No abstract

Divergent selection and local adaptation are responsible for many phenotypic differences between populations, potentially leading to speciation through the evolution of reproductive barriers. Here we evaluated the morphometric divergence among west European populations of Reed Bunting in order to determine the extent of local adaptation relative to two important selection pressures often associated with speciation in birds: migration and diet. We show that, as expected by theory, migratory E. s. schoeniclus had longer and more pointed wings and a slightly smaller body mass than the resident subspecies, with the exception of E. s. lusitanica, which despite having rounder wings was the smallest of all subspecies. Tail length, however, did not vary according to the expectation (shorter tails in migrants) probably because it is strongly correlated with wing length and might take longer to evolve. E. s. witherbyi, which feed on insects hiding inside reed stems during the winter, had a very thick, stubby bill. In contrast, northern populations, which feed on seeds, had thinner bills. Despite being much smaller, the southern E. s. lusitanica had a significantly thicker, longer bill than migratory E. s. schoeniclus, whereas birds from the UK population had significantly shorter, thinner bills. Geometric morphometric analyses revealed that the southern subspecies have a more convex culmen than E. s. schoeniclus, and E. s. lusitanica differs from the nominate subspecies in bill shape to a greater extent than in linear bill measurements, especially in males. Birds with a more convex culmen are thought to exert a greater strength at the bill tip, which is in agreement with their feeding technique. Overall, the three subspecies occurring in Western Europe differ in a variety of traits following the patterns predicted from their migratory and foraging behaviours, strongly suggesting that these birds have became locally adapted through natural selection.

The spatial management of fisheries has been repeatedly proposed as a discard mitigation measure. A number of studies have assessed the fishing suitability of an area based on units of by-catch or discard per unit effort. However, correct identification of fishing-suitable areas should assess biomass loss with respect to the benefits. This study therefore, proposes the analysis of by-catch ratios, which do represent benefit vs. loss and are standardized to a wide range of effort characteristics. Furthermore, our study proposes the use of two ratios: the proportion of total unwanted biomass out of the total catch as an indicator of the overall ecological impact, and the proportion of unwanted but regulated species biomass as a proxy for the economic impact on fishers resulting from the new European discard ban that prohibits the discard of regulated species. These discard ratios are modelled by means of a Bayesian hierarchical model, specifically, a spatio-temporal beta regression model, which has several advantages over the traditional arcsine transformation. Results confirm the standardizing capacity of by-catch ratios across vessels and identify at least two economically fishing-suitable areas where discards ratios are minimized by reducing unwanted catch.

22Reed bunting (Emberiza schoeniclus) subspecies vary considerably in bill size and shape and 23 seem to be at an early stage of speciation, in which bill might be indirectly causing 24 reproductive isolation. Hence, we evaluated whether bill size, as well as age and sex, are 25 associated with foraging niche in three West European subspecies of reed bunting: the thin-26 billed schoeniclus, the intermediate-billed lusitanica and the thick-billed witherbyi. Blood 27 sampling was undertaken at three sites in southwest Europe during the winter (when these 28 subspecies co-occur), and stable isotope analyses (carbon and nitrogen) were performed to 29 assess their foraging niches. Stable isotope analyses of potential food items confirmed 30 uniform baseline isotopic composition among sites. E. s. schoeniclus showed a significantly 31 broader isotopic niche than lusitanica and witherbyi, which seemed otherwise similar despite 32 the fact that witherbyi is more divergent in bill traits. Stable isotope ratios were consistent 33 with the latter two subspecies feeding on C3-plant-feeding insects, whereas schoeniclus diet 34 also included C4 plant material. Despite its lower sexual dimorphism, sex and age differences 35 were found only in schoeniclus, but these differences vary between locations in a complex 36 manner. Our results suggest that bill size and shape differentiated between northern, 37 migratory and southern, resident subspecies as a consequence of natural selection through 38 competition during the winter, which is now reflected in isotopic niche divergence between 39 subspecies. The potential roles of sexual selection, reed thickness and summer temperature on 40 the difference in bill size (and greater sexual dimorphism) between lusitanica and witherbyi 41 are discussed. 42 3

Analysis of an extensive European dataset confirms the large decline of widespread farmland birds across Europe. Common farmland birds have on average fallen in number by nearly half -the most severe decline of the bird groups considered. Among the 36 species that were classified as characteristic of farmland, 20 have declined, seven have increased, four have remained stable and trends of five were classified as uncertain. In parallel with the index of abundance, we show for the first time that an overall index of biomass of farmland birds in Europe has more than halved during the last 27 years. Differences between trends of farmland birds in four European regions are not significant, but trends in New EU Member States have been less negative than those in Old EU Member States. Long-distance migrants among the farmland birds have less negative trends than those that are short-distance migrants or residents in Europe. A wide range of studies suggest that changes in land and crop management have been the main cause of farmland bird declines, although population declines in arable landscapes of south and central-eastern Europe may be linked to land abandonment and afforestation. In contrast, populations of all common species taken together, or common forest species from within that group, have declined modestly over the last 27 years. Similarly, overall biomass of these two groups has declined slightly, although biomass of both has inceased over the last 5 years. The pattern of changes in bird abundance and biomass detected in European farmland birds suggests a considerable loss of European biodiversity and a likely loss of ecosystem function and services.