Mercury Exposure in Birds of Prey from Norway: Relation to Stable Carbon and Nitrogen Isotope Signatures in Body Feathers.

Mercury (Hg) and stable carbon and nitrogen isotope ratios were analysed in body feathers from nestlings of white-tailed eagles (Haliaeetus albicilla) (WTE; n = 13) and Northern goshawks (Accipiter gentilis) (NG; n = 8) and in red blood cells (RBC) from NG (n = 11) from Norway. According to linear mixed model, species factor was significant in explaining the Hg concentration in feathers (LMM; p < 0.001, estimate (WTE) = 2.51, 95% CI = 1.26, 3.76), with concentrations higher in WTE (3.01 ± 1.34 µg g-1 dry weight) than in NG (0.51 ± 0.34 µg g-1 dry weight). This difference and the isotopic patterns for each species, likely reflect their diet, as WTE predominantly feed on a marine and higher trophic-chain diet compared to the terrestrial NG. In addition, Hg concentrations in RBCs of NG nestlings were positively correlated with feather Hg concentrations (Rho = 0.77, p = 0.03), supporting the potential usefulness of nestling body feathers to biomonitor and estimate Hg exposure. Hg levels in both species were generally below the commonly applied toxicity threshold of 5 µg g-1 in feathers, although exceeded in two WTE (6.08 and 5.19 µg g-1 dry weight).

Large-scale movement patterns in a social vulture are influenced by seasonality, sex, and breeding region.

Quantifying space use and segregation, as well as the extrinsic and intrinsic factors affecting them, is crucial to increase our knowledge of species-specific movement ecology and to design effective management and conservation measures. This is particularly relevant in the case of species that are highly mobile and dependent on sparse and unpredictable trophic resources, such as vultures. Here, we used the GPS-tagged data of 127 adult Griffon Vultures Gyps fulvus captured at five different breeding regions in Spain to describe the movement patterns (home-range size and fidelity, and monthly cumulative distance). We also examined how individual sex, season, and breeding region determined the cumulative distance traveled and the size and overlap between consecutive monthly home-ranges. Overall, Griffon Vultures exhibited very large annual home-range sizes of 5027 ± 2123 km2, mean monthly cumulative distances of 1776 ± 1497 km, and showed a monthly home-range fidelity of 67.8 ± 25.5%. However, individuals from northern breeding regions showed smaller home-ranges and traveled shorter monthly distances than those from southern ones. In all cases, home-ranges were larger in spring and summer than in winter and autumn, which could be related to difference in flying conditions and food requirements associated with reproduction. Moreover, females showed larger home-ranges and less monthly fidelity than males, indicating that the latter tended to use the similar areas throughout the year. Overall, our results indicate that both extrinsic and intrinsic factors modulate the home-range of the Griffon Vulture and that spatial segregation depends on sex and season at the individual level, without relevant differences between breeding regions in individual site fidelity. These results have important implications for conservation, such as identifying key threat factors necessary to improve management actions and policy decisions.

Cuantificar el uso y la segregación del espacio, así como los factores extrínsecos e intrínsecos que los afectan, es crucial para aumentar nuestro conocimiento de la ecología de movimientos de cada especie y diseñar medidas eficaces de gestión y conservación. Esto es especialmente relevante en el caso de especies con gran movilidad y dependientes de recursos tróficos escasos e impredecibles, como son los buitres. En este trabajo se utilizaron datos GPS de 127 buitres leonados Gyps fulvus adultos capturados en cinco regiones de cría diferentes en España para describir los patrones de movimiento (tamaño y fidelidad del área de campeo y distancia acumulada mensual). También examinamos cómo el sexo, la estación del año y la región de cría determinaban la distancia acumulada recorrida y el tamaño y solapamiento entre áreas de campeo mensuales consecutivas. En conjunto, los buitres leonados mostraron un área de campeo anual muy extensa de 5027 ± 2123 km2, una distancia acumulada mensual media de 1776 ± 1497 km y una fidelidad mensual al área de campeo del 67.8 ± 25.5%. Sin embargo, los individuos de las regiones de cría más septentrionales mostraron áreas de campeo más pequeñas y recorrieron distancias mensuales más cortas que los de las más meridionales. En todos los casos, las áreas de campeo fueron mayores en primavera y verano que en otoño e invierno, lo que podría estar relacionado con las diferencias en las condiciones de vuelo y las necesidades tróficas asociadas a la reproducción. Además, las hembras mostraron mayores áreas de campeo y menor fidelidad mensual que los machos, lo que indica que estos últimos tienden a utilizar zonas similares durante todo el año. En conjunto, nuestros resultados indican que tanto los factores extrínsecos como los intrínsecos modulan el área de campeo del buitre leonado y que la segregación espacial depende del sexo y de la estación a nivel individual, sin que existan diferencias relevantes entre las regiones de cría en cuanto a la fidelidad individual al lugar. Estos resultados podrían tener importantes implicaciones para la conservación, como la identificación de los principales factores necesarios para mejorar las medidas de gestión y las decisiones políticas.

Scavenger guild and consumption patterns of an invasive alien fish species in a Mediterranean wetland.

Invasive Alien Species (IAS) alter ecosystems, disrupting ecological processes and driving the loss of ecosystem services. The common carp Cyprinus carpio is a hazardous and widespread IAS, becoming the most abundant species in many aquatic ecosystems. This species transforms ecosystems by accumulating biomass to the detriment of other species, thus altering food webs. However, some terrestrial species, such as vertebrate scavengers, may benefit from dead carps, by incorporating part of the carp biomass into the terrestrial environment. This study describes the terrestrial vertebrate scavenger assemblage that benefits from carp carcasses in a Mediterranean wetland. We also evaluate the seasonal differences in the scavenger assemblage composition and carrion consumption patterns. Eighty carp carcasses (20 per season) were placed in El Hondo Natural Park, a seminatural mesohaline wetland in south-eastern Spain, and we monitored their consumption using camera traps. We recorded 14 scavenger species (10 birds and four mammals) consuming carp carcasses, including globally threatened species. Vertebrates consumed 73% of the carrion biomass and appeared consuming at 82% of the carcasses. Of these carcasses consumed, 75% were completely consumed and the mean consumption time of carcasses completely consumed by vertebrates was 44.4 h (SD = 42.1 h). We recorded differences in species richness, abundance, and assemblage composition among seasons, but we did not find seasonal differences in consumption patterns throughout the year. Our study recorded a rich and efficient terrestrial vertebrate scavenger assemblage benefitting from carp carcasses. We detected a seasonal replacement on the scavenger species, but a maintenance of the ecological function of carrion removal, as the most efficient carrion consumers were present throughout the year. The results highlight the importance of vertebrate scavengers in wetlands, removing possible infectious focus, and moving nutrients between aquatic and terrestrial environments.

Bird electrocution on power lines: Spatial gaps and identification of driving factors at global scales.

Universal energy access is one of the targets of the Sustainable Development Goals (SDGs), and thus the deployment of electricity grids is expected to expand globally in the coming decades. However, the installation of power lines is not biodiversity-friendly. In particular, electrocution on power pylons is a major cause of bird mortality worldwide, including for some severely endangered species. Over the last decades, different studies have improved our understanding of the factors influencing the risk of electrocution in birds, but until now spatial gaps in our knowledge of these impacts and the factors driving global patterns of bird electrocution have not been assessed. In this study, we evaluated data from a total of 114 studies that provided information on bird mortality rates on power lines, and we analyzed the factors driving electrocution rates for all bird species, and then for all raptors and large eagles separately. Our results showed a high spatial distribution bias, as more than 80% of the studies were carried out in developed countries, mostly in Europe and North America. By contrast, no systematic studies have been found for Oceania and very few for South America and Africa. Europe showed the highest electrocution rates for birds, South America for raptor species and Africa for eagles. Socio-economic factors best-explained bird and raptor electrocution rates, while climate-related factors were the most influential for eagles. Contrary to our expectations, factors related to pylon design were the least influential on overall electrocution rates. Variables related to study design showed highly variable levels of influence. This could be due to the lack of standardized protocols. Although bird electrocution has been extensively studied, there are large areas where no studies have been carried out or for which data are inaccessible. This could be because in these areas the power distribution network is still sparse, or that most studies are not public or accessible to the international community. Researchers and managers should promote the publication of studies, as awareness is the first step to solving these problems. The factors identified could be applied globally to the design and planning of power grids and the identification of mortality hotspots. This would help mitigate the creation of new mortality hotspots, especially in developing countries where the installation of new power lines has been growing exponentially in recent years.

Dust and bullets: Stable isotopes and GPS tracking disentangle lead sources for a large avian scavenger.

Lead intoxication is an important threat to human health and a large number of wildlife species. Animals are exposed to several sources of lead highlighting hunting ammunition and lead that is bioavailable in topsoil. Disentangling the role of each in lead exposure is an important conservation issue, particularly for species potentially affected by lead poisoning, such as vultures. The identification of lead sources in vultures and other species has been classically addressed by means of stable-isotope comparisons, but the extremely varied isotope signatures found in ammunition hinders this identification when it overlaps with topsoil signatures. In addition, assumptions related to the exposure of individual vultures to lead sources have been made without knowledge of the actual feeding grounds exploited by the birds. Here, we combine lead concentration analysis in blood, novel stable isotope approaches to assign the origin of the lead and GPS tracking data to investigate the main foraging grounds of two Iberian griffon vulture populations (N = 58) whose foraging ranges differ in terms of topsoil lead concentration and intensity of big game hunting activity. We found that the lead signature in vultures was closer to topsoil than to ammunition, but this similarity decreased significantly in the area with higher big game hunting activity. In addition, attending to the individual home ranges of the tracked birds, models accounting for the intensity of hunting activity better explained the higher blood lead concentration in vultures than topsoil exposure. In spite of that, our finding also show that lead exposure from topsoil is more important than previously thought.

Spatiotemporal variations of organochlorine pesticides in an apex predator: Influence of government regulations and farming practices.

BACKGROUND: Intensification of agricultural practices has caused several negative effects to the environment. The use of fertilizers and pesticides may alter geochemical cycles or cause direct wildlife intoxication. Detrimental effects of organochlorine pesticides (OCPs) have forced the authorities to ban or restrict its use. This study evaluates the variation in levels of OCPs in a sentinel species in relation to changes in government regulations and the spatial configuration of agricultural practices around the nests. METHODS: Between 2003 and 2007, we analysed OCP levels in 256 blood samples of Eurasian Eagle-owl (Bubo bubo) chicks nesting in area of intensive commercial agriculture with historical frequent use of pesticides, in South-eastern Spain. We studied year-to-year variations in OCP concentrations and their relation with land use configuration around raptor nests by Generalized Linear Mixed Models (GLMM). RESULTS: OCPs were detected in 100% samples surveyed in 2003 and 2004, while dropped to 27% in 2005, 6.8% in 2006 and 6.3% in 2007, coinciding with the ban of OCPs. The presence of the main OCPs was related to agricultural practices. In particular, endosulfan and lindane were related to irrigated crops and urban areas, while DDT-related compounds and dieldrin were associated with dry land farming. CONCLUSIONS: OCP concentrations in blood samples of Eurasian Eagle-owls may respond quickly to the implementations of new regulations about the use of agricultural products. This raptor was confirmed as a good sentinel species allowing rapid detection of changes in pesticides use.

Spatial and temporal movements in Pyrenean bearded vultures (Gypaetus barbatus): Integrating movement ecology into conservation practice.

Understanding the movement of threatened species is important if we are to optimize management and conservation actions. Here, we describe the age and sex specific spatial and temporal ranging patterns of 19 bearded vultures Gypaetus barbatus tracked with GPS technology. Our findings suggest that spatial asymmetries are a consequence of breeding status and age-classes. Territorial individuals exploited home ranges of about 50 km2, while non-territorial birds used areas of around 10 000 km2 (with no seasonal differences). Mean daily movements differed between territorial (23.8 km) and non-territorial birds (46.1 km), and differences were also found between sexes in non-territorial birds. Daily maximum distances travelled per day also differed between territorial (8.2 km) and non-territorial individuals (26.5 km). Territorial females moved greater distances (12 km) than males (6.6 km). Taking into account high-use core areas (K20), Supplementary Feeding Sites (SFS) do not seem to play an important role in the use of space by bearded vultures. For non-territorial and territorial individuals, 54% and 46% of their home ranges (K90), respectively, were outside protected areas. Our findings will help develop guidelines for establishing priority areas based on spatial use, and also optimize management and conservation actions for this threatened species.

Genetic Signatures of Demographic Changes in an Avian Top Predator during the Last Century: Bottlenecks and Expansions of the Eurasian Eagle Owl in the Iberian Peninsula.

The study of the demographic history of species can help to understand the negative impact of recent population declines in organisms of conservation concern. Here, we use neutral molecular markers to explore the genetic consequences of the recent population decline and posterior recovery of the Eurasian eagle owl (Bubo bubo) in the Iberian Peninsula. During the last century, the species was the object of extermination programs, suffering direct persecution by hunters until the 70's. Moreover, during the last decades the eagle owl was severely impacted by increased mortality due to electrocution and the decline of its main prey species, the European rabbit (Oryctolagus cuniculus). In recent times, the decrease of direct persecution and the implementation of some conservation schemes have allowed the species' demographic recovery. Yet, it remains unknown to which extent the past population decline and the later expansion have influenced the current species' pattern of genetic diversity. We used eight microsatellite markers to genotype 235 eagle owls from ten Spanish subpopulations and analyse the presence of genetic signatures attributable to the recent population fluctuations experienced by the species. We found moderate levels of differentiation among the studied subpopulations and Bayesian analyses revealed the existence of three genetic clusters that grouped subpopulations from central, south-western and south-eastern Spain. The observed genetic structure could have resulted from recent human-induced population fragmentation, a patchy distribution of prey populations and/or the philopatric behaviour and habitat selection of the species. We detected an old population bottleneck, which occurred approximately 10,000 years ago, and significant signatures of recent demographic expansions. However, we did not find genetic signatures for a recent bottleneck, which may indicate that population declines were not severe enough to leave detectable signals on the species genetic makeup or that such signals have been eroded by the rapid demographic recovery experienced by the species in recent years.