Winter Roost Research Articles

Songflight behaviour and mating system of the pipistrelle bat (Pipistrellus pipistrellus) in an urban habitat

The songflight and the territorial behaviour of courting male pipistrelles (Pipistrellus pipistrellus) were observed in an urban habitat of this bat species, in the city of Bayreuth in Bavaria. (1) Within the city limits, from the middle of July to the end of October but most intensively in September, the male bats occupied courtship territories averaging about 200 m in diameter. At night they patrolled these territories along regular flight routes emitting characteristic advertisement calls. By day they sheltered in crevices in buildings. (2) The courtship territories were densely distributed in the center of the inner city and rarer at the outskirts. As all known larger winter roosts as well as the ‘invasion centers’ (typical late summer swarming sites of this species) also were in the inner city, territories were situated around winter quarters, but not in the vicinity of the nursery roosts, which were lying at the edge of the city and outside it. (3) The males evidently arrange their courtship territories in such a way that as many females as possible pass through them when they inspect the winter roosts. That is, they are not defending resources important to the females; instead, they position their courtship territories near the resources the females require. As male territories are densely packed, the males offer a possibility for mate choice to the females, so that the mating system also bears some likeness to a lek.

Winter bat activity in the Canadian prairies

Periodic arousal from hibernation among mammalian hibernators is poorly understood. In bats, arousal is often associated with flight. We acoustically monitored two rocky areas along the Red Deer River in southeastern Alberta for bat activity in autumn, winter, and spring months. We found bats to be active in all months and at unexpectedly cold temperatures (coldest activity –8 °C). Bats were active even when ambient temperatures remained below 0 °C during the day and night. We documented Myotis ciliolabrum (Merriam, 1886), Myotis evotis (H. Allen, 1864), and Eptesicus fuscus (Beauvois, 1796) flying outside hibernacula in winter. Active E. fuscus that we captured in mid-winter of 2004–2005 weighed less than bats captured in the fall, but masses ranged from 14.0 to 21.0 g, indicating that some individuals still had fat reserves. Captured individuals were of various ages, with a male bias. Using radiotelemetry, we located the first natural rock-crevice hibernacula for male and female E. fuscus in the Canadian prairies. Winter roosts were narrow, deep rock crevices or erosion holes located in steep valley walls. We found evidence to suggest that dehydration may be a driving force for winter flights.

Microsatellite Variation of Double-Crested Cormorant Populations in Eastern North America

Double-crested cormorants (Phalacrocorax auritus) exhibit highly adaptive and opportunistic foraging behavior. This flexibility in foraging and increases in population size have led to conflicts with aquaculture and recreational and commercial fishing (Duffy 1995). Although double-crested cormorants roosting in the lower Mississippi Valley appear to have minimal negative impact on sport fisheries, they may have a significant impact on commercial aquaculture production in this region (Glahn and Brugger 1995, Glahn et al. 1998). In 2003, the U.S. Fish and Wildlife Service released the Final Environmental Impact Statement on doublecrested cormorant management allowing more flexibility in control of these birds in areas where they are negatively impacting aquaculture, habitat for nesting colonial waterbirds, and other public resources (U.S. Fish and Wildlife Service 2003). The U.S. Fish and Wildlife Service’s Final Rule expands the 1998 Public Resource Depredation Order (50 CFR 21.47) to permit control of double-crested cormorants at winter roost sites in the vicinity of aquaculture facilities. Populations of double-crested cormorants declined sharply in the 19th and early 20th centuries followed by several periods of population growth in the middle and later decades of the 20th century (Hatch 1995). Atlantic and Interior/Great Lakes migratory populations have seen the greatest increase in breeding pairs. Between the 1970s and 1990s, double-crested cormorant populations in the Atlantic increased 4-fold to more than 96,000 pairs (Hatch 1995). Although double-crested cormorants experienced a marked increase in population size from the 1970s to the 1990s, recent estimates suggest a reduction in the overall rate of growth (Tyson et al. 1999). Although most populations of double-crested cormorants are migratory, a resident population (P. auritus subsp. floridanus) estimated at 10,000–30,000 individuals occurs in Florida (Brugger 1995, Hatch 1995). Population estimates for Florida suggest stable resident populations of P. auritus subsp. floridanus with increasing numbers of wintering birds from migratory subpopulations (Brugger 1995). It is unclear whether or not the resident subspecies in Florida is a genetically distinct lineage, separate from migratory populations. If genetic differentiation is sufficient, it is possible that this resident population may warrant special consideration in management and any control efforts. In addition to the population in Florida, smaller colonies of nonmigratory birds have become established in other areas of the southeastern United States (e.g., Mississippi Delta, Reinhold et al. 1998; Louisiana, Hatch and Weseloh 1999). Determining genetic distinctiveness of diverse populations of double-crested cormorants and the extent of gene flow are important for regional management decisions (Hatch and Weseloh 1999). It is thought that individuals exhibit high fidelity to a colony site; although, no data exist to support this claim (Hatch and Weseloh 1999). Reduction of populations on breeding grounds might prove more feasible than reduction of wintering birds because double-crested cormorants nest in distinct colonies that can be readily accessed. Control efforts on breeding grounds would be most effective at reducing depredation if the natal areas of wintering birds can be identified. The number of band returns is insufficient to establish a relationship between double-crested cormorant nesting colonies in the northern United States and Canada and the wintering, depredating populations in the southeastern United States. Genetic markers have been used to associate wintering dunlin (Calidris alpina) and Canada geese (Branta canadensis) with breeding populations (Pierson et al. 2000, Wennerberg 2001). Sufficient genetic differentiation among breeding populations is necessary to correctly assign samples of wintering birds to their natal areas. An analysis of variation in mitochondrial DNA (mtDNA) found no evidence of genetic differences among migratory and nonmigratory populations (Waits et al. 2003). However, microsatellite loci are known to evolve rapidly and, thus, may reveal population structure even in the absence of mtDNA structure. For example, Goostrey et al. (1998) used highly polymorphic microsatellite markers to assess population structure and differentiation in European populations of great cormorants (P. carbo subsp. sinensis and P. carbo subsp. carbo). They detected high levels of variation both within and among populations suggesting the potential for detecting differences among populations of double-crested cormorants. Our primary objectives are to 1) characterize the genetic 1 E-mail: claygreen@txstate.edu 2 Present address: Department of Biology, Texas State University, San Marcos, TX 78666, USA 3 Present address: Department of Biology, University of Memphis, Memphis, TN 38152, USA

Characteristics of Summer and Winter Roost Trees Used by Evening Bats (Nycticeius humeralis) in Southwestern Missouri

We radio-tracked 13 evening bats (Nycticeius humeralis) to 34 trees during the summer of 2003 and 10 evening bats to 29 trees during the winters of 2003 and 2004. We captured males in every month of the year and provide evidence suggesting that females are also year-round residents of southwestern Missouri. These captures extend the known winter range of N. humeralis at least 110 km northeast. Evening bats selected trees in late stages of decay during the summer, but during the winter they selected a higher proportion of live trees. Comparisons of summer and winter trees suggest that habitat characteristics are more important than tree characteristics in explaining variation between roosts used in the two seasons. Winter roost trees were located in areas with lower average tree height and higher densities of trees. Those attributes would likely cause problems with clutter when leaves are on the trees during summer.

Microhabitat use and social structure in Linnet Carduelis cannabina and Corn Bunting Miliaria calandra at a winter roost in central Spain

Capsule Both species selected particular patches for roosting, and Linnets but not Corn Buntings showed a social structure with males occupying the preferred roosting positions. Aims To evaluate microhabitat preferences of Linnet and Corn Bunting within a winter communal roost, and to examine roost structure according to sex, age and body size. Methods We captured Linnets and Corn Buntings along a habitat gradient in a reed-bed in central Spain when they were coming to roost. Each bird was sexed, aged, and several body traits were measured. We also characterized the habitat patches where the birds were trapped and grouped patches according to their similarity. Results Three groups of patches were defined according to reed structure. Linnets preferred patches with low density of high and thick shoots, while Corn Buntings preferably used patches with intermediate values for these variables. Interspecific competition for preferred positions was not evident. Male Linnets were proportionately more abundant in the preferred patches, and individuals in lower body condition, independent of sex, age or body size, occupied the non-preferred patches. Male Corn Buntings were less abundant, bigger in size, and showed better condition than females, although differences in body size and condition were not apparent among patches within the roost. Conclusion Our results suggest that among-patch differences in structure and location within a reed-bed generate microhabitats that differ in quality for roosting passerines. This habitat heterogeneity in turn seems to be responsible for the social spatial structure observed in Linnets, in which females and individuals in poor physiological condition were displaced, possibly through competition, towards non-preferred positions. The relatively small body size of Linnets compared to Corn Buntings might explain Linnets' preference for patches that seem to provide more protection against harsh weather conditions.

Winter diet of long-eared owls (Asio otus) at an urban roost in Wichita, Kansas

In February 2004, we collected 104 long-eared owl (Asio otus) pellets from beneath a large pine tree in northern Wichita, Kansas that served as a winter roost for approximately four individuals. A detailed analysis of this collection provided basic information on pellet morphology (length, width, total weight, and weight of skeletal remains), as well as gross (% mammal, % bird) and fine (mammalian species composition) determinations of the long-eared owl's winter diet in this urban location. Long-eared owl urban roosts are somewhat uncommon, and this information might be valuable to owl researchers and other ecologists interested in urban wildlife.

DOCUMENTATION OF AN URBAN WINTER ROOST OF THE SPOTTED BAT (EUDERMA MACULATUM)

We report the first documented use of a building as a winter roost by Euderma maculatum. We suggest that sufficient numbers of E. maculatum have been encountered in urban settings that researchers should consider these areas during the course of investigations of species occurrence. We recommend that urban settings in the vicinity of large cliff features be sampled systematically for the presence of E. maculatum.

Winter Roost-site Selection by Seminole Bats in the Lower Coastal Plain of South Carolina

The winter roost-site selection of most North American foliage-roosting bats is relatively unknown. We examined winter roost-site selection of Seminole bats (Lasiurus seminolus) in the Lower Coastal Plain of South Carolina during January 2004. Seminole bats used a variety of day-roost structures including the canopy of overstory hardwood trees, hanging vines, pine needle clusters suspended from understory vegetation, and leaf litter on the forest floor. Although reported for red bats (L. borealis), this is the first report of Seminole bats roosting in forest floor leaf litter. Winter roost selection differed from previous observations of summer roosts, which consisted almost exclusively of live overstory pine (Pinus spp.) trees. Roost-site selection in winter likely is related to ambient temperature and optimizing exposure to solar radiation during the day. Management decisions in southeastern forests should consider seasonal changes in roosting behavior to minimize adverse impacts on forest bats.

Use of an Underground Winter Roost by a Male Evening Bat (Nycticeius humeralis)

We report use of an underground roost by an adult male evening bat (Nycticeius humeralis) during winter in southwestern Missouri. The bat was fitted with a radio-transmitter and followed to tree roosts for 28 days before it was found in a hole covered by leaf litter at the base of a live white oak tree (Quercus alba). The bat remained in the underground roost for 3 days that coincided with extremely cold ambient temperatures before moving back to a tree roost.

MICROCLIMATE VERSUS PREDATION RISK IN ROOST AND COVERT SELECTION BY BOBWHITES

Knowledge of factors that influence habitat selection by wildlife leads to better understanding of habitat ecology and management. Therefore, we compared microclimate and predation risk as factors influencing the selection of stopping points (mid-day coverts, nocturnal roosts) by northern bobwhites (Colinus virginianus). Stopping points were located using radiomarked bobwhites in the Texas Panhandle, USA, during 2002–2003. We obtained blackbody temperatures of microclimates and assessed predation risk (angles of obstruction for aerial predators, vegetation profiles for terrestrial predators) at stopping points and paired random points. Summer coverts showed fewer degree-minutes of hyperthermic exposure (blackbody temperatures > 39°C; x̄ = 655.0, SE = 4.1 for coverts, x̄ = 2,255.5, SE = 4.9 for random; 1200–1600 hr) and a lower risk to predators (e.g., 95% confidence intervals [CIs] of angles of obstruction = 87.8–90.8° for coverts, 55.9–70.6° for random). Summer roost temperatures were similar to paired random sites (x̄ = 13.9°C, SE = 0.6 for roost, x̄ = 13.9°C, SE = 0.7 for random) as were winter roost temperatures (x̄ = −1.3°C, SE = 0.7 for roosts, x̄ = −1.4°C, SE = 0.8 for random). There were minor issues of habitat selection of winter or summer roosts based on predation risk (e.g., 95% CIs of vegetation profiles of summer roosts and random sites did not overlap at lower strata). We concluded other selection factors likely exist for winter roosts because microclimate and predation risk assessments between winter roosts and random sites showed no difference. Similarly, other selection factors may exist for summer roosts, as they showed only a weak difference in terrestrial predation risk and no difference in microclimate in comparison to random sites. We concluded microclimate was the primary selection factor for coverts because prevention of hyperthermia necessitated that bobwhites select cooler microclimates within the study area.

Morphometrics and ecology of Myotis cf. punicus (Chiroptera, Vespertilionidae) in Corsica

The presence of the Maghrebian bat, Myotis cf. punicus Felten, 1977, is reported from Corsica where it is found in low numbers throughout the island, at altitudes between 0 and 1480 m. Most of winter roosts and all breeding colonies are recorded at the lowest altitudes in bridges, caves, mines and buildings. Maghrebian bats forage in open habitats and prey up on Orthoptera, Coleoptera and Lepidoptera (caterpillars). The conservation status is discussed.

GRIFFON VULTURE (GYPS FULVUS) DISTRIBUTION AND DENSITY IN CRETE

Griffon vulture (Gyps fulvus) distribution and local density during 1996- 2002 as well as the main characteristics of the species' activity sites in Crete are described. Total area of occurrence has been estimated at 7000 km2 (85% of the island). 5500 km2 (67%) accounted for its vital range, namely breeding and foraging, with spatial and temporal differences in correspondence to transhumant livestock. In total 68 activity sites were detected: (a) 34 colonies, of which 62% on average were occupied by laying pairs in any one year; (b) six deserted colonies; and (c) 17 summer and 11 winter roosts. Most of the sites were found in southwest and northeast Crete on rocks of calcareous substrate. The species nesting and roosting sites were found on dolomitic and platy limestone cliffs, respectively. Mean altitude of activity sites was 650 m (SD = 442 m, range = 120-1900 m), whereas mean altitude of active colonies was 453 m (SD = 225 m, range = 120-1100 m). Cliffs were on average 182 m high (range = 40-540 m) fac...

Diet of great cormorants Phalacrocorax carbo sinensis wintering in Malause (South-West France)

The diet of cormorants roosting at Malause on the Garonne River (South- West France) was studied by analyzing pellets collected during the winter 2001- 2002. This roost held a mean of 550 cormorants between October 2001 and March 2002, making it one of the most important winter roosts in France. The diet contained 14 fish species, including 10 cyprinids. Cyprinids were the most abundant prey, representing 90 % of individual fish. Bream Abramis brama between 100 and 150 mm in length were the most abundant food items, while large bream ( >300mm total length) were also consumed. The proportion of pellets containing bream increased from 26 % in October- November to 69% in February- March. There was no significant change in the size of the bream over time. The next most abundant species was pikeperch Sander lucioperca present in 15.4% of the pellets from December- January but only 2.6% in February- March.

栃木県渡良瀬遊水地のチュウヒのペリットから見つかった鉛散弾

We collected a total of 296 pellets of Eastern Marsh Harriers Circus spilonotus from their winter roosts (two sites) in Watarase Marsh, Tochigi Prefecture between January 2002 and late February 2004. Out of these pellets 18 contained a total of 24 pieces of lead shot. Although most of the pellets (14) contained only one piece of shot, two pellets included two and three pieces of shot. Among the prey species found in the pellets along with lead shot, ducks accounted for 55.6%, and doves and crows 11.1%. A significantly higher frequency of lead shot in Marsh Harriers pellets was found in January and February, during the open season for game birds. Although lead poisoning is not yet known to have had any profound effect on the harriers using the study site, care must be taken to protect them from lead poisoning.

Communal roosts as structured information centres in the raven, Corvus corax

Summary Ravens (Corvus corax, L.) feed on rich but ephemeral carcasses of large animals. Non‐breeding juveniles forage socially and aggregate in communal winter roosts, which may function as ‘information centres’ regarding food locations. In a large roost in North Wales, regurgitated pellets on the forest floor contained a variety of prey remains, which were more similar for ravens that had roosted close together the same night. Sheep carcasses placed at varying distances from the roost were baited with colour‐coded plastic beads. These were ingested and regurgitated in pellets back at the roost in aggregations, the spatial distribution of which consistently reflected the geographical location of bait sites. Aggregations of beads at the roost grew daily with an increasing radius centred upon the first pellet per carcass. This mirrored the linear increase of six birds per day in the size of groups flying between roost and carcass each morning. Rates of recruitment were greater for carcasses closer to the roost. Groups were led by a single bird roosting centrally within the aggregation. When individually identifiable (37·5% of cases), these individuals were dominant at the carcass and were among the minority of birds involved in acrobatic display flights at preroost gatherings. When contrasted with data on two alternative groups of ravens peripheral to the main roost which foraged and roosted collectively, these results provide strong circumstantial evidence for raven roosts as structured information centres. The adaptive basis for competitive recruitment resulting in excessively large group sizes is also discussed.

Did Canada geese or other birds spread Cylindrocladium Black Rot of peanuts?

The initial appearance of Cylindrocladium black rot (Cylidrocladium crotalaria) of peanuts in Virginia was quite disperse and suggestive of having been spread by birds. Bird utilization of twenty peanut fields was observed at monthly intervals for one year. The 20 fields were located in two areas of southeastern Virginia. A total of 30 bird species were observed using these fields. Fecal material, soil from feet, and crop contents were taken from six bird species collected in the fields and analyzed forC. crotalariae. Soil samples from a blackbird (Icteridae spp.) winter roost in the area were also analyzed forC. crotalariae. None of the samples taken showed presence of the fungus. Microsclerotia of the fungus were force-fed by intubation to three species (12 birds each) of captive birds (Canada geese, Japanese quail, northern bobwhite) to determine viability after passage through the gastrointestinal tract. No viable microclerotia were detected (based on cultivation trials) in fecal material taken from birds intubated with microsclerotia. Two of 15 Canada geese each force-fed a porous bag container with 5000 microsclerotia yielded 3 and 2 viable microsclerotia each in feces. It was concluded that birds were not significant factors in spreading the Cylindrocladium black rot disease.

Juvenile hormone regulation of longevity in the migratory monarch butterfly.

Monarch butterflies (Danaus plexippus) of eastern North America are well known for their long-range migration to overwintering roosts in south-central Mexico. An essential feature of this migration involves the exceptional longevity of the migrant adults; individuals persist from August/September to March while their summer counterparts are likely to live less than two months as adults. Migrant adults persist during a state of reproductive diapause in which both male and female reproductive development is arrested as a consequence of suppressed synthesis of juvenile hormone. Here, we describe survival in monarch butterflies as a function of the migrant syndrome. We show that migrant adults are longer lived than summer adults when each are maintained under standard laboratory conditions, that the longevity of migrant adults is curtailed by treatment with juvenile hormone and that the longevity of summer adults is increased by 100% when juvenile hormone synthesis is prevented by surgical removal of its source, the corpora allatum. Thus, monarch butterfly persistence through a long winter season is ensured in part by reduced ageing that is under endocrine regulation, as well as by the unique environmental properties of their winter roost sites. Phenotypic plasticity for ageing is an integral component of the monarch butterflies' migration-diapause syndrome.

Aggressive behaviours and correlates of dominance in Purple Sandpipers Calidris maritima at a communal winter roost

Aggression and the competitive ability of individual Purple Sandpipers were studied at a communal winter roost in northeast England. Aggression was most intense in high winds and more frequent in moderate breezes than when wind speeds were high or low. Higher wind speeds resulted in a drop in aggression rate, as birds had to face into the wind to maintain their balance. The ability of an individual to secure a sheltered roost position was related to its size and sex, larger individuals being dominant over those smaller than themselves. Purple Sandpipers exhibit reversed sexual size dimorphism and females were thus dominant over males. There was also weak evidence that adults were dominant over first‐winter birds. The importance of size and sex in determining dominance at the roost is discussed in relation to the evolution of reversed sexual size dimorphism in Purple Sandpipers and similar shorebirds.

Characteristics of the northernmost population ofRhinolophus ferrumequinum in the Carpathian Basin

Roost utilisation byRhinolophus ferrumequinum (Schreber, 1774) was investigated between 1984 and 1998 in north-eastern Hungary. Exploration of summer and winter roosts, monitoring and bat-banding were implemented to find movements between the colonies. Data on roost utilisation by this species in south-eastern Slovakia, collected in a similar way, were included for comparison. Twenty-two marked bats were recaptured. The studied bats created nursery colonies in Hungarian churches and moved to Slovakian mines and caves to hibernate in winter. The population used two main hibernacula, two large nursery roosts and one temporary roost but several other roosts were also visited. The area occupied by the population was 5180 km2.R. ferrumequinum living in SE Slovakia and NE Hungary formed probably a separate population on the northern edge of the species range. This population is a part of the metapopulation of the species.

Winter roost occupancy and behaviour at evening departure of urban long‐eared owls

Roost occupancy and behaviour at evening departure were studied in long‐eared owls (Asio otus) at a large winter roost in the southern suburbs of the city of Milan, northern Italy. The number of roosting owls was strongly correlated with decreasing daylength, while it was weakly negatively correlated with temperature. Hence changes in photoperiod can be considered among the proximate factors promoting the winter aggregation of long‐eared owls. Behaviour at departure was influenced by cloud cover: birds departed earlier, and departures were at a higher altitude and less concentrated, with covered sky than with clear sky; the reasons for these behavioural differences remain unclear. Directions of departure showed that owls do not use the urban area for hunting, as no birds were observed flying towards the city, consistently with dietary data.