Aspects of red grouse Lagopus lagopus scoticus population dynamics at a landscape scale in northern England and the implications for grouse moor management

Red grouse Lagopus lagopus scoticus are an important game species in the United Kingdom, with many areas of heather moorland managed specifically to produce them for driven shooting. In order to effectively manage red grouse populations it is important to have an understanding of their population dynamics and to determine which of the vital rates most effect population growth and recovery and whether these parameters can be influenced by management activities. The focus of my research was to provide a greater understanding of the respective roles of juvenile dispersal, heather management and mortality causes in red grouse population dynamics at a landscape scale in northern England. The study was undertaken between 1999 and 2005 and encompassed four privately owned grouse moors, covering some 113 km(^2) of heather dominated moorland. Central to my research was the ability to accurately and efficiently survey the distribution and abundance of red grouse across the study area. To facilitate this I evaluated a distance sampling method to survey red grouse across the study area pre-breeding in spring and post-breeding in summer. The distance sampling technique proved a reliable, repeatable and practical method for extensive surveys of red grouse. Grouse distribution data were used to construct spatial patterns of grouse abundance at a moor scale using a geostatistical interpolation technique. Rotational heather burning is practised by grouse moor managers to create a mosaic of heather ages which provide food, shelter and nesting habitats for red grouse. To assess the spatial and temporal effects of heather burning on grouse, I used an earth observation technique, using satellite remote sensing to map the habitat mosaic across all four study moors in 2000. Temporal effects of heather burning, from 2000 to 2005 were studied on one moor, with annual heather burning mapped annually. Dispersal is an important element of population dynamics which influences population growth and spread, gene flow and disease transmission. I used radio telemetry to investigate the timing, frequency and distances of dispersal in juvenile red grouse. Dispersal distance differed between sexes, with juvenile females dispersing on average 861 m (±120 SE) compared to 343 m (±31 SE) recorded in males. Population growth did not appear to be limited by dispersal and abundance increased until the density dependent effect of the parasitic nematode worm Trichostrongyle tenuis caused a population crash. On the study moors, grouse moor management resulted in rapid population growth with population oscillations caused by density dependent strongylosis induced crashes. The main cause of mortality was found to be shooting and to dampen population oscillations, modified shooting programmes to limit population growth in conjunction with parasite control measures should be adopted to better manage grouse populations

Exploring the impact of common buzzard Buteo buteo predation on red grouse Lagopus lagopus scotica

PhD ThesisThe relationship between raptors and red grouse Lagopus Lagopus scotica is one of the most topical and contentious wildlife management issues in Britain. The common buzzard Buteo buteo is a generalist raptor which has increased in population and range in Britain during the last 40 years, which in most areas represents a recovery following historical declines. Increasingly, this has reignited conflict with managers of gamebirds concerned about the impact of buzzard predation. Whilst the impact of buzzards on reared pheasants Phasianus colchicus has previously been assessed, the impact of buzzards on red grouse has not been investigated. I aim to address this knowledge gap by providing an insight into the predator-prey relationship between buzzards and red grouse. I have explored the diet, foraging patterns and responses to changing prey abundances of buzzards on a moorland site managed for red grouse in south-west Scotland. First, I investigated the biases associated with methods of assessing raptor diet. I demonstrated that methodological biases exist and that these can vary over time in relation to natural temporal variations in raptor diet composition. I then investigated functional and numerical responses of buzzards to annual changes in prey abundance. Following declines in vole abundance, buzzards selected a wider range of prey, but consumption of red grouse did not increase, and there was no evidence of a numerical response. Results suggested that buzzard predation of red grouse may be incidental in nature, whereby high vole abundances encouraged buzzards to hunt in red grouse habitats. Next, I explored buzzard foraging patterns in relation to prey and habitat. Buzzard foraging intensity varied in line with annual variations in vole abundance, and buzzards hunted in areas with more red grouse during the winter. Buzzards avoided heather dominated areas in years when vole abundance was low, but not when vole abundances were high. Results again suggested that incidental buzzard predation of red grouse could increase when vole abundances are high. However, I found no evidence that variations in buzzard foraging intensity influenced grouse mortality indices. iii I then described buzzard diet during the winter with the aid of remote tracking methods. Buzzard diet was primarily composed of small mammals, and red grouse were less likely to feature in the diet of buzzards roosting in grassy areas. Next, I produced estimates of the potential removal of grouse by buzzards using bioenergetics modelling. The results suggested that whilst the removal of grouse by an individual buzzard is likely to be small, the total number of grouse removed could be considerable if buzzard populations are high and predation of grouse is additive to other causes of mortality. Finally, key results are discussed and placed in a wider context of upland and gamebird management in Britain. Recommendations are made for future study to improve our understanding of these systems, and for testing possible mitigation and management techniques. This study could have wider implications for the management of economically important or threatened species, alongside recovering populations of protected raptors, and may provide a useful framework for studying similar systems elsewhere

Fitting models of multiple hypotheses to partial population data: investigating the causes of cycles in red grouse

There are two postulated causes for the observed periodic fluctuations (cycles) in red grouse (Lagopus lagopus scoticus). The first involves interaction with the parasitic nematode Trichostrongylus tenuis. The second invokes delayed regulation through the effect of male aggressiveness on territoriality. Empirical evidence exists to support both hypotheses, and each hypothesis has been modeled deterministically. However, little effort has gone into looking at the combined effects of the two mechanisms or formally fitting the corresponding models to field data. Here we present a model for red grouse dynamics that includes both parasites and territoriality. To explore the single and combined hypotheses, we specify three versions of this model and fit them to data using Bayesian state‐space modeling, a method that allows statistical inference to be performed on mechanistic models such as ours. Output from the three models is then examined to determine their goodness of fit and the biological plausibility of the parameter values required by each to fit the population data. While all three models are capable of emulating the observed cyclic dynamics, only the model including both aggression and parasites does so under consistently realistic parameter values, providing theoretical support for the idea that both mechanisms shape red grouse cycles

Quantifying fenbendazole and its metabolites in self-medicating wild red grouse Lagopus lagopus scoticus using an HPLC–MS–MS approach

On red grouse estates in the UK the nematode parasite Trichostrongylus tenuis is often controlled by application of grit medicated with the anthelmintic fenbendazole (FBZ). To date, assessment of the efficacy has been inhibited by the inability to quantify uptake of FBZ by the birds. We have developed a simple and sensitive HPLC–MS–MS method for detecting and quantifying FBZ and its metabolites from a 300 mg sample of red grouse liver. This method could be used to improve the efficacy of medicated grit treatment by allowing the identification of conditions and application methods that optimize the uptake of FBZ. With the necessary modifications, our method will also be applicable to other wildlife species where self-medication is used for parasite control

The effects of parasites and food on red grouse (Lagopus lagopus scoticus)

The interaction between the parasite Trichostrongylus tenuis and food quality was investigated in red grouse Lagopus lagopus scoticus, to determine the cause of variation in population cycles between different areas (Scotland and England). Analysis of long-term data, field experiments and population modelling were carried out. Food quality, in terms of nutrient content of heather, was lower on Scottish grouse moors than on English moors. Parasite burdens were also lower in Scottish grouse populations, than in English grouse populations. A three-way interaction, between food, parasites and area (ScotlandlEngland), acting on breeding production, could explain the variation in population cycle period between areas. However, body condition of grouse was not affected by a food-parasite interaction. Experimental manipulation of food quality and parasite burden did not influence the breeding production of female grouse. Modelling the effects of a food-parasite interaction on grouse populations provided evidence that such an interaction could explain variation in cycle period between areas, although other factors are likely to be important in some cases. Red grouse are not unique, as other species also have cycles driven by food and parasites. Other species do not show cyclic population fluctuations because of having shared parasites, and a strong immune response. There is a specialist predator-prey relationship between red grouse and T. tenuis

Loss of heather moorland in the Scottish uplands: the role of red grouse management

Scottish upland moorland dominated by heather Calluna vulgaris is the primary habitat for red grouse Lagopus lagopus scoticus, and has been declining since the 1940s. At the same time red grouse numbers have also fallen. We compared land cover change on sites managed for grouse shooting (1945-1990), and on sites which were managed for grouse in the 1940s but on which management had stopped by the 1980s. Land cover type for sites (N = 229) containing >10% heather cover in the 1940s were examined during the 1940s, 1970s, and 1980s. Grouse management existed on 49% of sites in the 1940s, a number which had fallen to 20% by the 1980s. In the 1940s there were no significant differences in land cover type between areas that were managed for grouse, and areas that were not. However, differences emerged during the 1970s and 1980s; areas where grouse management had ceased by the 1980s showed an expansion in woodland cover from 6% in the 1940s to 30% in the 1980s, and a reduction in heather cover from 53% to 29%. In areas where active grouse management had been maintained, woodland increased from 3% to 10% and heather decreased from 51% to 41% during the same period. These changes may be, in part, a consequence of government agricultural and forestry policy. When profitable, grouse management reduces the attractiveness of such subsidies and thereby results in a slower loss of heathe

Grouse Status Survey and Conservation Action Plan, 2006-2010

Executive Summary Grouse have long attracted and fascinated people. Their display behaviour, and particularly their traditional communal mating grounds or leks,” have inspired poetry and folklore as well as scientific theories on sexual selection and the evolution of mating systems. In many parts of their range, grouse hunting still plays a major role in the culture, economy, and subsistence of local communities. The 2006-2010 Grouse Action Plan provides an overview to the distribution, status and threats to all 18 grouse species worldwide and identifies the most immediate conservation needs. It is a product of the joint expertise of the Grouse Specialist Group (GSG), a voluntary network of grouse professionals, and other grouse experts worldwide. The Grouse Action Plan was primarily written as a reference guide for decision makers, agency officials, resource managers and funding organisations, but also scientists and students who share the GSG´s goal of securing viable population of all species and subspecies of grouse in the wild. The Action Plan also aims to underline the importance of grouse conservation in a broader sense: as typical representatives of a wide spectrum of natural habitats, grouse are indicators of ecosystem health. Their indicator function and their attractiveness to people make grouse suitable flagship species to promote the conservation of ecosystems and biodiversity. At the time of compiling the 2000-2004 Grouse Action Plan (Storch 2000) in 1999, none of the grouse species were considered to be threatened following IUCN criteria, but three species with limited geographic distribution were listed as Near Threatened (IUCN 1996): Caucasian black grouse (Tetrao mlokosiewiczi), Chinese grouse (Bonasa sewerzowi), and Siberian grouse (Dendragapus falcipennis). In 2000, the newly recognized Gunnison sage-grouse (Centrocercus minimus) was listed as Endangered and the Caucasian black grouse was re-classified to Data Deficient. Shortly after, both the lesser prairie-chicken (Tympanuchus pallidinctus) and the greater prairie-chicken (Tympanuchus cupido) were added to the Red List as Vulnerable owing to rapid population declines, and the greater sage-grouse (Centrocercus urophasianus) was listed as Near Threatened (IUCN 2004). At a national level, 14 of the 18 species are red-listed in at least one country. Populations at the southern edge of a species´ range and in densely populated regions are most often red-listed. Healthy grouse populations require large areas of natural or semi-natural habitat. Thus they compete with increasing human populations and economic development. Based on questionnaire results from 47 countries, deterioration of habitats has been identified as the major threat to grouse worldwide. Habitat degradation, loss and fragmentation due to human land use are considered the most important threats. Other frequently named pressures are small population size, predation, direct exploitation and human disturbance. Current approaches to grouse conservation include legislation, protected areas, surveys and monitoring, habitat management, captive breeding, re-introduction and re-enforcement, predator control, reduction of human disturbance and education. Integrating habitat preservation and human land use practices remain to be the major challenge to grouse conservationists worldwide. After a short introduction to grouse and the Action Plan, the history of the Action Plan and the scientific basis of grouse conservation are outlined in Chapter 1. Chapter 2 provides an overview to the conservation biology of grouse and summarises major threats and current conservation measures. Brief accounts for each species are provided in Chapter 3, compiling information on status, taxonomy, distribution, population, ecology, cultural importance, threats, research needs and current and recommended conservation measures. In Chapter 4, conservation and research priorities are proposed for the most threatened taxa (Gunnison sagegrouse, greater and lesser prairie-chicken, greater sagegrouse, Chinese grouse, Caucasian black grouse, Siberian grouse, Attwater´s prairie-chicken, Cantabrian capercaillie, and Gunnison sage-grouse). The recommendations were sketched by leading specialists on the different taxa and provide preliminary outlines that may be used to develop detailed project proposals. Proposed measures span from population surveys, research into the effects of human land use on grouse habitats and populations and integration of land use practices and grouse conservation needs to population recovery programmes. Readers interested in the implementation of any part of the plan are requested to contact the chairman of the GSG or the relevant local correspondents (see http://www.gct.org.uk/gsg/). We hope that the Action Plan will find a wide distribution as a tool to promote and implement grouse conservation

Lynx impact on forest grouse : a study on the indirect effects of lynx on forest grouse through red fox

Lodjursstammen i Sverige har gått från att i princip vara helt utrotad 1920, till en livskraftig population nu 100 år senare. Att toppredatorer har en betydande roll i ekosystem och näringskedjor har bevisats flertalet gånger i olika studier. I denna rapport undersöks det ifall det finns ett indirekt positivt samband mellan lodjur och skogshöns. Detta undersöks med avseende på att lodjur dödar rödräv som står för en stor del av bortgången i skogshönspopulationer. De data som används för skogshöns och rödräv kommer från jägareförbundets viltdata.se och är den avskjutningsdata som finns för Västerbottens län. Datat över lodjur kommer från Västerbottens länsstyrelse där de sammanställt alla lodjursföryngringar som finns i länet. Datan för de olika arterna jämförs mot varandra med hjälp av beräkningar av korrelationskoefficienten samt linjär regression. Utifrån det tillgängliga datamaterialet gavs följande korrelationsvärden och R2-värden (för linjära samband): mellan lodjur och rödräv -0,11 respektive 1,8 % R2, rödräv och skogshöns -0,78 respektive 62 % R2 och lodjur och skogshöns 0,55 respektive 29 % R2. Resultatet visar att det finns ett positivt samband mellan skogshöns och lodjur samt ett negativt samband mellan skogshöns och rödräv. Det går dock inte att påvisa något statistiskt samband mellan lodjur och rödräv utifrån det nyttjade datamaterialet. Detta medför att det är svårt att avgöra ifall lodjur har en positiv inverkan på skogshönsen då rävstammen troligtvis regleras av något annat än lo.The lynx population in Sweden has increased to stable levels since 1920 when it almost went extinct. The importance of apex predators is widely known and has been proven to play an important role in both food chains and ecosystems. This report investigates if lynx have an indirect positive effect on forest grouse, in consideration of lynx predation on red fox and predation of red foxes on forest grouse. The Swedish hunting association (Jägareförbundet) provides the data that are used which covers all felled prey of forest grouse and red fox due to hunting in Västerbotten County in Sweden. The data for lynx are inventoried by the county administrative board (Länsstyrelsen) and is supposed to cover the whole county of Västerbotten. The given data sets were compared against each other with correlation coefficient and linear regression (R2-values). When comparing lynx and red fox the result is a correlation coefficient of -0,11 and R2 = 1,8 %. The same comparison with red fox and forest grouse, as well as lynx and forest grouse, results in correlation coefficients of -0,78 and 0,55 respectively R2-values of 62 % and 29 %. These results indicate that there exists a positive connection between lynx and forest grouse, as well as a negative connection between forest grouse and red fox. However, with the given data it is not possible to make any statistical conclusions concerning the connection between lynx and red fox. It is therefore uncertain whether lynx have any positive effect on forest grouse since there is some other factor that regulates the fox population

Population ecology of the red grouse, Lagopus lagopus scoticus, with particular reference to the effects of the parasite trichostrongylus tenuis

Trichostrongylus tenuis is a prevalent nematode parasite of red grouse Lagopus lagopus scoticus. It reduces breeding success and survival of birds, and as a result may be responsible for the cycles in bird density that occur in many red grouse populations. In this thesis I examine this host-parasite interaction, including testing the effectiveness of parasite control, studying the frequency distribution and spatial distribution of parasites in a grouse population, and investigating the nature of parasite-induced cycles in host numbers through theoretical modelling. Many grouse moors rely on the application of anthelmintic-coated grit for controlling nematode infection in red grouse. This grit is placed on the moor for the grouse to consume, which they do to aid digestion. However, a possible side effect of frequent dosing is the development of parasite resistance to the anthelmintic. I tested for resistance in parasites from 12 different moors in northern England, which varied in the timing of grit treatment and the quantity of grit applied to the moor. Egg hatch assays on T. tenuis eggs showed no evidence of resistance on any of the moors. Studying the spatial distribution of parasites in the environment, and the degree to which they coincide with the spatial arrangement of the hosts, is fundamental to understanding the host-parasite interaction. A detailed survey of the distribution of T. tenuis on an area of moorland in Teesdale, northern England, supported the hypothesis that the parasite population is not uniformly distributed among the host population: both adult parasites among hosts and eggs among caecal faeces were aggregated. Environmental factors and host characteristics played a role in determining the parasite distribution, with parasite infections being associated with age of birds and location on the moor. However T. tenuis egg concentration in caecal faeces on the moor was only weakly spatially auto-correlated suggesting that further intrinsic or extrinsic factors may be influential. Distribution of eggs on the moor was not related to the density of grouse. Finally, I developed an individual-based stochastic model, which specifically modelled the red grouse-7. tenuis interaction. This showed that the parasite could theoretically cause cycles in grouse abundance, with the spatial distribution of both the host and parasite being important in the occurrence of cycles. Adding density-dependent host mortality to the model had a stabilising influence on the host population, although the parasite still generated cycles in host numbers. In some cases this density dependence generated damped cycles in host numbers in the absence of the parasite. These cycles were amplified when parasite induced mortality was included, suggesting that the parasite can increased the cyclic tendency of the host population in these cases. Cycle periods were influenced by parasite-related parameters and were similar to those recorded in natural grouse populations

THE INTERACTION BETWEEN DEMOGRAPHY AND HARVESTING IN RED GROUSE

Many animal populations are threatened by human activity, including habitat loss and harvesting but recent advances in population ecology show that the age- and sex-structure are important when aiming to understand population dynamics. However, research on population dynamics often focuses on species that experience relatively little human disturbance and human caused mortality is often assumed not to affect population dynamics. An increasing number of studies shows short-term and long-term evolutionary and ecological consequences of harvesting. This has not only implications for the understanding of population dynamics but also for the management and conservation of species in human-dominated landscapes. This thesis aims to investigate the interaction between the demographic structure and harvesting in a fluctuating species, the red grouse (Lagopus lagopus scoticus) using a combination of empirical and theoretical approaches. The relative roles of age-related parasite burden, fecundity and shooting in driving population dynamics are assessed, and empirical data are used to parameterise a model examining the effect of harvesting on the population dynamics. The empirical part of the thesis starts with the investigation of the intensity and distribution of the parasitic nematode Trichostrongylus tenuis for three age-classes of red grouse before the breeding season. The intensity of the parasite increased with host age. Parasites in two-year-old grouse were more aggregated than in one-year-old and 3+-year-old grouse. This has implications for population dynamics because the aggregation of parasites within the host influences mortality rates. Females of the oldest age class (3+-years-old) were less fecund than younger grouse and interactions with nesting habitat and year were found to affect female fecundity. The age- and sex-structure of shot birds was compared with the age- and sex-structure of the population before shooting. More old birds were shot at small bag sizes but this bias decreased as more birds were shot. Old males were highly susceptible to shooting at the beginning of the season but susceptibility decreased with number of shooting events. A relationship between bag numbers and population density was found. An age- and sex-structured population model was used to examine the effect of harvesting on red grouse population dynamics. Selective harvest for or against a certain age class led to a skew in the sex ratio of the population and to a decrease in fecundity and therefore to a drop in population size and harvest yield. Parasites and the exclusion of young birds through aggressiveness affected the population dynamics and led to a skew in the harvest rate at which the maximum sustainable yield was attained. Shooting early in the season resulted in a higher yield because individuals were removed from the population before they contributed to the availability of free ranging stages of the parasite. The population model demonstrated that parasites, aggressiveness and harvesting interact and that harvesting is a significant factor in population dynamics. Overall, the current practice of shooting rarely more than 50% of the population seems to be a good precautionary principle. Uncertainty in the harvesting rate increased the probability of local extirpation of the population. Therefore, reliable estimates of the population, including the age and sex structure, are invaluable parts of red grouse management. This study showed that harvesting and the age and sex structure of the population are important drivers of red grouse population dynamics and an understanding of their interactions is important for sustainable management of red grouse