Royal Society for the Protection of Birds

About: Royal Society for the Protection of Birds is a nonprofit organization based out in Sandy, United Kingdom. It is known for research contribution in the topics: Population & Biodiversity. The organization has 670 authors who have published 1425 publications receiving 88006 citations. The organization is also known as: RSPB & Plumage League.

Changes in the status of waders breeding on wet lowland grasslands in England and Wales between 1982 and 1989

Abstract: A randomly selected sample of sites surveyed in 1982 for the Breeding Waders of Wet Meadows survey was re-visited in 2989 and information on numbers of breeding waders collected. This showed that over this period numbers of Lapwings Vanellus vanellus had declined significantly by 38%, whilst Oystercatchers Haematopus ostralegus had increased by 56%. There was no evidence of a change in numbers of Snipe Gallinago gallinago, Redshank Tringa totanusor Curlew Numenius arquata. In both 1982 and 1989 a high proportion of all Snipe and inland breeding Redshank occurred on nature reserves. Numbers of Snipe and Redshank (but not Lapwing) were less likely to have declined on reserves than on unprotected sites.

The functional response of oystercatchers (Haematopus ostralegus) searching for cockles (Cerastoderma edule) by touch

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.

The drivers of avian abundance: patterns in the relative importance of climate and land use

Abstract: Aim: Climate and land use can have important effects on the local abundances of species, but few studies have investigated the relative impacts of these factors. Here, we quantify the relative importance of climate, land use and surrounding population size in determining the abundances of birds across a continent. Location: Europe. Methods: We used species abundance models to identify the relative importance of different environmental predictors for estimating the local abundances of 342 species of European breeding birds. Models controlling for phylogeny were used to relate species life history and ecological traits to the climate:land use importance ratio. The mean of this ratio, across all species occurring in a given area, was mapped to explore spatial variation in the major drivers of abundance. Results: At the scale examined, climate is generally more important than land use in determining species abundances. However, the abundance of species in neighbouring areas is also a major correlate. Among climate variables, temperature is of greater importance than moisture availability in determining abundances. The relative importance of these variables varies with latitude, with temperature being most important in the north, and moisture availability in the south. Differences in the importance of specific drivers are related to species ecological traits: climate is more important for determining the abundance of species that have larger global ranges or a smaller body mass. Main conclusions: Abundances of species occurring in northern Europe, an area predicted to experience climatic changes of high magnitude, are most sensitive to climate, particularly temperature. Given the greater confidence in future projections of temperature than precipitation, this increases confidence in projections of the impacts of climate change on species in the north, whilst attempts to predict future populations in central and southern Europe may be dependent on less predictable changes in land use and precipitation.