The identity of a “grasshopper warbler”, discovered on October 4, 2016 at the Maasvlakte, Rotterdam, The Netherlands, was established by means of sequencing DNA that was isolated from a single small fecal sample collected in the field. Based on the sequence of short fragments of the mitochondrial cytochrome B (cytB) gene and three autosomal gene fragments, lactate dehydrogenase (LDH), myoglobine (MYO) and ornithine decarboxylase (ODC), the identification as a “pure” Lanceolatad warbler Locustella lanceolata was confirmed. This document describes all technical details and provides the connections between GenBank numbers, FLDO-sample codes, sequence haplotypes and sampling information