Using DNA metabarcoding to explore spatial variation in diet across European Hawfinch populations

The investigation of diet in avian species is essential to an understanding of their ecology and local adaptations, as well as long-term conservation. This can be particularly challenging due to the wide distribution and high ecological plasticity of many bird species. Dietary richness and variation are under-studied in woodland bird species, due primarily to challenges in accurately identifying plant and invertebrate taxa consumed. Within Europe, Hawfinch (Coccothraustes coccothraustes) have shown variation in population trends, with moderate declines across central and eastern Europe, while western European populations have shown moderate increases. Ecological drivers behind this differing trend are still unknown; one possibility is differences in diet, yet little research has been conducted into Hawfinch diet in mainland Europe or elsewhere. This study aimed to present the first molecular dietary analysis of Hawfinch populations across two European countries. Faecal samples were collected between January and July of 2019 from Hawfinch caught at six artificial feed sites: two in Denmark and four in Germany. DNA was successfully extracted from 80 samples and plant Internal Transcribed Spacer 2 (ITS2) and invertebrate Cytochrome Oxidase Subunit 1 (COI) barcodes were amplified. A total of 35 plant and 37 invertebrate taxa were found across the 80 Hawfinch faecal samples, with plant and insect orders Fagales and Lepidoptera respectively the most frequently detected. Hawfinch dietary composition differed significantly between European countries, suggesting Hawfinch can make use of available food resources which are likely to differ spatially. Our study shows how DNA metabarcoding can be used to provide novel ecological information associated with under-studied bird species, thus providing essential information for future management and conservation of Hawfinch and their habitats.Files containing raw Illumina sequencing data regarding Hawfinch diet described in Stenhouse et al. 2023.Funding provided by: Natural Environment Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000270Award Number