The chicks of herring gull (Larus argentatus) raised in captivity with an “urban” diet continue to prefer a “natural” diet based on shellfish and fish as adults, as demonstrated by a study carried out by scientists at the University of Exeter with chicks rescued after falling from roofs in cities in Cornwall, UK.
Raised in captivity (before being released), they were given a “marine” diet consisting mainly of fish and mussels, or an “urban” diet containing mainly bread and cat food.
As explained in a press release by the British universityEvery few days, the gull chicks were presented with a selection of the four foods in different bowls, to see which they preferred, and they all clearly favored fish.
“Our results suggest that, even when raised on an ‘urban’ diet of foods only found near people, these chicks are unlikely to seek out urban foods as adults,” said lead author Emma Inzani of the Ecology and Conservation Center at Exeter’s Penryn Campus in Cornwall.
“The foods that humans consume are usually abundant and easy to obtain, but when they have fish on hand, they clearly prefer it.”
An urban problem
Herring gulls are often considered a real problem in many cities, as they breed in noisy colonies on rooftops, scavenge for scraps of food in containers, and sometimes take food from people. However, the species is on the UK Conservation List of Most Concern due to its continuing population decline.
A combination of reduced fish stocks in UK waters, together with abundant and easy access to food waste in cities, explains why it is not very profitable for seagulls to expend much energy going to sea to forage.
Previous research has shown that parent gulls often change their diet and seek out more shellfish once their chicks hatch, possibly because shellfish and fish provide more nutrients than urban waste.
food experiment
In this new study, 27 chicks had access to food throughout the day, but half of them had urban food for 80% of the day and seafood for 20%, while the other half of the chicks received the opposite diet. .
When presented with the four foods together on days 5, 10, 15, and 35 of the study, both groups clearly chose fish, and even those who tried bread rarely ate much.
Chicks prefer seafood
The chick preferences for fish found in this study appear to reinforce the behavior observed in parental gulls to switch to a greater supply of marine foods after chick hatching.
“Animals can live and exploit urban areas for human food waste,” says lead author Dr. Neeltje Boogert. “However, this does not necessarily mean that they are thriving or that they prefer this food over making the best of a bad situation. “Further work is needed to investigate how the food young animals receive affects their later life, including their food choices, health and rearing.”
The article, published in the journal PeerJ, is titled: “Early-life diet does not affect preference for fish in herring gulls (Larus argentatus)” and can be consulted online at this link.
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