Interspecific and intraspecific differences in habitat use and their conservation implications for Palaearctic harriers on Sahelian wintering grounds

The floodplains of the West-African Sahel region have experienced extensive habitat transformation during the past four decades, coinciding with an impoverishment of raptor populations. We investigated foraging patterns of Palaearctic migratory Eurasian Marsh Harriers Circus aeruginosus, Pallid Harriers C.macrourus and Montagus Harriers C.pygargus on a floodplain system in northern Cameroon to assess species, sex- and age-related habitat preferences. Sex and age have rarely been incorporated into general studies of raptor habitat associations, despite clear evidence of intrasexual and age-related differences in foraging strategies and diet composition, potentially carrying strong conservation implications. We found evidence of sexual differences in foraging preference related to land use, particularly in the most sexually dimorphic Pallid Harrier, and evidence that juveniles used different habitats to adults. This constitutes the first quantitative documentation of such differentiation by Palaearctic raptors on African wintering grounds, indicating that general patterns of habitat use in wintering raptors may obscure sex- and age-specific preferences. Contrary to expectations, we found limited evidence for interspecific foraging segregation. Food partitioning by prey mass was related to harrier body mass and facilitated by a diverse availability of prey on human-transformed floodplains. Anticipated further large-scale conversion of floodplain habitat into predominantly desiccated grasslands raises concerns about the survival of wintering harriers.