Habitat selection and reproduction of red-backed shrikes (Lanius collurio) in relation to abundance of potential avian nest predators

Many studies of farmland bird species have related abundance of species to different habitat variables, whereas few studies have incorporated the effects of predation on habitat selection. However, it is generally assumed that prey species select habitat with low risk of predation, but the consequences for prey population growth of this avoidance behaviour remain largely unknown. During seven years, I studied habitat selection and reproduction of red-backed shrikes (Lanius collurio), a passerine bird inhabiting shrub-rich grasslands, in relation to abundance of potential avian nest predators (i.e. corvids). Results from several experiments with artificial nests designed to mimic redbacked shrike nests suggest that magpies (Pica pica) are the most frequent nest predators on artificial nests. To a lesser extent also hooded crows (Corvus corone cornix) and jays (Garrulus glandarius) depredated artificial nests. The results from the artificial nest experiments were validated through the patterns of predation of real red-backed shrike nests, as these were depredated at faster rates close to nests of magpies and hooded crows than elsewhere in the landscape. Furthermore, red-backed shrikes avoided to breed in grasslands located close to magpie and hooded crow nests. In addition, at the landscape scale, between-year changes in the spatial distribution of breeding magpies and hooded crows were followed by inverse changes in the distribution of red-backed shrikes. For example, when the distance to closest magpie nest decreased, or when the number of magpie nests within 1 km2 increased, red-backed shrikes avoided to breed in that area, despite a high abundance of suitable grasslands with a history of breeding red-backed shrikes. The behaviour of avoiding corvids was adaptive, as red-backed shrikes breeding far away from magpies and hooded crows experienced lower risk of nest predation than pairs breeding close to these corvids. My results partly contradict results of other studies, which have suggested that nest predators may not influence breeding habitat selection of farmland birds. Nevertheless, my results suggest that interspecific interactions such as nest predation may force individual birds to breed in habitats of lower quality. It is therefore possible that the observed population increases of many generalist predator species (e.g. corvids) may have contributed to the decline of farmland birds both in a direct way (i.e. low breeding success) and in an indirect way (i.e. successful nests produce fledglings of lower quality). Further studies on other populations and species are needed before the finer details of how nest predation may regulate populations of farmland birds may be fully understood.Viele Untersuchungen zu Brutvogelarten in der Agrarlandschaft setzen die Abundanzen einzelner Arten in Beziehung zu bestimmten Eigenschaften (Parametern) der Landschaft. Nur wenige Studien berücksichtigen interspezifische Wechselwirkungen, wie etwa den Einfluss von Prädatoren auf die Habitatwahl. Im Allgemeinen wird angenommen, dass Beutetierarten ein Habitat mit geringem Prädationsrisiko bevorzugen, wobei allerdings die populationsbiologischen Konsequenzen für Beutetiere mit einem solchen Meidungsverhalten weitgehend unbekannt sind. Die Habitatwahl und Reproduktion des Neuntöters (Lanius collurio), eines in buschreichem Grünland lebenden Singvogels (Passeriformes), wurde über 7 Jahre hinweg untersucht. Dabei standen Einflüsse von potentiellen Gelegeräubern, insbesondere Corviden, im Mittelpunkt der Untersuchung. Verschiedene Experimente mit künstlichen „Neuntöternestern“ ergaben, dass hauptsächlich Elstern (Pica pica) als Gelegeprädatoren auftreten. Daneben konnten aber auch mit geringerer Intensität Nebelkrähen (Corvus corone cornix) und Eichelhäher (Garrulus glandarius) als Nesträuber nachgewiesen werden. Die Ergebnisse der Experimente mit Kunstnestern bestätigten sich im Freiland dahingehend, dass Neuntöter bei der Brutplatzwahl die Nähe von Elstern und Nebelkrähen mieden. Darüber hinaus fand sich über die Jahre eine gegenläufige Beziehung zwischen den räumlichen Verteilungsmustern des Neuntöters und denen brütender Elstern und Nebelkrähen. Nahm etwa die Distanz zur nächsten brütenden Elster von einem zum nächsten Jahr hin ab, oder stieg die Brutdichte der Elster im Umkreis von einem km2 an, so wurden selbst gut geeignete, traditionelle Bruthabitate verlassen. Dieses Meidungsverhalten gegenüber Rabenvögeln hat einen hohen adaptiven Wert: Neuntöter, die in größerer Entfernung zu besetzten Elstern- und Rabenkrähennestern brüten, tragen ein geringeres Prädationsrisiko als in Nachbarschaft brütende Individuen. Die vorliegenden Ergebnisse widersprechen teilweise anderen Studien, wonach die Habitatwahl von Vogelarten der Kulturlandschaft nicht von Prädatoren beeinflusst wird. Darüber hinaus legen die Ergebnisse der vorliegenden Arbeit nahe, dass interspezifische Interaktionen (z.B. Risiko der Gelegeprädation) Individuen durchaus dazu veranlassen können, in Bruthabitate minderer Qualität zu wechseln. Es ist daher möglich, dass die festgestellten Populationszunahmen bei zahlreichen generalistischen Prädatoren (z. B. Corviden) sowohl direkt (z.B. geringerer Bruterfolg durch Prädation) als auch indirekt (z.B. Produktion von Küken geringerer Qualität in suboptimalen Habitaten) zur Abnahme von Vogelarten der Agrarlandschaft beitragen. Allerdings sind hier weitere detaillierte Studien an anderen Populationen und Arten der Agrarlandschaft notwendig um genauere Angaben zu einer möglichen Populationsregulation durch Nestprädatoren machen zu können

Stock Market Participation, Portfolio Choice and Pensions over the Life-cycle

In this paper we present a calibrated life-cycle model is able to simultaneously match asset allocations and stock market participation profiles over the life-cycle. The inclusion of per period fixed costs and a public pension scheme eradicates the need to assume heterogeneity in preferences, or implausible parameter values, in order to explain observed patterns. We find a per period fixed cost of less than two percent of the permanent component of annual labour income can explain the limited stock marker participation. More generous public pensions are seen to crowd out private savings and significantly reduce the estimates of these fixed costs. This is the first time that concurrent matching of participation and shares has been achieved within the standard preference framework

Association Mapping for Common Bunt Resistance in Wheat

Common bunt, caused by Tilletia caries and T. foetida, is a fungal disease of wheat world wide. Infection, occurring via seed borne teliospores, is generally controlled by the application of seed treatments prior to sowing. Farming systems like organic agriculture with a very limited range of organic seed treatments available rely heavily on common bunt resistance genes within wheat. In the framework of the BIOBREED project an association study in winter wheat was conducted, aiming at the identification of genetic loci linked to resistance towards common bunt in wheat. 152 European wheat cultivars were phenotyped for their resistance reaction for the two consecutive years 2011/12 at Agrologica research station at Mariager. Infection was scored as percent infected ears. The scorings were log-transformed to fit a disease scoring scale ranging from 1 to 9. The association analysis was performed for each year separately as well as for the mean scoring of the two years. The wheat cultivars were genotyped with DArT markers, yielding 1832 polymorphic loci. The association analysis was conducted using the computer program Genstat, with the ASReml module. Minimun allele frequency for the association analysis was set to 0.07. 13 out of the total of1832 marker in our study were linked to common bunt resistance in wheat (-log10(P) >3). These marker are located on 8 out of the 21 wheat chromosomes. Comparisons of these findings with other published results are difficult since only very little is known about the chromosomal location of common bunt resistance genes/QTL in wheat. Chromosome 2B was previously reported to carry gene(s) for common bunt resistance. Findings of our analysis are in accordance with this: 4 of the linked marker resided on this chromosome. Further, another two linked marker were found on chromosome 2D, another chromosome previously reported to carry common bunt resistance genes. Our study shows the possibilities of finding makers linked to common bunt resistance in wheat, and of using these markers for marker assisted selection of wheat cultivars tailored for the needs of organic agriculture

Common bunt resistant wheat composite cross populations

Utilising diverse populations instead of single line varieties is expected to lead to a number of advantages in cereal production. These include reduced epidemics of plant diseases, improved weed competition and better exploitation of soil nutrients, resulting in improved yield stability. However, a number of challenges must be met before diverse wheat populations can be introduced into commercial wheat production: one of these is the development of breeding technologies based on mass selection which enable breeders and farmers to improve specific traits in populations and maintain diversity at the same time. BIOBREED is a project started in Denmark in 2011 to meet these challenges for wheat population breeding. The project is focusing on the development of tools and methods for mass selection of traits relevant for organic and low input production, where it is expected that the highest benefits of utilizing diverse populations can be achieved. BIOBREED focuses on three main aspects of wheat population breeding for organic and low input production systems: i) common bunt (caused by Tilletia caries) resistance, ii) selection for improved protein content and iii) the influence on population diversity of different selection pathways. Selection for common bunt resistance in wheat composite cross populations 33 crosses were made between 23 common bunt resistant winter wheat varieties in order to generate two populations. Progeny of all crosses was bulked in the F 3 to constitute the first population Pop.No.Sel. Prior to the creation of the second population Pop.Sel, the F 3 of the parental crosses was sown as head-rows with common bunt infection. Only lines that showed resistance to common bunt were used to create Pop.Sel. in generation F 4 . Afterwards the two populations were grown with and without inoculation with common bunt in order to i) select for bunt resistance and ii) to be able to compare the effect on diversity of this selection step. Preliminary results show a higher level of common bunt resistance in Pop.Sel in the first year. Single seed sorting for protein content Prior to sowing the F 5 seed of the population Pop.Sel, the seed were sorted individually for protein content using a BoMill IQ Grain Quality Sorter 1002S. The fraction of seeds containing the 10% highest and another fraction containing the 10% lowest protein content were selected. The four populations, Pop.No.Sel, Pop.Sel, and Pop.Sel.high. Protein and Pop.Sel.low.Protein and the parental lines were sown in a randomized complete block yield trial at two locations in Denmark in order to assess their yield and quality parameters such as protein content and baking quality of the parents and there derived populations. Results are expected in the summer 2013. Diversity of wheat composite cross populations. The practical question of “how much diversity is needed in populations?” has not been answered yet. BIOBREED will aim to to quantify the levels of diversity in wheat composite cross populations after the different selection steps i) cultivation with and without common bunt inoculum, and ii) sorting for single protein content. In a fist attempt SSR markers will be used to describe the influence these different selection pathways will have on the population diversity. 90 SSR markers—about two markers per chromosome arm—will be used to describe the initial genetic diversity of the 23 parental lines. F 6 seed of the different populations will be analysed with the same markers and population diversity after different selection pathways will be quantified

Adding £2.3bn of debt to the accounts – social housing deregulation as an early test for the minority Welsh Government

Before the elections to the Welsh Assembly last week, Steffan Evans outlined how housing might be a key policy area around which bridges could be built in the Senedd. With the results now confirmed, we know Labour will need to work with other parties, but what will be the biggest issues facing the First Minister Carwyn Jones when it comes to housing? A major policy test will almost certainly be provided by the new classification of social housing

The Welsh Assembly after the elections: housing policy could be an area upon which to build a coalition

With the Welsh elections now only days away, the race to the National Assembly is entering its closing stages, writes Steffan Evans. With opinion polls continuing to suggest that no one party will gain sufficient votes to hold a majority in the Senedd, attention is sure to turn to potential coalitions after May the 5th

How extending the right to buy in England could change the relationship between the government and housing associations

In this article, Steffan Evans looks at how the extension of Right to Buy in England could alter the relationship between the government, the regulator and Housing Associations in England, and compares the situation in England with the situation in Wales