Chris V. Wernham

Impacts of piscivorous birds on salmonid populations and game fisheries in Scotland: a review

Abstract The Scottish populations of salmonids are important both ecologically and economically. Game fisheries for Atlantic salmon Salmo salar, sea trout Salmo trutta trutta and brown trout Salmo trutta fari are all highly acclaimed and generate substantial levels of income for Scotland, but many populations are in decline and efforts are being made to ensure the future sustainability of these species. These declines have led to a focus on the impact of piscivorous bird predation on fish populations. The purpose of our review was to assess the evidence for population-level impacts on salmonid populations, and/or economic impacts on Scottish game fisheries of predation by the four primary UK freshwater piscivorous bird species: cormorant Phalacrocorax carbo, goosander Mergus merganser, red-breasted merganser Mergus serrator and grey heron Ardea cinerea. There is evidence that these birds can, in some situations, remove large numbers of fish from stocked and natural fisheries. However, a lack of information on fish population levels, the numbers and species composition of feeding birds, and robust calculations of fish consumption has hampered the conversion of the results of the existing studies into useful quantitative measures of impact. As a consequence, few studies have demonstrated any reductions in numbers of breeding fish or fish productivity due to predation by piscivorous birds, or direct economic loss to fisheries in Scotland. We support a previous recommendation for a reiterative procedure of modelling, experimentation and remodelling to assess the impacts of piscivorous birds on fisheries. Wide-scale studies of the movements of piscivorous birds, their feeding locations in relation to river characteristics, and the factors that make fish particularly vulnerable to predation are seen as important areas for future research.

European Monitoring for Raptors and Owls: State of the Art and Future Needs

Abstract Sixty-four percent of the 56 raptor and owl species that occur in Europe have an unfavorable conservation status. As well as requiring conservation measures in their own right, raptors and owls function as useful sentinels of wider environmental “health,” because they are widespread top predators, relatively easy to monitor, and sensitive to environmental changes at a range of geographical scales. At a time of global acknowledgment of an increasing speed of biodiversity loss, and new, forward-looking and related European Union biodiversity policy, there is an urgent need to improve coordination at a pan-European scale of national initiatives that seek to monitor raptor populations. Here we describe current initiatives that make a contribution to this aim, particularly the current “MEROS” program, the results of a questionnaire survey on the current state of national raptor monitoring across 22 BirdLife Partners in Europe, the challenges faced by any enhanced pan-European monitoring scheme for raptors, and some suggested pathways for efficiently tapping expertise to contribute to such an initiative.

Use of ring recoveries to monitor long-term changes in the survival rates of British and Irish Cormorants Phalacrocorax carbo

Ring recovery data were used to assess changes in the survival rates of Cormorants in Britain and Ireland between 1965 and 1994. It was found that 99% were ringed as nestlings, thus necessitating an assumption of constant reporting rate across age-classes. The wide geographical spread of ringing effort since 1965 produced sufficient recoveries to enable analyses of trends in survival and reporting rates, but regional subdivisions of the data resulted in high sampling correlations between survival estimates. The assumption of a constant reporting rate across age-classes may be violated for British and Irish Cormorants, because first-year birds are more likely to be shot or caught in fishing nets than older birds and they have a differing seasonal pattern of recoveries. A simple simulation showed that first-year, but not adult, survival estimates were particularly sensitive to age-specific variation in reporting rates. However, the observed trend in first-year survival appeared robust to the assumption of c...

Variation in the diurnal activity of breeding Short‐eared Owls Asio flammeus: implications for their survey and monitoring

Capsule The proportion of time during which breeding Short‐eared Owls could be seen during daylight hours was low and assessment of seasonal variation in their detection likelihoods suggests that surveys may only be able reliably to identify pairs that successfully reach the chick‐rearing stage. Aims To identify the most appropriate times of day and stages of breeding for surveying and to contribute towards the development of feasible survey protocols. Methods Fixed point watches sampled the activity of breeding Short‐eared Owls in three extensive study areas in Scotland during two breeding seasons; 2006 and 2007. Results The proportion of time for which breeding owls were visible during daylight hours was low (4.8% of the time for the season March–July) and there was a statistically significant effect of stage of breeding and also of time of day within some stages of breeding on the proportion of time during which owls were visible. There was a greater than 75% likelihood of seeing owls during a combined total of four hours of watching (1) in the evenings during incubation (mid‐April to mid‐May), (2) mornings and evenings during chick‐rearing (June), and (3) early morning and late evening during fledging (July). The likelihood of seeing key territorial behaviours was always low. The mean distance from an observer at which owls were first detected in 2006 was 495 m (95% CI: 390–601 m), and significantly greater in 2007 at 741 m (95% CI: 651–832 m). Conclusion The interpretation of field surveys of breeding Short‐eared Owls should take into account the effect of season and time of day on the likelihood of detection. Surveys may only be able to reliably identify pairs that successfully reach the chick‐rearing stage and, therefore, the most robust survey/monitoring unit may be pairs that successfully hatch young. Distances at which owls could be reliably detected suggest that a survey of any defined area will require vantage points separated by a minimum distance of about 1.5 km with allowance for topography and a 180° field of view. Evidence of a disturbance or deterrence effect of field surveyors on the owls supports the need for unobtrusive survey methods.

Overview of raptor monitoring activities in Europe

Abstract Despite the key role of raptors (including birds of prey Falconiformes and owls Strigiformes) in ecosystems and their sensitivity to environmental change, a well coordinated, Europe-wide monitoring of raptors is lacking. EURAPMON, a Research Networking Programme of the European Science Foundation, was launched with the aim of establishing a sustainable Europewide network for monitoring of raptors. An overview of current monitoring schemes for raptor populations in 28 European countries, as reported by EURAPMON National Coordinators at the workshop in Murcia (Spain) in 2012, showed existing monitoring schemes to be limited to a restricted number of species (mostly diurnal and rare raptor species). The most widely monitored species are the Golden Eagle Aquila chrysaetos amongst diurnal raptors and the Eagle Owl Bubo bubo amongst owls. Broad coverage of a species range across Europe is reached only for restricted-range species. The key driver for monitoring, which is mostly coordinated by NGOs, is conservation, and the main end users are governmental institutions. International collaboration in the field of monitoring of raptors is mainly regional and not yet pan-European in scale. The involvement of volunteers in raptor monitoring was perceived as the main strength of many schemes, but insufficient manpower and a focus on rare species were recognised as the main weaknesses across Europe as a whole. Among priorities identified for the future development of monitoring schemes are: improvements to national coordination; support to increase the number of volunteers; and assurances of stable funding. Further analysis of EURAPMON questionnaires will identify knowledge gaps, which will steer good practice guidance on survey methodologies; the need for the latter was identified as the main benefit that National Coordinators expect to gain from international networking

The influence of survey frequency on population estimates of moorland breeding birds

Capsule A minimum of four constant‐effort‐search survey visits are required to generate reliable population estimates of breeding birds on moorland that are not subject to biases associated with varying levels of detectability through the season. Aims To investigate the influence of the number and the combination of survey visits on the population estimates of breeding birds on moorland. Methods Four constant‐effort‐search surveys (80–100 minutes per km2 per visit) of moorland in southwest Scotland were undertaken in each of six years, 2003–2008. Using standard protocols, the numbers of apparent territories that would have been identified for each possible combination of survey visits were determined.glms were used to assess the influence of the frequency of survey visits, and different combination scenarios on the derived population estimates for Red Grouse, European Golden Plover, Common Snipe, Eurasian Curlew, Sky Lark, Winter Wren and Stonechat. Independent assessments of population density were made by transect sampling for Red Grouse and Sky Lark. Results Robust population estimates were possible from three survey visits for European Golden Plover, Eurasian Curlew and Stonechat. However, there were differences between species in the seasonal variation of their detectability. Four survey visits would underestimate the populations of Red Grouse (probably by 67–91%), Sky Lark (probably by 31–61%) and Winter Wren (by an undetermined proportion). Common Snipe were also likely to be underestimated after four survey visits, but the value of the derived estimate as an index of population density deserves further investigation. Conclusions If there is a need to carry out a multi‐species survey on moorland, we suggest that a minimum of four survey visits is required to ensure the derivation of reliable population estimates for a suite of the most readily detectable species. Population estimates derived from three or fewer survey visits risk biases through uneven sampling in periods of differing detectability. With evidence for changes in the breeding phenology of birds associated with changing climate or weather patterns, it arguably becomes more important to ensure that surveys sample an adequately broad period of the breeding season.

Bird ringing in Britain and Ireland in 2001

This is the 65th annual report of the British Trust for Ornithologys Ringing Scheme covering work carried out and data received in 2001. As part of the BTOs production of the landmark Migration Atlas: movements of the birds of Britain & Ireland, which will review movements of birds using Britain & Ireland, novel approaches to the investigation of the movement patterns and distances were developed. These allow the objective comparison of whether different species are sedentary, short‐distance or long‐distance migrants and the investigation of differential migration between birds of different age and sex. The BTO continues to carry out a programme of work investigating the declines in bird populations. In 2001, an investigation of Song Thrush population dynamics showed that the survival rates of young birds was key in the population decline; reduction in survival rates also seemed to have driven the fall in numbers of Marsh Tits. Work on movements of waders between roosts on the Moray Basin showed little movement for most species; important information when the possible effects of disturbance are being considered. An investigation of the biometrics of the Redshank wintering on Severn Estuary found that the proportions of Icelandic and British breeders varied between sites; again an important factor in assessing the possible consequences of disturbance. A pilot project, which is investigating the collection of data on movements and demography of farmland passerines in winter is described. Data collected as part of the Constant Effort Sites (CES) Scheme showed significant changes in the numbers of seven species between 2000 and 2001. Of these, five resident species (Blackbird, Blue Tit, Great Tit, Chaffinch and Greenfinch) and one migrant (Whitethroat) showed increases. Only one species (Willow Warbler) decreased. By contrast, productivity tended to be low with 11 species, both residents (Dunnock, Robin, Blackbird, Long‐tailed Tit, Blue Tit, Greenfinch and Reed Bunting) and migrants (Sedge Warbler, Reed Warbler, Blackcap and Chiffchaff) showing significant declines. Progress on the EURO‐CES project, which aims to develop standard protocols for CES fieldwork and data capture across Europe is reported. Data sets for 86 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The first detailed analysis of Pied Flycatcher data from RAS‐type studies showed that survival rates vary between different areas of the country and confirms the value of this project. The numbers of birds ringed in 2001 (648,936) was 16% below the mean of the previous five years (1996–2000), largely as a result of Foot and Mouth Disease, which restricted the areas ringers had access to. The recovery total (10,692) was 6% lower than the five‐year mean (1996–2000). Recoveries of 195 BTO‐ringed birds and 77 birds ringed abroad are presented in the report and include a number of unusual or significant movements. Of particular note are the first recovery of a Great White Egret involving Britain & Ireland, the first recoveries of BTO‐ringed Honey Buzzards, a BTO‐ringed American Golden Plover recovered in Italy, an Hungarian‐ringed Knot found in England and the first foreign‐ringed Yellow‐browed Warbler (from Norway) to be reported in Britain & Ireland.

Development of the British and Irish ringing scheme and its role in conservation biology

We review the development of scientific and conservation objectives for the British and Irish Ringing Scheme, which has been run by the BTO since 1937. A brief introduction to the workings and growth of the scheme is provided. The types of data collected via ringing and their status within the Scheme are discussed. We demonstrate how ringing contributes to important areas of conservation science within Britain and Ireland (integrated population monitoring and studies of population dynamics, research on migration and other movements and a range of other applied uses). Recent and current development of mechanisms for increasing the conservation value of data from the Ringing Scheme, and future directions towards this aim, are also discussed.

Bird ringing in Britain and Ireland in 2000

This is the 64th annual report of the British Trust for Ornithologys Ringing Scheme presenting work carried out and data received in 2000. Ringing birds is an important tool for conservation and research, providing information on survival, productivity and movements of birds. Much progress has been made in developing Integrated Population Monitoring (IPM) models to identify key aspects of a species’ biology. Studies on Marsh and Willow Tits and on Bullfinches focussed on developing models for these species, which are of particular conservation concern. A further study described some advances in statistical theory that can be used in IPM models. A study of Redshank movements showed differences before and after closure of a tidal barrage in Cardiff Bay in south Wales. Data collected by the Constant Effort Sites (CES) Scheme showed mixed fortunes for breeding birds. Adult numbers increased significantly for four species (Long‐tailed Tit, Sedge Warbler, Reed Warbler and Whitethroat) and four species showed significant declines (Linnet, Garden Warbler, Blackcap and Willow Warbler). Similarly, productivity increased significantly for three species (Blue Tit, Blackcap and Willow Warbler) and decreased significantly for three species (Reed Warbler, Chaffinch and Bullfinch). Initial work on a project to develop standard CES methods across Europe is described. 101 datasets for 43 species were submitted for the Retrapping Adults for Survival (RAS) Project. The number of birds ringed in 2000 (734,235) was 8% lower than the five‐year mean 1995–1999. The recovery total (10,912) was 6% below the mean of the previous five years (1995–1999). Recoveries of 156 BTO‐ringed birds and 81 birds ringed abroad are presented in the report, including a number of significant movements of an unusual nature. Particularly noteworthy are the first report abroad of a BTO‐ringed Shorelark, the first BTO‐ringed Whinchat to be recovered on the wintering grounds and a Great Tit that was ringed at Rybachiy in Russia in September 1999 and recaught in Cleveland in February the following year.

The Scottish Raptor Monitoring Scheme: Objectives, Achievements in the First Four Years, and Plans for Future Development

Abstract The Scottish Raptor Monitoring Scheme (SRMS) comprises 7 partner organizations and was established in 2002 after i) the publication of the UK Governments Raptor Working Group Report that made recommendations for enhanced monitoring, ii) increased applied data needs (e.g., for site designation), and iii) concerns for the status of some species. The SRMS has 3 major objectives: i) to facilitate cooperation between parties; ii) to provide robust information on Scottish raptor populations by determining trends in numbers, range, survival, and productivity and understanding the causes of change; and iii) to maintain high and uniform standards for the collection, collation, auditing, and analysis of data and reporting of information. Data are collected for 19 species: 14 diurnal raptors, 4 owls, and 1 corvid, the Common Raven. Here we describe the development of the scheme, challenges, and achievements during its first 4 y, the nature and value of the data collected, and plans for the future.