Analysis of genetic parentage in the tawny owl (Strix aluco) reveals extra-pair paternity is low

We have investigated genetic parentage in a Swiss population of tawny owls (Strix aluco). To this end, we performed genetic analysis for six polymorphic loci of 49 avian microsatellite loci tested for cross-species amplification. We found one extra-pair young out of 137 (0.7%) nestlings in 37 families (2.7%). There was no intra-specific brood parasitism. Our results are in accordance with previous findings for other raptors and owls that genetic monogamy is the rule. Female tawny owls cannot raise offspring without a substantial contribution by their mates. Hence one favoured hypothesis is that high paternal investment in reproduction selects for behaviour that prevents cuckoldry.

Disponibilidad de micromamíferos en el área de campeo del cárabo común en los bosques de Burceña (Valle de Mena): Primeros resultados del estudio

[ES] Este trabajo forma parte de un proyecto en el que se estudian dos poblaciones de cárabo común (Strix aluco); una en Durango (Bizkaia) y otra en Burceña (Burgos). Este trabajo se ha llevado a cabo en Burceña y en él se muestran los primeros resultados del uso del espacio de estas rapaces nocturnas y su disponibilidad de alimento en los bosques de esta zona. Para ello hemos obtenido localizaciones de diez cárabos durante un año para conocer los territorios de cada uno y hemos capturado en vivo la dieta principal de esta ave, micromamíferos. Estos resultados los hemos relacionado entre sí para saber si influye el uso del espacio en las capturas de micromamíferos. Estas dos variables también las hemos relacionado con el tipo y la edad de los bosques muestreados. Según los resultados obtenidos podemos afirmar que sí existe una influencia del uso en las capturas, demostrando una relación negativa; es decir, donde se han capturado más micromamíferos es en los bosques que menos frecuentan los cárabos, que a su vez, son los bosques menos accesibles para estas rapaces. ABSTRACT This investigation is part of a work project whereby two Tawny owl (Strix aluco) populations are studied. One of them lives in Durango, Biscay and the other one in Burceña, Burgos. This specific work took place in Burceña and lasted one year. It shows the first results of the study on the use of the space of the Tawny owls and the food availability in their woodland range area. We spotted and traced the home range of ten different tawny owls, and also trapped small mammals which are the staple diet of these owls. We compared both the results obtained in order to know if the use of the area is related to the capture of small mammals. These two variables (space-capture) were also related to the type and age of the sampled forests. The results obtained show that it is true there is an influence of the use of space upon the captures proving to be a negative relation, that is, the largest numbers of micromammals were captured in the woodlands where there are fewer owls, because they are the least accessible forests for these birds of prey.

Sex- and melanism-specific variations in the oxidative status of adult tawny owls in response to manipulated reproductive effort.

Oxidative stress, determined by the balance between the production of damaging reactive oxygen species (ROS) and antioxidant defences, is hypothesized to play an important role in shaping the cost of reproduction and life history trade-offs. To test this hypothesis, we manipulated reproductive effort in 94 breeding pairs of tawny owls (Strix aluco) to investigate the sex- and melanism-specific effects on markers of oxidative stress in red blood cells (RBCs). This colour polymorphic bird species shows sex-specific division of labour and melanism-specific history strategies. Brood sizes at hatching were experimentally enlarged or reduced to increase or decrease reproductive effort, respectively. We obtained an integrative measure of the oxidative balance by measuring ROS production by RBCs, intracellular antioxidant glutathione levels and membrane resistance to ROS. We found that light melanic males (the sex undertaking offspring food provisioning) produced more ROS than darker conspecifics, but only when rearing an enlarged brood. In both sexes, light melanic individuals had also a larger pool of intracellular antioxidant glutathione than darker owls under relaxed reproductive conditions (i.e. reduced brood), but not when investing substantial effort in current reproduction (enlarged brood). Finally, resistance to oxidative stress was differently affected by the brood size manipulation experiment in males and females independently of their plumage coloration. Altogether, our results support the hypothesis that reproductive effort can alter the oxidative balance in a sex- and colour-specific way. This further emphasizes the close link between melanin-based coloration and life history strategies.

Food availability and predation risk, rather than intrinsic attributes are the main factors shaping the reproductive decisions of a long-lived predator

Funded by Natural Research Limited Natural Environment Research Council studentship. Grant Numbers: NE/J500148/1, NE/F021402/1

As rodovias e as aves de rapina nocturnas relação entre a densidade, o habitat e a mortalidade

As estradas e tráfego inerente surgem como a criação antrópica mais conspícua e penetrante na paisagem natural, sendo considerados os principais agentes causadores de fragmentação e destruição de habitats, assim como representam um obstáculo físico sem precedentes, limitando as relações directas entre os indivíduos, por diminuição da frequência de dispersão e aumento da mortalidade por atropelamento, impedindo o fluxo natural de genes e suscitando o aumento de fenómenos de inbreeding e perda de heterozigotia. Todos os impactes deletérios associados às rodovias são claramente perceptíveis em vertebrados, onde as aves de rapinas nocturnas não são excepção. Uma vez que estas rapaces beneficiam das suas bermas e orlas, como locais de poiso, nidificação ou como corredores de dispersão através da paisagem, são frequentemente vítimas de mortalidade por atropelamento em estradas, sendo esta problemática considerada actualmente uma das mais recentes e importantes formas de mortalidade não natural em rapinas nocturnas e vinculada como um dos maiores problemas de conservação que afecta este grupo. Não obstante, esse mútuo efeito de atracção/repulsa das estradas a estas rapaces, as rodovias criam uma barreira específica que limita a dinâmica, comportamento e densidade populacional das espécies residentes, reconhecendo-se que o isolamento daí resultante, pode comprometer a viabilidade populacional a longo prazo, podendo mesmo conduzir a altos riscos de extinção das populações locais devido a efeitos estocásticos. Mediante esta problemática, este trabalho debruçou-se sobre um único objectivo principal: a avaliação do impacte das rodovias e do tráfego, na densidade das aves de rapina nocturnas. Este estudo foi efectuado na região Alentejana, abrangendo uma área de cariz tipicamente mediterrânico, delimitada pelas localidades de Montemor-o-Novo, Arraiolos e Évora, sendo seccionada por 143 quilómetros de estradas, divididas em autoestrada, rodovias com elevada e reduzida densidade de tráfego. A monitorização das rapinas nocturnas foi conduzida em dois anos amostrais (2005 e 2007), tendo sido focalizada sobretudo em duas espécies de Strigiformes, a Coruja­ do-mato Strix aluco e o Mocho-galego Athene noctua, recorrendo ao uso de playbacks com reprodução de vocalizações de indivíduos conspecíficos. Foram usadas 32 variáveis explicativas integradas em três grandes grupos: variáveis de estrada, métricas da paisagem, uso do solo, tendo sido analiticamente testadas, recorrendo à aplicação de Modelos Lineares Generalizados. Os principais resultados obtidos demonstram que as variáveis de estrada, aliadas à densidade de tráfego e ruído inerente à sua circulação, são provavelmente, responsáveis por um comportamento de repulsa das espécies de aves de rapina nocturnas em estudo, apresentando estas densidades mais elevadas longe de áreas antropicamente perturbadas e, portanto, de menor qualidade que se encontram adjacentes às rodovias. Todavia a presença de habitat favorável a estas rapaces é provavelmente o descritor com maior poder estatístico no que concerne à sua distribuição e densidade, sendo os montados densos e a presença de zonas agrícolas de sequeiro, positivamente correlacionadas, respectivamente com a densidade de casais reprodutores de Coruja-do-mato e Mocho-galego. Mediante a observação dos resultados será veemente a aplicação de medidas de mitigação específicas, que fundamentalmente considerem o afastamento dos efectivos populacionais longe das estradas e tráfego, conservando e assegurando as características estruturais, requisitos e qualidade dos habitats, de modo a incrementar e garantir a viabilidade e densidade das populações, fidelizando a territorialidade e permanência destas aves nestas áreas. Adicionalmente deverá investir-se na conectividade das manchas de paisagem fragmentada pelas rodovias, criando opções de conservação estratégicas, em zonas ecologicamente mais sensíveis, que não somente minimizem o efeito de repulsa reconhecido nestas aves, mas também os níveis de mortalidade por atropelamento, tornando os ecossistemas mais funcionais para a sobrevivência destes rapaces. ABSTRACT; Roads and traffic are the most conspicuous and pervasive human creation, being the great responsible for fragmentation and habitats destruction, reducing animal movement through landscape, which implies decrease of gene flow and loss of variability that can fragmented populations, thus reducing their sizes and densities. All deleterious impacts associated with roads are clearly visible in vertebrates, where owls aren't exception, being frequent victims of road mortality, since they can use roadside habitats and edges for hunting, nesting or dispersal corridors through the landscape, being nowadays one of the most recent and important causes of non­natural mortality in owls and has been recognized as one of the largest conservation problems affecting this group. However, the attractive and avoidance effect of roads and his edges on owls creates a barrier effect that limits dynamics, behaviour and breeding density of resident species, recognizing that possible isolation, could compromise populations survival, make them more vulnerable to high risks of local extinction due to stochastic effects. Despite that, several authors suggest that owls use roads to hunt, as marginal habitats, or for navigation corridors through the landscape ln this context, the major aims of this study was to verify if there are negative effects of roads on the density of owls, considering traffic as an influencing factor. This study was conducted in Alentejo, covering a typical Mediterranean area, including three main localities Montemor-o-Novo, Évora and Arraiolos, being sectioned by 143 km of roads, including highway, roads with high traffic density, and the remaining with low traffic density. The owl census was conducted in two sampling years (2005 and 2007) and was focused mainly on Little owl Athene noctua and Tawny Owl Strix aluco species, using the playback technique, with conspecific calls. We used 32 explanatory variables, mainly included in three groups: road variables, landscape metrics and land use, having been analytically tested, with application of Generalised Linear Models. The main results show that noisy roads with high traffic density are probably the most responsible for the avoidance behaviour of owls, under the study area, showing density depression near high anthropogenic disturbed areas adjacent to roads. However, the presence of habitat quality to these birds is probably the descriptor with greater statistical power, considering its distribution and density, with the dense oak woodland and croplands and arable lands, positively correlated, respectively with Tawny owl and Little owl density. ln consequence, the great conservation effort should be done in order to keep breeding populations away from roads and traffic, ensuring the structural features, requirements and quality of its habitats in order to enhance and ensure the viability and density of owl's populations in these areas. ln addition, it is important to invest in connectivity between roadside fragmented patches, creating strategic conservation options, in sensitive areas, which minimize the avoidance effect, recognized in owls, but also road-kill levels, making ecosystems more functional to survival of these top predators.

Short- and long-term consequences of food resources on Ural owl Strix uralensis reproduction

Life-history theory states that although natural selection would favour a maximisation of both reproductive output and life-span, such a combination can not be achieved in any living organism. According to life-history theory the reason for the fact that not all traits can be maximised simultaneously is that different traits compete with each other for resources. These relationships between traits that constrain the simultaneous evolution of two or more traits are called trade-offs. Therefore, during different life-stages an individual needs to optimise its allocation of resources to life-history components such as growth, reproduction and survival. Resource limitation acts on these traits and therefore investment in one trait, e.g. reproduction, reduces the resources available for investment in another trait, e.g. residual reproduction or survival. In this thesis I study how food resources during different stages of the breeding event affect reproductive decisions in the Ural owl (Strix uralensis) and the consequences of these decisions on parents and offspring. The Ural owl is a suitable study species for such studies in natural populations since they are long-lived, site-tenacious, and feed on voles. The vole populations in Fennoscandia fluctuate in three- to four-year cycles, which create a variable food environment for the Ural owls to cope with. The thesis gives new insight in reproductive costs and their consequences in natural animal populations with emphasis on underlying physiological mechanisms. I found that supplementary fed Ural owl parents invest supplemented food resources during breeding in own self-maintenance instead of allocating those resources to offspring growth. This investment in own maintenance instead of improving current reproduction had carry-over effects to the following year in terms of increased reproductive output. Therefore, I found evidence that reduced reproductive costs improves future reproductive performance. Furthermore, I found evidence for the underlying mechanism behind this carry-over effect of supplementary food on fecundity. The supplementary-fed parents reduced their feeding investment in the offspring compared to controls, which enabled the fed female parents to invest the surplus resources in parasite resistance. Fed female parents had lower blood parasite loads than control females and this effect lasted until the following year when also reproductive output was increased. Hence, increased investment in parasite resistance when resources are plentiful has the potential to mediate positive carry-over effects on future reproduction. I further found that this carry-over effect was only present when potentials for future reproduction were good. The thesis also provides new knowledge on resource limitation on maternal effects. I found that increased resources prior to egg laying improve the condition and health of Ural owl females and enable them to allocate more resources to reproduction than control females. These additional resources are not allocated to increase the number of offspring, but instead to improve the quality of each offspring. Fed Ural owl females increased the size of their eggs and allocated more health improving immunological components into the eggs. Furthermore, the increased egg size had long-lasting effects on offspring growth, as offspring from larger eggs were heavier at fledging. Limiting resources can have different short- and long-term consequences on reproductive decisions that affect both offspring number and quality. In long-lived organisms, such as the Ural owl, it appears to be beneficial in terms of fitness to invest in long breeding life-span instead of additional investment in current reproduction. In Ural owls, females can influence the phenotypic quality of the offspring by transferring additional resources to the eggs that can have long-lasting effects on growth.

How long is a piece of Strix? Methods in measuring and measuring the measurers

An experiment to quantify intra- and interobserver error in anatomical measurements found that interobserver measurements can vary by over 14% of mean specimen length; disparity in measurement increases logarithmically with the number of contributors; instructions did not reduce variation or measurement disparity; scale of the specimen influenced the precision of measurement (relative error increasing with specimen size); different methods of taking a measurement yielded different results, although they did not differ in terms of precision, and topographical complexity of the elements being considered may potentially influence error (error increasing with complexity). These results highlight concerns about introduction of noise and potential bias that should be taken into account when compiling composite datasets and meta-analyses.

The breeding season of the American barn owl (Strix pratincola) in South Carolina

This document contains information on the breeding season of the American Barn Owl in South Carolina.

Living on voles - plastic life of the Ural owl

Individuals face variable environmental conditions during their life. This may be due to migration, dispersion, environmental changes or, for example, annual variation in weather conditions. Genetic adaptation to a novel environment happens through natural selection. Phenotypic plasticity allows, however, a quick individual response to a new environment. Phenotypic plasticity may also be beneficial for individual if the environment is highly variable. For example, eggs are costly to produce. If the food conditions vary significantly between breeding seasons it is useful to be able to adjust the clutch and egg size according to the food abundance. In this thesis I use Ural owl vole system to study phenotypic plasticity and natural selection using a number of reproduction related traits. The Ural owl (Strix uralensis) is a long-lived and sedentary species. The reproduction and survival of the Ural owl, in fact their whole life, is tied to the dramatically fluctuating vole densities. Ural owls do not cause vole cycles but they have to adjust their behaviour to the rather predictable population fluctuations of these small mammals. Earlier work with this system has shown that Ural owl laying date and clutch size are plastic in relation to vole abundance. Further, individual laying date clutch size reaction norms have been shown to vary in the amount of plasticity. My work extends the knowledge of natural selection and phenotypic plasticity in traits related to reproduction. I show that egg size, timing of the onset of incubation and nest defense aggressiveness are plastic traits with fitness consequences for the Ural owl. Although egg size is in general thought to be a fixed characteristic of an individual, this highly heritable trait in the Ural owl is also remarkably plastic in relation to the changes in vole numbers, Ural owls are laying the largest eggs when their prey is most abundant. Timing of the onset of incubation is an individual-specific property and plastic in relation to clutch size. Timing of incubation is an important underlying cause for asynchronous hatching in birds. Asynchronous hatching is beneficial to offspring survival in Ural owl. Hence, timing of the onset of incubation may also be under natural selection. Ural owl females also adjust their nest defense aggressiveness according to the vole dynamics, being most aggressive in years when they produce the largest broods. Individual females show different levels of nest defense aggressiveness. Aggressiveness is positively correlated with the phenotypic plasticity of aggressiveness. As elevated nest defense aggressiveness is selected for, it may promote the plasticity of aggressive nest defense behaviour. All the studied traits are repeatable or heritable on individual level, and their expression is either directly or indirectly sensitive to changes in vole numbers. My work considers a number of important fitness-related traits showing phenotypic plasticity in all of them. Further, in two chapters I show that there is individual variation in the amount of plasticity exhibited. These findings on plasticity in reproduction related traits suggest that variable environments indeed promote plasticity.

Collective violence : a study of the gendered and socio-economic factors behind early modern Italian and English witch hunts

In this study, I build upon my previous research in which I focus on religious doctrine as a gendered disciplinary apparatus, and examine the witch trials in early modem England and Italy in light of socio-economic issues relating to gender and class. This project examines the witch hunts/trials and early modem visual representations of witches, and what I suggest is an attempt to create docile bodies out of members of society who are deemed unruly, problematic and otherwise 'undesirable'; it is the witch's body that is deemed counternormative. This study demonstrates that it is neighbours and other acquaintances of accused witches that take on the role of the invisible guard of Bantham's Panoptic on. As someone who is trained in the study of English literature and literary theory, my approach is one that is informed by this methodology. It is my specialization in early modem British literature that first exposed me to witch-hunting manuals and tales of the supernatural, and it is for this reason that my research commences with a study of representations of witches and witchcraft in early modem England. From my initial exposure to such materials I proceed to examine the similarities and the differences of the cultural significance of the supernatural vis-a.-vis women's activities in early modem Italy. The subsequent discussion of visual representations of witches involves a predominance of Germanic artists, as the seminal work on the discernment of witches and the application of punishment known as the Malleus Meleficarum, was written in Germany circa 1486. Textual accounts of witch trials such as: "A Pitiless Mother (1616)," "The Wonderful Discovery of the Witchcrafts of Margaret and Philippa Flower (1619)," "Magic and Poison: The Trial ofChiaretta and Fedele (circa 1550)", and the "The Case of Benvegnuda Pincinella: Medicine Woman or Witch (1518),"and witchhunting manuals such as the Malleus Melejicarum and Strix will be put in direct dialogue with visual representations of witches in light of historical discourses pertaining to gender performance and gendered expectations. Issues relating to class will be examined as they pertain to the material conditions of presumed witches. The dominant group in any temporal or geographic location possesses the tools of representation. Therefore, it is not surprising that the physical characteristics, sexual habits and social material conditions that are attributed to suspected witches are attributes that can be deemed deviant by the ruling class. The research will juxtapose the social material conditions of suspected witches with the guilt, anxiety, and projection of fear that the dominant groups experienced in light of the changing economic landscape of the Renaissance. The shift from feudalism to primitive accumulation, and capitalism saw a rise in people living in poverty and therefore an increased dependence upon the good will of others. I will discuss the social material conditions of accused witches as informed by what Robyn Wiegman terms a "minoritizing discourse" (210). People of higher economic standing often blamed their social, medical, and/or economic difficulties on the less fortunate, resulting in accusations of witchcraft.

Short-term Response of Breeding Barred Owls to Forestry in a Boreal Mixedwood Forest Landscape

Forestry and other activities are increasing in the boreal mixedwood of Alberta, with a concomitant decrease in older forest. The Barred Owl (Strix varia) is an old-growth indicator species in some jurisdictions in North America. Hence, we radio-tagged Barred Owls in boreal mixedwood in Alberta to determine whether harvesting influenced habitat selection. We used three spatial scales: nest sites, i.e., nest tree and adjacent area of 11.7 m radius around nests, nesting territory of 1000 m radius around nests, and home range locations within 2000 m radius of the home range center. Barred Owls nested primarily in balsam poplar (Populus balsamifera) snags > 34 cm dbh and nest trees were surrounded by large, > 34 cm dbh, balsam poplar trees and snags. Nesting territories contained a variety of habitats including young < 80-yr-old, deciduous-dominated stands, old deciduous and coniferous-dominated stands, treed bogs, and recent clear-cuts. However, when compared to available habitat in the study area, they were more likely to contain old conifer-dominated stands and recent cutblocks. We assumed this is because all of the recent harvest occurred in old stands, habitat preferred by the owls. When compared with random sites, locations used for foraging and roosting at the home range scale were more likely to be in young deciduous-dominated stands, old conifer-dominated stands and cutblocks > 30 yr old, and less likely to occur in old deciduous-dominated stands and recent cutblocks. Hence, although recent clearcuts occurred in territories, birds avoided these microhabitats during foraging. To meet the breeding requirements of Barred Owls in managed forests, 10–20 ha patches of old deciduous and mixedwood forest containing large Populus snags or trees should be maintained. In our study area, nest trees had a minimum dbh of 34 cm. Although cut areas were incorporated into home ranges, the amount logged was low, i.e., 7%, in our area. Hence more research is required to determine harvest levels tolerated by owls over the long term.