Marsh Harrier Circus aeruginosus diet and hunting habitat selection in the breeding season: implications for lowland breeding waders

Abstract

ABSTRACT Capsule A temporal mismatch between peak Marsh Harrier hunting activity and wader chick availability means that in most years waders contribute a negligible component of Marsh Harrier breeding season diet when nesting adjacent to lowland grassland, despite a spatial overlap in their habitat use. Aims To examine the potential for conservation conflict with breeding waders by assessing spatio-temporal patterns in Marsh Harrier hunting activity and examining historical and recent data on Marsh Harrier breeding season diet. Methods We monitored Marsh Harrier hunting behaviour in relation to time-in-season and habitat characteristics, and examined nest hatching records of Marsh Harrier and wader nests (Northern Lapwing Vanellus vanellus, Common Redshank Tringa totanus, Black-tailed Godwit Limosa limosa) for evidence of temporal overlap between hunting peaks and predicted wader chick availability. We also recorded prey provisioning to Marsh Harrier broods using nest cameras (2013–2015) and combined this with Marsh Harrier diet studies across Europe from 1942 to 2016. Results Wader adults and chicks contributed only a small proportion (average 1.5%) to the diet of Marsh Harriers nesting adjacent to breeding wader habitats between 1942 and 2016. This was likely due to a temporal mismatch in the peak of harrier hunting and the predicted availability of wader chicks in most years, despite a spatial overlap in habitat use between wader chick-rearing and Marsh Harrier hunting. Conclusion Conservation conflict between breeding Marsh Harriers and waders on lowland grassland is likely to be minimal in most years, with little evidence of waders as harrier prey items. However, harrier hunting activity increases through the breeding season, driven by the timing of their nesting and chick-rearing, and hunting activity was highest over field centres, where waders breed, so later-nesting wader pairs are still at risk. Wader conservation strategies that encourage survival of early wader nests may therefore limit predation and conservation conflict with Marsh Harriers.