International audienceStopover studies have concentrated so far mostly on mechanisms regulating the temporal organisation on the day-to-day level. Taking advantage of the small and isolated island of Helgoland in the North Sea, we investigated the stopover and departure behaviour of a nocturnal migrant by using radio telemetry. Special attention was paid particularly to nocturnal behaviour, their departure times within the night, and departure directions. Here, we show that Northern Wheatears, , performed regularly nocturnal exploratory flights on nights before and on departure night, which might be a common behaviour of nocturnal migrants to evaluate meteorological conditions aloft prior to departure. We proposed that migrants being prepared for an endurance flight would depart early in the night within a short time window, whereas individuals departing with low fuel load would be less prone to take off early. Our data, however, could not support this hypothesis. In respect of the migratory direction, there was a significant correlation between departure direction and departure fuel load. Northern Wheatears with high departure fuel loads headed more towards the north than lean migrants, which departed mostly towards the nearest coastline, i.e. east to south. Thus, birds with high fuel loads showed their seasonally appropriate migratory direction irrespective of the ecological barrier ahead, whereas lean birds avoided this direction. To our knowledge, this is the first study that investigates the relationship of fuel load and departure direction in a free-flying songbird
Species conservation and forage production are both important, yet conflicting components of sustainable grassland management. We modeled forage production and conservation value as dependents in a chain of responses and effects, starting with abiotic environmental conditions that affect the spatial distribution of land uses and biotic ecosystem properties. We asked which relationships in this causal chain determine trade-offs between forage production and conservation value. Abiotic and biotic ecosystem properties were recorded on 46 plots in the coastal marshes of Northwest Germany. Plant and bird conservation values were calculated using Red Lists, and sales of forage-based agricultural products were assessed by interviewing farmers. We used a structural equation model to determine responses and effects. Groundwater depth and salinity represent the ultimate causes for the spatial variation in sales and conservation value. The water gradient translated into more proximate causes, such as land-use intensity affecting aboveground net primary productivity, forage quality, and species richness. Plant species conservation and forage production were segregated along the water gradient, and both bird conservation and forage production depended on grassland management, albeit at different fertilization levels. Our study points to segregation and integration as two spatial strategies to react to trade-offs between services.ARTICLE HISTORY
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.