Diet and foraging habitats of non-breeding white storks (Ciconia ciconia) in Bulgaria

Abstract

The diet of non-breeding White Storks was studied by pellet analysis and included mainly insects (99.9%, n=28947) with a predominance of grasshoppers (Orthoptera, 76.1%), and beetles (Coleoptera, 26.1%). The bush crickets Decticus albifrons/verrucivorus were the most numerous prey (29.9% by items), occurring in almost all pellets (98% occurrence in pellets, n=147) and predominating in half of them (49.7%). The grasshopper associations in the pellets specify foraging mainly in mesophytic grasslands that usually replace abandoned fields and overgrown pastures with a low level of grazing. The xerophytic grass-shrubby habitats, not rare on stony terrains, were of less importance, providing around 20% by prey. The typical aquatic inhabitants and the use of carrion around villages were exceptions in the study diet. The number of innutritious materials in the pellets rose when the White Storks hunted on nippy and agile grasshoppers and decreased when the main pray was slower beetles taken from the ground. The roosting of non-breeding White Storks disappeared when their preferred feeding habitats were ploughed up in the following years.