Earthworms in the diet of herring gulls (Larus argentatus) breeding on an off-shore island

Pellets of indigestible material regurgitated by Herring Gulls Larus argentatus breeding on Lady Isle, Firth of Clyde, Scotland, were collected in 2018 and 2019 and examined for earthworm chaetae. Nearly two-thirds (65.6%) of the 314 pellets came from gulls that had consumed one or more earthworms. Significantly fewer pellets (57.6%) contained chaetae in 2018, a relatively dry May to July, than in 2019 (72.0%) when rainfall was close to the long-term average for May to July. There were significant associations between the presence of large quantities of terrestrial vegetation in the pellet and the detection of large numbers of earthworm chaetae and/or fragments of terrestrial arthropods, suggesting that recent consumption of these food items is likely when pellets contain large quantities of vegetation.