Bigger-brained gull species thrive in urban spaces

Despite the reputation for being the trash pandas of the bird world, seagulls are kind of the masters of evolution. They can survive and thrive alongside humans, have a remarkable memory, and some have been observed using pieces of food to bait fish the way primates use tools. The seagull species that have bigger brains that are also more likely to nest on coastal cliffs may also be better adapted to breed in urban environments.

A study published April 25 in the journal Frontiers in Ecology and Evolution found that more than half of cliff-nesting gull species that also nest in cities and towns have bigger brains. Species such as the Herring Gull, the Lesser Black-backed Gull, and the Black-legged Kittiwake potentially have a behavioral flexibility that allows them to nest in more challenging locations like rooftops.

“Many people will be familiar with gulls nesting and foraging in urban areas,” Madeleine Goumas, study co-author and a postdoctoral researcher specializing in herring gulls at the University of Exeter in England, said in a statement. “It’s not something you might expect from a seabird, so we wanted to try to understand why they do it.”

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In the study, the team combed through various research databases to find records of urban breeding and foraging among gulls and data on brain size by species. They then mapped a range of the different species present.

Out of 50 gull species, 13 were recorded as using urban areas to breed, while 13 were recorded using urban areas to forage for food. Nine species bred and fed in more building-heavy environments.

When they compared the figures for breeding with the birds’ known habits and brain size, they found that 10 out of the 19 cliff-nesting gull species (53 percent) also nested in urban areas. Only three out of 28 (11 percent) of generally non-cliff-nesting species nested in both spaces.

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“We found that gull species with larger brains are more likely to be cliff-nesters, and cliff-nesting species are more likely to breed in urban areas,” study co-author and University of Exeter evolutionary biologist Neeltje Boogert said in a statement. “We also found that cliff-nesting is probably not something that was shared by the ancestor of gulls, so it is a relatively recent adaptation.”

They also point out that this is not a fixed or instinctive behavior in most gulls. The non-cliff-nesting gull species nest exclusively on the ground, most most traditionally cliff-nesting species can nest in both spaces.

“This suggests that bigger brains enable these gull species to be flexible with regard to where they choose to nest, and this allows them to use unconventional sites, like buildings, for raising their young,” said Goumas.

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In terms of foraging, the researchers found that neither brain size nor the shape of their wing were good indicators of seagull behavior in urban environments. The team also looked at the status of the gulls on the International Union on Conservation of Nature’s Red List. The gulls with stable or increasing populations were more than twice as likely to be observed using urban habitats than the species that are decreasing. Of the 10 Threatened or Near Threatened species, only the Black-legged Kittiwake was known to use urban spaces.

Observing how gull species function in populated areas with humans and buildings is important for conservation. Seeing what factors allow some to survive and thrive while others do not can inform why some aren’t faring as well.

“Urbanization is a major problem for a lot of animals,” said Goumas. “It looks like some gull species have managed to overcome some of the challenges that prevent other animals from using urban areas, but we need more long-term studies as well as comparative studies on other taxa to fully understand the impacts of urban living.”