Showing papers by "Royal Society for the Protection of Birds published in 2003"

Farmland biodiversity: is habitat heterogeneity the key?

Abstract: Agricultural intensification has led to a widespread decline in farmland biodiversity measured across many different taxa. The changes in agricultural practices affect many different aspects of the farmland habitat, but agricultural industry, policy and much previous research has tended to be concerned with specific sectors or practices (e.g. pesticide use or cereal husbandry). Here, we review the empirical literature to synthesize the research effort that has been directed to investigate specific practices or goals to make general statements regarding the causes and consequences of farmland biodiversity decline. We argue that the loss of ecological heterogeneity at multiple spatial and temporal scales is a universal consequence of multivariate agricultural intensification and, therefore, that future research should develop cross-cutting policy frameworks and management solutions that recreate that heterogeneity as the key to restoring and sustaining biodiversity in temperate agricultural systems.

Measuring the changing state of nature

Abstract: Most attempts to quantify the impact of humanity on nature and bring it to public attention have centred around estimates of extinction rates Suggestions that these figures have been exaggerated are, in our view, misplaced, but extinction rate estimates do face other problems – inevitable uncertainty, an arguably weak link to economic value, and insensitivity to short-term change We therefore look here at other large-scale measures of the changing state of nature, focusing on recent analyses of trends in population size, numbers of populations and habitat extent In spite of being limited by sampling inadequacies, these data provide a sensitive short-term complement to the long-term perspective gained from considering extinction rates that can be linked directly both to economic values and to public concerns Although further work is needed on extinction rates, we conclude that significant new emphasis should be placed on instituting broader, more systematic monitoring of habitats and populations

A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material

Abstract: Summary 1. The potential of using stable isotope signatures of avian claws in order to infer diet and habitat use was investigated. 2. Highly significant relationships observed between stable carbon and nitrogen isotope ratios ( δ 13 C, δ 15 N) in the claws and body feathers of resident birds were expected since it was predicted that they were synthesized in the same habitat and approximately the same time of year. 3. Likewise the non-significant relationships observed between δ 13 C and δ 15 N in the claws and tertial feathers of neotropical migrant birds were also predicted since the claws were synthesized in the wintering area and the tertials in the breeding area. 4. The growth rates measured in the claws of five species of palearctic passerines provide evidence that this tissue should integrate dietary and habitat information over a medium temporal scale (probably weeks to months). 5. It is suggested that claws may offer a unique combination of attributes to the isotope ecologist: they are non-invasively sampled; metabolically inert but grow continuously, and are therefore a more flexible tool than feathers. 6. It is also suggested that that the stable isotope signatures in the claws of mammals and reptiles may provide similar information.

Dung and nest surveys: estimating decay rates

Abstract: 1. Wildlife managers often require estimates of abundance. Direct methods of estimation are often impractical, especially in closed-forest environments, so indirect methods such as dung or nest surveys are increasingly popular. 2. Dung and nest surveys typically have three elements: surveys to estimate abundance of the dung or nests; experiments to estimate the production (defecation or nest construction) rate; and experiments to estimate the decay or disappearance rate. The last of these is usually the most problematic, and was the subject of this study. 3. The design of experiments to allow robust estimation of mean time to decay was addressed. In most studies to date, dung or nests have been monitored until they disappear. Instead, we advocate that fresh dung or nests are located, with a single follow-up visit to establish whether the dung or nest is still present or has decayed. 4. Logistic regression was used to estimate probability of decay as a function of time, and possibly of other covariates. Mean time to decay was estimated from this function. 5. Synthesis and applications. Effective management of mammal populations usually requires reliable abundance estimates. The difficulty in estimating abundance of mammals in forest environments has increasingly led to the use of indirect survey methods, in which abundance of sign, usually dung (e.g. deer, antelope and elephants) or nests (e.g. apes), is estimated. Given estimated rates of sign production and decay, sign abundance estimates can be converted to estimates of animal abundance. Decay rates typically vary according to season, weather, habitat, diet and many other factors, making reliable estimation of mean time to decay of signs present at the time of the survey problematic. We emphasize the need for retrospective rather than prospective rates, propose a strategy for survey design, and provide analysis methods for estimating retrospective rates.

Assessing the diet of great skuas, Catharacta skua, using five different techniques

Abstract: Several different techniques have been used to study the diet composition of skuas and gulls in polar regions. In this study, we assessed the diet of great skuas using five techniques (pellets, prey remains, spontaneous regurgitates, observed feeds and water off-loading). The estimates of diet derived from each sampling technique during a single breeding season were generally similar. Although it is easy to collect large samples of pellets and remains, these over-estimate the amount of indigestible material in the diet. Prey remains provide a high degree of taxonomic accuracy, but may under-estimate prey swallowed whole. Water off-loading provides unbiased estimates of chick diet but only during a short period in the breeding season. It may also stress birds, and is labour-intensive. Spontaneous regurgitates are useful for assessing chick and adult diet but are difficult to collect systematically, and differing prey digestibility may bias results. Observed feeds are time consuming to record and over-represent easily identifiable prey. Technique-dependent biases highlight that sampling methods should be selected on the basis of sample sizes, time, taxonomic detail and age of study birds. Biomass may be estimated using pellets with correction factors, and also spontaneous regurgitates and water off-loading, but prey remains and observed feeds may be more inaccurate.

Causes and Effects of Temporospatial Declines of Gyps Vultures in Asia

Abstract: There are eight species in the genus Gyps : Gyps africanus , G. coprotheres, and G. rueppellii in Africa; G. bengalensis , G. indicus , G. tenuirostris , G. himalayensis in Asia; G. fulvus in Europe, Africa, and Asia. The ranges of many of these species overlap, and wintering G. fulvus overlap with several resident species in Asia and Africa (Fig. 1). Gyps species share a similar feeding ecology, scavenging the soft tissues of large mammals, usually ungulates. They tend to be colonial nesters and communal feeders, feeding alongside conspecifics and other vulture species. Densities of Gyps vultures can be high in areas with suitable breeding habitat and abundant carrion. An extreme example is G. bengalensis , which often lives in close association with humans. During the 1970s and early to mid-1980s, densities of 12 nests/km 2 were recorded at Keoladeo National Park, Rajasthan, India (Prakash 1989), and there were nearly 3 nests/km 2 in the city of Delhi (Galushin 1971), where flocks of several thousand birds were present at carcass dumps. As recently as 1985, G. bengalensis was regarded as “possibly the most abundant large bird of prey in the world” (Houston 1985). Despite Gyps population declines across Southeast Asia, until recently only one species of Africa, G. coprotheres, was considered globally threatened (vulnerable; BirdLife International 2000), largely because of the indiscriminate use of poisons in southern Africa (Mundy et al. 1992). Following the recent population crash in Gyps species across the Indian subcontinent, three other species, G. bengalensis, G. indicus, and G. tenuirostris , are now listed as critical ( BirdLife International 2000), placing them among the most threatened birds in the world.

Modelling the daily food requirements of wintering great cormorants: a bioenergetics tool for wildlife management

Abstract: Summary 1. Great cormorants Phalacrocorax carbo , Linnaeus are large piscivorous birds which occur in Asia, Australia, Africa, Europe and North America. Their European breeding population has increased by at least 15% per annum over the last 15 years, reaching a total of c . 200 000 pairs in the late 1990s. There are concerns that this increase is adversely affecting freshwater fish populations throughout Europe, but real assessment requires a detailed knowledge of cormorant food requirements. 2. The daily food intake (DFI) of great cormorants has been measured during the breeding season, but little is known about DFI in winter when these poorly insulated birds experience consistently low temperatures. DFI is likely to vary widely according to abiotic and biotic conditions, making predictions about impact particularly difficult. 3. We modelled DFI for great cormorants wintering at Loch Leven, Scotland, using behavioural data recorded via radio-tracking of free-ranging individuals, metabolic measurements obtained from captive birds, and published data. DFI was estimated to be 672 g day − 1 (predicted maximum range 441‐1095 g day − 1 ), values similar to DFI of great cormorants breeding under temperate conditions and of other aquatic bird species. 4. During winter great cormorants at Loch Leven decreased their average dive time and increased dive efficiency (higher proportion of time spent underwater). They nonetheless spent 130 min day − 1 in the water and allocated more than a third of their daily energy budget to diving. 5. Synthesis and applications : In view of the need for the sound management of cormorant populations, we present a general bioenergetics model, based on simple behavioural and dietary inputs, that computes an estimate of DFI outside the breeding season for a range environmental conditions and habitats. An interactive computer programme for this model is available (http://www.cepe.c-strasbourg.fr) to help scientists and managers estimate local values for average, minimum and maximum DFI.

Good foragers can also be good at detecting predators

Abstract: The degree to which foraging and vigilance are mutually exclusive is crucial to understanding the management of the predation and starvation risk trade-off in animals We tested whether wild-caught captive chaffinches that feed at a higher rate do so at the expense of their speed in responding to a model sparrowhawk flying nearby, and whether consistently good foragers will therefore tend to respond more slowly on average First, we confirmed that the time taken to respond to the approaching predator depended on the rate of scanning: as head-up rate increased so chaffinches responded more quickly However, against predictions, as peck rate increased so head-up rate increased and mean length of head-up and head-down periods decreased Head-up rate was probably dependent on peck rate because almost every time a seed was found, a bird raised its head to handle it Therefore chaffinches with higher peck rates responded more quickly Individual chaffinches showed consistent durations of both their head-down and head-up periods and, therefore, individuals that were good foragers were also good detectors of predators In relation to the broad range of species that have a similar foraging mode to chaffinches, our results have two major implications for predation/starvation risk trade-offs: (i) feeding rate can determine vigilance scanning patterns; and (ii) the best foragers can also be the best at detecting predators We discuss how our results can be explained in mechanistic terms relating to fundamental differences in how the probabilities of detecting food rather than a predator are affected by time In addition, our results offer a plausible explanation for the widely observed effect that vigilance continues to decline with group size even when there is no further benefit to reducing vigilance

The Challenge of Measuring Global Change in Wild Nature: Are Things Getting Better or Worse?

Abstract: The Ministerial Declaration made at the World Summit on Sustainable Development in Johannesburg agreed to protection and restoration of the integrity of our planet's ecological systems and identified as a major priority a significant reduction in the rate of current biodiversity loss at national and global levels. This goal is essentially a reformulation of that of the Convention on Biological Diversity agreed to in Rio de Janeiro 10 years ago. For us to have any idea of where we are in relation to this goal, we need information on current global trends in the status of natural systems. By 2005 it is envisaged that the Millennium Ecosystem Assessment (MA) will have provided a comprehensive account of global biodiversity from a compilation of existing data, but that is a long time to wait. What can we say now about trends in the state of wild nature since the United Nations' 1992 Conference on Environment and Development in Rio de Janeiro? Here, we briefly review recent global trends in habitat area in as many broadly defined natural habitats as possible and in indices of animal populations characteristic of those habitats. The information available indicates continuing declines in habitat area and species, but that data are extremely sparse.

Habitat and weather are weak correlates of nestling condition and growth rates of four UK farmland passerines

Abstract: Agricultural intensification is believed to have driven declines of farmland bird populations and the invertebrates and weeds on which they feed. We investigated whether habitat and weather, as surrogates for food availability, influenced nestling growth rates and condition of four farmland passerines (Skylark Alauda arvensis, Chaffinch Fringilla coelebs, Linnet Carduelis cannabina and Yellowhammer Emberiza citrinella). We also tested whether nestling growth rates or condition influenced whether a brood subsequently fledged, starved or was depredated. Linnet nestlings are fed almost exclusively on seeds, and were unaffected by weather. Nestlings of the other species are fed mainly invertebrates and were affected negatively by rain but positively by increasing minimum temperatures and daily hours of sunshine. Condition and growth rates of Linnet nestlings were lower in nests further from oilseed-rape fields, rape seeds being important in the diet of this species. Nestlings of the other three species were unaffected by availability of habitats selected by parents foraging for nestling food. Brood fate was not influenced by growth rates or condition for any species. Most models explained little variation in the response variable. Possible reasons, including the possibility that parents trade off their own survival prospects to ensure reproductive success, are discussed.

Demography and population trends of the Atlantic Yellow-nosed Albatross

Abstract: The Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) breeds only at the Tristan da Cunha archipelago and Gough Island in the central South Atlantic Ocean, and is threatened by mortality from longline fisheries operating in the South Atlantic. Demographic data have been collected from two study colonies on Gough Island and Tristan da Cunha for 20 years. Annual variation in the number of breeding birds was strongly correlated between the two islands, and over the whole study period both study populations have trended downward at around 1.2% per year. The number of established breeders on Gough Island has declined more rapidly, and significantly, at an annual rate of 2.3%. Monitoring established breeders may be a sensitive means of detecting population trends. Average breeding success (67–69%) and breeding frequency (66–65%) were very similar on the two islands. On Gough Island immature and adult annual apparent survival averaged 88 ± 3% and 92 ± 1%, respectively, and apparent survival ...

Measurement of habitat predictor variables for organism/habitat models using remote sensing and image segmentation

Abstract: Robust predictive models of the effects of habitat change on species abundance over large geographical areas are a fundamental gap in our understanding of population distributions, yet are urgently required by conservation practitioners. Predictive models based on underpinning relationships between environmental predictors and the individual organism are likely to require measurement of spatially fine-grained predictor variables. Further, models must show spatial generality if they are to be used to predict the consequences of habitat change over large geographical areas. Remote sensing techniques using airborne scanning laser altimetry (LiDAR) and high resolution multi-spectral imagery allow spatially fine-grained predictor variables to be measured over large geographical areas and thus facilitate testing of the spatial generality of organism-habitat models. These techniques are considered using the skylark as an example species. A range image segmentation system for LiDAR data is described which allows ...

Summer diet and body condition of Song Thrushes Turdus philomelos in stable and declining farmland populations

Abstract: Summer diet and body condition were compared in two farmland Song Thrush Turdus philomelos populations in south-east England. One population on mixed farmland was stable and the other on arable farmland was rapidly declining. Summer diet was dominated by earthworms, snails, beetles and insect larvae (mainly Coleoptera and Lepidoptera). In both populations there was a pronounced seasonal decline in the quality of the diet, with preferred earthworms dominating prey items during March-April and snails dominating during June and July. Dry weather during late summer was associated with reduced proportions of earthworms and snails, and increased proportions of spiders in the diet, and dry soil conditions had a weak negative influence on the body weights of chicks (in the arable population) and adults. Despite a tendency for earthworms to constitute a higher proportion of the diet in the stable population, and for snails to constitute a higher proportion of the diet in the declining population, the body condition of chicks and adults appeared to be unrelated to diet composition and did not differ between study populations. Changes in agricultural practices have probably caused a major reduction in the availability of key summer food resources for Song Thrushes on lowland farmland, and we speculate that breeding thrushes mitigate the impacts of food shortage on chicks by confining their nesting attempts to localities and periods where invertebrate food resources are adequate to raise a brood of young.

Separating the Tristan Albatross and the Wandering Albatross Using Morphometric Measurements

Abstract: Recent taxonomic revisions of the Wandering Albatross sensu lato has resulted in four separate species, the rarest of which is the Tristan Albatross (Diomedea dabbenena). We present the first detailed morphometric measurements of the male and female of the Tristan Albatross. The results are used to separate this species from the more common nominate taxon of Wandering Albatross (Diomedea exulans) from South Georgia. The Tristan Albatross is smaller than the Wandering Albatross in all measured variables, and males are larger than females in both species. A combination of bill measurements discriminated 97-98% of individuals of the two species, and tarsus and bill measurements allowed the sex of birds from both species to be determined. If the sex of the bird is known, then bill length should identify all individuals to species. This result is useful to allow fishery observers to correctly identify albatrosses killed on longlines in the Atlantic Ocean. However, care has to be taken outside this region, because the Tristan Albatross is very similar in size to published measurements of Gibson’s Albatross (Diomedea gibsoni) and the Antipodes Albatross (Diomedea antipodensis), both of which breed off New Zealand and are thought to range across the South Pacific Ocean.

Status, ecology, behaviour and conservation of Raso Lark Alauda razae

Abstract: In October 2001, the world population of Raso Lark Alauda razae, confined to the uninhabited, arid islet of Raso in the Cape Verde Islands, was estimated at between 128 and 138 birds, of which 61–66% were males. The biased sex ratio was confirmed by standardized observations of randomly selected birds. The male-dominated sex ratio may result from differences in bill morphology and feeding methods. The males spent much time digging for the bulbs of the nutsedge Cyperus bulbosus, whereas females were seen to dig far less frequently. These differences may have been due to significant sexual differences in bill size. Both sexes also took a range of invertebrate prey, particularly lepidopteran larvae. Unpaired males showed differences in behaviour to paired males, particularly with respect to song flight length. Measurement of museum skins suggested significant seasonal changes in bill size, possibly related to changes in diet or feeding methods. Bill sizes in both sexes were highly variable, but significantly more variable in males. Nest predation, almost certainly by a near-endemic gecko, was extremely high, Mayfield estimates suggesting a nest survival rate of less than 5% between the onset of laying and the end of incubation. Cats and dogs were thought to be absent, although analysis of droppings shows that both have been present in the recent past. Analysis of historical data shows a strong correlation between population size and rainfall, and numbers of birds have fallen to extremely low levels during droughts. The conservation of the species is discussed in the light of these findings.

The status and recent breeding performance of the critically endangered Northern Bald Ibis Geronticus eremita population on the Atlantic coast of Morocco

Abstract: The main wild population of the Northern Bald Ibis Geronticus eremita breeds on the Atlantic coast of Morocco in the Agadir region. This paper describes the numbers of breeding pairs over the last two decades, the recent breeding performance, the causes of egg and chick losses and their conservation implications. Since 1980 there has been no overall decline in numbers with, over the last 5 years, 59-74 pairs breeding and a peak prebreeding population of around 220 birds. In contrast with the now extinct Northern Bald Ibis populations in Turkey and elsewhere in Morocco, the birds are present in the Agadir region throughout the year and do not appear to migrate from the area outside the breeding season. Breeding performance is highly variable from one year to the next but does not appear to be related to rainfall in the vicinity of the colonies as has been reported elsewhere. It is suggested that coastal fogs in this region may buffer the adverse impacts of low rainfall and may in part account for the year-round residency of the birds. The main causes of breeding failures have been loss of eggs to predators and, most importantly, poor chick survival as a result of starvation and predation. Conservation action to date has focused on reducing the negative influences on breeding success but it is recognized that for such a long-lived bird adult survival is also likely to be an important limiting factor on the population size.

Influence of Seed Mixture and Hydrological Regime on the Establishment of a Diverse Grassland Sward at a Site with High Phosphorus Availability

Abstract: Three experiments were undertaken to investigate the influence of seed mixture on the establishment of a target grassland community on a site with high available phosphorus. In the first experiment autumn- and spring-sown commercial seed mixtures were compared with seed harvested from a nature reserve with respect to their ability to produce an inundation grassland community similar to that described by the British National Vegetation Classification (NVC) as Agrostis stolonifera–Alopecurus geniculatus grassland (MG13). In the second experiment the composition and sowing rate of a commercial seed mixture were altered to investigate whether these factors were significant in the establishment of a sward similar to MG13. Similarly, in the third experiment the composition of a commercial seed mixture designed to achieve an alternative community, Cynosurus cristatus–Caltha palustris grassland (NVC code MG8), was sown. The vegetation resulting from each of these treatments was monitored with permanent quadrats for a 3-year period, and the hydrological regime of each quadrat location was modeled and quantified. The results showed that seed mixture, timing of sowing, and seeding rate had an initial effect on the vegetation that established. However, by the third year of monitoring there were no significant differences between these treatments, and hydrological regime had become the most important factor in determining the distribution of species. The vegetation was less diverse than predicted from germination tests and decreased in diversity over the monitoring period. It is suggested that this may be a result of the hydrological regime being unsuitable for several of the sown species or due to the extremely high available phosphorus concentration in the soil. This study highlights the need to understand the soil and hydrological conditions of a site before choosing a target community and designing a seed mixture.

Effects of weather on the survival and growth of Corncrake Crex crex chicks

Abstract: Weather conditions during the early life of precocial chicks of some bird species have marked effects on survival and may also cause changes in adult population size. In this paper, we use data from broods with radiotagged mothers to examine correlations of growth rates and survival of Corncrake Crex crex chicks in Scotland and Ireland with temperature and rainfall. The loss of whole broods before they reached independence was infrequent and not correlated with temperature or rainfall. Loss of some chicks from broods before independence usually occurred and multiple regression analysis indicated that the proportion of chicks that survived increased with decreasing initial brood size, increasing temperature and decreasing rainfall. However, the magnitude of the effects of weather on survival were quite small. The rate of weight gain of chicks varied considerably within and among broods. The mean daily weight gain rate of broods decreased significantly with increasing rainfall, and variation in the weight of chicks within broods was greater for broods whose mean rate of weight gain was low.

Developing Environmental Education, a Review of a Scottish Project: International and Political Influences.

Abstract: An attempt to promote environmental education in Scotland was started in the 1970s by a group representing several sectors of education. It set in action a chain of events which can be seen as a coherent project relatively independent of developments elsewhere, although parallel with them, and from a starting-point which was more one of urban renewal than of rural preservation. It progressed through interaction between promoters, practitioners and public, within the surrounding framework of government policy, and illustrated many of the difficulties encountered by educators in complex political processes. The time is now appropriate to review the outcomes and prospects of the project. This paper is particularly concerned with the part played by the political system and the international context. The analysis shows a complex and largely negative interaction with the political and administrative systems relating to formal education. The influence of international events was generally marginal, but at its be...

Habitat requirements of the Seychelles Black Paradise Flycatcher Terpsiphone corvina: a re‐evaluation of translocation priorities

Abstract: The critically endangered Seychelles Black Paradise Flycatcher Terpsiphone corvina was once found on at least five of the inner (granitic) islands in the Seychelles archipelago, western Indian Ocean. Currently, it is only found on two islands, with c. 98% of the world population (c. 150-200 individuals) occurring on the 10-km 2 island of La Digue. Creation of additional island populations is therefore considered crucial in improving its conservation status. The presence of native broad-leaved plateau forest in proximity to wetland areas is proposed as an important selection criterion when considering the suitability of other islands for translocation, due to the presumed importance of insect prey (dependent on water) in the diet. We quantified habitat use, territory composition, the effect of water on invertebrate abundance, and foraging and breeding success to determine the importance of native broad-leaved woodland and wetland areas for Flycatchers. Flycatcher territories contained significantly more native broad-leaved woodland (88%) than its availability on the plateau (43%); Flycatchers used native tree species significantly more for both foraging (81%) and nesting (95%) than their availability within territories (71%); and territory size varied inversely with the density of native broad-leaved tree species. Native broad-leaved forest was associated with semipermanent and permanent water bodies and availability of native forest habitat was a good predictor of territory distribution. The number of aerial insects trapped was higher close to water, but there was no effect of the proximity to water on the number of insects counted on foliage. The majority of identified prey species in adult diet were not dependent on water: Orthoptera and Lepidoptera were the most common prey groups, comprising 66% of identified prey items. There was no effect of proximity to water on foraging or breeding success (c. 35%): depredation was the major factor determining breeding success, and accounted for the majority of nest failures. The importance of wetland areas to Flycatchers therefore appears to have been over-emphasized. The implications for translocation and conservation of the Flycatcher are discussed.

The management and restoration of damaged blanket bog in the north of Scotland

Abstract: Summary The blanket bogs of Caithness and Sutherland are the finest examples of their type in the world. Restricted to a few parts of the world where cool, oceanic climatic conditions prevail, Britain holds approximately 13% of the total global resource of blanket bog, of which the bogs of Caithness and Sutherland form the largest and most intact area. In recent times, extensive areas of the peatlands of Caithness and Sutherland have been damaged – principally through drainage and forestry. In 1994, the Royal Society for the Protection of Birds (RSPB) purchased Forsinard Estate in the heart of the peatlands as part of a EU LIFE funded project on blanket bog conservation. In partnership with Scottish Natural Heritage and Caithness and Sutherland Enterprise, this four year RSPB led project promoted a number of initiatives on awareness raising and ecotourism as well as a range of practical demonstrations on restoring damaged blanket bog. More recently, a follow up LIFE Peatlands Project was launched in 2001 ...

The Scottish Crossbill - what we know and what we don't

Abstract: The Scottish Crossbill Loxia scotica is Britain’s only endemic bird. Given this status, together with its small population size and its assumed association with the few remaining scraps of native pinewood, the Scottish Crossbill has the highest of conservation designations. Its biology is poorly known, however, making it difficult to implement conservation measures. Here, we review some recent work which is investigating different aspects of the biology of crossbills in general and the Scottish Crossbill in particular. Museum, field and laboratory-based studies examining biometrics, vocalisations, feeding ecology, movements and genetics have now clarified some of the interrelationships between the three crossbill species which are now recognised as breeding in Britain. Such efforts are also helping to identify the future research priorities required to maintain populations. Alan Harris T he Scottish Crossbill Loxia scotica is one of Britain’s most charismatic and, at the same time, one of its most enigmatic birds: charismatic in that it is designated as Britain’s only avian endemic species and so is a flagship for natural heritage; but enigmatic in that there are still considerable gaps in our knowledge about fundamental aspects of the biology and ecology of crossbills in general and Scottish Crossbills in particular. Recent and on-going work by the RSPB, the University of Aberdeen, the Centre for Ecology and Hydrology, Forest Enterprise and other crossbill enthusiasts has meant that our understanding of the biology of the Scottish Crossbill is improving. The aim of this paper is to review some of the findings of this work, and put them into context with the problems associated with the conservation of the Scottish Crossbill. The Scottish Crossbill has had a somewhat turbulent taxonomic history. It was initially described as a subspecies of the Common Crossbill L. curvirostra, in 1904, because it is intermediate in size between Common and Parrot Crossbills L. pytyopsittacus. The typespecimen was collected on 26th December 1870 in Ross-shire and named L. c. scotica (Hartert 1904). There is, however, overlap in wing length and bill length measurements between Scottish Crossbill and both Common and Parrot Crossbills (Knox 1976), and there are no diagnostic plumage differences. Given its intermediate size, there were also calls to classify Scottish Crossbill as a subspecies of Parrot Crossbill (see Knox 1975 for a review), but this convention was not widely accepted (Witherby et al. 1943). The Scottish Crossbill L. scotica is currently regarded as a full species by the BOU, and consequently is Britain’s only endemic bird (Voous 1977; BOURC 1980). Its designation as a species was based on the observation that Scottish Crossbills maintained their intermediate size between Common and Parrot Crossbills, despite repeated invasions by Common Crossbills from the Continent (Knox 1976). Furthermore, Scottish and Common Crossbills were found to breed sympatrically in Deeside, but they apparently did not hybridise (Knox 1990a,b). Consequently, Scottish Crossbills satisfied the Biological Species Concept (Mayr 1963) that species are ‘groups of interbreeding natural populations that are reproductively isolated from other such groups’. At this stage, Parrot Crossbills were not known to be breeding in Scotland, so potential hybridisation between Scottish and Parrot Crossbills was not regarded as an issue. It is thought that the Scottish Crossbill is a relict species derived from a crossbill population which was isolated in the Caledonian pine forests of Scotland when Britain became separated from continental Europe after the last glaciation (Nethersole-Thompson 1975; Murray 1978; Voous 1978). During this period of isolation, the Scottish Crossbill could have evolved its unique intermediate size characteristics from an ancestral stock of either Common or Parrot Crossbills in response to the available Scots Pine Pinus sylvestris cones (tougher than spruce Picea cones, yet less likely to be frozen) (Knox 1975; 1990a). An alternative hypothesis is that the Scottish Crossbill has remained similar to an ancestral stock of Parrot Crossbills, and that Parrot Crossbills in mainland Europe increased in size when Common Crossbills began to invade from the east and breed sympatrically with Parrot Crossbills (NethersoleThompson 1975). This process is known as ‘character displacement’ (Mayr 1963). The Caledonian pine forest, which once covered much of Highland Scotland, has been reduced in size over the past 5,000 years as a result of forest clearance by farmers and perhaps climate change (Smout 1993; Tipping 1994). Consequently, less than 1% of the Caledonian forest remains and occurs only as scattered fragments, primarily in Deeside and Strathspey. The largest fragment is Abernethy Forest. With its endemic species status, supposed small population size and restricted ancestral habitat, the Scottish Crossbill has been given the highest categories of conservation importance: it is of global conservation concern (as a result of data deficiency); a Species of European Conservation Concern Category 1; and it is on the ‘Red list’ of Birds of Conservation Concern in the UK (Tucker & Heath 1994; Gregory et al. 2002). Clearly, there is a need for a conservation programme to safeguard this species, and a UK Biodiversity Action Plan was drawn up for the Scottish Crossbill (Anon 1995). A fundamental problem with the Scottish Crossbill, however, is the difficulty of identifying it in the field, because it is so similar in appearance to both Common and Parrot Crossbills (Knox 1990c). This has led to uncertainty about its range within Britain (Knox, in Gibbons et al. 1993), its population size (Nethersole-Thompson 1975) and its habitat 101 British Birds 96 • March 2003 • 100-111 The Scottish Crossbill – what we know and what we don’t

Catching methods and biometrics of breeding Ring Ouzels Turdus torquatus torquatus in northeast Scotland

Abstract: Between 1999 and 2002, we caught 116 (54 male and 62 female) breeding adult Ring Ouzels Turdus torquatus torquatus in Glen Clunie, northeast Scotland. Four different catching methods are described and their success assessed. There was no evidence that any catching method had a detrimental effect on either nest outcome, or the frequency of second breeding attempts in the same year. Plumage characteristics were used to age and sex birds caught, following their use to age and sex migrants and museum specimens. These characteristics were found to be reliable for all 19 birds of known age. Males had, on average, longer wings and deeper and whiter gorgets than females, but they were not heavier. Among both males and females 2+ year birds had, on average, longer wings than 2nd year birds, and 2+ year females were also heavier and had whiter gorgets than 2nd year birds.

Promoting survival prospects of rare plants

Abstract: Summary The distributions of Scottish rare plants are well known and we have a good understanding of the communities and habitats in which they occur. But how do we ensure that populations are maintained or enhanced? The ecological processes that determine current population size and distribution must be understood. We review the type of information from monitoring that is required to assess change in species status and to guide conservation management. Managing for habitats must be the right approach to conserving species, but we need to take careful consideration of the individual requirements of different species. Environments fluctuate at a range of spatial and temporal scales; we review the evidence that rare plant species respond to such fluctuations. We consider that there might be a danger that overprotecting some habitats, by trying to maintain constant ideal management prescriptions, might be putting some species at risk. We believe that conservation managers can resolve the apparent conflicts b...