This document with ZENODO URL https://doi.org/ 10.5281/zenodo.6982812 was prepared as supplementary information to the following article to appear in Dutch Birding: Siberische Noordelijke Klapekster bij Nuenen in november 1909; written by Justin J F J Jansen, Pepijn Kamminga, Martin Brandsma, Reuven Yosef & Peter de Knijff. Summary On 25 November 1909, a grey shrike Lanius was purchased by Rijksmuseum voor Natuurlijke Historie (now Naturalis Biodiversity Center) at Leiden, Zuid-Holland, Netherlands (skin RMNH.AVES1663). The bird, a first-winter female, was collected at Nuenen, Noord-Brabant, Netherlands. It was at the time identified as Great Grey Shrike L excubitor. The bird was recently re-identified as a Northern Shrike L borealis (L b borealis or L b sibericus). Here we describe all relevant technical aspects of the DNA-study that was performed in order to support this identification. For this we used a toe pad sample. We obtained a mitochondrial Cytochrome B fragment of 893 bp. which gave a 100% match with L b sibericus. This was the first record for the Netherlands, and chronologically the second for Europe.