bluuebunny/crossref_metadata_2025 huggingface dataset:
Sand burial effects on seed germination, seedling emergence and establishment of Panicum virgatum
Authors: Zhang Jianhua , Maun M. A.
Published: July 2006

Studies in the field and in a greenhouse were conducted to examine the effects of sand burial on seed germination, seedling emergence and establishment of Panicum virgatum L. on the foredunes of Lake Erie. Under natural conditions, the seedlings emerged from sand burial depths ranging from 0 to 11 cm, with a mean ± SD of 4.73 ± 1.82 cm. The frequency distribution of the depth of emergence of seedlings in the field was significantly skewed to the right and platykurtic. In the greenhouse, some seedlings emerged from a burial depth of as much as 16 cm. Although percent germination of seeds was not affected by sand burial, the percent emergence and the rate of emergence of seedlings were significantly reduced by excessive sand burial. Seedling mortality was found only among seedlings that emerged from sand burial depths of 10 cm or more. In the field, all the seedlings established in one growing season had originally emerged from sand burial depths of less than 12 cm. Within this burial range, seedlings from shallower burial depths had lower chances of establishment than expected, whereas those from deeper burial depths had higher probabilities of establishment than expected.
The bog climax hypothesis: fossil arthropod and stratigraphic evidence in peat sections from southeast Alaska, USA
Authors: Klinger Lee F. , Elias Scott A. , Behan‐Pelletier Valerie M. , Williams Nancy E.
Published: July 2006

The hypothesis that bogs are climax (structurally and compositionally stable) communities has been proposed for several large regions including southeast Alaska. A logical consequence of the bog climax is the hypothesis that, where there is infrequent large‐scale physical disturbance, landscape‐level changes from early successional woodland to late successional peatland should have occurred during the Holocene. This hypothesis is tested in southeast Alaska using analyses of fossil arthropods and site stratigraphy, as well as a review of the ecological literature.

Results indicate at least three major landscape types have dominated since deglaciation: deciduous woodland (about 9000 to 6000 yr BP), coniferous woodland (about 6000 to 3000 yr BP), and peatland (about 3000 yr BP to present). Other paleoecological and ecological studies from around the region provide evidence for directional changes, both past and present, from woodland to peatland. Furthermore, there is no clear evidence for peatland to woodland transitions in the absence of large‐scale disturbance. These results suggest that the bog climax hypothesis deserves a more careful examination by ecologists studying succession.
The diet of black guillemots Cepphus grylle in Shetland
Authors: Ewins P. J.
Published: July 2006

The diet of black guillemotsCepphus grylle(L.) was studied in Shetland between 1982 and 1985, both during and outside the breeding season. Full‐grown birds consumed a wide variety of fish and invertebrate species in summer, broadly reflecting the diversity of the inshore benthic fauna. In winter a greater diversity of invertebrates was taken, which assumed increased importance in the diet as the availability of benthic fish probably declined. Chicks were fed a diet of fish, with 70–80% being sandeelsAmmodytes marinusand butterfishPholis gunnelluson the island of Mousa. Sandeels were delivered more frequently in the early morning, coincident with a peak in their feeding activity. Older chicks were fed significantly longer fish. The composition of chick diet varied significantly with date, not chick age. A seasonal decline in the proportion of sandeels in the chick diet may have reflected changes in Zooplankton abundance, but the possibility that intensive industrial fishing of sandeels had adversely affected local stocks can not be ruled out.
Response by coypus to catastrophic events of cold and flooding
Authors: Doncaster C. P. , Micol T.
Published: July 2006

Population dynamics of the coypu, Myocastor coypus, were studied in central‐West France. This species has recently colonized temperate regions despite physiological sensitivity to cold weather. Live‐trapping over three years demonstrated that increasing population densities from summer into autumn were associated with a faster population turn‐over, homogeneous dispersion, and reduced rates of weight gain. Densities fell by 71% over a cold winter in which canals froze for 20 consecutive days, and by 69% over a mild winter with a flood of 5 weeks duration. Mortality was high in the coldest weather, and 45% of those surviving had frost lesions. A scarcity of males after the cold winter (up to 1♂: 3.3♀) was matched in a nearby population at artificially low density, where dispersing males predominated after the flood. The effect of the cold winter on reproductive output was to synchronize littering in summer, at a time of rich food supply. It was concluded that a flexible response to winter conditions enabled coypus to minimize the effects of extreme events and maximize their colonizing potential.
Water relations, temperatures, and mineral nutrients in Pedicularis dasyantha (Scrophulariaceae) from Svalbard, Norway
Authors: Gauslaa Yngvar , Odasz Ann Marie
Published: July 2006

The arctic vascular hemiparasite Pedicularis dasyantha has a lower diffusion resistance for water vapour than any associated species. Excised leaves die within one hour of drought stress under laboratory conditions, in spite of a high succulence. Transpiration rates of P. dasyantha in the field are almost two times higher than in Dryas octopetala, which is the most important host within investigated sites.

Diffusion resistances are higher in inflorescences than in leaves, probably because the dense pubescence reduces transpiration rates and raises temperatures in inflorescences to 14°C above air temperature on clear days.

Pedicularis dasyantha contains significantly more N, P, and especially K than its host. The high rate of transpiration probably enables the hemiparasite to capture a larger fraction of nutrients supplied by the xylem of its host.
A survey of the Van Mijen fiord, Svalbard, as habitat for ringed seals, Phoca hispida
Authors: Lydersen Christian , Jensen Per Magne , Lydersen Espen
Published: July 2006

The ringed seal breeding habitat of the Van Mijen fiord, Svalbard, Norway, was studied from 30 March to 22 May 1986. A Siberian husky dog was used to detect ringed seal birth lairs and breathing holes. Fifteen percent of the total fiord areas was sampled. We estimated the densitites of birth lairs and breathing holes to be 0.04 km‐2 and 1.30 km‐2, respectively. The Van Mijen fiord was a poor ringed seal breeding habitat compared with breeding habitats investigated both in Canada and other parts of Svalbard. The main reason is probably shallow snow depth and lack of structures such as pressure ridges around which enough snow could accumulate for the ringed seal females to be able to dig out their lairs. The number of seals inhabiting the area during the breeding period 1986 was approximately 125 animals.
Microhabitat relationships of five co‐occurring saxicolous mosses on cliffs and scree slopes in eastern Newfoundland
Authors: Hedderson Terry A. , Brassard Guy R.
Published: July 2006

The microhabitat relationships of five mosses, which co‐occur on cliffs and scree‐slopes in eastern Newfoundland, were evaluated by discriminant functions (DFA) and multiple regression analysis (MRA). The first three discriminant functions account for 91.3% of the among‐species variation in microhabitat characteristics, and are interpreted as representing species separation along 1) water deficit, 2) pH, and 3) temperature gradients. Multiple regression of individual species’abundances on measured microhabitat variables was successful, and highly significant regression equations accounting for 78% to 91% of variation in abundance were developed for all but one of the species studied. The combined DFA and MRA results show that the five moss species have distinct and different microhabitats within the cliff/scree‐slope habitat. Microdistribution of Grimmia torquata, an arctic‐montane moss at its southern limit, appears to be determined by sensitivity to high summer temperatures. Two southern mosses at their northern limit (Aulacomnium androgynum, Isothecium myosuroides) appear to be limited by water availability and, possibly, by low winter temperatures. The abundance of two species whose distributions extend both north and south of the study area (Encalypta procera, Eurhynchium pulchellum) shows no clear relationship with microclimate, though the microdistribution of the former species appears to be highly dependant on pH.
Differences in uptake of persistent pollutants for predators feeding in aquatic and terrestrial habitats
Authors: Larsson Per , Woin Per , Knulst Johan
Published: July 2006

Persistent pollutants in mustelid species (e.g. otter, mink, marten) were investigated. For a given animal, concentration of PCB and DDT in muscle were correlated with concentrations in its anal gland secretion. The correlation suggests that small samples of secretion could be used for pollutant analysis thereby eliminating the need to sacrifice animals. There was also a correlation between muscle and liver concentrations of these compounds, indicating a partitioning between different organs.

Furthermore, we showed that habitat differences between species led to interspecific variation in the uptake of persistent pollutants. Mink, which mainly feed in aquatic environments, contained a higher proportion of p, p‐DDT than marten, which feeds on terrestrial prey. Differences in PCB uptake were also noted between the two predators, though the congener distribution was heavily domined by a few hexa‐ and heptachlorobiphenyls.
Nest site selection in Norwegian woodpeckers
Authors: Hågvar Sigmund , Hågvar Geir , Mønness Erik
Published: July 2006

The nest site selection of seven Norwegian woodpeckers, Dryocopus martius, Picus viridis, P. canus, Picoides tridactylus, Dendrocopos leucotos, D. major and D. minor, was compared. The following parameters were measured at the nesting tree: forest type, tree species, the tree's “degree of decay”, the height of the tree, the hole's height above the ground, the stem's diameter at the hole and 0.5 m above the ground, earlier holes in the stem, and whether the tree was broken or not. Several differences between species were found in forest type and tree species. The use of weakened and dead nesting trees tended to increase with decreasing size of the bird. The following parameters usually decreased with decreasing size of the species: the height of the tree and of the nesting hole, and the stem's diameter at the hole and near the ground. Overlap in nest site parameters was calculated for four species, D. martius, P. viridis, D. major and D. minor, common nesters in Populus tremula. Overlap between D. minor and the other three species was low, whereas considerable overlap was found between D. martius and P. viridis. Both species prefer large, old Populus tremula trees.
Fecundity and egg viability in relation to female body size in Neodiprion sertifer (Hymenoptera: Diprionidae)
Authors: Heliövaara Kari , Väisänen Rauno , Varama Martti
Published: July 2006

Relationships between female size and fecundity, egg viability and embryonal development were studied in Neoriprion sertifer. Sawfly females, reared from the 1st instar larvae on Scots pine needles heavily affected by industrial pollutants or on relatively unpolluted needles, were induced to lay eggs parthenogenetically in the field in Finland. Females reared on polluted needles were smaller and oviposited an average of 68.8 eggs, and those reared on unpolluted needles 79.4 eggs per female. However, the higher egg viability in the former group masked the effect of reduced female size. This compensation was primarily related to the size of the females, larger individuals producing relatively fewer viable eggs in both groups.
Competition for nest‐boxes among four vertebrate species: an experimental study in orange groves
Authors: Barba E. , Gil‐Delgado J. A.
Published: July 2006

The experiment was carried out in eastern Spain from 1986 to 1988. The nest‐boxes were placed at the height where natural holes occur, visited twice a week, and cleaned after every breeding season. Four vertebrate species used the nest‐boxes: great tit Parus major, house sparrow Passer domesticus, tree sparrow Passer montanus, and black rat Rattus rattus. The first species to occupy the nest‐boxes, the great tit, was the least able to defend them. During the third year breeding by the great tit in the nest‐boxes decreased markedly, probably due to the increase of house sparrow and black rat occupation. We suggest that differences among species in their ability to discover and use new holes could allow some inferior competitors to breed in a habitat along with more aggressive competing species.
Home range and habitat use of wolverines Gulo gulo in Yukon, Canada
Authors: Banci Vivian , Harestad Alton S.
Published: July 2006

Home ranges and habitat use are described for three adult female, one adult male, and one subadult male wolverines in the Kluane Game Sanctuary, Yukon. When long distance excursions are not included, home ranges of wolverines in the Kluane Game Sanctuary were between 76 and 269 km2 for females and 209 and 269 km2 for males. Habitat use of females was similar to habitat availability. Males used subalpine coniferous habitats more frequently than other habitat types during winter. Although individual variation in the use of forest cover types, aspects, slopes and elevations was apparent, seasonal use did not differ from availability for each sex. Within the 1590 km2 study area, three adult males and six adult females were present, corresponding to a density of one resident wolverine 177 km‐2.
Predation on amphibian eggs and tadpoles by common predators in acidified lakes
Authors: Henrikson Britt‐Inger
Published: July 2006

Eggs and three different stages of premetamorphic tadpoles of moor frog Rana arvalis and common toad Bufo bufo were offered to the following potential predators in acidified lakes: newt Triturus vulgaris, water beetles Rhantus exoletus and Dytiscus lapponicus, dragonfly larvae Leucorrhinia dubia and Aeshna spp., water boatman Notonecta glauca and water bugs, Cymatia bonsdorffi, Glaenocorisa p. propinqua, and Corixa dentipes.

The predation pressure on eggs of R. arvalis was low due to thick jelly. The eggs of B. bufo were not attractive to predators with chewing mouth parts due to unpalatability but predators with sucking mouth parts were not repulsed. Tadpoles of R. arvalis were eaten by all predators but tadpoles of B. bufo were unpalatable to most predators. The predators used in the experiments are the new top predators in acidified fishless lakes. They may contribute to the reduction of populations of R. arvalis in acidified areas.
Numbers of litters, litter size and survival in two species of microtines at two elevations
Authors: Innes Duncan G. L. , Millar John S.
Published: July 2006

The number of litters, litter size and survival of Clethrionomys gapperi and Microtus pennsylvanicus were documented at two elevations (1450 m; 2240 m) in the Canadian Rocky Mountains to determine if those life history traits changed with the length of the breeding season. The high elevation was colder, had fewer frost‐free days, and more precipitation than the low elevation. The length of the breeding season of C. gapperi and M. pennsylvanicus averaged 8 d and 34 d longer, respectively, at the low elevation than at the high elevation. In both species and at both elevations, most females survived only long enough to produce one or two litters. Litter size was significantly greater at the high elevation than at the low elevation in M. pennsylvanicus, but not different in C. gapperi. Overall, nestling survival was greater at the low elevation than at the high elevation in M. pennsylvanicus, but not different in C. gapperi. Summer and winter survival rates were not different between elevations in either species. Differences in litter size and nestling survival between elevations in M. pennsylvanicus may be related to differences in habitat quality.
Feathers of birds of prey as indicators of mercury contamination in southern Finland
Authors: Solonen Tapio , Lodenius Martin
Published: July 2006

Mercury levels in feathers of nestling (162 broods) and fully‐grown individuals (n = 48) were studied. Within feather variation was considerable in many individual flight feathers. In juv. ospreys the mercury levels in distal parts of secondary coverts were significantly higher than those in proximal parts (p<0.01). In total feathers, the mercury levels were higher and their variations were larger in ad. than in juv. accipiters. Various irregularities in the mercury levels in different parts of the plumage of a bird seem to support the hypothesis that the mercury in the food eaten during feather growth considerably affects the mercury levels of the feathers, while the regular trends mainly support the hypothesis that the amount of mercury stored in body tissues is a determining factor of plumage levels. The importance of these factors seems to vary depending particularly on the age of the birds. From the result of this study, feathers as indicators of environmental mercury pollution should preferably be from nestlings. Small feathers are preferable to larger ones, and total feathers should be analysed rather than only parts of them.
Comparative phenology of four satyrine butterflies inhabiting dry grasslands in Sweden
Authors: Wickman Per‐Olof , Wiklund Christer , Karlsson Bengt
Published: July 2006

The phenology of the satyrine butterflies Coenonympha pamphilus L., Lasiommata megera L., Hipparchia semele L. and Maniola jurtina L. was compared under seminatural conditions with Festuca ovina as the food‐plant. Coenonympha pamphilus shows striking phenotypic plasticity as revealed by initiating cohorts at successive dates during the whole flight period. Growth rate is finely tuned depending on season, and larvae can hibernate in any of the three first instars, but also aestivate when 'surplus’time is available. Hipparchia semele and M. jurtina have reduced growth rates as last instar larvae at the beginning of summer. Lasiommata megera, which has an obligate bivoltine life cycle, shows the highest overall growth rate of all four species. Results suggest that egg size variation has consequences for the life cycles of these species.
Influence of temperature, photoperiod and nutrition on growth and consumption of Chaetopteryx villosa (Trichoptera)
Authors: Wagner Rüdiger
Published: July 2006

Chaetopteryx villosa Fabr. is uni‐ or semivoltine. The species was reared at 6°C and 10°C (8 h light, 16 h dark = LD 8/16) and at 10°C and 14°C (LD 14/10). Larval instar duration and pupal period decreased with increasing temperature. Instars II‐IV were completed within 2‐5 wk. Vth instar larvae pupated after two to twelve months. Pupal development required between one and three months. At 6°C no specimens pupated. At 10°C, LD 14/10 accelerated the development of instars II, IV, V and pupae. Head capsule widths were different between laboratory and field specimens. Relative consumption rate (RCR) ranged between 3.07 ± 1.12 (instar II, 14°C) and 0.09 ± 0.05 (instar V 6°C) mg mg‐1 d‐1. Growth rate, relative growth rate and efficiency of conversion were calculated. In a field experiment fine particulate versus coarse particulate organic material were tested as food sources. FPOM‐fed specimens were smaller than those fed with FPOM + CPOM. Pupation was initiated earlier in the FPOM fed group and lasted longer than in the other groups.
Resource partitioning among three woodpecker species Dendrocopos spp. during the breeding season
Authors: Török János
Published: July 2006

Food composition, prey size utilization and foraging behaviour of three sympatric woodpecker species (Dendrocopos major, D. medius, D. minor) were studied in an oak forest near Budapest during the breeding season in 1983 and 1984. Considering these three aspects of feeding, the great spotted woodpecker is a generalist species. Food composition of this species resembled the arthropod supply on the bark of trees more than those of the other two species. The bark of the trees seems to be a relatively unproductive microhabitat in the breeding season, so woodpecker species use, to different degrees, the food supply of the foliage as well. The food and the foraging behaviour of the middle spotted woodpecker show that this species feeds on prey living both on barks and in the foliage; it occupies‐an intermediate position between the great and the lesser spotted woodpeckers. Prey size did not correlate with predator size suggesting that woodpeckers adapted not to the summer resources but rather the winter ones.
Foraging dynamics of muskoxen in Peary Land, northern Greenland
Authors: Klein David R. , Bay Christian
Published: July 2006

Muskoxen Ovibos moschatus in northern Greenland (79‐83°N) are at the northern limit of their distribution and exist under seasonal extremes dominated by nearly 10 months of winter, much of which is without sunlight. The period of summer vegetative growth is less than two months. In the Kap København area (82°30′N), diversity of plant species is low (76 species of vascular plants) and forage biomass in major vegetation types in summer varies from over 40 g m‐2 in sedge‐dominated fens to ≤5 g m‐2 in polar barrens. Nonetheless, 90‐95% of the ice‐free area consists of barren ground or sparcely vegetated polar desert. During summer, muskoxen apparently foraged opportunistically to maximize intake, with sedges the major food item in fens while willows were the major dietary component when on willow‐dominated slopes. Quality of summer forage was high during its early phenological stages, with 21‐28% crude protein and 60‐75% in vitro digestibility. Microhistological analysis of winter feces indicated dominance by graminoids. Muskoxen spent > 50% of their daily activity feeding, which fits a cline of increasing feeding time with increasing latitude in summer. Increased feeding times at high latitudes appears to be a function of both reduced forage biomass and need to maximize forage intake during the brief summer period when forage quality is high. Movement rates in summer while foraging were inversely related to available forage biomass. Seasonal activity of muskoxen peaks during the rutting period (July‐September) and then declines gradually through early winter to a low in late winter (March‐April).
Fecundity of the newts Triturus cristatus, T. marmoratus and their natural hybrids in relation to species coexistence
Authors: Arntzen J. W. , Hedlund Linda
Published: July 2006

The two larger newt species in Europe, Triturus cristatus and T. marmoratus, have largely exclusive distributions but live in sympatry in a small area in western France, where they also hybridize. Triturus cristatus is increasing in abundance in the area at the expense of T. marmoratus, although this study shows that T. marmoratus has higher relative lifetime reproductive success. Triturus marmoratus lays more eggs than its relative under controlled conditions, and more T. marmoratus eggs in relation to its relative abundance are found in natural breeding sites. The hybrids are even more fecund, but their eggs and embryos have a lower survival rate.

The data are compared for age at maturity and species longevity, and estimates of lifetime reproductive success show that T. marmoratus females are more fecund than T. cristatus females. There are no differences between the species in survival of the embryos. It is therefore not clear why T. cristatus is replacing T. marmoratus, but changes in terrestrial habitats due to human activity might be the explanation.
Population structure of lakeshore willows and ice‐push events in subarctic Québec, Canada
Authors: Bégin Yves , Payette Serge
Published: July 2006

The effects of ice‐push on shoreline population age structure of Salix planifolia was investigated at Clearwater Lake, a large lake (1270 km2) located in the eastern Canadian subarctic. Twenty‐three willow stands located along a gradient of exposure to ice features were studied along the shoreline of a large island. Stand characteristics are significantly correlated with the degree of shore exposure. Drift‐ice action maintains continuously vegetation free substrata furthering willow colonization in shoreline habitat. Well‐rooted shrubs withstand disturbance through vegetative regenetation, that is profuse basal sprouting in response to ice‐scouring and breakage of stems. Age structure of basal shoots is highly correlated with ice‐scar dates. The rapid turnover of stem metapopulations frequently damaged by ice allows the shrubs to live older than usually. During recent decades, drift‐ice activity contributed to maintain a fast changing shore zone, favourable for the development of shrub populations. High frequency and magnitude of ice‐push events were caused by periodic high spring water levels.
The effect of heather beetle Lochmaea suturalis on vegetation in a wet heath in NE Scotland
Authors: Scandrett Eurig , Gimingham C. H.
Published: July 2006

An outbreak of heather beetle Lochmaea suturalis on a wet heath in north‐east Scotland was monitored. In many respects, the outbreak was similar to those described in lowland heaths; it started at a particular locus and when the Calluna vulgaris was depleted, spread throughout the heath. Population size then decreased annually due to some undetermined exogenous factor. A contributory factor may be the high incidence (35%) of parasitoid infestation which is density independent and, thus, not controlling.

There is no evidence that the hairiness of the var. hirsuta of Calluna has an effect on herbivory by Lochmaea. The distribution of larvae through the canopy is neither influenced by the morphology of Calluna, nor by the associated species, and appears to be at random. This probably represents the distribution of eggs since little lateral migration of the larvae takes place.

The response of the vegetation to herbivory is not simple. Associated with decreased cover of Calluna is an increase in Sphagnum plumulosum and Hypnum jutlandicum and reduction in S. compactum and Pleurozium schreberi. Changes seem to depend on initial vegetation and other parameters not measured (e.g. proximity of propagules, microclimate). Regeneration of Calluna does occur, largely by layering; although seedling occurrence increases in some areas, especially in Sphagnum, it seems unlikely that this will make a major contribution to the recovery of Calluna.
Comparisons of habitat availability and habitat use by an allopatric cohort of juvenile Atlantic salmon Salmo salar under conditions of low competition in a Norwegian stream
Authors: Heggenes Jan
Published: July 2006

Allopatric Atlantic salmon parr occupied a wider and lower range of mean water velocities than have been previously reported for parr in sympatry. With regard to depth, substrate and cover no substantial differences were found. Different fish sizes did not affect habitat use by parr significantly, neither did habitat use change during the season. Habitat availability strongly influenced observed habitat use thus, invalidating use of habitat suitability curves based on observations of habitat occupancy by fish only. The allopatric parr consistently selected habitats different from the available habitat, i.e. had preferences also in the absence of intraspecific interactions between age classes. Habitat conditions not used by the fish were more readily identifiable than habitats used. The parr rarely used shallow (≤ 10 cm) and deep (> 60 cm) stream areas, low mean water velocities (< 10 cm s‐1), fine substrate (sand and finer) and stream areas without cover. However, the calculated habitat preferences were also affected by habitat availability. Multivariate analysis did not identify any of the habitat variables as substantially more important than the others, but suggested that the importance of variables may vary with type of habitat studied.
Arthropod corpses in a temperate grassland: a limited supply?
Authors: Retana J. , Cerdà X. , Espadaler X.
Published: July 2006

The disappearance of arthropod corpses in a temperate grassland of the Mediterranean coast (Barcelona, Spain) has been analyzed in this study. The mean time in which the corpses stayed out in the field is less than five minutes (x̄= 285 ± 282 s), in a range of 2‐2228 s. This holds true in cleared areas as well as in high vegetation areas. Ants are the principal scavengers of this type of remains, although the species that collect them vary according to the time of day and season of year, with the corpses’disappearance being the most rapid during the middle hours of the day, precisely when ants’density on the ground is less. The reason for this was the peak daytime abundance of insectivore, opportunisms ants. Anyway, the short time lapse that the prey stay in the field ‐ at any time of the day ‐ can be considered as an indirect estimate of the scarcity of these resources.
Increasing insect abundance by killing deciduous trees: a method of improving the food situation for endangered woodpeckers
Authors: Aulén Gustaf
Published: July 2006

A total of 135 trees were girdled or notched in a forest area close to the river Dalälven in central Sweden. The purpose was to see whether good microhabitats for wood‐living insects could be created and if so, could be used as food for the endangered white‐backed woodpecker Dendrocopos leucotos. The chosen tree species were three of the most frequent used for foraging by the white‐backed woodpecker, i.e. aspen Populus tremula, birch Betula alba and common alder Alnus glutinosa.

The process of dying and decay in the manipulated trees was followed for eight to nine years, and the following variables were studied: tree condition, tree structure, wood‐condition, consistency of bark and cambium, frequency of polypori, foraging marks made by woodpeckers and abundance of insect species of importance as food for woodpeckers. Notched aspen died faster and were more quickly colonized by wood‐living insects than were girdled aspen. Since the notched aspen was also reduced more quickly to low stumps or lost their bark, their value for wood‐living insects was short‐lived. Notched birch died almost as quickly as girdled birch but were populated by slightly fewer insect species. Notching, in general, seemed to create good foraging trees in the short‐term whereas girdling produced trees of a longer‐term value. In order to improve the local food situation for the white‐backed woodpecker, a combination of the two methods is suggested. Nonetheless, both must be seen as emergency measures and cannot compensate for a large‐scale reduction in the abundance of old deciduous trees in the forest.
Snow‐patch foraging by pink‐footed geese Anser brachyrhynchus in south Iceland
Authors: Fox A. D. , Gitay H. , Boyd H. , Tomlinson C.
Published: July 2006

The pre‐nesting feeding behaviour of pink‐footed geese was studied in hayfields in southern Iceland during the late spring of 1989. Persistent snow‐patches protected underlying grass from the effects of severe night‐time frost. Areas within 1 m of snow‐patches had significantly greater amounts of green material than those further away; green material contained more than double the protein of brown, dead material, which predominated in open fields. Geese spent nearly 60 times more time feeding within 1 m of snow patches than expected by chance, and 20 times more time within 2–5 m. Their feeding rates here were faster and their step rate slower than further away. In this way, the geese selected the prime forage as soon as it became available.
Comparisons of three woodland sites in NW Britain differing in richness of the epiphytic Lobarion pulmonariae community and levels of wet acidic deposition
Authors: Farmer A. M. , Bates J. W. , Bell J. N. B.
Published: July 2006

The environment of three Quercus petraea‐dominated woodlands differing in species richness of the epiphytic Lobarion pulmonariae alliance was surveyed. Data on occurrence of epiphytes, air pollution and bark‐ and soil‐chemistry are presented. Within a given wood, individuals (of Q. petraea or Fraxinus excelsior) that support the growth of Lobaria spp. were found to have higher bark pH and higher bark Ca, K and Mg contents than individuals lacking these lichens. The most acidic bark was found at Seatoller Wood (Cumbria), a site which experiences strongly acidic rainfall. However, Old Garrock Wood (SW Scotland), although receiving acidic precipitation, had high bark pH and cation contents possibly due to the high levels of exchangeable cations in the soil. The results suggest that while bark pH is important in determining the occurrence of Lobaria spp., bark chemistry is determined by a combination of factors including tree species, atmospheric chemistry and soil nutrient status.
Sex ratio in a wild population of twospotted spider mites
Authors: Krainacker David A. , Carey James R.
Published: July 2006

The influence of week of season, leaf position on plants, population size and population growth rate on twospotted spider mite adult and functional sex ratio was determined for wild populations found on field corn. Adult sex ratio became less female biased as the mite population per plant increased. Adult sex ratio became increasingly female biased at higher leaf positions on the plant. Population growth rate (measured as proportion eggs in the population) was positively correlated with the proportion females in the adult population. Functional sex ratio (ratio of sexually available females to males) was positively influenced by population growth rate. The other factors studied only slightly influenced this parameter. Ecological implications of these findings are briefly discussed.
Thermal constraints and optimization of winter feeding and habitat choice in white‐tailed deer
Authors: Schmitz Oswald J.
Published: July 2006

I examined the activity and habitat choice of white‐tailed deer in winter to determine how deer balance feeding in habitats which may expose them to cold with resting in sheltered habitats. Average heat gain or loss of deer for feeding, resting and walking in four habitats in each of 24 h were estimated for two winter periods (early‐mid and late winter). These values were used in a dynamic optimization model to predict the hourly behavior‐habitat choices which enable deer to maintain thermal homeostasis, minimize the risk of exceeding lethal body temperatures and satisfy daily energy requirements. The behavior and habitat choices observed under natural conditions were consistent with the model predictions. Deer foraged for the maximum time that was thermally possible in both sampling periods and they used exposed habitats without incurring high heat losses. Deer appeared to avoid overheating in sheltered habitats during daylight and avoid hypothermia in exposed habitats at night.
The seasonal periodicity of algae on Antarctic fellfield soils
Authors: Davey Martin C.
Published: July 2006

Investigation of the seasonal changes in composition of an immature Antarctic fellfield cyanobacterial/microalgal community has demonstrated a repeated periodicity. The community consisted of only 14 species. Early spring growth of filamentous chlorophytes under snow and ice was followed by summer dominance of the community by cyanobacteria, particularly Phormidium autumnale. Limitation of the chlorophyte populations appeared to be a result of either dehydration of the soil or increased irradiance. The population maximum of the cyanobacteria occurred in mid‐summer, although there were no obvious reasons for the cessation of growth at this time, and declined rapidly in late summer. Regrowth of the community occurred from very small inocula each spring, most of the biomass having been lost during late summer or during the washout associated with the spring thaw. This regrowth demonstrates the potential for the population to establish an immature fellfield community very rapidly foliowing exposure by glacial retreat or physical disturbance.
Bryophytes and decaying wood– a comparison between managed and natural forest
Authors: Andersson Lars I. , Hytteborn Håkan
Published: July 2006

A comparative study was made of one managed forest and one natural forest regarding the supply of decaying wood on the ground and the occurrence of bryophytes on the wood, especially epixylic specialists.

The total substrate surface of wood is larger in the primeval forest. The larger quantity of decaying wood increases the probability of wood occurring in ail decay stages. Logs of Populus tremula occurred only in the natural forest. An important proportion of the wood substrate in the natural forest consisted of logs of large diameter class; these logs were missing in the managed forest. Fiftyfour bryophyte species were found on decaying wood. They were separated into four different groups. Facultative epiphytes first colonized decaying wood, followed by epixylic specialists and finally by competitive epigeics. Opportunistic generalists showed a more irregular pattern of occurrence. The bryophyte flora on decaying wood was most species rich in the natural forest. Sixteen epixylic specialists occurred here, several considered to be threatened by forest management, while only 5 of these species occurred in the managed forest.

The higher frequency of epixylic specialists in the natural forest is related to the greater frequency of favourable habitats, specifically: logs of large diameter, decayed wood, Populus tremula and (to a lesser extent) Picea abies.
Social overwintering and food distribution in the bank vole Clethrionomys glareolus
Authors: Ylönen Hannu , Viitala Jussi
Published: July 2006

We studied overwintering in the bank vole Clethrionomys glareolus in four 0.5 ha enclosures in an abandoned field in central Finland in the winter 1987/88. In two of the enclosures food was offered evenly distributed over the whole enclosed area (Even Enclosures = EE), in the two others food was offered in one feeding patch with four feeding chambers 2 m apart (Patchy Enclosures = PE). Food was provided in about the same amount in both enclosures. The experiment commenced in early October, with 13 females and 11 males in EEs and 12 + 13 voles in PEs. After two months the voles in the PEs were concentrated around the feeding patches. Territoriality was not observed in EEs, instead the voles formed small exclusive overwintering groups consisting of 2‐3 females and at least one male. The size of the home range of the females and males was identical during mid‐winter as the voles were non‐breeding. By the onset of breeding, range size increased in both sexes, but significantly more in males, however. The survival was about the same in all populations. Every population showed a mid‐winter decline suggesting the effect of the mustelid predators observed in and around the enclosures. In the PEs the overwintering aggregations lasted until the maturation of the first litters. Food distribution affected the spatial distribution of the populations. We conclude that the patchiness of the habitat and especially the availability of food are the most important factors determining the social structure of overwintering populations.
Home range size and activity of the wood lemming, Myopus schisticolor
Authors: Andreassen Harry P. , Bondrup‐Nielsen Søren
Published: July 2006

We present the results from a radiotelemetric study on space use and activity in a natural population of the wood lemming Myopus schisticolor. Male home ranges were larger than females, and the ratio female home range to male home range was smaller than expected compared to other small rodents. Males moved distances 4‐12 times longer than females. We argue that this difference in mobility gives a higher probability of capturing males than females in snap trap studies. If there is a sex biased trappability, this might explain the increasing female biased sex ratio during the snow free season (1:1 in spring, 3:1 [female:male| in autumn), as a higher mortality of males during the reproductive season.
Diet selection by vertebrate herbivores in the high arctic of Greenland
Authors: Klein David R. , Bay Christian
Published: July 2006

Microhistological analysis of fecal droppings indicates that graminoids (sedges, grasses, and rushes) and the only willow present, Salix arctica, are primary food items of the muskox Ovibos moschatus, arctic hare Lepus arcticus, and collared lemming Dicrostonyx groenlandicus in northern Greenland (79°‐83°N). Plant biomass available during the peak growing season varied with vegetation types from < 2 g m−2 in polar barrens to 34 g m−2 in sedge fens. The clustered distribution of vegetation minimizes competition among vertebrate herbivores.
Responses by the capercaillie Tetrao urogallus, and the willow grouse Lagopus lagopus, to the green matter available in early spring
Authors: Pulliainen Erkki , Tunkkari Paavo S.
Published: July 2006

Food matter eaten in the first snowless spots early in the spring by capercaillie Tetrao urogallus and willow grouse Lagopus lagopus was studied in Finnish Forest Lapland. When the snow disappears, both species change to feeding mainly on the plants available in the snowless spots, although male capercaillie does not exploit this nutritious diet to the same extent as female capercaillie and willow grouse. Selection in favour of nitrogen and phosphorus‐rich food items, i.e. Betula pubescens, male catkins Eriophorum vaginatum, flower buds, and Equisetum spp., stems and tips, seems to be characteristic especially of the female capercaillie, whose winter diet is poor in these elements. Female capercaillie also feeds on more plant species or different parts of plants at one time than willow grouse, while no differences were recorded between male and female willow grouse in the composition of their spring food. The crowberry Empetrum hermaphroditum, almost regularly produces a bountiful berry crop in northern Finland, and since it overwinters well, it represents an easy source of energy and water available almost every spring. The quality and/or the quantity of the green food matter available early in the spring may fluctuate considerably and be of importance for short‐term fluctuations in the populations of these tetraonid species.
Marrow fat content, sex and age of red deer killed by wolves in winter in the Carpathian Mountains
Authors: Okarma Henryk
Published: July 2006

Age, sex and legbone marrow fat content of 90 red deer Cervus elaphus killed by wolves Canis lupus in winter in southeastern Poland were examined 1984–1988. The majority of kills were calves (44%) and hinds (40%); stags formed only 16%. The average age of hinds was 7.2 yr compared to 5.3 yr in stags. Animals older than 10 yr comprised only 13% of prey. Adults showed high femoral fat content (> 80%) throughout the winter (76% in early winter and 52% in late winter). Among calves femur marrow fat varied through the winter. In early winter 70% of calves had a high fat content (> 80%), though by late winter only 20% had such a high fat content, whilst 43% had low fat content (< 20%).
Body size – prey size relationships in European stoats Mustela erminea: a test case
Authors: King Carolyn M.
Published: July 2006

From the close correlation between the body size of European stoats and the mean size of their vertebrate prey it ought to be possible to predict the body size of European stoats living on a prey fauna of a given size distribution. In New Zealand, stoats of European stock have lived for > 100 yr on a prey fauna containing fewer small and more large vertebrate prey than in Europe. They have become generally larger than their ancestors, as expected – especially the females. The vertebrate prey size index for New Zealand stoats extends the correlation predicted from European data. New Zealand stoats also eat large numbers of native insects. If these are included the local prey size indices are lower but still tend to vary with the substantial local variation in body size of stoats within New Zealand. Recent results from southern Ireland also fit the European correlation, but the few data so far available from Northern Ireland do not.
Floral display and pollination success in Achillea ptarmica (Asteraceae)
Authors: Andersson Stefan
Published: July 2006

In a natural population of the self‐incompatible Achillea ptarmica, many‐headed inflorescences attracted most pollinators (flies), and each pollinator visited more heads on large inflorescences than on smaller ones. The visitation rate did not increase disproportionately with inflorescence size, as would be expected if clusters of heads had a synergetic effect on pollinator attraction. Both the calculated visitation rate per head and the percentage seed set increased slightly as a function of head number. The removal of rays from all heads in the inflorescence reduced the approach rate by 51%, but had only a small negative effect on seed set (12%). Hence, ray removal probably affected male fertility (pollen donation) to a greater extent than female fertility. The decline in pollination success was similar for all inflorescence sizes, suggesting that ray and inflorescence size have independent effects on the total display, and thus represent separate targets for pollinator‐mediated selection. Residual variation in seed set was strongly correlated with patch identity, indicating clonal or environmentally induced differences in female reproductive success.
Latitudinal patterns in the size of European butterflies
Authors: Nylin Sören , Svärd Lena
Published: July 2006

The importance of seasonality in shaping latitudinal size patterns was investigated in 16 species of lycaenine and satyrine butterflies with distributions in Sweden and continental Europe. Species without shifts in voltinism within the study area generally displayed clear size clines, increasing in size from north to south within Sweden. These species were also larger in continental Europe than in Sweden. In northern temperate areas a linear model for mean size at different latitudes seems to be a reasonable approximation for most species in this category. The size patterns for three species with shifts from univoltinism to bivoltinism at latitudes within Sweden were more reminiscent of the “saw‐tooth”‐pattern predicted by theory for such cases. The results suggest that size patterns in European butterflies to a large extent is governed by the length of the favorable season at different latitudes, affecting selection for development time and size. Altitude and drought also affect the effective season length and may amplify or complicate latitudinal patterns.
Seasonal use of illuminated areas by foraging northern bats Eptesicus nilssoni
Authors: Rydell Jens
Published: July 2006

Foraging northern bats Eptesicus nilssoni were monitored from a car along a 27 km line transect in southern Sweden every week during a 14 month period by means of a bat detector. The number of bats observed along the transect was highly correlated with air temperature, and no bats were observed at temperatures < 6°C. Hence, feeding was infrequent in April and May as well as in September and October and did not occur at all from November to March. In summer, the bats were observed in forest and farmland, but in spring and autumn most bats were detected along rows of street‐lights. By attracting insects, artificial lights apparently provide local patches of food for some species of bats during periods which may be critical for their survival and reproduction.