Overview
- A field experiment across nine towns in Cornwall tested 61 herring gulls with recordings of five men speaking calmly or shouting the same phrase.
- About half of the gulls flew off within a minute when they heard shouting, compared with 15% for calm speech.
- Roughly 70% of birds stayed near the food when played a robin‑song control, confirming the human voice was perceived as threatening.
- Recordings were level‑matched to exclude loudness effects, indicating gulls detect human vocal tone in a way previously shown mainly in domesticated species.
- Published in Biology Letters, the study supports simple, non‑violent deterrence for a species of conservation concern and notes bolder foraging in tourist hotspots such as St Ives.