts had a greater density of conifers and larger trees (deciduous and coniferous) than random wooded sites and presumably provided vultures nocturnal perches with favorable microclimates, increased food availability, and enhanced soaring conditions. Roosts that contain large conifers (>56 cm dbh and >21 m tall) and are near (50-200 m) habitat features that contribute to air currents should be preserved for wintering vultures. J. WILDL. MANAGE. 54(1):77-83 Populations of black and turkey vultures in the Mid-Atlantic region have declined in recent decades (Brown 1976). A knowledge of both winter use and habitat characteristics associated with communal roosts is required to manage habitat for wintering populations of vultures. Previous studies of vulture roosts focused on roost dynamics (Sweeney and Fraser 1986, Taylor 1986), behavioral interactions and movements (Stewart 1978; Rabenold 1983, 1986; Coleman and Fraser 1989), and thermoregulation (Byman 1985, Clark and Ohmart 1985). With the exception of 1 communal vulture roost study in southcentral Pennsylvania (Wright et al. 1986), little is known about winter use and characteristics of roosts in the Mid-Atlantic region. Our objectives were to determine winter use of communal roosts by black and turkey vultures in southern Pennsylvania, northern Maryland, and northeastern Virginia and to describe habitat characteristics of communal roosts. J. D. Fraser, H. G. Hughes, and W. L. Myers reviewed the manuscript, and J. W. Grimm provided statistical advice. We thank J. S. Coleman and W. L. Myers for comments on the manuscript and J. F. Karish and H. J. Greenlee for cooperation with all aspects of the study. Funding was provided by the Max McGraw Wildlife Foundation, the Pennsylvania Cooperative Fish and Wildlife Research Unit, and the Jesse Rossiter Rapp Scholarship of the School of Forest Resources, The Pennsylvania State University. This is Journal Series Paper 7892 of the Agricultural Experiment Station, The Pennsylvania State University, University Park.

Variability in Parrot Flock Size: Possible Functions of Communal Roosts

This study documents flock size in mixed-species parrot/parakeet flocks in tropical dry forest of Costa Rica. Variability in flock size was quantified on a diurnal basis, between nesting and nonnesting periods, and during departures from roost sites in the early morning. Flock size was greater when animals were congregating near the roost site near dusk than during the rest of the day or when the birds were departing the roost. Flocks were smallest in the first half of the dry season when they are reported to nest. Three hypotheses (Information Center [IC], Diurnal Activity Center [DAC], and a general foraging hypothesis) all make predictions relating the size of specific types of flocks to the density and distribution of food resources. As predicted, by the foraging hypothesis, diurnal flock size was positively related to the density of potential fruit resources, and flocks were largest when resources were uniformly distributed. However, contrary to predictions of the IC and DAC hypotheses, roosting flock size was not related to the density and distribution of food resources. The size of flocks departing roost sites in the morning was small, and evidence suggested that these flocks may have been avoiding following the flocks that left previously.

Diurnal rhythms and seasonal changes in the roosting behaviour of Indian mynaAcridotheres tristis (Linnaeus)

The present study deals with the awakening and roosting behaviour of mynas. In the annual cycle of these mynas, 3 distinct phases were noticed—the pre-breeding season (November–March), breeding season (April–July) and post-breeding season (August–October). The various roosting activities of mynas such as the time of waking up and calls, the time of arrival and departure of the first bird and up to the last bird, communal noise and the time of final settlement at the communal roost show a systematic diurnal and seasonal changes in relation to the times of sunset and sunrise (i.e. the light and dark periods of a 24h day). These changes were found to be consistent at all the roosts under observations and during all the years of the study. These changes seem to be governed by endogenous rhythms, which are slightly altered due to the endocrine secretions particularly in the breeding season and are also modified due to the adverse climatic conditions.

Movements of wing-tagged StarlingsSturnus vulgarisfrom an urban communal roost in winter

The daytime dispersal of Starlings from an urban winter communal roost was monitored by colour marking 1424 birds according to age and sex. Reports received from members of the public suggested that dispersal was homogeneous with respect to age and sex composition at all distances from the roost. There was evidence that dispersal was geographically heterogeneous with respect to sex composition, and this observation is discussed in relation to correlated variation in agricultural practices.

Flock Organization, Dispersion and Territorial Behaviour of Wintering Hooded Cranes Grus monacha in Izumi and Akune, Kyushu

1) Flock organization, dispersion and terriorial behaviour of the wintering Hooded Cranes Grus monacha were studied in Izumi and Akune, southwestern Kyushu from 1980 to 1984.2) Most of the cranes spent the daytime at a feeding site adjacent to their roost, but about 10% of them flew out in the early morning and returned in the evening. All cranes gathered in two communal roosts at night.3) A total of 83 different units (solitary birds and flocks) was observed by line censuses outside the feeding site.One solitary bird was observed(1.2%)and flocks(98.8%)ranged from two to 102birds. The flock sizes of less than ten birds in order of frequency were three(36.1%), two (16.9%), four(14.5%), six(3.6%), five(2.4%), eight(1.2%), and nine(1.2%). The two-bird flocks consisting of adults were thought to be pairs, and three-bird flocks with one juvenile and four-bird flocks with two juveniles were thought to be families. Large-size flocks consisted of solitary immature birds, solitary adults, pairs and families.4) Territorial, resident and wandering units were observed outside the feeding site. In the territorial units, semi-territorial units which were subordinate to the neighbouring units but excluded other units, were observed. The territorial and resident units were pairs or families. The wandering units were solitary birds, pairs, families or mixed flocks. Excluding units which had hostility towards other units and little site attachment, were obserded at the feeding site.5) Alert, threat-approaching, attacking and confronting were described as territorial behaviour. Both sexes defended their territory, while a male took the active role in direct attacks on intruders. Territory size was 54, 790 m2. One territory was kept by the same flock throughout several winters.6)Immature birds and solitary adults are thought to join the mixed flocks, forming pairs with the members of the flocks. Such pairs may leave the mixed flocks to establish their own territories.7) The number of territorial cranes was less than 8.4%, which is thought that cranes gathered at the feeding site and did not hold territories outside the site because the food was short. However, pair and family territories are the most stable in term of efficiency in defense when they maintain territories.

Incidence of Toxoplasma infection in a population of European starlings Sturnus vulgaris from central England.

A sample of European starlings, Sturnus vulgaris, culled from a communal roost in a city in Central England, was examined for infection with Toxoplasma. Eleven (8%) of 133 birds were confirmed as infected after horizontal passage of brain homogenate through mice. Serological examination, using the indirect and direct agglutination tests, proved unsatisfactory for screening starlings for Toxoplasma infection. If the proportion of starlings infected with Toxoplasma in this sample is representative of the population as a whole, then this bird could play an important role in the maintenance of the infection in urban environments.

Avian Communal Roosting: A Test of the "Patch-Sitting" Hypothesis

Major starling roosts (2,000 to 100,000 birds) cannot be fully explained on the basis of information transfer, predation, migration, or limited habitat. Radiotelemetry has revealed that each starling returns daily to feed on its own stable diurnal activity center (DAC), but stops briefly at supplemental feeding areas (SFAs) on its way to and from distant communal roosts. We test and find supported a new hypothesis (Caccamise and Morrison 1986) that DAC-based starlings select roosts that reduce commuting costs to SFAs far from their DACs. As predicted, DAC-based adults used SFAs that were nearer their roosts than their DACs, and used more distant roosts where SFAs were more widely spaced. In starlings, major communal roosts appear to be aggregations containing large numbers of patchsitting birds roosting near especially rich sources of food.

Recruitment to food in black vultures: evidence for following from communal roosts

Experimental and observational evidence from a 5-year study of a partially marked population of black vultures, Coragyps atratus, suggests that individuals can find food by following others from overnight roosting groups. Natural food sources usually lasted long enough for recruitment to occur. Black vultures formed larger roosting groups and had enhanced second-day recruitment during winter, when their main food source was least abundant. Successful foragers returned to experimental food sources on subsequent days and generally preceded new arrivals. Arrivals at bait were clumped on days of discovery and second days, but incoming groups were larger on second days and highly skewed towards early arrivals. In general, adults arrived at baited sites earlier than young adults and juveniles. During natural roost departures, adults were as likely to depart at the head of departing groups as at the rear, while young were concentrated in the rear. Birds removed experimentally from the population long enough to be naive about the location of food followed others from the roost when reintroduced. Control adults (birds caught and handled but not restrained for long) were not concentrated in the rear of roost-departing groups, as were experimental adults. Juveniles tended to follow regardless of recent experience. These results suggest that roost attendance facilitates foraging for black vultures; these roosts probably function as information centres.

Evidence for Resource-based Communal Roosting by European Starlings

Evidence for Resource-based Communal Roosting by European Starlings

Food Habits of Black and Turkey Vultures in Pennsylvania and Maryland

In 1983 and 1984, we studied black (Coragyps atratus) and turkey (Cathartes aura) vulture foraging behavior in Pennsylvania and Maryland by observing 21 radio-tagged vultures and collecting 134 regurgitated pellets. Radio-tagged vultures consumed 21 different kinds of carrion. Domestic animals were consumed more often (62%) than wild ones (38%). Black vultures fed more on large carrion (>20 kg) than did turkey vultures. Remains in pellets indicated greater use of wild sources of carrion than did observation of radio-tagged birds, possibly because large, domestic carrion was more digestible. Sixty-five percent of feeding was initiated from 3 to 7 hours after sunrise. Black vultures fed earlier, foraged in larger groups, fed longer at fewer locations, and fed closer to the main communal roost than did turkey vultures. Vultures use of domestic carrion makes the establishment of feeding stations a practical method of supplementary feeding. The 2 species may benefit unequally from feeding programs because of different foraging strategies. J. WILDL. MANAGE. 51(4):733-739 Although black and turkey vultures are present in many areas of North America, both species are declining in some regions (Brown 1976). These species have been little studied, and the causes of reported declines are unknown. Both species weigh approximately 2,000 g, and Prather et al. (1976) reported that captive turkey vultures consume approximately 140 g of food each day, yet little is known about food habits or feeding behavior of either species. The few existing reports about these species' food habits are either anecdotal (Pearson 1919) or are based primarily on regurgitated-pellet analysis (Thiel 1976, Paterson 1984, Prior 1986, Yahner et al. 1986). Although this method can provide information about some of the prey eaten, highly digestible items tend to be underestimated, and carrion with a large component of indigestible material is overestimated. Food availability may be an important factor in communal roost dynamics, shifts in vulture distribution, and competition between the species. To add to the understanding of vulture foraging dynamics we determined the species of animals that made up their food resource, the origin of these animals (domestic or wild), the distribution of carrion used (small and dispersed vs. large and clumped), and differences between the 2 species' food habits. We thank the Eastern Parks and Monument Assoc., the Natl. Park Serv., and Virginia Polytechnic Inst. and State Univ. for funding and logistic support of this research. Thanks to L. Haynes, H. Greenlee, T. D. Alderson, C. A. Pringle, M. R. Richmond, M. Tenney and J. Roberts for help with collection and analysis of the data.

Use of Communal Roosts and Foraging Areas by Bald Eagles Wintering in the Klamath Basin

Patterns of use of 5 communal roosts and 3 feeding areas by bald eagles (Haliaeetus leucocephalus) in the Klamath Basin of southern Oregon and northern California were investigated during the winters of 1978-79 and 1979-80. Bald eagles arrived in late October and were most abundant during late January. Counts peaked at approximately 500 eagles, which constitutes one of the largest wintering concentrations in the lower 48 states. Numbers declined from February through March. There were several major shifts in use of roosts and feeding areas within and between years, which depended on the location of an accessible food supply (mainly waterfowl), which in turn was affected by weather, season, and human activities. Comparisons in bald eagle behavior are made between several locations, and common aspects are described. J. WILDL. MANAGE. 51(2):415-420 Winter concentrations of bald eagles usually occur in areas of high food availability from the southern Alaskan coast to central California, from Montana to Texas, and along the Mississippi River and its tributaries. Bald eagles are opportunistic foragers, and their foraging behavior and habitat use vary considerably. Foods during winter include carrion and live prey consisting of several species of fish, waterfowl, and even small mammals (Hancock 1964, Swisher 1964, Lish 1973, McClelland 1973, Servheen 1975, Stalmaster 1976, Steenhof 1976, Griffin 1978, Keister 1981, Frenzel 1985). Bald eagles often change prey and foraging areas during the winter and sometimes fly long distances to different wintering areas (Young 1983, Lingle and Krapu 1986, Isaacs and Anthony 1987). The proximity of communal roosts to feeding areas varies considerably; distances range from 0.25 km along rivers (Hansen et al. 1980) to 24.0 km in basins (Edwards 1969). Type of roosting habitat also varies from relatively small deciduous trees (Steenhof 1976) to large coniferous trees (Hansen et al. 1980, Keister and Anthony 1983). Successful management of wintering populations of bald eagles requires an understanding of the reasons for variability in foraging behavior and habitat use. The purpose of this paper is to describe the concurrent use of communal roosts and foraging areas by bald eagles and to identify factors that influence variable use of these areas. This study was conducted under the auspices of the Oreg. Coop. Wildl. Res. Unit; Oregon State Univ., Oreg. Dep. Fish and Wildl. (ODFW), U.S. Fish and Wildl. Serv. (USFWS), and the Wildl. Manage. Inst. cooperating. The USFWS and the Nat. Conserv. funded the study under Contract 14-16-009-79018. This is Oregon State Univ. Agric. Exp. Stn. Tech. Pap. 7579. We thank D. C. Sasse, R. R. Opp, R. A. Ingram, J. V. Towman, J. L. Hainline, R. C. Fields, and J. F. Wegener as well as others at Lava Beds Natl. Monument (LBNM), Modoc and Klamath Natl. For., ODFW, Klamath Basin Natl. Wildl. Refuge, and U.S. Bur. Land Manage. for help with coordinated roost counts. Living accomodations were provided by ODFW, and the hospitality shown by J. F. Wegener at LBNM was greatly appreciated. J. A. Crawford, D. Faulkenberry, F. B. Isaacs, and K. Steenhof reviewed earlier drafts of the manuscript.

Social structuring at a communal roost of Choughs Pyrrhocorax pyrrhocorax

The social structure of a communal roost of Choughs Pyrrhocorax pyrrhocorax was studied between July and September 1985. Different age classes within the roost were spatially segregated. Third‐year birds were significantly more likely to attack another Chough and roosted in the densest part of the roosting flock. First‐year birds roosted significantly lower down the roost cliff and on the periphery of the flock.

Communal roosting by RobinsErithacus rubecula

Communal roosts of Robins were observed in Cambridge, England. They were occupied front July to February and contained very few, if any, territorial birds. Numbers at roosts were highest when the non-territorial population was swollen by evictions from territories in autumn and by pair formation in spring. It has been suggested that communal roosting enables Robins to regulate their population density. I argue that estimation of density is likely to be of direct advantage to individuals.

The diet of RavensCorvus coraxin Orkney

An analysis of 945 pellets from various territories and communal roosts on Mainland Orkney suggested that the diet of Ravens was dominated by lagomorph carrion, supplemented by shore feeding, egg predation, a little scavenging of large mammal carcases and some ground foraging for invertebrates and vegetable material. There was little variation in pellet contents between 1982 and 1983, but significant seasonal variation, with less lagomorph but more large mammal remains, eggshell, feathers and seashore items in the breeding season. Terrestrial invertebrate remains were more frequent in pellets from late summer and autumn, cereal in February, berries in late autumn, and rodents in October and December. Pellets from territories near to extensive seaweed-covered shores contained more seashore food and bird feathers. Large amounts of eggshell in pellets were associated with the presence of coastal heathland and the absence of tilled agricultural land. Dietary studies of Ravens list a great diversity of foods, ...

Avian Communal Roosting: Implications of Diurnal Activity Centers

Most current explanations of avian communal roosting focus on benefits derived at the roost itself and assume that the roost is the individual's base of operation. A very different view of communal roosting emerges when the birds are marked individually. A recent radiotelemetric study of communally roosting European starlings (Sturnus vulgaris) revealed that individuals are far more faithful to their diurnal activity centers (DAC's) than to their roosts (Morrison and Caccamise 1985). Studies of other communally roosting species have suggested that DAC's are probably not unique to starlings. The finding that at least some communally roosting species have DAC's has important implications for both foraging-based and predation-based interpretations of communal roosting. Our studies of starlings suggest that foraging factors were of primary importance in the evolution of both DAC's and communal roosting. Foraging daily on a familiar DAC may have benefits similar to those of holding a territory. Furthermore, DAC-based birds should forage away from the DAC only when the food intake rate in the supplemental feeding area (SFA) more than compensates for the cost of commuting to that SFA. And finally, although DAC-based birds probably join small communal roosts near their DAC's to reduce the risk of nocturnal predation, they join much larger, more distant roosting groups primarily to reduce commuting costs to supplemental feeding areas. We hypothesize that major communal roosts may simply be aggregations of individuals roosting as close as possible to especially rich feeding areas. Our patch-sitting hypothesis generates predictions that clearly distinguish it from other foraging-based hypotheses. We encourage researchers to look for DAC-based behavior in other species and to consider a DAC-based perspective when formulating and testing hypotheses about communal roosting.

Reaktion einer Gebirgsstelzen-Winterpopulation (Motacilla cinerea) auf den extremen Kaltlufteinbruch im Januar 1985

During the extremely cold winter 1984/85 six Grey Wagtails (Motacilla cinerea) frequented a communal roost (Baden-Wurttemberg) up to January 4th. A midwinter movement is supposed. The breeding population decreased by 50%.