Foraging habitat selection by the Eastern Marsh Harriers Circus spilonotus breeding in agricultural landscape

Abstract

We studied the habitat selection of foraging Eastern Marsh Harrier Circus spilonotus breeding in an agricultural landscape. Hunting flights of harriers were surveyed around nesting sites in the Hachiro-gata reclaimed area of Akita Prefecture, Japan. The habitat types at locations where harriers attempted to capture prey were recorded. For comparison, random points were selected from an area where harriers were seen to fly. The relationship between habitat use and habitat type was analyzed using a Generalized Linear Model. Our results indicate that pastures, wheat fields, and grasslands along major irrigation canals and minor drainage canals were selected significantly as foraging habitat by harriers. These habitat types had relatively high abundances of either voles or frogs, and had maximum vegetation height (median of four surveys) of about 1 m or less, which was shorter than in nearby reed beds of intermediate height. Despite their abundance near nesting sites, rice fields, with a low abundance of voles, frogs, and birds, were rarely used by foraging harriers. These results indicate that grasslands with suitable vegetation structure (including crops) and supporting high prey abundance are important foraging habitats for harriers.