Spatial behaviour and food choice of the Garden Warbler Sylvia borin during the non-breeding season

Abstract

Information regarding the spatial behaviour of migratory bird species on their wintering ground is important in understanding the factors that can influence breeding success and population size. The Garden Warbler Sylvia borin is a migratory species that has been well studied in West Africa. However, information regarding its spatial behaviour during the non-breeding season in sub-Saharan Africa is still limited. Consequently, we investigated the 50% and 95% kernel density home-range size and overlap as well as food choice of 10 radio-tracked Garden Warblers at Amurum, central Nigeria and Obudu, south-eastern Nigeria. Home-range overlap was estimated using the kernelUD function within the package adehabitat in R. The mean home-range was 7.0 ha and 3.3 ha at Amurum and Obudu, respectively, whereas the core of the home-range was on average 1.5 ha and 0.7 ha, respectively. Mean home-ranges were larger than the average territory of individuals on the temperate breeding grounds. Home-range overlap ranged between 19% and 57% at Amurum and 39% and 71% at Obudu, suggesting that Garden Warblers are not territorial during the non-breeding season in Nigeria. The diet of the Garden Warblers at both sites comprised of berries and insects and several individuals were often observed foraging together.