The Diet of Nestling Abdim's Stork Ciconia abdimii in Niger

Abstract

Although the Abdim's Stork (Ciconia abdimii) is a common breeder in the Sahel zone across Africa, its diet during the breeding season has never been studied. Chick meals were sampled in stork nests in West and Central Niger during early July and late August, representing early and mid rainy seasons in the area. The diet consisted of amphibians (Bufo sp.) and a range of insects with grasshoppers (Orthoptera) as the dominant (23 species) group making up 30% and 59% of prey biomass in July and August, respectively. In terms of frequency of occurrence, the important Sahelian pest species Oedaleus senegalensis was the most common grasshopper in the stork chick diet. There was a marked seasonal difference in the relative importance of insects and vertebrates: in July amphibians made up 61% of diet by wet weight, and insects 38%, while in August insects made up 92% of prey wet weight, and amphibians only 6%. The high dependency on amphibians in July was a surprise, but suggests that toads may be the key prey for the adult storks during the incubation period when toads become active while major new insect generations have not yet emerged. The increased importance of insects later in the rainy season reflects the emergence of new generations of grasshoppers, where, in particular, the locally (too) abundant Oedaleus senegalensis becomes the main prey.