Year-round relevance of manure heaps and its conservation potential for declining farmland birds in agricultural landscape

Abstract

Agricultural intensification has resulted in the homogenization of landscape structure and a massive loss of farmland biodiversity. Despite various conservation attempts, farmland bird populations are continuously declining leading to local extinctions and range contractions of many species. These declines are tightly connected with decreased abundance and availability of crucial food resources within farmland, resulting in reduced reproductive success during breeding and low survival during winters of farmland bird species. Therefore, identification of high‐quality foraging habitats in farmland and its seasonal changes could be useful for farmland bird conservation. In this study, we investigated the year-round importance of manure heaps for birds in intensively-used agricultural landscapes. We compared species richness and abundance of birds on manure heaps and adjacent farmland during breeding, post-breeding and wintering seasons. Furthermore, we compared abundance and species richness between permanent and temporal manure sites. We found that abundance and species richness of all birds, farmland specialists and red-listed species were higher at manure sites than at control sites within adjacent farmland in all seasons. The differences in abundances and species richness between manure heaps and control sites were larger in winter, except for species richness of farmland specialist for which this difference was largest in spring. Additionally, we found that permanent manure sites had higher abundances and species richness of all birds and farmland specialists in autumn than temporary manure sites. In spite of the negative impact of manure facilities to surrounding environment, this study brings first comprehensive evidence of year-round importance of manure heap stands for bird communities, including species with conservation concern and thus uncovers its hidden potential for farmland bird conservation in agricultural landscapes.