No abstract

Agricultural intensification and land‐use changes are major factors impacting farmland biodiversity. The Ortolan Bunting Emberiza hortulana is the long‐distance trans‐Saharan migratory passerine that has undergone the most dramatic decline among all European farmland birds. The factors responsible for this decline may originate from the breeding grounds, migration stopovers and/or overwintering quarters. Very little is known about conditions on the species' wintering grounds, but a recent study has highlighted the utmost importance of the traditionally managed agroecosystems in the Ethiopian Highlands as a key wintering area, apparently harbouring as much as 90% of the world's Ortolan Bunting population. Using radiotracking and line transect surveys, this study aimed to provide fine‐grained information about species–habitat relationships in the Ortolan Bunting overwintering quarters. Our results showed the importance, at the landscape scale, of small‐scale agriculture, notably of traditionally managed, cereal‐dominated fields interspersed with semi‐natural structures. At a foraging‐site scale, on the other hand, patches of bare ground in combination with large areas of post‐harvesting stubble represented key habitat features. Stubbles provide an essential food resource and bare ground promotes ground foraging by enhancing food accessibility. The maintenance of a traditional agricultural economy will be essential to maintain the habitat potential for the Ortolan Buntings overwintering in the Ethiopian Highlands and will be instrumental in preserving its world population from further decline.

1. The intensification of farming practices exerts detrimental effects on biodiversity. Most research has focused on declines in species richness at local scales (alpha-diversity) although species loss is exacerbated by biotic homogenization that operates at larger scales (i.e. affecting beta-diversity). The majority of studies have been conducted in temperate, industrialized countries while tropical areas remain poorly studied. Agricultural landscapes of sub-Saharan Africa are still largely dominated by small-scale subsistence farming, but strenuous efforts to intensify farming practices are currently spreading to meet a growing food demand. It is therefore crucial to understand how these intensified practices affect biodiversity to mitigate their negative impacts.2. We investigated how farming system (small-vs. large-scale farming) and landscape complexity (semi-natural vegetation cover) drive bird species composition, community turnover and beta-diversity patterns in Ethiopian Highlands' agroecosystems. We evaluated the following hypotheses: (1) large-scale farming homogenizes bird communities, (2) community turnover is higher in smallscale farms, (3) interactive effects between landscape complexity and farming systems shape avian communities and (4) heterogeneity of field sizes increases community turnover at larger scales.3. Bird communities underwent greater compositional changes along the landscape complexity than along the agricultural intensity gradient. Contrary to our expectations, beta-diversity was not significantly lower within large-scale farms (no biotic homogenization), and complex landscapes that still offer a high amount of semi-natural vegetation promoted community turnover in both farming systems.4. Semi-natural vegetation cover mediated how avian communities responded to agricultural intensification: the compositional differences between small-and

Although avian haemosporidian parasites are widely used as model organisms to study fundamental questions in evolutionary and behavorial ecology of host-parasite interactions, some of their basic characteristics, such as seasonal variations in within-host density, are still mostly unknown. In addition, their interplay with host reproductive success in the wild seems to depend on the interaction of many factors, starting with host and parasite species and the temporal scale under study. Here, we monitored the intensities of infection by two haemosporidian parasites (i.e. Plasmodium relictum and P. homonucleophilum) in two wild populations of great tits (Parus major) in Switzerland over three years, to characterize their dynamics. We also collected data on birds reproductive output (i.e. laying date, clutch size, fledging success) to determine whether they were associated with infection intensity before (winter), during (spring) and after (autumn) breeding season. Both parasite species dramatically increased their within-host density in spring, in a way that was correlated to their parasitaemia in winter. Infection intensity before and during breeding season did not explain reproductive success. However, the birds which fledged the more chicks had higher parasite burdens in autumn, which were not associated with their parasite burden in previous spring. Our results tend to indicate that high haemosporidian parasite loads do not impair reproduction in great tits, but high resource allocation into reproduction can leave birds less able to maintain low parasitaemia over the following months.