Effective conservation plans and design of Special Protection Areas (SPAs) for protected species should take into account ranging behaviour and foraging habitats, and this is particularly important for wide-ranging species. Montagu's harriers Circus pygargus are ground-nesting semi-colonial raptors typical of agricultural habitats. We studied the foraging behaviour of 14 radio-tracked male Montagu's harriers, in order to investigate the distance from nests of foraging birds, the extent to which foraging range overlapped with SPAs designated for this species, and foraging habitat selection within foraging ranges. Average foraging range size, estimated from either minimum convex polygon or kernel 90%, was larger than 100 km2. Only 19 ± 11% of the foraging ranges were within SPA limits. Cereal (the main habitat used for nesting) was slightly counterselected for foraging, and most prey (64%, n=117) captured in that habitat were insects. Hunting attempts occurred significantly more frequently than expected in alfalfa, where most prey captured were small mammals (70%, n=102). Use of this habitat for foraging increased throughout the season. Most prey captured in other habitats (mainly tree crops, shrubs or uncultivated land) were birds (83%, n=43). SPAs included a higher proportion of cereal, but a lower proportion of alfalfa than areas outside SPAs. Overall, our results show that breeding Montagu's harriers use an area for foraging much larger than current sizes of most SPAs for the species, that habitats selected for foraging differ from those used for nesting and that preferred foraging habitats were less common inside SPAs than outside. Conservation management for this species should aim to protect foraging habitats within a large radius of the colonies, probably requiring measures to be applied outside protected areas. More generally, SPAs designed without including information of ranging behaviour and foraging habitats may be ineffective.