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.