Field margins as substitute habitat for the conservation of birds in agricultural wetlands

Abstract

AbstractBreeding birds in agricultural landscapes have declined considerably since the 1950s and the beginning of agricultural intensification in Europe. Given the increasing pressure on agricultural land, it is necessary to identify conservation measures that consume little productive land. We tested the hypothesis that field margins represent substitute habitats for bird species in agricultural wetlands. We monitored bird species in 86 crop fields in rice paddy landscapes of Camargue (southern France), a wetland of international importance for birds. We investigated whether the area of three types of field margins (grass strips, hedgerows and reed strips) within a 500 m buffer around each studied crop field had an effect on the abundance of three groups of birds defined based on their primary habitat (reedbeds, grasslands, and forest edge species). We controlled for the area of each semi-natural habitat (wetlands, grasslands, and woodlands), crop diversity and mean crop field size. Our study confirms that bird guilds are favored by the cover of their primary habitat but are also influenced by the cover of field margins. Reedbed birds are favored by the cover of wetlands and reed strips, grassland birds are favored by the cover of grasslands and wetlands and negatively impacted by the cover of woodlands and hedgerows, while forest edge birds are favored by the cover of hedgerows and negatively impacted by the cover of reed strips. These results suggest that field margins may represent substitute habitats for reedbed and forest edge bird species and highlight their importance for biodiversity conservation in wetland agricultural landscapes. However, our results also suggest that increasing the area of hedgerows and reed strips may have a negative effect on grassland birds and forest edge birds, respectively. Recommendations for field margin management in agricultural wetlands should therefore be tailored to local conservation priorities.