Showing papers by "Royal Society for the Protection of Birds published in 1993"

Lead poisoning in wild populations of Marsh Harriers Circus aeruginosus in the Camargue and Charente‐Maritime, France

Abstract: Lead poisoning of waterfowl, through the ingestion of spent gunshot, has been recognized as a mortality factor for over a century. However, in Europe relatively little attention has been paid to raptors that may ingest shot embedded in the flesh of prey. The present study examines the incidence of lead poisoning in wild Marsh Harriers Circus aeruginosus trapped at two sites in France, the Camargue and Charente-Maritime. Eight captive Marsh Harriers (controls) had blood lead (PbB) concentrations of 5.3–10.8 μg per dl. Of 94 wild birds trapped during the winters of 1990/1991 and 1991/1992 either in baited clap traps or in mist nets at night roosts, 29 (31%) had elevated (>30 μg/dl) PbB concentrations and 13 (14%) had concentrations indicative of clinical poisoning (> 60 μg/dl). Similar percentages of birds caught using the two trapping methods had elevated (>30 μg/dl) PbB concentrations. However, clap netting appeared to select for more heavily contaminated birds and for juvenile birds, although the two are not necessarily correlated. In the Camargue, significantly more females than males trapped in clap nets had elevated PbB concentrations. The incidence of shot in regurgitated Marsh Harrier pellets increased significantly between October and December, indicating increased exposure to lead as the hunting season progressed. There appeared to be a parallel increase in PbB concentrations throughout the hunting season, although this could not be clearly demonstrated as sex ratios were different during different sampling periods. Elevated PbB concentrations of harriers in the Camargue are likely to result primarily from the ingestion of shot in the flesh of crippled or unretrieved waterfowl and in Charente-Maritime, from eating crippled or dead mammals. Other raptors at risk from lead poisoning and solutions to this problem are discussed.

Status of the Hen Harrier Circus cyaneus in Scotland in 1988–89

Abstract: A sample survey of Hen Harriers in 1988–89 was based on 10-km squares according to their category of proof of breeding in 1968–72. From this sample the Scottish population was estimated at 570±150 pairs with 95% confidence. Seventy-one pairs were found on Orkney and 389 proved or probable pairs and a further 139 possibles were located elsewhere. About 60 pairs nested in England and Wales. An expansion of range since 1968–72 is mapped. Numbers have fallen on some grouse moor study areas. Nesting success on grouse moors was only 14% compared with 40% on other heather moors and 66% in young conifer plantations. Many of these failures on grouse moors were due to human persecution and by conservative estimates, 30–80 breeding adult birds were illegally killed each summer.

The effects of aero-generators on moorland bird populations in the Orkney Islands, Scotland

Abstract: In order to ascertain the effects of aero-generators on breeding birds, two moorland plots in Orkney's West Mainland were censused each year between 1981 and 1989 One plot was immediately adjacent to the aero genera for site while the other acted as a control Although the bird populations in the plots were not large enough to state categorically that the aero-generators caused no declines, their effects appear to have been minimal The only species to have been adversely affected by the development of the site was Red-throated Diver Gavia stellata and its decline was probably the result of factors other than the operation of the aerogenerators

The adaptive significance of brood size and time of breeding in the dipper Cinclus cinclus (Aves: Passeriformes) as seen from post‐fledging survival

Abstract: We assessed the post-fledging survival of dippers Cinclus cinclus from 743 broods in relation to brood size, time of hatching and territory quality. We paid particular attention to assessing whether contrasting breeding performance along unproductive (i.e. acidic) and productive (i.e. circumneutral) rivers represented strategies which optimized the number of surviving young. For all brood sizes, post-fledging survival varied significantly through the breeding season, with most survivors coming from attempts in the peak period of hatching. After correcting for these seasonal effects, the most common brood size overall, of four, was also the most productive as seen from post-fledging survival; differences in the frequency of occurrence and survival between broods of four and five were marginal. Moreover, a change in the modal brood size from five to four occurred as the season progressed. consistent with a shift in brood productivity. Broods at acidic sites were significantly smaller than at circumneutral sites; while brood size four was the most productive at both types of site, brood size three was the second most productive at acidic sites, while brood size five was the second most productive at circumneutral sites. Dippers at acidic sites bred significantly later than at circumneutral sites, but post-fledging survival declined most rapidly through the season at the former. These survival data provide evidence from both seasonal and spatial patterns that brood sizes in the dipper may be optimized in ways consistent with the enhancement of productivity. By contrast, delayed breeding at acidic sites contrasted with the patterns expected from optimization, instead reflecting resource scarcity.

Wintering seaducks in Britian and Ireland: Populations, threats, conservation and research priorities

Abstract: 1. This paper provides a detailed review of the status and distribution of wintering seaducks (Scaup, Eider, Long-tailed Duck, Common Scoter, Velvet Scoter and Red-breasted Merganser) in Britain and Ireland. It is based on a literature review plus analysis of National Waterfowl Counts (NWC) and other data. A summary of current knowledge of wintering seaducks is provided together with information on threats to populations, conservation goals and research needs. 2. Each species is examined in turn, with the emphasis on aspects of the population, habitat use, current distribution, trends and history. Important areas for individual species are highlighted. 3. Overall, seaduck populations have changed considerably, those for Eider and Red-breasted Merganser having expanded greatly, whilst those for Scaup, Common and Velvet Scoter have declined during historical and/or recent times. The trend for Long-tailed Ducks is unclear. British population estimates are considered to be out of date and need to be revised. The premier areas for seaduck communities are highlighted, thus providing basic information for conservation action and future monitoring. 4. Seaduck populations are threatened in a number of ways and the main factors are discussed. Oil pollution and the actions of commercial fisheries are the most important current threats. Conservation goals are suggested. These include an urgent need to develop appropriate domestic legislation to facilitate the protection of seaduck populations. Such legislation is currently almost entirely lacking. 5. Some priorities for research, particularly for better population monitoring of seaducks in British and Irish waters, are provided. These include: alterations to the NWC scheme to allow the collation of opportunistic counts, made when the conditions are amenable for censusing seaducks; extension of the scheme into areas not currently surveyed (e.g. most parts of Ireland); and the establishment of intensive survey programmes to monitor seaducks in the key areas of Britain and Ireland. It is hoped that this paper will serve to stimulate interest and commitment from all who play a part in safeguarding our seaduck heritage.

Lead determination in avian blood : application to a study of lead contamination in raptors from France

Abstract: Marsh harriers and other raptors may become poisoned by ingesting lead gunshot in the flesh of their prey Blood lead is a suitable indicator of exposure to lead The method usually used in our laboratory for the analysis of human blood induced coagulation of avian blood In this paper we report upon the optimization and quality control of a method to determine lead in avian blood samples Samples were prepared using a diluent and matrix modifier Analysis was carried out using graphite furnace AAS with a L'vov platform and Zeeman-effect background correction The method was validated using international intercalibration comparisons of lead in human blood The method proved to have a high degree of sensitivity, reproducibility and accuracy The detection limit was low (0004 ppm) The method used is discussed in relation to those previously used for lead analysis in avian blood

Preliminary survey of the avifauna of Mt Tchabal Mbabo, west-central Cameroon

Abstract: The montane forests of western Cameroon are well known for their endemic birds. The most northerly such forests probably occur on Mt Tchabal Mbabo, where a preliminary survey of the avifauna in 1990 found 12 montane species, of which six represented significant range extensions, among them the threatened Ploceus bannermani. Given the increasing human pressures on other montane forests in Cameroon, Mt Tchabal Mbabo may be attractive for future conservation because of its comparative lack of human disturbance. Densities of indigenous people are low and there is a lack of significant hunting and firewood-gathering, the precipitous nature of the northern slope makes human intrusions difficult, and the lack of human disturbance may mean that local animal populations are stable.Les forets d'altitude de l'ouest du Cameroun sont bien connues pour leurs populations endemiques d'oiseaux. Les forets les plus au nord sont celles du Mont Tchabal Mbabo, ou un recensement preliminaire de la faune aviaire en 1990 a revele 12 especes, dont six avaient une aire de repartition relativement grande, y compris l'espece menacee Ploceus bannermani. Etant donne l'accroissement des pressions humaines sur les autres forets d'altitude au Cameroun, le Mont Tchabal Mbabo pourrait se reveler interessant pour des programmes de conservation futurs, compte tenu d'une perturbation humaine relativement inexistante. Les densites de population indigene y sont faibles, et la chasse ainsi que le ramassage du bois pour les besoins domestiques ne sont pas significatifs. Les pentes abruptes du nord rendent difficile toute intrusion humaine, et l'absence de perturbations dues a l'homme pourrait signifier la stabilite des populations animales locales.

Tanzanian coastal forests – new information on status and biological importance

Abstract: This paper presents the current results of a continuing survey of the distribution, status and biological importance of Tanzanian coastal forests. The Frontier-Tanzania Coastal Forest Research Programme has shown that at least 34 locations, and possibly another eight, support important coastal forests. There are probably 350–500 sq km of forest remaining, with most sites smaller than 20 sq km. Most sites, and 75–85 per cent of the total area, are located in Forest Reserves. Coastal forest supports many endemic taxa and many individual forests support species and subspecies known from nowhere else. All these forests are severely threatened and effective conservation action is a priority. The Frontier-Tanzania project findings are contributing to conservation programmes co-ordinated by the Wildlife Conservation Society of Tanzania and the World Wide Fund for Nature (Tanzania).