Quantifying the decline of the Martial Eagle Polemaetus bellicosus in South Africa

Abstract

Human populations in Africa are growing at a faster rate than in any other region; this growth will exert increasing pressures on the continent's wildlife resources and declines in wildlife are already being observed. Species occupying higher trophic levels may be amongst the most useful indicators of this pressure and raptorial birds have already proven to be particularly useful in highlighting problems with their environment. The Martial Eagle is an African endemic which is thought to be declining and was recently uplisted to globally Vulnerable, although data on population trends are almost entirely lacking. The Southern African Bird Atlas Project (SABAP) 1 and 2 are citizen science projects that represent a rare opportunity, within an African context, to quantify population changes over a 20-year period. We use data from these surveys to explore changes in reporting rates for this species in South Africa between SABAP 1 (1987-1992) and SABAP 2 (2007-2012) at the scale of quarter-degree grid cells. Previous research suggests that such comparisons accurately reflect changes in breeding numbers for this species. We found an overall decline in reporting rates of c.60%, with more cells showing loss or declines (75%) than those showing colonisation or increases (25%). No differences in reporting rate change were found between provinces, suggesting a relative uniform decline across the country. There were, however, differences between biomes with declines recorded in all biomes apart from Albany Thicket, Succulent Karoo and Fynbos (south-western biomes). Declines differed inside and outside protected areas, with larger declines outside (64%) than inside (42%) protected areas, although even within large protected areas significant declines were observed. These results support the uplisting of the species' conservation status and suggest that even within protected areas the species is not immune to the drivers of decline.