Urban Seagulls Still Prefer Seafood

Although known for the penchant for thrown-away junk food, urban seagulls still prefer their own natural diet of raw fish, according to new research.

After raising suburban herring gull chicks in captivity and feeding them either a marine diet of mackerel and mussels or an “urban” diet of cat food and bread, the researchers from the University of Exeter observed that the chicks strongly favored the seafood.

The findings were published in PeerJ.

Gluttonous gulls

To understand if urban seagulls really prefer eating discarded processed food over their natural seafood diet, the Exeter researchers fed the two diets, in two different ratios, to 27 herring gull chicks, which had been rescued after falling off roofs in towns across Cornwall, UK.

All chicks had access to food all day, but half had urban food for 80% of the day and seafood for 20%, while the other half were given the opposite dietary ratio.

The cat food consisted of chicken, turkey, lamb and beef pieces combined with jelly and gravy. The brown bread was chosen a low-protein option as it “is commonly consumed by gulls in urban areas from domestic garbage”.

Regardless of the dietary group, the team found that all chicks preferred the raw fish and almost all refused to eat the bread offered. 

“Our results suggest that, even when reared on an ‘urban’ diet of foods found only around people, these chicks might be unlikely to seek out urban foods as adults,” said lead author Emma Inzani, a PhD student at the University of Exeter’s Centre for Ecology and Conservation.

“Human-associated foods are often both reliably present and easy to obtain – but when fish is available, they clearly prefer it.”

The high-protein fishy diet also appeared to benefit the chicks; those fed on mackerel and mussels were significantly heavier at the last weigh-in than their cat food-fed counterparts.

The chicks’ seafood preference aligns with previous research that observed parent gulls switching to provisioning more marine-sourced foods upon chick hatching.

“Animals can live and exploit urban areas for human food waste,” said senior author Dr. Neeltje Boogert.

“However, this does not necessarily mean they’re thriving or that they prefer this food, rather than making the best of a bad situation.”

“More research is needed to investigate how the food young animals receive affects their later life, including their food choices, health and breeding.”

Reference: Inzani E, Kelley L, Thomas R, Boogert NJ. Early-life diet does not affect preference for fish in herring gulls (Larus argentatus). PeerJ. 2024. doi: 10.7717/peerj.17565

This article is a rework of a press release issued by the University of Exeter. Material has been edited for length and content.