Seasonal and ontological variation in diet and age-related differences in prey choice, by an insectivorous songbird

The diet of an individual animal is subject to change over time, both in
response to short-term food fluctuations and over longer time scales as an
individual ages and meets different challenges over its life cycle. A
metabarcoding approach was used to elucidate the diet of different life
stages of a migratory songbird, the Eurasian reed warbler (Acrocephalus
scirpaceus) over the 2017 summer breeding season in Somerset, UK. The
faeces of adult, juvenile and nestling warblers were screened for
invertebrate DNA, enabling the identification of prey species. Dietary
analysis was coupled with monitoring of Diptera in the field using yellow
sticky traps. Seasonal changes in warbler diet were subtle whereas age
class had a greater influence on overall diet composition. Age classes
showed high dietary overlap, but significant dietary differences were
mediated through the selection of prey; i) from different taxonomic
groups, ii) with different habitat origins (aquatic versus terrestrial)
and iii) of different average approximate sizes. Our results highlight the
value of metabarcoding data for enhancing ecological studies of
insectivores in dynamic environments.