Agricultural landscape composition as a driver of farmland bird diversity in America
In agriculture-dominated landscapes, agricultural
intensification and associated landscape homogenization have caused large
declines in farmland biodiversity. This study was aimed at determining how
agricultural landscape composition drives community diversity and composition
of farmland birds in the characteristic bocage landscape in Brittany (NW
France) on a broad scale. Using bird atlas data from the region (2004–2008; 10
× 10 km), we analyzed the importance of different components of agricultural
landscape composition (types of crops, amount of semi-natural covers and
elements, and artificial lands) on the alpha diversity and beta diversity of
farmland birds of different functional groups, defined depending on the degree
of farmland specialization and ecological requirements.
Agricultural landscape composition features
explained a small amount of variation in alpha and beta diversity, particularly
for specialists and residents. Cereal crops were negatively correlated with
alpha diversity of all the functional groups considered whereas rotational
grasslands were negatively associated with migrant and insectivorous alpha
diversity. Although shrublands are not common in Brittany, they were positively
associated with the occurrence of some species and particularly with alpha
diversity of all the functional groups but specialists and residents. At the
spatial grain of analysis, community composition was mainly driven by a
gradient of alteration of the bocage.
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