Summary1. In recent years, marine predator and seabird tracking studies have become ever more popular. However, they are often conducted without first considering how many individuals should be tracked and for how long they should be tracked in order to make reliable predictions of a population's home-range area. 2. Home-range area analysis of two seabird-tracking data sets was used to define the area of active use (where birds spent 100% of their time) and the core foraging area (where birds spent 50% of their time). Analysis was conducted on the first foraging trip undertaken by the birds and then the first two, three and four foraging trips combined. Appropriate asymptotic models were applied to the data, and the calculated home-range areas were plotted as a function of an increasing number of individuals and trips included in the sample. Data were extrapolated from these models to predict the area of active use and the core foraging area of the colonies sampled. 3. Significant variability was found in the home-range area predictions made by analysis of the first foraging trip and the first four foraging trips combined. For shags, the first foraging trip predicted a 56% smaller area of active use when compared to the predictions made by combining the first four foraging trips. For kittiwakes, a 43% smaller area was predicted when comparing the first foraging trip with the four combined trips. 4. The number of individuals that would be required to predict the home range area of the colony depends greatly on the number of trips included in the analysis. This analysis predicted that 39 (confidence interval 29-73) shags and 83 (CI: 109-161) kittiwakes would be required to predict 95% of the area of active use when the first four foraging trips are included in the sample compared with 135 (CI 96-156) shags and 248 (164-484) kittiwakes when only the first trip is included in the analysis. 5. Synthesis and applications. Seabird and marine mammal tracking studies are increasingly being used to aid the designation of marine conservation zones and to predict important foraging areas. We suggest that many studies may be underestimating the size of these foraging areas and that better estimates could be made by considering both the duration and number of data logger deployments. Researchers intending to draw conclusions from tracking data should conduct a similar analysis of their data as used in this study to determine the reliability of their home-range area predictions.

Abstract. Population-level estimates of species' distributions can reveal fundamental ecological processes and facilitate conservation. However, these may be difficult to obtain for mobile species, especially colonial central-place foragers (CCPFs; e.g., bats, corvids, social insects), because it is often impractical to determine the provenance of individuals observed beyond breeding sites. Moreover, some CCPFs, especially in the marine realm (e.g., pinnipeds, turtles, and seabirds) are difficult to observe because they range tens to ten thousands of kilometers from their colonies. It is hypothesized that the distribution of CCPFs depends largely on habitat availability and intraspecific competition. Modeling these effects may therefore allow distributions to be estimated from samples of individual spatial usage. Such data can be obtained for an increasing number of species using tracking technology. However, techniques for estimating population-level distributions using the telemetry data are poorly developed. This is of concern because many marine CCPFs, such as seabirds, are threatened by anthropogenic activities. Here, we aim to estimate the distribution at sea of four seabird species, foraging from approximately 5,500 breeding sites in Britain and Ireland. To do so, we GPS-tracked a sample of 230 European Shags Phalacrocorax aristotelis, 464 Black-legged Kittiwakes Rissa tridactyla, 178 Common Murres Uria aalge, and 281 Razorbills Alca torda from 13, 20, 12, and 14 colonies, respectively. Using Poisson point process habitat use models, we show that distribution at sea is dependent on (1) density-dependent competition among sympatric conspecifics (all species) and parapatric conspecifics (Kittiwakes and Murres); (2) habitat accessibility and coastal geometry, such that birds travel further from colonies with limited access to the sea; and (3) regional habitat availability. Using these models, we predict space use by birds from unobserved colonies and thereby map the distribution at sea of each species at both the colony and regional level. Space use by all four species' British breeding populations is concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures in this area. The techniques we present are applicable to any CCPF.

Summary1. Low winter food availability is probably critical in the declines of many farmland bird species in Europe, leading to the implementation of ameliorative agri-environment scheme options. To date, however, there has been no experimental test of the effectiveness of such options. 2. We report the results of two large-scale, 3-year, controlled experiments investigating the effects of supplementary winter seed provision on breeding farmland bird abundance. In each experiment, the use of winter feeding sites by birds was monitored and the availability of alternative, seed-rich habitat in the surrounding area was measured. The Winter Food for Birds (WFFB) project also included variable levels of food provision. Breeding bird abundance was then monitored in experimental and control areas. The Bird Aid project targeted yellowhammer Emberiza citrinella L., corn bunting Emberiza calandra L. and tree sparrow Passer montanus L., while WFFB considered 11 species that used supplementary winter food. 3. Comparisons of trends in breeding abundance between experimental and control areas revealed little evidence for positive effects of feeding, but there was great variation in the use of feeding sites by each species, and therefore in the seed quantity birds received. 4. Declines for yellowhammer, robin and dunnock were less steep where more food was provided in WFFB areas (a fourfold difference in seed provision across 1·5 times the land area). 5. Analysing trends with respect to weight-of-use of winter food revealed significant, positive relationships for yellowhammer (both projects) and up to five other species, depending on the control terms applied. Thus, positive effects of feeding on population change depend on the effective supply of seed to the species of interest. The hypothesis that winter food is currently limiting the populations concerned is also supported. 6. Synthesis and applications . Effective winter food provision to farmland bird populations has the potential to halt, and perhaps to reverse, declines in abundance. In practice, this means that agri-environment measures supplying significant quantities of winter food, such as stubbles preceded by low-input cereals, should succeed in changing population trends if they provide resources at the times of greatest need and if there is sufficient uptake.

Summary 1.Recent theoretical modelling has provided important insights into how habitat loss may affect local populations through impacts on individual fitness (survival, body condition, fecundity). Despite this, attempts to provide empirical evidence of such impacts on displaced individuals have been limited. Using a before-after-control-impact (BACI) approach, we report how a sudden loss of wintering habitat impacted on the body condition and survival of redshank Tringa totanus. 2. The intertidal mudflats of Cardiff Bay, UK, were inundated with freshwater in November 1999 following impoundment by a barrage, resulting in the displacement of c. 300 redshank to adjacent habitat on the Severn Estuary. Movements and the survival of these birds were monitored through observations of colour-marked individuals. Comparative survival rates were calculated for marked populations at the main recipient site, Rhymney, and a control site. 3. Displaced redshank had difficulty maintaining their mass in the first winter postbarrage closure: adults previously only recorded at Cardiff Bay were significantly lighter than those previously recorded at Rhymney. 4. Survival rates of displaced redshank also declined. The estimated annual survival of adult Cardiff Bay redshank fell from 0·846 in the 2 years pre-barrage closure to 0·778 in the 3 following years because of a significant decline in winter survival (P = 0·0006). In comparison, there was no significant change in the survival of adult Rhymney redshank, and adult survival at the control site was actually greater post-barrage closure than beforehand. The lack of decline in these rates and the similarity between those of Cardiff Bay adults pre-barrage closure and Rhymney adults indicate that the increase in winter mortality of Cardiff Bay birds resulted from their displacement. 5. Synthesis and applications. This study provides the first conclusive empirical evidence that habitat loss can impact individual fitness in a bird population. Adult redshank displaced from Cardiff Bay experienced poor body condition and a 44% increase in mortality rate. Without an increase in the recruitment of first-winter birds, such a change is likely to reduce substantially local population size. The results reported here should help to inform governments, planners and non-governmental organizations (NGOs) seeking to understand how developments might impact on animal populations.

Quantifying the behavior of motile, free‐ranging animals is difficult. The accelerometry technique offers a method for recording behaviors but interpretation of the data is not straightforward. To date, analysis of such data has either involved subjective, study‐specific assignments of behavior to acceleration data or the use of complex analyses based on machine learning. Here, we present a method for automatically classifying acceleration data to represent discrete, coarse‐scale behaviors. The method centers on examining the shape of histograms of basic metrics readily derived from acceleration data to objectively determine threshold values by which to separate behaviors. Through application of this method to data collected on two distinct species with greatly differing behavioral repertoires, kittiwakes, and humans, the accuracy of this approach is demonstrated to be very high, comparable to that reported for other automated approaches already published. The method presented offers an alternative to existing methods as it uses biologically grounded arguments to distinguish behaviors, it is objective in determining values by which to separate these behaviors, and it is simple to implement, thus making it potentially widely applicable. The R script coding the method is provided.