The potential of White Stork Ciconia ciconia nest lining to evaluate the functional diversity of coleopteran fauna – a case study of a novel non-invasive method of bioindicative evaluation across a land-use intensity gradient

Collecting arthropod samples is usually very invasive because these organisms die during sampling, and it is hard to obtain a statistically robust sample. The availability of arthropods is critical for the survival of the youngest White Stork Ciconia ciconia nestlings conditioning the productivity of their populations; thus, the species is a strong predator of a variety of epigeic insects. At the time of the dietary shift and progressive drying of climatic conditions due to climate change or/and in dry habitats replacing wetlands, the role of such termophilic taxa as certain Coleoptera is often underestimated. Here, we evaluated the coleopteran component of the diet of the White Stork using the nest lining material, i.e. fragmented remains of regurgitated pellets, and related the community indices of Coleopteran fauna to the landscape structure within a radius of 2.5 km around nests. In eight nests in SE Poland, we found a massive accumulation of beetle remains representing 32 277 individual Coleopteran prey items, from which 17 252 were identified to the family level. Our analysis showed a significant relationship between the landscape structure and beetle communities, as well as the abundance of dominant prey taxa and share of three major functional guilds (herbivores, scavengers, and predators). The three most abundant prey taxa were large bodied epigeic taxa representing three families: carabidae, silphidae, and scarabidae, whose contribution increased with the share of tree cover and decreased with the share of arable land. The contribution of herbivorous and predatory beetles increased with the share of arable land. We have evidenced that the analysis of nest lining material provides a taxonomically informative data on beetle communities and can be a valuable tool in biondicative assessments of Coleopteran biodiversity. Given the widespread nesting of White Stork near landfills (increasing the productivity of their local populations), further studies assessing the role of the Coleopteran component, particularly the contribution of necrophagous or saprophagous beetles, in the diet of early nestlings of this bird species are essential.