Big-brained seagulls choose more challenging nesting sites

Seagull species with larger brains are more likely to choose cliffs for nesting and may also be better adapted to urban environments, such as the rooftops of buildings, according to a recent study led by the University of Exeter.

Exploring the link between brain size, wing shape, nesting habits, and urban adaptation, the experts discovered that over half of cliff-nesting gull species are nesting in urban settings, a significant contrast to the 11% of non-cliff-nesting species doing the same. 

Seagulls nesting in challenging environments

The research highlights a correlation between larger brain sizes and the ability to adapt to more challenging nesting environments.

“Many people will be familiar with gulls nesting and foraging in urban areas,” said lead author Madeleine Goumas, a former postdoctoral research associate at Exeter’s Center for Ecology and Conservation. “It’s not something you might expect from a seabird, so we wanted to try to understand why they do it.”

Seagulls nesting in urban settings 

The research involved a comprehensive review of existing studies, analyzing urban breeding and foraging behaviors among different seagull species. 

The findings revealed that 13 of the 50 gull species have adapted to urban environments for breeding, with the same number identified as urban foragers; nine species engage in both behaviors.

The data showed that 53% of cliff-nesting gull species were found to nest in urban areas, compared to only 11% of non-cliff-nesters. 

Seagulls with larger brains

“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,” said senior author Neeltje Boogert, a senior lecturer in biosciences at Exeter.

“It’s also not a fixed behavior in most gulls. While non-cliff-nesting species nest exclusively on the ground, most cliff-nesting species nest either on cliffs or the ground.”

“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.”

Regarding foraging behavior, the study concluded that neither brain size nor wing shape, which influences maneuverability, were definitive factors in predicting urban foraging activities.

Implications for conservation

The scientists also examined the conservation status of these seagulls, discovering that those with stable or growing populations were more likely to utilize urban habitats compared to those in decline. Among the ten gull species listed as Threatened or Near Threatened, only the black-legged kittiwake was observed using urban settings.

“Whether or not species use urban areas has important implications for conservation,” Boogert explained. “If we can understand the factors that allow animals to use urban areas, we can better understand how to help those that aren’t faring so well.”

“Urbanization is a major problem for a lot of animals. 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,” Goumas added.

This research is part of a broader investigation into gull behavior, which includes studies on how gulls prefer food handled by humans and how maintaining eye contact can deter them from stealing food.

More about seagull nesting behaviors 

Seagulls are fascinating creatures, particularly when it comes to their nesting behaviors, which exhibit some unique strategies adapted to their environments. 

Generally, seagulls are colonial nesters, meaning they prefer to nest in large groups, which offers protection against predators. The location of these colonies can vary widely, including isolated, flat roofs of buildings, sandy beaches, or rocky cliffs near the sea.

Nesting strategies

A typical nesting site is chosen for its safety from ground predators and its proximity to food sources. Seagulls are quite adaptable and may adjust their nesting strategies based on their environment. For instance, urban gulls might nest on man-made structures, while those in more natural settings will choose spots that offer natural protection.

When building their nests, seagulls use a variety of materials, including sticks, seaweed, and feathers, constructing them to cradle their eggs securely. A seagull’s nest is relatively simple, not much more than a scrape on the ground or a slight mound to keep the eggs in place.

Mating pairs 

Seagulls are also particularly defensive of their nesting sites. Both the male and female participate in nest building and the care of the young. The mating pair typically forms a bond that can last many years and is reinforced each season through ritual behaviors and mutual care.

Breeding season

The breeding season is a noisy time in a gull colony, filled with calls and aggressive interactions between neighbors and intruders. Eggs are generally laid from late March through May, with the specifics depending on the location and species. The incubation period for seagull eggs lasts about three to five weeks, and both parents share the duty of warming the eggs.

Once hatched, the chicks are semi-precocial, meaning they are relatively mature and mobile from the moment of birth, yet remain dependent on their parents for food and protection. The young are usually ready to fly and leave the nest within six weeks after hatching, though parental care may continue until they are fully capable of independent survival.

The study is published in the journal Frontiers in Ecology and Evolution.

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