Showing papers by "Royal Society for the Protection of Birds published in 1998"
TL;DR: One of the most important bird breeding and over wintering sites in the west of Europe, the Coto Doñana, was severely impacted by the release of 5 million cubic meters of acid waste from the processing of pyrite ore causing sustained pH decreases and resulting in massive metal contamination of the impacted ecosystem.
119 citations
TL;DR: Large–scale, long–term data from a national bird census scheme is used to examine whether magpies and sparrowhawks could have depressed the rates of year–to–year population change in 23 songbird species, finding that they are unlikely to have caused songbird declines.
Abstract: During the last 30 years, there have been marked declines in the populations of many British songbirds breeding on farmland, while two of their main predators, sparrowhawk ( Accipiter nisus ) and magpie ( Pica pica ), have spread back into areas from which they had disappeared. The causes of the songbird declines remain unclear but given the coincidence in timing, it might appear that increased predation could be responsible. Although many studies have failed to find links between changes in the populations of breeding songbirds and mortality from avian predators, previous work has, with few exceptions, involved only short–term studies on small spatial scales. Here we use large–scale, long–term data from a national bird census scheme to examine whether magpies and sparrowhawks could have depressed the rates of year–to–year population change in 23 songbird species. Our results indicate that magpies and sparrowhawks are unlikely to have caused the songbird declines because patterns of year–to–year population change did not differ between sites with and without these predators.
100 citations
TL;DR: The seedbanks from the Betula spp.
Abstract: 1 Many areas of lowland heaths are being lost due to invasion by Betula spp., Pinus sylvestris, Pteridium aquilinum, Rhododendron ponticum and Ulex europaeus. One of the factors influencing the success of restoration of heathland on such sites will be the content of their viable seedbanks.
2 Ten heathland areas in the Poole Basin area of Dorset, where succession to one or more of the above species had occurred were studied. The viable seedbanks of the successional sites were compared with those of nearby heathland using Canonical Discriminant Analysis.
3 The seedbanks of all the successional stages were significantly different from the seedbank of the heath.
4 The seedbanks from the Pinus sylvestris and Pteridium aquilinum successional stages contained significantly lower numbers of heathland species than did the heathland seedbank, although few non heathland species were present.
5 The seedbanks from the Betula spp., Rhododendron ponticum and Ulex europaeus successional sites contained both significantly lower numbers of heathland species and significantly higher numbers of non heathland species than the heathland seedbank.
6 The results are discussed in relation to the restoration of heathland on successional sites and the use of the seedbank as a source of propagales for the establishment of heathland species.
73 citations
TL;DR: In this paper, the authors investigated the cost-effectiveness of government expenditure by comparing the cost of grant aid with the ecosystem restoration potential of new woodlands and found that the most cost-effective woodlands were established close to existing woodlands using natural colonisation techniques.
71 citations
TL;DR: There were about three-year cycles in the populations of arctic foxes and lemmings, and the breeding productivities of brent geese and curlew sandpipers on the Taimyr Peninsula, Russia as discussed by the authors.
Abstract: There were about three-year cycles in the populations of arctic foxes, and the breeding productivities of brent geese and curlew sandpipers on the Taimyr Peninsula, Russia, The populations of arctic foxes and lemmings changed in synchrony. The breeding productivities of the birds tended to be good when the arctic foxes were increasing in numbers and poor when the arctic foxes were decreasing. There was a negative relationship between arctic fox numbers (or occupied lairs) and the breeding productivity of brent geese in the following year. Although there was evidence of wide-spread synchrony In the lemming cycle across the Taimyr Peninsula, some localities showed differences, However, such sites would still have been influenced by the general pattern of fox abundance in the typical tundra zone of the Taimyr Peninsula, where most of the arctic foxes breed and from which extensive movements of foxes occur after a decline in lemming numbers. The results support a prey-switching hypothesis (also known as the alternative prey hypothesis) whereby arctic foxes, and other predators, feed largely on lemmings when these are abundant or increasing, but switch to birds when the lemming population is small or declining. The relationships between arctic foxes, lemmings and brent geese may be further influenced by snowny owls which create fox-exclusion zones around their nests, thus providing safe nesting areas for the geese.
71 citations
TL;DR: In this paper, the authors conducted a survey of 77 saltmarsh sites around the coast of Britain in 1985 and 1996 and found that breeding densities were lowest on heavily grazed plots, and there was some evidence, from the larger number of survey sites for which data were available in 1985, that breeding density tended to be highest on lightly grazed and moderately/heavy grazing plots.
Abstract: 1. Saltmarsh habitats support c. 50% of the population of redshank Tringa totanus breeding in Britain. Between 1985 & 1996, breeding densities declined significantly by 23%. This paper tests the hypothesis that this decline resulted from changes in the extent of important saltmarsh habitats for nesting redshank, and/or a change in the intensity of grazing.
2. We surveyed breeding redshank densities, the extent of saltmarsh habitats, and the intensity of grazing on a sample of 77 saltmarsh sites around the coast of Britain in 1985 and 1996. From these data, we constructed statistical models that described breeding densities in relation to a range of habitat and grazing variables for each of the surveys, and examined changes in breeding density between the surveys, in relation to changes in the important habitat and grazing variables included in these models.
3. During both surveys, breeding densities were lowest on heavily grazed plots, and there was some evidence, from the larger number of survey sites for which data were available in 1985, that breeding densities tended to be highest on lightly grazed saltmarsh. Multiple regression modelling, incorporating a range of habitat variables and grazing intensity, also showed this effect, although in 1996 interpretation of the relationship between breeding density and grazing intensity was complicated because both grazing intensity and a habitat variable accounted for a similar component of the variance in breeding density. These models also showed that certain habitat variables were significant correlates of breeding density, particularly the extent of sea-couch grass, which was positively correlated with breeding density in both survey years. During 1985, breeding densities were also correlated with the extent of a number of other saltmarsh habitats, which did not significantly correlate with breeding densities in 1996. In addition to the measured habitat and grazing variables, densities also showed significant regional variation in Britain during both surveys.
4. Of the habitat and grazing variables included in the multiple regression models of breeding density, only the intensity of grazing changed between 1985 and 1996, showing a significant increase. Breeding densities declined most markedly on sites that had experienced an increase in the intensity of grazing from ungrazed/lightly grazed to moderate/heavily grazed. This suggests that an increase in the intensity of grazing was the most likely explanation for the decline in breeding densities observed between 1985 and 1996. Causal explanations for the increase in grazing intensity are discussed.
5. Assuming that the grazing intensity data were representative of grazing management on saltmarshes throughout Britain, then we estimate that 1665 ha of saltmarsh experienced an increase from ungrazed/light grazing to moderate/heavy grazing over the 11 years between 1985 and 1996. This is comparable to the 2100 ha of saltmarsh that are expected to be lost to erosion over the next 20 years. We also estimate that 6388 ha, or 14·6%, of saltmarsh in Britain was heavily grazed in 1996.
6. Our analysis of the redshank survey data, together with these figures, suggest that heavy grazing is a significant threat to saltmarsh habitats and its breeding redshank, on a national scale at present. We urgently need a detailed assessment of the grazing management of saltmarshes in Britain, and how grazing management is affected by agricultural policy, as a precursor for the introduction of provisions to ensure that the decline in breeding redshank does not continue.
69 citations
TL;DR: A survey of habitats at 17 reedbed sites in the UK which currently hold or have recently held breeding bitterns Botaurus stellaris has shown significant differences between sites with decreasing and sites with increasing numbers of birds over the period 1979 to 1994.
50 citations
TL;DR: The RSPB is attempting to establish heathland and acid grassland on 158 ha of arable land at Minsmere, ultimately to benefit two species of rare breeding birds, the stone curlew Burhinus oedicnemus and the woodlark Lullula arborea as mentioned in this paper.
49 citations
TL;DR: It is suggested that kleptoparasitism might be infrequent because birds could reduce its likelihood by adjusting their behaviour, with only a minimal cost in terms of a reduced intake rate.
47 citations
TL;DR: Winter oystercatcher abundance in the Burry Inlet was correlated, however, with the number of birds wintering in the UK, and the abundance during spring was reduced, suggesting that overwinter cockle losses due to predation, fishing, and other sources of mortality cause increased prey depletion when the biomass of cockles at the start of the winter is small.
Abstract: 1. The Burry Inlet estuary in South Wales supports internationally important numbers of oystercatchers Haematopus ostralegus during the winter, where they feed predominantly on cockles Cerastoderma edule. The cockle population has been fished commercially for over a century.
2. The depletion of cockle stocks by commercial fisheries and disturbance to feeding birds has caused conflicts between fishing and nature conservation interests in Europe. Therefore, the aim of our study was to investigate the relationship between oystercatcher numbers, the biomass of cockles present at the start of the winter, and the biomass of cockles landed by the fishery during the winter. Our analyses are based on data from 11 winters, covering the period 1982/83–1992/93.
3. The abundance of oystercatchers during winter (measured as total bird-days during September to February inclusive) was not significantly related to the biomass of cockles at the start of the winter, or the biomass landed by the fishery. Winter oystercatcher abundance in the Burry Inlet was correlated, however, with the number of birds wintering in the UK.
4. The abundance of oystercatchers during spring (measured as total bird-days during March and April) was positively correlated with the biomass of cockles at the start of the winter, and negatively correlated with the biomass landed by the fishery over the winter. The most likely explanation for this is that birds disperse from the Burry Inlet earlier in spring when the biomass of cockles at the start of the winter is small and/or the biomass landed by the fishery is large.
5. The most likely causal explanation for this dispersal is that overwinter cockle losses due to predation, fishing, and other sources of mortality cause increased prey depletion when the biomass of cockles at the start of the winter is small. An increase in fishery landings during winter could therefore cause a reduction in oystercatcher abundance during spring. Considerably higher levels of fishing effort in future could conceivably cause a reduction in the abundance of oystercatchers during winter, although, at present, there is no evidence to suggest that fishing affects oystercatcher abundance at this time.
6. The Burry Inlet cockle fishery is a low intensity fishery, removing < 25% of the available stock, and using traditional fishing methods such as hand gathering. Even at these low levels of fishing effort oystercatcher abundance was reduced during spring. The introduction of more efficient modern fishing methods, such as tractor or suction dredging could therefore cause a decline in the abundance of oystercatchers within the estuary, if the level of exploitation increased as a result. Current levels of exploitation therefore need to be maintained. Reliable predictive models are now required for quantifying the impact of fishery management on the abundance of birds and cockles. A precautionary approach to management is required at other sites where a lack of data means that it is difficult to assess the impact of fishing effort on oystercatcher or cockle abundance.
47 citations
TL;DR: Data presented in this paper suggest that birds attempting to maximize their intake rate incur significant costs, in addition to those associated with searching for and handling prey, which are included in the Charnov model.
Abstract: 1. We describe the functional response of oystercatchers (Haematopus ostralegus L.) searching for cockles (Cerastoderma edule L.) by touch, using a multiple-prey version of the disc equation developed by Charnov (1976).
2. The model includes probabilistic time costs associated with the successful and unsuccessful handling of prey, seasonal changes in the flesh content of prey, and factors that affect prey availability. The encounter rate with cockles is estimated using a simple random search model. This model calculates the likelihood that a bird would locate a cockle buried in the sand per unit of time spent searching, as a function of the touch area of buried cockles (the largest cross-sectional area of the shell enlarged by the surface area of the bill-tip) and the bird’s probing rate.
3. Prey profitability increased with cockle size, and the model predicted birds should preferentially take cockles > 15 mm in length to maximize their rate of energy intake. The birds showed a systematic seasonal departure from the model’s predictions. During late winter, the observed and predicted maximum intake rates for individual birds were comparable. However, the mean size of cockles observed being taken by the birds was consistent with the predicted mean size taken by a bird, including all size classes in its diet, rather than the predicted size for a bird taking only size classes > 15 mm (for a bird maximizing its intake rate). During early winter, observed intake rates were lower than predicted values for a bird feeding unselectively, suggesting birds either reduced their searching effort, preferentially ignored the larger, more profitable size classes, or experienced longer time costs. The lower than expected intake rates observed during early winter resulted from prey choice: birds preferentially ignored the larger, more profitable size classes.
4. Data presented in this paper suggest that birds attempting to maximize their intake rate incur significant costs, in addition to those associated with searching for and handling prey, which are included in the model. Such costs could include a risk of bill damage when attacking large cockles, an increased risk of parasitism associated with large cockles, or a mass-dependent metabolic or predation cost incurred by birds storing any excess ingested food in the form of fat.
5. A simple graphical model is presented to show how such costs, together with the need to achieve a given intake rate to avoid starvation, might interact to determine optimal intake rates. Within this framework, the maximum intake rate predicted by Charnov’s model should be viewed as a means of describing the constraints on intake rates, rather than as an explicit optimality model. Depending on energy demands and the costs of maintaining a given intake rate, birds could experience a range of optimal intake rates, but only under certain conditions would the optimal intake rate be the maximum. This has implications for models of the dispersion of predators across a gradient of resource densities, and behaviour-based models of population dynamics, both of which implicitly assume that a predator would maximize its fitness by maximizing its rate of energy intake.
TL;DR: Widespread declines in eggshell thickness since the nineteenth century were found in all species and the effect of acid deposition on the availability of calcium–rich prey is a plausible explanation.
Abstract: The thickness of eggshells of four species of thrush, Turdus spp., was estimated by an index based on the mass and linear dimensions of blown eggs in museum collections from Britain. Shell thickness was also measured directly for two species and was highly correlated with the index. Widespread declines in eggshell thickness since the nineteenth century were found in all species. There have been no previous reports of trends in eggshell thickness of this long duration and large spatial scale. The cause of the declines is unknown, but, for three of the four species, eggshell thinning began before the introduction of the organochlorine pesticide DDT, which caused eggshell thinning in predatory and fish–eating birds from 1947 onwards. The effect of acid deposition on the availability of calcium–rich prey is a plausible explanation.
TL;DR: In this paper, the authors used a combination of questionnaires, Geographical Information System (GIS) and advanced line transect techniques, using repeatable methodology which should be applicable to other cryptic forest species.
TL;DR: In this article, the authors report the results of two surveys of the same sample of 77 saltmarsh sites around the coast of Great Britain, conducted in 1985 and 1996 to estimate breeding abundance and the conservation status (i.e. stable, increasing or declining) of redshank Tringa totanus nesting on saltmarshes.
TL;DR: The European Commission has initiated a programme to investigate coastal zone management (CZM) throughout the European Union and to address the objective and targets outlined in the European 5th Environmental Action Programme.
TL;DR: The main objective of the Uluguru Slopes Planning Project as mentioned in this paper was to research the resource utilisation practices of villagers and their attitudes to forest conservation in the Uluuguru, through a socio-economic survey using participatory techniques.
Abstract: The Uluguru Mountain forests of Eastern Tanzania are of high importance both for the conservation of biodiversity, and as a water catchment area for major urban centres. Only about 270 km2 of forest is thought to remain, mostly inside forest reserves. The most biologically valuable sub-montane forest has been badly affected by habitat destruction and only a small area in the north-east Ulugurus remains. The main objective of the Uluguru Slopes Planning Project was to research the resource utilisation practices of villagers and their attitudes to forest conservation in the Ulugurus, through a socio-economic survey using participatory techniques. The findings demonstrated both that local communities are aware of the importance of forest conservation and that excellent examples of sustainable land management do exist. The results of the survey fed in to the planning of a follow-up project (funded by DANIDA), a key element of which will be the dissemination of this best practice more widely around th...
TL;DR: In the Highlands of Scotland, Catt et al. as discussed by the authors found that game birds such as red grouse Lagopus lagopus, tetrao tetrix and capercaillie (Tetrao urogallus L) living in native pinewoods in Scotland collided at a rate of 3 collisions a~' against 1.8 m high deer fences.
Abstract: Birds die due to collisions with many static man-made objects, particularly wires (powerlines, ski-tows and fences) (Avery, 1978; Faanes, 1987; Bevanger, 1990; Alonso et al., 1994). Although these events are common, the effect that fatal collisions have on bird populations has rarely been studied. Catt et al. (1994a) found that capercaillie (Tetrao urogallus L.) living in native pinewoods in Scotland collided at a rate of 3 collisions km"' a~' against 1.8 m high deer fences. This led to an annual mortality of 32 per cent, higher than all other causes of mortality combined. Further work showed that collisions against deer fences, particularly by gamebirds, were widespread in the Highlands of Scotland. In one year, 115 red grouse Lagopus lagopus (L.), 25 black grouse Tetrao tetrix L. and 31 capercaillie collided with 134.8 km of fences in and around woods, primarily conifer plantations. Smaller numbers of owls, pigeons and passerines also died (Petty, 1995; Baines and Summers, 1997). These mortalities are of conservation concern, particularly because capercaillie and black grouse are two of 23 species which have declined by over 50 per cent in
TL;DR: The concept of sustainable development is severely tested on one of the most fundamental issues of all: growing our food as discussed by the authors, which was recognized at the Earth Summit in Rio de Janeiro in 1992 as the guiding principle for both economic development and environmental protection.
Abstract: Growing human demands on land use and economic development are clearly central issues for the management of both the World economy and environment. Arresting economic growth is clearly not a realistic option and so conservationists have to find ways of achieving conservation in the context of development, i.e. through sustainable development. Recognized at the \"Earth Summit\" in Rio de Janeiro in 1992 as the guiding principle for both economic development and environmental protection, this concept is severely tested on one of the most fundamental issues of all: growing our food. Technological development, land use reforms and growing yields and production are clearly necessary to feed both the current generation and future generations in the developed and developing World. Predictions for World population growth hover around 9-11 billion people (double the current) by 2025. Growing affluence will lead to changes in the nature of diets (especially increased meat consumption in societies where grains have been dominant) and hence World demand for food (Rayment 1995)It was once fashionable to talk of food mountains in Europe, now the reverse problem of food shortage is back on the agenda. What does this mean for conservation? What can we do about it? Many practical bird conservation problems stem from changing land use. Familiar problems include: