Changes in the distributions of Red and Grey Squirrels in Scotland

Changes in the distribution of Red and Grey Squirrels in Forestry Commission land were examined using a replacement index for the period of 1980–94. Data from each administrative region in Scotland were examined separately. No region was found to have experienced a significant replacement of Red Squirrels by Grey Squirrels. However, significant trends in the area occupied by one or both Squirrel species were observed in the Borders and Strathclyde. Other areas appear to have experienced little or inconsistent changes in the last 15 years.     

松鼠生态学研究现状与展望

松鼠(Sciurus vulgaris)是一种广泛分布于欧亚大陆的树栖杂食性啮齿动物。在欧洲,由于入侵种北美灰松鼠(S.carolinensis)的引入,松鼠的数量急剧减少,松鼠的生态学研究受到广泛的关注。在中国,松鼠因贮食坚果的习性而受到重视。本文从个体生态学、种群生态学、种间关系和行为生态学的角度对松鼠生态学研究成果进行了综述。松鼠是哺乳动物生态学研究很好的模式种,以下5个方面的研究将成为松鼠生态学研究的新方向:(1)不同分布区松鼠的比较生态学;(2)与森林天然更新的关系;(3)集合种群动态及其对生境破碎化的响应;(4)分子系统地理学;(5)作为景观管理的实验种。     

Assessing the potential for Grey Squirrels Sciurus carolinensis to compete with birds at supplementary feeding stations

Supplementary feeding of birds, particularly in urban areas, is often associated with increased population size and fecundity. In the UK, the non‐native Grey Squirrel Sciurus carolinensis is common in rural and urban habitats. It exploits supplementary feeders and may induce interference competition by excluding birds, but empirical evidence of this is unavailable. Using controlled model presentation experiments, we demonstrate that Grey Squirrels could reduce bird use of supplementary feeders and induce interference competition. Total bird resource use was reduced by 98% and most species exhibited similar sensitivities. The likelihood and magnitude of interference competition will depend on how rapidly displaced birds find alternative food sources; it will be greatest where there are high Grey Squirrel densities and few supplementary feeders. Other studies suggest that supplementary feeding increases Grey Squirrel numbers, and the species is also predicted to expand its non‐native range across most of Europe. Our data indicate that Grey Squirrels may eventually alter the net effect of supplementary feeding on bird populations across the European continent; increased use of squirrel‐proof feeders may help to minimize such effects.     

Caching behaviour of Red Squirrels Sciurus vulgaris under conditions of high food availability

Members of the genus Sciurus store seed when plentiful by scatterhoarding. Such caches are impossible to defend and vulnerable to both interspecific and intraspecific competitors. In view of the delicate position held by Red Squirrels Sciurus vulgaris L. in Britain it is of value to extend to this species studies of the methods whereby such competition is reduced. Caching behaviour in a population of Red Squirrels living in a protected reserve and receiving supplementary food was studied for 18 months. Two main aspects were investigated; their ability to find caches they had not made, and their efforts to reduce competition for caches they did make. Stapanian & Smith (1978) predicted that caches are made at an optimal density and that the entire 360d? arc around a resource is used. This study upheld this second prediction but not the first for the population of Red Squirrels in question. In addition, it is suggested that caching cannot be considered to be permanent under conditions of surplus food.     

Effects of mountain pine beetle on fuels and expected fire behavior in lodgepole pine forests, Colorado, USA

In Colorado and southern Wyoming, mountain pine beetle (MPB) has affected over 1.6 million ha of predominantly lodgepole pine forests, raising concerns about effects of MPB-caused mortality on subsequent wildfire risk and behavior. Using empirical data we modeled potential fire behavior across a gradient of wind speeds and moisture scenarios in Green stands compared three stages since MPB attack (Red [1-3 yrs], Grey [4-10 yrs], and Old-MPB [～30 yrs]). MPB killed 50% of the trees and 70% of the basal area in Red and Grey stages. Across moisture scenarios, canopy fuel moisture was one-third lower in Red and Grey stages compared to the Green stage, making active crown fire possible at lower wind speeds and less extreme moisture conditions. More-open canopies and high loads of large surface fuels due to treefall in Grey and Old-MPB stages significantly increased surface fireline intensities, facilitating active crown fire at lower wind speeds (>30-55 km/hr) across all moisture scenarios. Not accounting for low foliar moistures in Red and Grey stages, and large surface fuels in Grey and Old-MPB stages, underestimates the occurrence of active crown fire. Under extreme burning conditions, minimum wind speeds for active crown fire were 25-35 km/hr lower for Red, Grey and Old-MPB stands compared to Green. However, if transition to crown fire occurs (outside the stand, or within the stand via ladder fuels or wind gusts >65 km/hr), active crown fire would be sustained at similar wind speeds, suggesting observed fire behavior may not be qualitatively different among MPB stages under extreme burning conditions. Overall, the risk (probability) of active crown fire appears elevated in MPB-affected stands, but the predominant fire hazard (crown fire) is similar across MPB stages and is characteristic of lodgepole pine forests where extremely dry, gusty weather conditions are key factors in determining fire behavior.     

Provision of supplementary food for wild birds may increase the risk of local nest predation

In countries such as the UK, USA and Australia, approximately half of all households provide supplementary food for wild birds, making this the public's most common form of active engagement with nature. Year‐round supplementary feeding is currently encouraged by major conservation charities in the UK as it is thought to be of benefit to bird conservation. However, little is understood about how the provision of supplementary food affects the behaviour and ecology of target and non‐target species. Given the scale of supplementary feeding, any negative effects may have important implications for conservation. Potential nest predators are abundant in urban areas and some species frequently visit supplementary feeding stations. We assess whether providing supplementary food affects the likelihood of nest predation in the vicinity of the feeder, by acting as a point attractant for potential nest predators. We provided feeding stations (empty, peanut feeder, peanut feeder with guard to exclude potential nest predators) in an area of suburban parkland in the UK and monitored the predation rate of eggs placed in artificial nests located at distances that replicated the size of typical suburban gardens. Nest predators (Magpies Pica pica, Grey Squirrels Sciurus carolinensis) were frequent visitors to filled feeders, and predation caused by Magpies, European Jays Garrulus glandarius and Grey Squirrels was significantly higher when nests were adjacent to filled feeders. The presence of a feeder guard did not significantly reduce nest predation. As supplementary feeding is becoming increasingly common during the breeding season in suburban habitats, we suggest that providing point attractants to nest predators at this time may have previously unconsidered consequences for the breeding success of urban birds.     

Distribution and status of the Red Squirrel (Sciurus vulgaris) and Grey Squirrel (Sciurus carolinensis) in Ireland

The distributions of the Red and Grey Squirrel were surveyed in Northern Ireland and the Republic of Ireland between 1994 and 1996. Survey methods differed between the two studies. In the former, all suitable habitat, of at least 15 ha, was inspected for species presence or absence. In the Republic, data were gathered through questionnaires to governmental and independent wildlife bodies. The combined results indicate that the Red Squirrel remains widespread and locally abundant, and is present in all but two counties. The Grey Squirrel is now more widespread than ever before, and can be found in 22 of the 32 counties. Its range expansion has varied from 0 km/yr to an estimated 13.4 km/yr, as various geographical features, principally rivers, have hindered its progress in certain directions.     

Bone breccias, bone dumps, and sedimentary sequences of the western Limeworks, Makapansgat, South Africa

The sediments in the western side of the Makapansgat Limeworks were either precipitated as speleothems, represented in the earlier massive deposits, or were deposited as coarsening clastic sediments, mainly representing later deposits. Between the earlier deposits and the main sedimentary phase, the stratigraphic sequence was inverted twice to a considerable height by the unusual deposition of subaqueous speleothem. Bone-bearing deposits, including the Main Quarry Bone Breccia and the well-known Grey Breccia belong, in time, to the lower part of the clastic deposits called the Red Silts. Australopith fossils have been found in the Grey Breccia dumped material and, in situ, from the dolomite clast breccia on the Main Quarry entrance buttress. Whatever the problems may be in provenancing some of the material from the Limeworks dumps, there is no doubt that the three rows of blocks on the southern side of the dumps belong to the Grey Breccia, and other rows contain red sediment sufficient for them to be safely associated with the Red Silts. There is no reason why this material should not be prepared with confidence as to its stratigraphic provenance. In any case, stratigraphic evidence, presented here, shows that there is little difference in time between the deposition of the bone-bearing breccias.     

Comparison of methods for obtaining population estimates for Red Squirrels in relation to damage due to bark stripping.

The relation between population density and the extent of damage incurred by bark stripping behaviour was investigated in a Scots Pine plantation known to have suffered considerable damage. Population density was estimated by three non-interventionist methods that could potentially be applied elsewhere: line surveys, drey counts and cone counts. The different methods of estimating the population size proved to be consistent and produced an unusually high value of four Red Squirrels per hectare. Within the study area, fresh damage was related to local population densities.     

Grey Partridge Perdix perdix in the UK: recovery status,set‐aside and shooting

The Grey Partridge Perdix perdix is a European Species of Conservation Concern and a priority species under the UK Biodiversity Action Plan. The Game & Wildlife Conservation Trust (GWCT) launched a major programme to help partridge recovery in the UK, built on the GWCT’s Partridge Count Scheme (PCS) and including a demonstration site from 2002. We contrast the national picture of no population change since 1999 from BTO monitoring with a doubling of spring pair density on PCS sites. At the demonstration site, where set‐aside was used for habitat creation, Grey Partridge breeding density increased six‐fold, to 18 pairs/km², then fell back. The drop coincided with bad weather but also with the disappearance of rotational set‐aside when the set‐aside rate fell to zero, which halved the amount of brood‐rearing habitat. Non‐rotational set‐aside remained unchanged, as did the amount of nesting habitat that it provided. Grey Partridge density was significantly linked to rotational set‐aside, especially wild bird cover, but not to non‐rotational set‐aside. The demonstration project also showed that, with appropriate precautions, it was possible to shoot over 60% of Red‐legged Partridges Alectoris rufa while maintaining Grey Partridge losses below 5%. On PCS sites, the annual change in spring density in recent years differed in relation to neither shooting pressure nor intensity of Red‐legged Partridge releasing. Provision of brood‐rearing habitats and game cover increased with the latter, and probably counteracts the shooting losses of Grey Partridges on Red‐legged Partridge shoots when, as on PCS sites, active measures keep those losses below 20%. Targeted personal advice channelled through the PCS has been fundamental to these successes and must be expanded.     

Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet

Diet analyses are central to the study of avian trophic ecology, and stable isotope analyses have made an increasing contribution in the last two decades. Few isotopic studies have assessed the diet of raptor species, which are more frequently analysed by conventional diet methods such as pellet analysis. In this study, we compare prey consumption estimates of nestling Bonelli's Eagles Aquila fasciata from conventional pellet analysis (in terms of items and biomass) and stable isotopic mixing models (SIAR) using δ¹³C, δ¹⁵N and δ³⁴S of feathers. The pellet analysis showed that European Rabbits Oryctolagus cuniculus, pigeons (mainly Common Wood Pigeons Columba palumbus and Domestic Pigeons Columba livia dom.), Red‐legged Partridges Alectoris rufa, passerines, Yellow‐legged Gulls Larus michahellis and Eurasian Red Squirrels Sciurus vulgaris were the main prey, so they were selected for diet reconstructions in SIAR. At the population level, mean prey consumption estimates were similar for pellets (both items and biomass) and SIAR. At the territory level, the weighted kappa statistic showed good ordinal scale agreement in main prey consumption between items or biomass and SIAR. Although the intraclass correlation coefficient showed poor method agreement when considering all prey in the same analysis, the intraclass correlation coefficients for each prey category showed significant agreement between pellets and SIAR when estimating the consumption of Rabbits, pigeons and Gulls, with lower agreement for passerines and Squirrels. Lastly, there was poor method agreement for estimates of Partridges. Our results suggest an overall agreement between the pellet analysis and SIAR when estimating nestling Bonelli's Eagle diet at both the population and, to a lesser extent, the territory level, supporting the usefulness of isotopic mixing models when identifying the terrestrial and marine components of raptor diets.     

Decolorization of simulated textile dye baths by crude laccases from Trametes hirsuta and Cerrena unicolor

In this study crude laccases from the white‐rot fungi Cerrena unicolor and Trametes hirsuta were tested for their ability to decolorize simulated textile dye baths. The dyes used were Remazol Brilliant Blue R (RBBR) (100 mg/L), Congo Red (12.5 mg/L), Lanaset Grey (75 mg/L) and Poly R‐478 (50 mg/L). The effect of redox mediators on dye decolorization by laccases was also assessed. C. unicolor laccase was able to decolorize all the dyes tested. It was especially effective towards Congo Red and RBBR with 91 and 80% of color removal in 19.5 h despite the fact that simulated textile dye baths were used. Also Poly R‐478 and Lanaset Grey were partially decolorized (69 and 48%, respectively). C. unicolor laccase did not need any mediators for removing the dyes. However, T. hirsuta laccase was only able to decolorize simulated Congo Red and RBBR dye baths (91 and 45%, respectively) in 19.5 h without mediators. When using mediators the decolorization capability was enhanced substantially, e.g. Poly R‐478 was decolorized by 78% in 25.5 h. On the whole, both laccases showed potential to be used in industrial applications.     

Minimum population size and distribution of Grey Crowned Cranes Balearica regulorum in Rwanda: an aerial and ground survey

The iconic Grey Crowned Crane Balearica regulorum is facing an increase in threats to its wetland habitat and poaching for the captive trade market. This has resulted in an enduring long-term decline in population numbers, which led to the species being listed as Endangered in the IUCN Red List. In Rwanda, Grey Crowned Cranes are threatened by human factors often driven by conditions of poverty, livelihood disadvantage and lack of conservation awareness. Previous population estimates suggested there were fewer than 500 Grey Crowned Cranes left in Rwanda. The Rwanda Wildlife Conservation Association and its partners have been working to eliminate the illegal trade and boost the population numbers in Rwanda. In August 2017, the first national census of Grey Crowned Cranes in Rwanda was carried out to serve as a baseline and to increase the accuracy of previous estimations. The survey was conducted over three days using both aerial and ground survey techniques. The results show that at least 487 Grey Crowned Cranes occur in Rwanda and include details on distribution and habitat type. Challenges for Grey Crowned Crane conservation at different sites are discussed, such as wetland transformation for agriculture, and illegal activities in protected marshlands. To ensure the long-term viability of this species, there is a need for upscaling of conservation efforts in key crane areas, continued monitoring of the crane population including trans-boundary collaboration, and strategies to promote the sustainable use of wetlands.     

The use of nest boxes by the Red Squirrel Sciurus vulgaris in a coniferous habitat

This paper describes the results of a 4-year study examining the use of nest boxes by Red Squirrels. Two different designs of nest box were erected in a conifer woodland which supported a high density of animals; spring population estimates were between 3.5 and 4.0 individuals per hectare. Boxes were used by adults, subadults, lactating females and their young. Breeding females more frequently used the larger of the two box designs, although this preference was not statistically significant. There was no difference in the mean sizes of litters found within the two box types. The mean size of litters present in boxes was 2.7 (n = 31, SE = 0.23) which was similar to the mean litter size of 2.5 (n = 8, SE = 0.50) found in dreys. Thus, nest boxes proved to be a valuable research tool for monitoring parturition dates, litter sizes, nestling sex ratios, and preweaning mortality.     

Nest-site selection by crossbills Loxia spp. in ancient native pinewoods at Abernethy Forest,Strathspey, Highland

Capsule Birds preferred stands with a particular density of trees, perhaps to avoid predation, and they selected aspects sheltered from prevailing winds.

Aim To describe the nesting habitat and tree selection by crossbills in a restricted pinewood habitat in Scotland.

Methods Scots Pines used by nesting crossbills were described and compared with randomly selected pines. Nest aspect was related to wind strength and direction.

Results The crossbills selected trees at a density of 50–60 trees/ha. Such stands may be sufficiently dense to provide cover, yet occur at a low enough density to minimize being visited by potential arboreal predators, such as Red Squirrels and Pine Martens. Crossbills tended to nest on lateral branches on the northeast side of crowns. Tree crown development was not asymmetric, so the birds may choose the northeast side to shelter from the prevailing southerly to westerly winds.

Conclusion Stands of pines at a low density need to be maintained for the benefit of crossbills.     

Circulating lipoprotein cholesterol concentrations in the summer-active ground squirrel (Spermophilus lateralis): a comparison with those in humans and rabbits.

1. The concentrations of total cholesterol (free cholesterol plus cholesteryl ester) in the sera and in two lipoprotein fractions of golden-mantled ground squirrels (Spermophilus lateralis) were measured and compared to those found in humans and New Zealand White rabbits (Oryctolagus cuniculus). 2. Squirrels showed significantly higher concentrations of total serum cholesterol (TSC; P less than 0.0005), high density lipoprotein cholesterol (HDL-C; P less than 0.0005), and very low density plus low density lipoprotein cholesterol (VLDL + LDL-C; P less than 0.0005) than those in rabbits. 3. Squirrels had significantly higher TSC (P less than 0.0005) and HDL-C (P less than 0.0005) concentrations than did humans. 4. Squirrels additionally exhibited significantly lower TSC/HDL-C ratios than did rabbits (P less than 0.005) or humans (P less than 0.0005). 5. The significant differences in lipoprotein metabolism observed in this study between the active hibernator and non-hibernators, may reflect the marked biochemical and physiological adjustments hibernating species make throughout their circannual cycle.     

Rattlesnake Rattles and Burrowing Owl Hisses: A Case of Acoustic Batesian Mimicry

Burrowing owls nest and roost in ground squirrel burrows, a refuge frequently used by rattlesnakes. When cornered, burrowing owls produce a vocal hiss that has been suggested to mimic a rattlesnake's rattle. To test this hypothesis, we conducted an experiment using two populations of Douglas ground squirrels that differ in their evolutionary histories with rattlesnakes. Both squirrel populations were sympatric with burrowing owls. Squirrels from a population subjected to natural selection by rattlesnakes treated the owl hiss as cautiously as they did the rattle, and responded with greater caution to the rattle and hiss than to two control sounds. Squirrels from a rattlesnake-free area, however, were less systematic in differentiating among the rattle, the hiss, and the control treatments. Such variation between ground-squirrel populations provides evidence that the burrowing owl's defensive hiss currently functions as an acoustic Batesian mimic of a rattlesnake's rattle.     

The role of birds and mammals in Korean pine (Pinus koraiensis) regeneration dynamics

This study examined the interrelationships of the fall seed-foraging guild with Korean pine (Pinus koraiensis) and its regeneration. The study took place in old-growth and secondary-growth forests in Northeastern China. Foraging behavior, seed transportation distance, and cache location of various birds and mammals were observed. Regeneration characteristics of Korean pine were also analyzed using plots in various vegetation cover types, successional stages, and topographical situations. Ten species of vertebrates were able to harvest seed from the closed-cone Korean pine. Of these, the Eurasian nutcracker, Eurasian nuthatch, red squirrel, and Siberian chipmunk were found to be potential seed dispersal agents. The nutcracker was the most important dispersal agent, easily acquiring seed with its large pointed bill, carrying up to 62 seeds in one trip, carrying seed at least 4 km, and placing seed in a variety of sites 2.5–3 cm deep in the soil. The Eurasian nuthatch carried a single seed per trip at distances less than 50 m, needed nutcrackers to open the cones and expose seed before they could acquire seed, and occasionally cached seed in the soil. Red squirrels were uncommon visitors to the tree tops of Korean pine, carried cones shorter distances than nutcrackers, and were only found under forest canopies. Human harvest of cones by knocking off branches also affected squirrel behavior and reduced future cone crops. Siberian chipmunks also collected seed from cones in trees and appeared to transport seed less than 50 m. Six other species were observed in this study successfully harvesting seed from cones but were not potential seed dispersers. Natural seedling establishment was found to be over 1000 seedlings/ha except on old-growth pine-hardwood sites. Squirrels were commonest here, but few seedlings survived past the 2nd year due to the intense shading. Second-growth forest types, including aPicea plantation where nutcrackers cached seed daily, and an old-growth pine-hardwood selective-harvest site, had the greatest regeneration. In conclusion, most natural regeneration of Korean pine in this part of its range is due primarily to the Eurasian nutcracker. Nutcrackers can aid forest managers in reaching desired stocking levels after disturbance, as well as a more natural-appearing forest. Squirrels, chipmunks, and nuthatches are minor seedling establishment agents. Korean pine seed is an important food source used by at least 22 species of forest wildlife.