Arthropod taxa in faeces of chicks of Black-tailed Godwits and Northern Lapwings in Germany and the Netherlands revealed by DNA metabarcoding

Meadow-bird chicks are dependent on arthropods, many of which are undergoing serious declines. For many insectivorous bird species it is currently unknown which arthropod taxa are included in their diet and contribute to chick growth and survival. As prey taxa consumed by chicks are difficult to determine through visual observations, we used DNA metabarcoding to identify arthropod species in faecal samples of Black-tailed Godwit Limosa limosa limosa and Northern Lapwing Vanellus vanellus chicks. Faecal samples were collected from chicks in breeding populations on agricultural and restored grasslands in Germany and the Netherlands. We used frequency of occurrence (FOO, the number of samples in which a taxon was detected) and relative read abundance (RRA, percentage of DNA reads of a taxon present within a sample) to determine species presence in faeces. While FOO indicates how often taxa may be eaten, RRA is an approximation of ingested biomass, making these variables complementary in the interpretation of the results. We found 25 arthropod or mollusc orders in the faeces of each species, with 114 families and 366 identified species included in the faeces of Black-tailed Godwits and 112 families and 313 identified species in the faeces of Lapwing chicks. Diptera (flies and mosquitoes) had the highest FOO in both species and also the highest RRA. In both species the RRA of Coleoptera (beetles) was second highest, followed by Hymenoptera (sawflies, wasps, bees and ants) in Black-tailed Godwits and Stylommatophora (land snails and slugs) in Lapwings. Overall, in Lapwing, the RRA of soil-dwelling organisms was higher than in Black-tailed Godwits. Our detailed species lists are a first step towards elucidating the requirements of developing chicks within these specific habitats and will aid restoration of habitats providing arthropod food resources.