Search

Adult sex ratios (ASRs) have proved to correlate with population trends, which make them potential useful indicators of a species’ population trajectory and conservation status. We analysed ASRs and proportion of juveniles in flocks of an endangered steppe bird, the Little Bustard Tetrax tetrax, using surveys made during the non-breeding period in seven areas within its Western European range (one in Portugal, four in Spain, and two in France). We found overall male-biased ASRs, as all the seven surveyed areas showed a male-biased ASR mean value. Five areas were below the threshold median value (female sex ratio = 0.4) considered to be consistent with an increased probability of extinction, according to earlier population viability analyses for the species.Wealso found a significant positive correlation between female ratio and the proportion of young individuals in the non-breeding flocks surveyed. Our results (strongly male-biased ASRs) support the hypothesis that the viability of Little Bustard populations in Western Europe is threatened by an excess of female mortality, something that should be quantified in the future, and emphasise the value of monitoring sex ratio as a population viability indicator in species where monitoring survival is difficult to achieve., Comunidad de Madrid S2013/MAE-2719 S2013/MAE2719, Ministry of Science and Innovation, Spain (MICINN) Spanish Government

In this chapter, we focus mainly on the behavioural ecology of the little bustard (i.e. how behaviour relates to ecology and evolution), with particular emphasis on breeding behaviour, sexual selection and mating systems, as well as their relevance for little bustard conservation. We discuss the evolutionary forces that drive the species’ lekking behaviour and its variations under the framework of sexual selection theory. We also discuss other less studied aspects of little bustard behavioural ecology (sperm competition, personality traits, and parent–offspring conflicts). The little bustard mating system is described in most localities as an exploded lek strategy but can be quite flexible, and a variety of situations ranging from resource-based monogamy to classical leks have been suggested. Several non-exclusive theoretical models of lek formation have been proposed and are all consistent, to some degree, with the little bustard’s lekking behaviour. However, two models (hotshot and black hole) seem particularly appropriate to describe the little bustard mating system at different spatial scales. On larger scales, female mobility and harassment by individual males may induce male aggregation as described by the black hole mechanism. At smaller scales, female preference for particularly attractive males (hotshot) or certain lek sizes may induce an initial clustering, which would be further maintained and structured as a result of the hotshot mechanism. Overall, the female choice seems to be based on multiple criteria (male snort call rate, plumage traits and displays). Habitat quality and resources within male territories are variable, and evidence suggests that these determine male settlement, but no evidence supports a decisive role in mate choice. Evidence regarding sperm competition in little bustard is scarce as well as contradictory. The apparently long time elapsing between mating and laying would allow for potential cryptic female choice through sperm competition, but the apparently low rate of copulation suggests that sperm competition might not be intense in little bustards. Evidence from decoy experiments and observations suggests that male and female little bustard behaviours (displays, behaviour during captures) are variable but consistent (repeatable) within individuals and may define individual personalities. These aspects of little bustard behaviour, and their relevance for conservation, also deserve further study.

Knowledge of feeding ecology of declining species, such as farmland birds, is essential to address their conservation requirements, especially when their habitats are suffering important reductions of trophic resources. In this study, we apply a metabarcoding approach to describe the diet composition of six of the most significant farmland birds inhabiting European cereal pseudo-steppes: little bustard, great bustard, pin-tailed sandgrouse, black-bellied sandgrouse, red-legged partridge, and common quail. We further studied seasonal diet variations (autumn to spring) in all species but the common quail, whose diet was studied during spring and summer. We show that study species´ diets mostly consisted of plants, although in the case of little bustard and great bustard arthropods are also highly relevant. Among arthropods, we found high proportions of thrips, arachnids, and springtails, which were previously unreported in their diet, and some taxa that could be used as antiparasitic food. Moreover, we report that little bustard’s diet is the least rich of that of all studied species, and that diet of all these species is less diverse in winter than in autumn and spring. Diet composition of these declining species supports the importance of natural and semi-natural vegetation and landscape mosaics that can provide a wide variety of arthropods, plants, and seeds all year-round., This paper contributes to the REGRESSEDS project (CGL2016-75278-R funded by MINECO, Spain). This study is also a contribution to project Sistemática, Biogeografía, Ecología del comportamiento y Evolución (IT1163-19) funded by Basque Country Government. Additional funds for this study were provided by the projects 201630E096 funded by CSIC (recipient BA) and AGROPERDIZ (SBPLY/17/180501/ 000245) funded by the “Junta de Comunidades de Castilla-La Mancha” and “Fondo Europeo de Desarrollo Regional” (recipient FM & BA). Xabier Cabodevilla was supported by a Ph.D. grant, financed by the Basque Country Government (grant no. PRE_2018_2_0273).

Entre 2010-2016 monitoreamos 28 puestas de sison comun Tetrax tetrax mediante el seguimiento de ocho hembras adultas equipadas con GPS en la plana de Lleida, en la depresion del Ebro (NE Espana), con objeto de dilucidar algunos aspectos relacionados con el comportamiento de nidificacion e incubacion de la especie. Ademas de describir estos comportamientos, utilizamos modelos lineales generalizados mixtos para conocer aquellos factores que determinan la probabilidad de eclosion, tales como la fecha de puesta, el habitat de nidificacion y el comportamiento de incubacion. Encontramos una elevada capacidad (53%) para efectuar puestas de reposicion tras el fracaso de las puestas. Los nidos fracasados representaron el 67,9% de las puestas, debido principalmente a la baja tasa de eclosion de las puestas de reposicion (16,7%), pero tambien de las primeras puestas (44%). La principal causa de fracaso fue el abandono o depredacion de los nidos (58%), mientras que las practicas agricolas fueron las responsables del 38,9% de los fracasos. Encontramos un incremento en el riesgo de fracaso por abandono o depredacion hacia el final de la incubacion. El riesgo de fracaso fue mas alto en las puestas tardias, aunque este hecho parece estar directamente relacionado con la siega del cereal y con el cambio de sustrato de nidificacion, de cereal a alfalfa, que se produce a lo largo de la estacion reproductora. Asi mismo, encontramos un efecto negativo del tamano del campo donde se encontraban los nidos y del habitat circundante sobre la probabilidad de eclosion, que relacionamos con la disponibilidad de alimento para la hembra. Medidas dirigidas a mejorar la provision de alimento para las hembras, incrementando la densidad de lindes en los campos y la disponibilidad de barbechos, podrian favorecer su condicion corporal antes y durante la incubacion, asi como proporcionar un habitat adecuado para las puestas de reposicion. patrones de riego y siega adaptativos en los campos de alfalfa durante la epoca de nidificacion podrian contribuir a incrementar el exito de eclosion de las puestas de reposicion.

Non-natural mortality is a major threat to animal conservation worldwide. Its origins are extremely diverse and include infrastructures that cause animal casualties. Its effects are widely felt and so prioritization criteria are necessary when implementing mitigation actions. Most of the threats causing non-natural mortality have in common the fact that they are distributed unevenly across several spatial scales. Thus, here we present a protocol for prioritizing conservation measures in: (i) population fractions suffering from high levels of non-natural mortality whose demographic effects are the most serious, and in (ii) areas with the highest risk of casualties due to heterogeneities in both spatial use by individuals and the inherent hazards of the infrastructures causing mortality. To do so, the protocol consist of 5 steps: 1) to identify sink populations over large geographical areas; 2) to identify sink areas of high mortality within target populations; 3) to identify areas intensively used by individuals in target areas; 4) to identify spatial points or individual infrastructures showing high mortality risk; and 5) using direct evidence of casualties to complete information on high-risk sites and infrastructures. To show the potential of this protocol, we use as an example the mitigation of mortality due to electrocution in Bonelli’s eagle in SW Europe, where this species is of conservation concern. Thanks to the retrofitting of dangerous pylons, we demonstrate that our protocol can help restore Bonelli’s eagle territories to levels that will ensure the persistence of the studied population. In addition, we show that our criteria enhance the optimization of resource investment in mortality mitigation as our criteria identify the pylons with the most devastating effects on the population. To summarize, we provide the basis for a framework applicable to many different species and scenarios whose costs in terms of mitigation actions and benefits in terms of population viability prospects can be explicitly calculated Part of this study andthe implementation of corrective measures in power lines were possible thanks to three agreements between power linecompanies (FECSA-ENDESA, Estabanell y Paysa S.A., and Electra Caldense S.A.), local administrations (Diputaci o de Barcelona)and the Universitat de Barcelona (2000e2007). The research projects GL2004-03189, CGL2007-64805/BOS, CGL2010-17056 and CGL2013-41565-P run by the Spanish Government, and project 13/38 by MAVA Foundation also contributed to this work

The Lleida plain is a flat and dry region in Western Catalonia (NE Spain), at the eastern edge of the Ebro Valley depression. The central part of the area is now devoted to intensively irrigated farmland, but a surrounding belt of steppe and pseudo-steppe and low intensity farming, mainly occupied by winter cereal, olive trees and almond trees, remains. The area still hosts a rich community of steppe land birds. Some are dependent on low intensity dry cereal farming and fallow, such as the little bustard (Tetrax tetrax), Montagu’s harrier (Circus pygargus) and calandra lark (Melanocorypha calandra). Other, such as the pin-tailed sandgrouse (Pterocles alchata) and black-bellied sandgrouse (Pterocles orientalis) inhabit the few remaining large spots of fallow land, while the Dupont’s lark (Chersophilus duponti) and lesser short-toed lark (Alaudala rufescens) are both associated to the remaining patches of natural steppes or halophytic vegetation. The greater short-toed lark (Calandrella brachydactyla) and the European thick-knee (Burhinus oedicnemus) favour areas of little disturbed wastelands, fallow or ploughed land. Although more generalist, the lesser kestrel (Falco naumanni) or the European roller (Coracias garrulus) also find in these low intensity farming areas one of their last strongholds in Catalonia. The single remaining Iberian population of lesser grey shrike (Lanius minor), on the verge of extinction, is also located within these steppes. All these species experienced severe population declines during the last decade of the twentieth century and the first decade of the twenty-first. Strong opposition to the Segarra-Garrigues irrigation system, launched at the start of the twenty-first century and aiming to transform most of the remaining steppes of the Lleida plain into intensified irrigated crops, has boosted many conservation actions, which are reversing or halting the negative trends for some of these species. These actions include, among others, the declaration of eight Special Protection Areas (SPAs), the renting or acquisition and management of steppe-land and fallow land, the provision of nesting sites, the implementation of breeding programs to reintroduce or reinforce some populations, or the mitigation of power lines to reduce collision risk. Although there is room for some optimism, the persisting intensification of agriculture outside and inside the SPAs, and the industrial and urban development of the area are still of great concern. We need a change in the rural development concept, from one that values only economic services to one that values social and ecological services as well, if we want some room for steppe-land birds in the Lleida plain.

SummaryThe Little Bustard Tetrax tetrax (Linnaeus, 1758) is a medium-sized, ‘Near Threatened’ steppe bird, whose Iberian population has been alarmingly declining over recent decades. Although this population loss has been mainly attributed to agricultural intensification, there is no information on Little Bustard adult mortality levels and their drivers. Based on a joint effort combining all the tracking data on adult Little Bustards collected over a period of 12 years by all research teams working with the species in Iberia, we found that annual anthropogenic mortality is likely to have a critical impact on the species, with values almost as high as the mortality attributed to predation. Collision with power lines was found to be the main anthropogenic threat to the adult population (3.4–3.8%/year), followed by illegal killing (2.4–3%/year), which had a higher impact than initially foreseen. Our work shows how poorly understood and previously unknown threats are affecting the survival of the most important Little Bustard population in Europe.

As the only endemic neotropical parrot to have recently lived in the northern hemisphere, the Carolina parakeet (Conuropsis carolinensis) was an iconic North American bird. The last surviving specimen died in the Cincinnati Zoo in 1918 [1]. The cause of its extinction remains contentious: besides excessive mortality associated to habitat destruction and active hunting, their survival could have been negatively affected by its range having become increasingly patchy [2] or by the exposure to poultry pathogens [3, 4]. In addition, the Carolina parakeet showed a predilection for cockleburs, an herbaceous plant that contains a powerful toxin, carboxyatractyloside, or CAT [5], which did not seem to affect them but made the birds notoriously toxic to most predators [3]. To explore the demographic history of this bird, we generated the complete genomic sequence of a preserved specimen held in a private collection in Espinelves (Girona, Spain), as well as of a close extant relative, Aratinga solstitialis. We identified two non-synonymous genetic changes in two highly conserved proteins known to interact with CAT that could underlie a specific dietary adaptation to this toxin. Our genomic analyses did not reveal evidence of a dramatic past demographic decline in the Carolina parakeet; also, its genome did not exhibit the long runs of homozygosity that are signals of recent inbreeding and are typically found in endangered species. As such, our results suggest its extinction was an abrupt process and thus likely solely attributable to human causes. Gelabert et al. report the whole genome of the extinct Carolina parakeet and provide evidence of its phylogeny, adaptation to a toxic cocklebur diet, and demographic history. The lack of signs of recent inbreeding typically found in endangered species suggests its abrupt extinction was human mediated., This work was supported by ERC Consolidator Grant 681396 “Extinction Genomics” to M.T.P.G. and M.S.-V., Obra Social ‘‘La Caixa’’ and Secretaria d’Universitats i Recerca ( GRC2017-SGR880 ) to T.M.-B. and C.L.-F., BFU2017-86471-P and PGC2018-101927-B-I00 from MINECO/FEDER, UE to T.M.-B, and PGC2018-095931-B-100 from MINECO/FEDER, UE to C.L.-F. T.M.-B. is also supported by a U01 MH106874 grant and Howard Hughes International Early Career and CERCA Programme (Generalitat de Catalunya). A.A. is partially supported by the Strategic Funding UID/Multi/04423/2019 through national funds provided by the Portuguese Foundation for Science and Technology (FCT) and the European Regional Development Fund —program PT2020 , by the European Structural and Investment Funds —Competitiveness and Internationalization Operational Program-COMPETE 2020, and by National Funds through the FCT under the project PTDC/CTA-AMB/31774/2017(POCI-01-0145-FEDER/031774/2017 ).

Analysis of the 949 and 434 cases of mortality of Booted Eagle Aquila pennata and Short-toed Snake Eagle Circaetus gallicus, respectively, recorded by wildlife rehabilitation centres in Spain over a 16-year period (1990–2006) shows that power lines (19.5 and 35.2 %, respectively) and killing (32.5 and 22.9 %, respectively) were the main known causes of death. Multinomial regression models were used to analyse geographical and temporal variations in the causes of death. For the Booted Eagle, both factors (zone and year) were statistically significant, while there were only significant temporal variations for the Short-toed Snake Eagle. In the Booted Eagle, killing occurred more frequently than expected in the east and north of the country compared to the other Spanish regions. Power line casualties were significantly more frequent in the southern and eastern regions, and less common in the north. In both species, the multinomial models indicate that while the number of cases of killing significantly decreased during the 16 years studied, power line casualties increased. Our study suggests that human-induced mortality continues to be the main factor contributing to mortality for Spanish Booted Eagles and Short-toed Snake Eagles. Since a reduction in the mortality caused by human activities is a priority in the conservation strategies for raptor species, management guidelines are discussed.

Variation in avian migratory behaviour is widespread, not only among species but also within species, and can involve shifts from sedentary at low latitudes to migratory at high latitudes. This leads to a situation whereby non-migratory populations of a species at lower latitudes are periodically joined by migratory conspecifics during winter. Determining spatio-temporal dynamics in distribution and structure of different populations is crucial to our understanding of their ecology and interactions, but it is often difficult or impossible to separate resident from migrant populations. Here, we used the winter distribution of Marsh Harrier (Circus aeruginosus) in the Iberian Peninsula (southwest Europe) to analyse the potential of spatial distribution models and stable isotope analyses of feathers (deuterium, δ2H) to evaluate differences in spatial distribution of migrant and resident raptor populations in southern Europe. Overall, ring recoveries and isotopic assignment showed that most migrant harriers wintering in the Iberian Peninsula had a central and northern latitudinal European origin. Our results revealed segregation in the winter distribution of migrant and resident Marsh Harrier populations in the Iberian Peninsula. These results have important conservation implications, suggesting that ecological conditions and potential stressors could greatly differ among resident and migrant populations in winter. Our approach provided a useful methodological procedure to evaluate the wintering spatial segregation of European populations of a raptor species and presents a new challenge to the study of their ecological consequences.

We monitored the number of pairs and the diet of Black-winged Kite Elanus caeruleus on the Lleida Plains (Catalonia, NE Spain) from 1998 to 2012. We examined the diet by means of pellet analysis. Nesting was irregular with peak numbers in some years (2009-2010). We found a positive relationship between the percentage of rodents in the diet and breeding success, an inverse relationship between dietary breadth and breeding success, a negative relationship between dietary breadth and the percentage of rodents in the diet and no significant variation in diet composition or breeding success between low kite population and high kite population years. All of this was consistent with the response of a specialist predator taking advantage of rodent outbreaks. We conclude that the breeding of the Black-winged Kite on the Lleida Plains is more consistent with the existence of irruptive events than with a real colonization of the area.—Llorente-Llurba, E., Bota, G., Pujol-Buxo, E., Bonfil, J., Galvez, M., Montes, G., Bas, J., Moncasi, F., Pont, F. & Manosa, S. (2019). Diet composition and breeding success of the Black-winged Kite on the Lleida Plains in relation to population size. Ardeola, 66: 33-50.

Species distribution patterns are determined not only by habitat preferences but also by biotic factors. Particularly, the presence of conspecifics may yield different types of benefits and costs for the individuals involved. This study analyses the spatial distribution of Little Bustard families during the breeding season in relation to the dis- tribution of male core areas in three Spanish populations of the species. A compositional analysis is used to evaluate habitat selection and the habitat types most preferred by females with offspring. Spatial analyses were performed to evaluate the proximity of Little Bustard families to male core areas and male displaying sites. The habitat selection pat- tern was similar between regions, with semi-permanent vegetation and stubbles as most preferred habitats while oth- ers, such as ploughed land, were avoided. Families were located closer to male core areas than expected by chance and were spatially associated to male displaying sites. Little Bustard females may obtain different benefits from this spatial association such as access to more food resources and chances for second matings after a clutch loss. Also in stubbles, the capture of prey by chicks would be easier and semi-permanent habitats would serve as shelter. These results high- light the importance of intraspecific interactions in the definition of the habitat selection pattern of females and fami- lies. This study shows how spatial point pattern analysis may be a useful tool for integrating landscape and behaviour- al ecology.

We investigated the ranging behaviour during the breeding season of 18 radiotracked little bustard (Tetrax tetrax) males, a disperse-lekking species inhabiting the cereal pseudo-steppes. The average kernel 95% home range was 60 ± 50 ha and the average cluster 85% area was 17 ± 17 ha. Range structure was as relevant as home range size for explaining the variation in the ranging behaviour of males, which could be partially explained by age, habitat quality and site. Ranging behaviour varied from males defending small and concentrated home ranges with high habitat quality, to males holding larger home ranges composed by several arenas. Our results suggest that social dominance and resource availability may affect ranging behaviour of males during the breeding season. Also, mating systems constraints may play a role on the use of space of males within the lekking ground. The ranging behaviour of a given male may be determined by a tendency to reduce and concentrate the home range as age and social status increase, and several fine-tuning mechanisms adjusting the ranging behaviour to the prevailing environmental or social factors on a given site and year.

Capsule Diet composition and feeding behaviour of breeding birds differed between areas of high and low agricultural intensification. Aims To analyze diet composition and feeding behaviour of Marsh Harriers Circus aeruginosus in agricultural landscapes with different degrees of agricultural intensification. Methods Diet composition and feeding behaviour was assessed by focal observations at nests during breeding seasons in 2001–03 in two agricultural areas within the eastern Ebro Basin (on the northern Iberian Peninsula) which differed in their degree of agricultural intensification: a traditional non-irrigated and non-intensively managed farmland area; and an irrigated and intensively managed farmland area. Results Marsh Harriers in the intensively managed area took higher percentages of small mammals than harriers in the traditional area managed at low-intensity, where they also had a more diverse diet. Male delivery rates increased throughout the breeding season in the intensively managed area. On the ...

Cereal pseudo-steppes hold the largest proportion of declining bird species in Europe. Understanding how this process of decline is driven is essential for designing adequate management practices. The little bustard (Tetrax tetrax) is one of such threatened steppe-land bird species, which has suffered recent dramatic range constrictions and population declines. Although low breeding success has been claimed to be the main threat for the viability of future little bustard populations, the surprising lack of studies dealing with ecological requirements of broods hinders the implementation of efficient conservation practices. We studied the ranging behaviour and the reproductive success of a little bustard population by means of female radio-tracking conducted during 2006–2008 breeding seasons in the Ebro basin (NE Spain). We recorded an average breeding success of 0.27 chicks/hen, which is not enough to sustain a viable population according to the demographic models for the species. Early-laid clutches showed more probabilities to hatch and to fledge. This was associated to two different ranging patterns (i.e. sedentary versus wandering respectively) which depended on the ability of the hen and its chicks to settle in suitable areas harbouring enough arthropods and shelter for chicks. Such resources decrease drastically as the breeding season progresses. Overall, data suggest that agricultural practices associated to agricultural intensification, particularly early harvest, reduce breeding success both directly by nest destruction and indirectly through a decrease on resource availability for broods. Based on our findings on the characteristics and structure of the home range of little bustard broods, we propose the creation of a network of permanent vegetation plots interconnected by high-quality field margins as a management practice to raise the breeding success of little bustards and other ground-nesting birds on cereal farmland.

We studied foraging habitat use and selection of the Western Marsh-Harrier (Circus aeruginosus) in agricultural areas, by radio-tracking seven individuals in the Ebro Basin (northern Iberian Peninsula). Generalized Linear Mixed Models indicated that the probability that a certain point within the study area was used by harriers was influenced by both distance to the nesting site and habitat. Probability of occurrence decreased with the distance to the nesting site and increased in wetlands and herbaceous crops (both those with high-intensity agricultural practices and those with low-intensity agriculture). In areas dominated by high-intensity herbaceous crops (irrigated maize, cereal, and alfalfa), marsh-harriers (n = 2) did not use all crop types equally throughout the year; they selected different crops in relation to the crop stage (growing, fallow, and stubble) and to particular agricultural practices (irrigated, unirrigated).

Agricultural intensification over the last 60 decades has been linked to decreases in biodiversity and in the breeding populations of several avian species in farmlands. However, agricultural intensification has not affected all species in the same way and transformed landscapes can still provide suitable habitats for species tolerant to some degree of anthropogenic change. Understanding habitat selection in man-made landscapes is a pre-requisite to effective management and conservation of the species that use them. However, habitat-related choices made by individuals occupying these landscapes are often difficult to explain, as the cues they use may be decoupled from the ecological context in which they evolved. Here, we investigated nesting habitat selection in a ground-nesting raptor breeding mainly in wetlands, which, unlike many other species occupying farmlands, has experienced a population increase in some agricultural regions. We used multivariate analysis to assess the extent to which habitat characteristics, human disturbance or proximity to other occupied sites influenced nesting-site occupancy. Our results indicate that Marsh harriers occupied breeding sites according to habitat cues obtained at two complementary spatial scales (i.e. the breeding site and the foraging area). This study indicates that a raptor species that uses human-made structures such as ponds for breeding while exploiting their surrounding crops for hunting can take advantage of agricultural intensification. Environmental disturbances are often viewed only in terms of their harmful impacts on the affected species. However, human activities are causing many types of alterations in natural landscapes that can be exploited by certain species with positive responses towards these transformations. The adaptation of some raptors to human-altered environments, such as the Marsh harrier in our study area, raises doubts regarding the appropriateness of using such species as indicators of natural habitat quality.

Bird electrocution on power lines is an important conservation problem that affects many endangered species. We surveyed 3,869 pylons in the Barcelona Pre-littoral Mountains (Catalonia, NE Spain) and collected 141 carcasses of electrocuted birds, mainly raptors and corvids. Univariate analysis indicated that metal pylons with pin-type insulators or exposed jumpers, with connector wires, located on ridges, overhanging other landscape elements, and in open habitats with low vegetation cover were the most dangerous. A logistic regression model indicated that the probability of a pylon electrocuting a bird was mainly related to pylon conductivity, distribution of the conductive elements on the cross-arms, cross-arm configuration, habitat, topography, whether the pylon was overhanging other landscape elements, and presence of rabbits (Oryctolagus cuniculus). We validated the predictive power of this model by using a random sample of 20% of all pylons surveyed. We found that bird mortality was aggregated mainly on pylons assigned a high probability risk by the model. Pylons included in the very high electrocution risk category (9.2%) accounted for 53.2% of carcasses, whereas pylons classified in the low electrocution risk category (54.5%) only accounted for 3.5% of mortality. Power companies employed this classification to prioritize the correction of 222 pylons by installing alternate cross-arms and suspended jumpers and isolating wires and jumpers. We evaluated the effectiveness of this mitigation strategy. A significant fall in the mortality rate on corrected pylons combined with the lack of any reduction in the mortality rate in a sample of 350 noncorrected pylons indicated that the model selected adequately the most dangerous pylons and that the applied correction measures were effective. Consequently, our strategy may be a useful tool for optimizing efforts and resources invested in solving the problem of bird electrocution.

Capsule We describe four techniques for the capture of Little Bustards according to their age, sex and season, and discuss their adequacy for different research objectives.

Studies of ranging behaviour can provide valuable information on the ecological requirements of a species. They may be an essential tool in designing conservation policies (Sutherland 1998, Tella et al. 1998) as they provide the information needed to predict the consequences of land-use change on species’ habitat use, especially in regions subject to major habitat transformations. In particular, knowledge of the temporal and spatial variation in ranging behaviour is needed to understand space-use patterns over species’ complete annual cycles and over a range of habitats (Blanco et al. 1998, Tella & Forero 2000, Peterjohn 2003). However, this sort of information is available for only a few species, and even then does not usually cover the non-breeding season (Suarez et al. 1997). Marsh Harriers Circus aeruginosus occur within a wide range of open habitats, including agricultural landscapes. After a dramatic population decline during 1960–80, mainly due to drainage of wetlands, contamination and direct persecution, the European population has recovered in recent decades and is currently classified as ‘Secure’ (Cramp & Simmons 1994, BirdLife International 2004). Within the Iberian Peninsula, the increase and spread of the Marsh Harrier population has been noticeable in some agricultural regions, including those dominated by intensified farmlands. This is the case in the Catalan Ebro Basin (Spain), where the breeding population increased from eight breeding pairs in 1997 to 51 in 2008 (Departament de Medi Ambient i Habitage de la Generalitat de Catalunya unpubl. data). However, little is known about the ranging behaviour of the Marsh Harrier in these agricultural areas. The objective of our study was to investigate the ranging behaviour and foraging-area requirements of the Marsh Harrier throughout the complete annual cycle in a representative agricultural area within the Iberian Peninsula.

Capturing wild animals for research or conservation purposes may cause some adverse effects, which is only acceptable if these are outweighed by conservation benefits. We used information from 3 on-going telemetry studies on the endangered little bustard (Tetrax tetrax) in Western Europe to evaluate the risk factors associated with capture and handling. Of 151 telemetered birds, 23 (15.2%) exhibited impaired mobility and coordination after release, probably related to the occurrence of capture myopathy. Among the 23 impaired birds, 10 (43.5%) died before recovering normal mobility (6.6% of all birds captured). Logistic regression analyses identified longer handling time, longer restraint time, use of cannon nets, and capture of juveniles as inducing factors for these disorders. We conclude that little bustard is fairly susceptible to suffering ataxia and paresia after release as a result of restraint associated with capture and manipulation. Researchers can reduce this risk by keeping handling and restraint time below 10–20 minutes, particularly when using cannon nets or when capturing juveniles.

The Eagle Owl Bubo bubo, which feeds mainly on rabbits and partridges, has been persecuted widely for causing damage to game interests. Although it is a protected species throughout Europe, there is a noteworthy gap in the scientific literature on the causes of mortality in this top predator. Here, we assess the relative importance and the geographical and temporal variation of human-related causes of death by reviewing 1,576 files of individuals admitted to wildlife rescue centres in Spain, a stronghold for Eagle Owls. The main known cause of death was interaction with powerlines followed by persecution and collisions with game fences and cars. There were within-year variations in the distribution of persecution, electrocution and collisions with game fences. Some man-induced causes of mortality were seen to depend on both the geographical region and the period of the year; moreover, mortality within each region was also year-dependent. Since there are strong socio-economic and ethical components involved, management guidelines are discussed bearing in mind such points of view.

Whether predators can limit their prey has been a topic of scientific debate for decades. Traditionally it was believed that predators take only wounded, sick, old or otherwise low-quality individuals, and thus have little impact on prey populations. However, there is increasing evidence that, at least under certain circumstances, vertebrate predators may indeed limit prey numbers. This potential role of predators as limiting factors of prey populations has created conflicts between predators and human hunters, because the hunters may see predators as competitors for the same resources. A particularly acute conflict has emerged over the past few decades between gamebird hunters and birds of prey in Europe. As a part of a European-wide research project, we reviewed literature on the relationships between birds of prey and gamebirds. We start by analysing available data on the diets of 52 European raptor and owl species. There are some 32 species, mostly specialist predators feeding on small mammals, small passerine birds or insects, which never or very rarely include game animals (e.g. hares, rabbits, gamebirds) in their diet. A second group (20 species) consists of medium-sized and large raptors which prey on game, but for which the proportion in the diet varies temporally and spatially. Only three raptor species can have rather large proportions of gamebirds in their diet, and another seven species may utilise gamebirds locally to a great extent. We point out that the percentage of a given prey species in the diet of an avian predator does not necessarily reflect the impact of that predator on densities of prey populations. Next, we summarise available data on the numerical responses of avian predators to changing gamebird numbers. In half of these studies, no numerical response was found, while in the remainder a response was detected such that either raptor density or breeding success increased with density of gamebirds. Data on the functional responses of raptors were scarce. Most studies of the interaction between raptors and gamebird populations give some estimate of the predation rate (per cent of prey population taken by predator), but less often do they evaluate the subsequent reduction in the pre-harvest population or the potential limiting effect on breeding numbers. The few existing studies indicate that, under certain conditions, raptor predation may limit gamebird populations and reduce gamebird harvests. However, the number and extent of such studies are too modest to draw firm conclusions. Furthermore, their geographical bias to northern Europe, where predator–prey communities are typically simpler than in the south, precludes extrapolation to more diverse southern European ecosystems. There is an urgent need to develop further studies, particularly in southern Europe, to determine the functional and numerical responses of raptors to gamebird populations in species and environments other than those already evaluated in existing studies. Furthermore, additional field experiments are needed in which raptor and possibly also mammalian predator numbers are manipulated on a sufficiently large spatial and temporal scale. Other aspects that have been little studied are the role of predation by the non-breeding part of the raptor population, or floaters, on the breeding success and survival of gamebirds, as well as the effect of intra-guild predation. Finally there is a need for further research on practical methods to reduce raptor predation on gamebirds and thus reduce conflict between raptor conservation and gamebird management., The work was financially supported by the EuropeanCommission, and is part of project REGHAB (ReconcilingGamebird Hunting and Biodiversity; contract no.EVK2-CT-2000-200004).

Research conducted in several Mediterranean areas indicates that most populations of steppe birds are currently experiencing population declines associated with intensification of traditional agri- cultural practices. By using habitat suitability modeling (HSM), our aim was to use available environ- mental data sets, including land use and relief, to model the current distribution of nine steppe bird species in the agriculture dominated areas of the Catalan Ebro basin (northeast Iberia). We then employ HSM to quantitatively assess the future impact of land use changes on the potential distribution range of these species under two scenarios following irrigation of present extensive cereal steppes in the area. HSM analyses showed a close association between steppe bird distribution and the extent of extensive cereal agriculture in flat areas. Although the sensitivity to planned irrigation schemes was species spe- cific, we estimated significant decreases in distribution after irrigation for seven of the nine species ex- amined, i.e. the Little bustard, the Montagu's harrier, the Roller and the Calandra lark, the species pre- dicted to be more severely affected by predicted decreases in area exceeding 50%. Overall, core steppe habitats where most valuable steppe species may co-occur are expected to be mostly impacted and de- crease by 74 to 81% after irrigation of only 28 to 36% of the cereal cropland in the region. Future maintenance and survival of viable populations of steppe birds will rely on our ability to enlarge the network of protected areas and to implement agri-environmental measures targeting current species core habitats in low-intensity farmland.

Persistent organochlorine compounds (pesticides and polychlorinated biphenyls) were determined in 24 northern goshawk (Accipiter gentilis) and eight Eurasian buzzard (Buteo buteo) samples of eggs collected between 1988 and 1999 in La Segarra (northeast Spain), in order to evaluate the changes in exposure and detrimental effects during this period. In the study area, both species exhibited similar levels of contamination, which may be related to their similar diet, mainly based on European rabbits (Oryctolagus cuniculus) in terms of biomass. The buzzard showed contamination levels similar to those found in other Spanish areas, but the levels found in the goshawk were much lower. The shell index in goshawk eggs was inversely correlated to concentration of p,p'-DDE. In late eighties, the concentrations of p,p'-DDE and heptachlor-epoxide in goshawk eggs were positively correlated to the biomass percentage of passeriforms in the diet. In goshawk samples, a decline in HCB concentration in the 1990s as compared to the 1980s was detected. Surprisingly, p,p'-DDE concentrations did not decline, as could be expected from the ban on DDT use. On the contrary, the highest p,p'-DDE concentrations were detected in some samples from the nineties, which also showed the lowest shell indices. This may be related to a severe reduction of rabbit population after 1989 that produced an increase in the consumption of passeriformes, which are known to accumulate higher levels of organochlorine compounds. Our study suggests that monitoring programs aiming to detect temporal trends in chemical contamination should take into account changes in diet composition before any conclusion can be drawn.

We evaluated the effect of conspecific abundance and habitat quality of leks on the territorial behaviour of males in an exploded lekking species, the Little Bustard (Tetrax tetrax). The hypothesis that males more intensely defend territories with higher conspecific abundance and better habitat quality was evaluated experimentally analysing the agonistic response of experimental males to male decoys placed on their displaying areas. Decoy experiments showed that the intensity of display territory defence by little bustard males is density dependent. The time experimental males took to return to their display sites after decoy placement decreased with abundance of both males and females. The strength of their final response was positively associated to local male and female abundance in the vicinity of their display sites. Habitat quality also influenced males' display territory defence since the intensity of male response increased with the degree of natural vegetation cover. Habitat quality was particularly relevant in explaining variation of experimental males' snort call rate, which decreased with the degree in plough cover and increased with the number of fields in the lekking area. Snort call rate decreased with the level of male aggregation and was lowest in males exhibiting the strongest aggressive response to decoys. These results add new evidence for the density dependence of species' breeding territorial behaviour, supporting density-dependent models of lek formation and reinforcing the role of resources defence in exploded lek mating systems., FC and JM-P were supported by a JAE-Doc contract funded by Spanish Research Council and the European Social Fund (ESF), and ELG was funded by a FPU grant from the Spanish Ministry of Education. This paper contributes to projects CGL2004-06147-C02-01, CGL2004-06147-C02-02 and CGL2009-13029/BOS of the Spanish Ministry of Science, as well as to the REMEDINAL2 network of the Community of Madrid (S-2009/AMB/1783).

The Spanish Bonelli's Eagle populations have decreased markedly because of high mortality. We recorded 424 cases of dead eagles between 1990 and 1998 in Spain which after cross-comparison corresponded to 377 individuals. Electrocution (55% of deaths), followed by direct persecution (26%) were the main causes of death. No differences in the cause of death were found between sexes. Non-adult eagles mostly died of electrocution whereas adults were mainly the victims of persecution. A log-linear model showed that these differences were associated with a difference in the spatial distribution of age classes, rather than to age or experience per se. Persecution was the main cause of death in breeding areas and electrocution in non-breeding areas. There were differences between regions: electrocution was the main cause in Catalonia and Central Spain (50% and 86% respectively) whereas direct persecution was the main cause in Levant and Northern Spain (52% and 43% respectively). We recommend that steps are taken i...

Bird electrocution rates in Secanos de Lerida, an important bird area in central Catalonia (northeast Spain), were estimated based on 804 visits to 507 electric pylons between 1995 and 1999. Electrocution caused a minimum of 160 victims on 67 pylons. Victims were corvids (36%), diurnal birds of prey (60%) and owls (4%). Electrocution rates ranged between

The Ebro delta (NE Spain) is a 320 km2 wetland area ofinternational importance for conservation. The area is devotedto rice farming and receives large amounts of pesticides.Industrial pollutants are also carried to the delta by the river.The information accumulated during the last 25 year on the effectof such pollution on the biota is reviewed in order to identifythe existing gaps and needs for management. Organochlorinepesticides were legally used until 1977, which has resulted inthe widespread presence of these compounds in the Ebro deltabiota. Lethal, sublethal or other detrimental effects of thesepesticides on wildlife in the area were poorly investigated, butnegative effects on the reproduction of ducks and herons werereported. Nowadays, polychlorinated biphenyls (PCBs) are themain responsible of organochlorine pollution in the area:concentrations in biota samples are higher than levels observedin nearby coastal areas, as a result of the significant PCBinputs by the river which, in 1990, were evaluated at 126 kgyr-1. The massive use of herbicides is thought to havecontributed to the elimation of macrophyte vegetation in thelagoons during the eighties, which had strong consequences ondiving ducks and coot populations. Weed control is also relatedto the loss of biodiversity held by rice fields. The massive andinadequate use of organophosphorus and carbamate pesticides(involving more than 20 000 t yr-1) has produced somewaterbird mortality events, and may have direct and indirecteffects on other non-target organisms. The accumulation in thesoil of lead pellets used in waterfowl shooting is estimated tokill some 16 300 waterbirds in the Ebro delta every year.

During 1980-97, trichomoniasis was detected in nestlings of Bonelli's eagle Hieraaetus fasciatus in Catalonia (Spain). In 1993 Trichomonas gallinae was isolated in 36% of nestlings (n = 39) and affected 41% of broods (n = 22). Overall, trichomoniasis was one of the most important single nestling mortality factor, accounting for 22% of total chick mortality, and causing the death of 2% of chicks. Trichomoniasis deaths took place during the second half of the nestling period. The median age at death was 45.5 days. Although the presence of the parasite was not related to the composition of the diet or parental age, pairs that developed the disease ate more pigeons and included more often non-adult birds. At present trichomoniasis apparently has little demographic impact on the Bonelli's eagle population in Catalonia, but the eventual spread of this disease in chicks and its unknown effects on adults might be of concern.

A census of four species of syntopic parrots was carried out using distance sampling methods on Sao Sebastiao island, SE Brazil. Most of the 33 593 ha island is covered by mature and secondary Atlantic rainforest. Almost 80% of these forests are within the Ilhabela Park. Although the species counted have marked differences in size and weight, density (individuals/km2) and estimated population size in 23 500 ha of well-preserved forests were similar: Amazona farinosa (13.82 ± 5.94; 3247 ± 1395), Pionus maximiliani (15.79 ± 7.04; 3712 ± 1654), Brotogeris tirica (15.05 ± 4.87; 3537 ± 1143) and Pyrrhura frontalis (13.06 ± 5.53; 3068 ± 1298). Encounter rates of Forpus crassirostris and Pionopsitta pileata were very low, which suggests that there is only a small population of these species on the island. The Sao Sebastiao forests still support healthy populations of parrots. Although woodpecker population estimates on the island are large enough to provide nesting sites for parrots, competition for holes with other secondary cavity nesters such as toucans, flycatchers and tytiras, and the selective cutting of dead trees for canoe construction, which is a common practice on the island, may limit hole availability for parrots.

Four little bustards (Tetrax tetrax) (one adult and three juvenile males), captured with leg nooses and fitted with a backpack radiotag, died after capture. The first bird was found after 16 days with its left foot caught in the harness and died after 1 day. The other birds showed symptoms of capture myopathy after release, such as the difficulty or inability to fly and/or walk. They died after 5, 6, and 8 days, respectively. At necropsy, muscles affected in all cases were those from the legs, and these were diffusely pale and dull, with a soft friable texture. Microscopically these muscles had multiple foci of myofiber fragmentation, loss of striation, and necrosis; a mononuclear cell infiltrate was observed in muscle from two birds. These findings suggest the little bustard is susceptible to capture myopathy and that caution should be exercised during its capture and handling.

The basic demographic parameters of six Bonelli's eagle Hieraaetus fasciatus populations in Spain and France were calculated from field data obtained in the last 15 years. Average annual productivity ranged from 0.36 to 1.24 young/pair and average annual adult survival from 84% to 96%. Preadult survival (from fledging to recruitment) was estimated at 10%. All the populations were declining at annual rates ranging from −7.3 to −1.1%. Although no statistically significant disagreement was observed between the predictions of a Leslie matrix model fitted to the population parameters and the real trends, some populations declined faster and others more slowly than expected. These differences were interpreted as a result of differential emigration, recruitment rates or preadult survival not accounted for by the model. Since the intrinsic population growth rate was about four times less sensitive to changes in preadult survival than to changes in adult survival, and about ten times less sensitive to changes in fecundity and predispersal survival, conservation efforts must be primarily directed towards increasing adult and preadult survival. Power line casualties and direct persecution must be eliminated in order to reduce mortality. Priorities on research should address dispersal, mortality and habitat relationships involving these two parameters. Monitoring should be extended to other populations.

In response to climate changes that have occurred during Pleistocene glacial cycles, taxa associated to steppe vegetation might have followed a pattern of historical evolution in which isolation and fragmentation of populations occurred during the short interglacials and expansion events occurred during the long glacial periods, in contrast to the pattern described for temperate species. Here, we use molecular genetic data to evaluate this idea in a steppe bird with Palaearctic distribution, the little bustard (Tetrax tetrax). Overall, extremely low genetic diversity and differentiation was observed among eight little bustard populations distributed in Spain and France. Mismatch distribution analyses showed that most little bustard populations expanded during cooling periods previous to, and just after, the last interglacial period (127,000-111,000. years before present), when steppe habitats were widespread across Europe. Coalescent-based methods suggested that glacial expansions have resulted in substantial admixture in Western Europe due to the existence of different interglacial refugia. Our results are consistent with a model of evolution and genetic consequences of Pleistocene cycles with low between-population genetic differentiation as a result of short-term isolation periods during interglacials and long-term exchange during glacial periods., This is a contribution to Project CGL2004-06147-C02-01 of the Spanish Ministerio de Ciencia e Innovación.

The population of the Vulnerable Spanish imperial eagle Aquila adalberti has experienced a gradual recovery from 38 pairs (1974) to 198 (2004). We analysed the spatial and temporal variation of the demographic parameters for 1981–2004. Annual productivity was 1.19–1.32 chicks per female and adult survival rate 0.918–0.986. Survival during the post-fledging period was 0.894 and the annual survival rate of the dispersing individuals was 0.561. Three phases of population evolution were distinguished: growth (1981–1993), stability or slight decrease (1994–1999) and growth (2000–2004). Variation in adult survival seems to explain this pattern for the first two periods. However, a large disparity between the observed growth rate and the modelled population growth in 2000–2004 is best explained if we assume that a decrease in the age of recruitment took place. This is supported by the recent increase in the frequency of non-adult birds in breeding pairs. The survival of unpaired eagles in dispersal areas is becoming more important for the maintenance of current population growth. Spatial variation of adult survival and breeding success is not congruent with the observed growth rate of the population, which suggests the existence of an important flow of individuals between populations. These results highlight the importance of addressing the conservation of the species from a global perspective and the need to focus on adult survival in breeding territories and on non-adult survival in dispersal areas., The field work was funded by the Consejerías de Medio Ambiente of Madrid, Castilla y León, Castilla-La Mancha and Extremadura. This study was funded by the Direccion General para la Biodiversidad through TRAGSA and Fundacio Bosch i Gimpera of the University of Barcelona, and the European Commission through LIFE project 03/NAT/E/000050.

We studied annual and geographical variation in the proportion of breeding non-adult (, This study was funded by the Ministerio de Medio Ambiente, through TRAGSA and Fundació Bosch i Gimpera of the University of Barcelona and by the framework of the National Strategy and Recovery Plans for the species by the Dirección General para la Biodiversidad of the Ministerio de Medio Ambiente and the Consejerías de Medio Ambiente of the Autonomous Communities of Madrid, Castilla y León, Castilla-La Mancha and Extremadura; and by the European Commission throughout LIFE-projects 99/NAT/E/006336 and 03/NAT/E/ 000050.