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Seabirds and pinnipeds are vulnerable to reductions in prey availability, especially during the breeding season when spatial constraints limit their adaptive capacity. There are growing concerns about the effects of fisheries on prey availability in regions where large commercial fisheries target forage fish., For breeding seabirds and pinnipeds, prey availability depends on a combination of abundance, accessibility, patchiness and distance from the colony. An understanding of the aspects of prey availability that determine foraging success is essential for the design of effective management responses., We used a mechanistic individual-based foraging model based on observed data for two seabird species, the Peruvian Booby Sula variegata and Guanay Cormorant Phalacrocorax bougainvilliorum, to simulate the foraging patterns of seabirds feeding on schooling fish. We ran the model over simulated prey fields representing eight possible combinations of high or low prey abundance, shallow or deep prey, and broadly distributed or spatially concentrated prey., The results highlight the importance of the accessibility of prey. Depth distribution was the primary factor determining modelled foraging success for both species, followed by abundance, and then spatial configuration., Synthesis and applications. The individual-based foraging model provides a spatially explicit framework for assessing the effects of fisheries on the foraging success of seabirds and other central place foragers, and for evaluating the potential effectiveness of marine-protected areas and other fisheries management strategies for safeguarding central place foragers in dynamic ecosystems. Our analysis indicates that broad-scale fisheries management strategies that maintain forage fish above critical biomass levels are essential, but may need to be supplemented by targeted actions, such as time-area closures, when environmental conditions lead to low prey abundance or reduce prey accessibility for seabirds or pinnipeds of conservation concern. The individual-based foraging model is adaptable and could be reconfigured for application to other species and systems. [ABSTRACT FROM AUTHOR]

Although density-dependent regulation of population growth is thought to be relatively widespread in nature, density-independent models are often used to project the population response to drivers of change. Such models are often considered to provide a maximum estimate of mortality and therefore offer a precautionary approach to impact assessment. However, this perception assumes that density dependence operates as compensatory (negative density dependence), and overlooks that other forms of density dependence, such as depensation (positive density dependence), would generate a contrasting population response., Currently, there is debate about including density-dependent mechanisms in models that assess the impact of offshore wind farms on marine bird populations. Density dependence is considered poorly understood for this group of species. Consequently, it is either excluded from assessments, or incorporated in a compensatory form that has little empirical validation., We reviewed the evidence for compensatory and depensatory regulation of 31 marine bird species, and conducted a meta-analysis to examine the functional shape of density-dependent population growth. The evidence was also evaluated in relation to established species-specific indices of wind farm vulnerability in order to assess whether compensatory mechanisms are likely to offset losses associated with collision or displacement., Compensatory regulation was reported across all of the demographic processes and focal groups considered, and was attributed to a variety of causal mechanisms. The strength of compensatory population growth appeared consistent between colonies; however, the regulation of productivity was highly context-dependent with a similar number of studies reporting compensatory, depensatory and insignificant effects. Depensation was consistently attributed to increased rates of predation at lower population densities., Synthesis and applications. We conclude that among marine bird species with high vulnerability to wind farms, compensatory regulation is unlikely to offset large and sustained losses from the breeding population. In addition, depensation has the potential to accelerate population declines and generate local or regional extinctions, especially in smaller colonial species. Consequently, density-independent models will not offer a consistently precautionary approach for assessing the potential impact of wind farms on marine bird populations. Instead, assessments should examine the potential population response using a range of density-dependent structures. [ABSTRACT FROM AUTHOR]

As part of global efforts to reduce dependence on carbon-based energy sources there has been a rapid increase in the installation of renewable energy devices. The installation and operation of these devices can result in conflicts with wildlife. In the marine environment, mammals may avoid wind farms that are under construction or operating. Such avoidance may lead to more time spent travelling or displacement from key habitats. A paucity of data on at-sea movements of marine mammals around wind farms limits our understanding of the nature of their potential impacts., Here, we present the results of a telemetry study on harbour seals Phoca vitulina in The Wash, south-east England, an area where wind farms are being constructed using impact pile driving. We investigated whether seals avoid wind farms during operation, construction in its entirety, or during piling activity. The study was carried out using historical telemetry data collected prior to any wind farm development and telemetry data collected in 2012 during the construction of one wind farm and the operation of another., Within an operational wind farm, there was a close-to-significant increase in seal usage compared to prior to wind farm development. However, the wind farm was at the edge of a large area of increased usage, so the presence of the wind farm was unlikely to be the cause., There was no significant displacement during construction as a whole. However, during piling, seal usage (abundance) was significantly reduced up to 25 km from the piling activity; within 25 km of the centre of the wind farm, there was a 19 to 83% (95% confidence intervals) decrease in usage compared to during breaks in piling, equating to a mean estimated displacement of 440 individuals. This amounts to significant displacement starting from predicted received levels of between 166 and 178 dB re 1 μPa(p-p). Displacement was limited to piling activity; within 2 h of cessation of pile driving, seals were distributed as per the non-piling scenario., Synthesis and applications. Our spatial and temporal quantification of avoidance of wind farms by harbour seals is critical to reduce uncertainty and increase robustness in environmental impact assessments of future developments. Specifically, the results will allow policymakers to produce industry guidance on the likelihood of displacement of seals in response to pile driving; the relationship between sound levels and avoidance rates; and the duration of any avoidance, thus allowing far more accurate environmental assessments to be carried out during the consenting process. Further, our results can be used to inform mitigation strategies in terms of both the sound levels likely to cause displacement and what temporal patterns of piling would minimize the magnitude of the energetic impacts of displacement. [ABSTRACT FROM AUTHOR]

The article focuses on the lack of sound science in assessing wind farm and its impacts on seabirds across Great Britain and European Union (EU). It mentions the negative impact of renewable energy generation such as wind turbines on birds and bats. It also mentions the cumulative impacts on breeding colony seabirds from several wind farms.

1. Spain holds > 95% of the European breeding population of the Eurasian griffon vulture Gyps fulvus. Vultures provide important ecosystem services in carcass removal and influence emissions of greenhouse gases. Despite the known toxicity of the non-steroidal anti-inflammatory drug diclofenac to this species and other Gyps vultures, in March 2013 the Agencia Española de Medicamentos y Productos Sanitarios (AEMPS) approved the use of two medicines containing diclofenac for veterinary use in horses, pigs and cattle in Spain. 2. To assess the potential impact of medicated ungulate carcasses on Eurasian griffon vulture populations in Spain, we first used information on the metabolism and elimination of diclofenac from medicated cattle and pigs to calculate residue levels in relation to time elapsed between dosing and death. Secondly, probabilities of the death of a vulture per meal were calculated based upon experimental studies of diclofenac toxicity. Finally, annual numbers of vulture deaths expected to be caused by diclofenac were obtained by multiplying the death rates per meal by the estimated numbers of vulture meals taken from expected numbers of medicated carcasses suggested by AEMPS. 3. Assuming that vultures feed on carcasses that were treated with diclofenac 8 h before the animal's death, the annual number of vulture deaths caused by diclofenac was estimated at 715-6389, depending upon the estimate of numbers of medicated carcasses assumed and the version of the dose–response model used. Using a density-independent simulation model of a vulture population, the expected rate of decline of the Spanish population of Eurasian griffon vultures caused by these deaths is 0·9-7·7% per year. A density-dependent simulation model also indicated substantial population-level effects. Formal estimates of precision and sensitivity analyses of effects of unmeasured variables highlight the uncertainty of estimates using currently available data. 4. Synthesis and applications. Due to the possibility of causing an important impact on vulture populations, our findings justify a precautionary ban on the veterinary use of diclofenac in Spain and encourage the use of meloxicam, a vulture-safe alternative drug. A programme of monitoring of non-steroidal anti-inflammatory drug contamination of ungulate carcasses available to vultures and of moribund and dead obligate and facultative avian scavengers would be needed to be confident that a damaging level of contamination is not present. [ABSTRACT FROM AUTHOR]

Telemetry has become an important method for studying the biology and ecology of animals. However, the impact of tracking devices and their method of attachment on different species across multiple temporal scales has seldom been assessed. We compared the behavioural and demographic responses of two species of seabird, Lesser Black-backed Gull Larus fuscus and Great Skua Stercorarius skua, to a GPS device attached using a crossover wing harness. We used telemetry information and monitoring of breeding colonies to compare birds equipped with a device and harness, and control birds without an attachment. We assessed whether tagged birds have lower short-term breeding productivity or lower longer term overwinter return rates (indicative of overwinter survival) than controls. For Great Skua, we also assessed whether territory attendance within the breeding season differed between tagged and control birds. As with previous studies on Lesser Black-backed Gull, we found no short-term impacts on breeding productivity or long-term impacts on overwinter return rates. For Great Skua, there was no evidence for impacts of the device and harness on territory attendance or breeding productivity. However, as found by a previous study of Great Skuas using a different (body) harness design, there was strong evidence of reduced overwinter return rates. Consequently, a device attached using a wing harness was considered suitable for long-term deployment on Lesser Black-backed Gulls, but not on Great Skuas. These findings will inform the planning of future tracking studies. [ABSTRACT FROM AUTHOR]

In evolutionary and ecological studies, demographic parameters are commonly derived from detailed information collected on a limited number of individuals or in a confined sector of the breeding area. This partial monitoring is expected to underestimate survival and recruitment processes because individuals marked in a monitored location may move to or recruit in an unobservable site., We formulate a multi-event capture-recapture model using E- SURGE software which incorporates additional information on breeding dispersal and the proportion of monitored sites to obtain unbiased estimates of survival and recruitment rates. Using simulated data, we assessed the biases in recruitment, survival and population growth rate when monitoring 10-90% of the whole population in a short- and a long-lived species with low breeding dispersal. Finally, we illustrate the approach using real data from a long-term monitoring program of a colony of Scopoli's shearwaters Calonectris diomedea., We found that demographic parameters estimated without considering the proportion of the area monitored were generally underestimated. These biases caused a substantial error in the estimated population growth rate, especially when a low proportion of breeding individuals were monitored., The proposed capture-recapture model successfully corrected for partial monitoring and provided robust demographic estimates., Synthesis and applications. In many cases, animal breeding populations can only be monitored partially. Consequently, recruitment and immature survival are underestimated, but the extent of these biases depends on the proportion of the area that remains undetected and the degree of breeding dispersal. We present a new method to obtain robust and unbiased measures of survival and recruitment processes from capture-recapture data. The method can be applied to any monitored population regardless of the type of nests (e.g. artificial or natural) or breeding system (e.g. colonial or territorial animals), and it only relies on an estimate of the proportion of the monitored area. The unbiased estimates obtained by this method can be used to improve the reliability of predictions of demographic population models for species' conservation and management. [ABSTRACT FROM AUTHOR]

Seabirds have been incidentally caught in distant-water longline fleets operating in the Southern Ocean since at least the 1970s, and breeding numbers for some populations have shown marked trends of decline and recovery concomitant with longline fishing effort within their distributions. However, lacking is an understanding of how forms of among-individual heterogeneity may interact with fisheries bycatch and influence population dynamics., We develop a model that uses comprehensive data on the spatial and temporal distributions of fishing effort and seabird foraging to estimate temporal overlaps, fishery catchability and consequent bycatch. We apply a population model that is structured by age, sex, life stage and spatially to Crozet Island wandering albatross and explore how heterogeneity in susceptibility to capture may have influenced the population's demography over time., A model where some birds were assumed to be more susceptible to fisheries bycatch was able to successfully replicate the observed trend in breeding pairs. Considerably poorer fits were found without this assumption. Results suggested that the more susceptible birds may have been removed from the population by the 1990s., The model was also able to highlight areas, times and fleets prone to increased bycatch. Knowledge of these factors should assist fisheries and conservation management bodies to quantify and reduce seabird bycatch through spatial management and fleet-specific mitigation efforts., Synthesis and application. Many seabirds show complex life histories that make them highly susceptible to additional incidental mortality from fishing vessels. By applying a population model that integrates key aspects of seabird and fishery dynamics, we were able to explain the observed trends in the breeding population of Crozet wandering albatross and identify key areas and fleets where further mitigation may be required. In addition, the potential removal of a category of birds that shows increased susceptibility to capture has important implications for the conservation management of this population and other iconic species incidentally caught by large-scale commercial fisheries. [ABSTRACT FROM AUTHOR]

Many emerging methods for ecological monitoring use passive monitoring techniques, which cannot always be used to identify the observed species with certainty. Digital aerial surveys of birds in marine areas are one such example of passive observation and they are increasingly being used to quantify the abundance and distribution of marine birds to inform impact assessments for proposed offshore wind developments. However, the uncertainty in species identification presents a major hurdle to determining the abundance and distribution of individual species., Using a novel analytical approach, we combined data from two surveys in the same area: aerial digital imagery that identified only 23% of individuals to species level and boat survey records that identified 95% of individuals to species level. The data sets were analysed to estimate the effects of environmental covariates on species density and to produce species-specific estimates of population size., For each digital aerial observation without certain species identification, randomized species assignments were generated using the observed species proportions from the boat surveys. For each species, we modelled several random realizations of species assignments and produced a density surface from the ensemble of models. The uncertainty from each stage of the process was propagated, so that final confidence limits accounted for all sources of uncertainty, including species identification., In the breeding season, several species had higher densities near colonies and this pattern was clearest for three auk species. Sandeel density was an important predictor of the density of several gull species., Synthesis and applications. This method shows it is possible to construct maps of species density in situations in which ecological observations cannot be identified to species level with certainty. The increasing use of passive detection methods is providing many more data sets with uncertain species identification and this method could be used with these data to produce species-specific abundance estimates. We discuss the advantages of this approach for estimating the abundance and distribution of birds in marine areas, particularly for quantifying the impacts of offshore renewable developments by making the estimates derived from the older digital surveys more comparable to the recently improved surveys. [ABSTRACT FROM AUTHOR]

Seabirds that consume more than one prey type may adjust their foraging to maintain provisioning rates for their chicks. How energetically effective are these strategies, and what are the implications for the management of seabirds and their marine habitat?, A multi-species functional response links consumption rates to the availability of multiple prey types, but fitting multi-species functional responses to field data can be difficult, requiring consumption measurements over a range of different prey abundances. Such detailed data may be especially difficult to obtain in marine ecosystems., We used annual time-series data on chick provisioning for the common guillemot Uria aalge together with abundance indices for its two main prey (lesser sandeel Ammodytes marinus and sprat Sprattus sprattus) to parameterize a multi-species functional response for parents provisioning chicks at a major North Sea colony from 1992 to 2005., The fitted model reproduced changes in diet and consumption rate which were consistent with changes in local prey abundance including a long-term decline in sandeels., The model predicted that energy intake by chicks would be more sensitive to changes in sprat abundance than sandeel abundance. Guillemots appeared able to adjust their foraging tactics over a wide range of prey abundances to maintain a consistent energetic intake rate for chicks., Synthesis and applications. Our results suggest guillemot chicks obtain adequate calorific intake from their parents despite fluctuating prey abundances, conferring some resilience in the face of environmental variation. The parameterized multi-species functional response model can be used to estimate levels of severe prey shortage that compromise provisioning. It also enables us to interpret predator consumption rates so that these can be used as a metric of prey availability. Further, quantifying trophic links between marine prey and apex predators is needed to support the development of multi-species models in which the predators can be included. Such models are needed as tools to effectively manage the marine ecosystem, taking into account the objectives of fishing, conservation and the need to maintain Good Environmental Status. [ABSTRACT FROM AUTHOR]

Climate change and fishing impact marine ecosystems, potentially modifying the availability of small pelagic fish to marine top predators. Some seabirds that primarily rely upon these resources have switched to feeding on fishery waste. It has therefore been argued that seabirds might become dependent upon this artificial resource., To test this hypothesis, we studied the foraging behaviour of Cape gannets Morus capensis breeding off the coast of South Africa using high-resolution Global Positioning System-tracking in relation to the availability of pelagic fish assessed by acoustic at-sea surveys, and fishing effort by the two main south African fisheries (purse seiners that compete with seabirds for pelagic fish, and demersal trawlers that process fish at sea and discharge fish waste) tracked with vessel monitoring systems. Conjoint seabird, fish and fisheries information were analysed at mesoscale ( c. 100 km) and sub-mesoscale ( c. 10 km) in years of high (2002), medium (2009) and low (2005) pelagic fish biomass within gannets' foraging range., We found substantial inter-annual variability in spatial use by breeding gannets, which was driven primarily by pelagic fish availability. At the mesoscale, birds and purse seiners exploited similar marine areas, but no fine-scale dependence of birds on purse seiners was detected. Crucially, fine-scale dependence of gannets upon trawlers producing fishery waste was only detected in 2005, when pelagic fish biomass was lowest, indicating a direct effect of trawlers on gannet foraging behaviour in the absence of natural prey., Further overlap analyses of gannet and trawler foraging areas during 2002-2010 confirmed that breeding birds only seek trawlers when pelagic fish availability is low, strongly suggesting reversible seabird dependency upon fishery waste., Synthesis and applications. Our study demonstrates that seabirds such as Cape gannets depend on fishery waste when their natural prey is scarce, but revert to feeding on natural resources whenever available, showing highly flexible foraging behaviour. These results have important implications in the context of the anticipated legislation banning at-sea disposal of fishery waste in different regions, including European seas, highlighting the necessity to concomitantly promote sustainable fishing allowing the restoration of pelagic fish stocks. [ABSTRACT FROM AUTHOR]

Feral pigs (Sus scrofa) are an invasive species that disrupt ecosystem functioning throughout their introduced range. In tropical environments, feral pigs are associated with predation and displacement of endangered species, modification of habitat, and act as a vector for the spread of exotic vegetation and disease. Across many parts of their introduced range, the diet of feral pigs is poorly known. Although the remote location and difficult terrain of far north Queensland makes observing feral pig behaviour difficult, feral pigs are perceived to seek refuge in World Heritage tropical rainforests and seasonally 'crop raid' into lowland sugarcane crops. Thus, identifying how feral pigs are using different components of the landscape is important to the design of management strategies. We used the stable isotope composition of captured feral pigs to determine the extent of rainforest and sugarcane habitat usage. Recently grown hair (basal hair) from feral pigs captured in remote rainforest indicated pigs met their dietary needs solely within this habitat. Stable carbon and nitrogen isotope values of basal hair from feral pigs captured near sugarcane plantations were more variable, with some individuals estimated to consume over 85% of their diet within a sugarcane habitat, while a few consumed as much as 90% of their diet from adjacent forested environments. We estimated whether feral pigs switch habitats by sequentially sampling δ13C and δ15N values of long tail hair from a subset of seven captured animals, and demonstrate that four of these individuals moved between habitats. Our results indicate that feral pigs utilize both sugarcane and forest habitats, and can switch between these resources. [ABSTRACT FROM AUTHOR]