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The largest-ever study on neophobia, or fear of novelty, has discovered the key reasons why some bird species are more fearful of new things than others.

Published in the journal PLOS Biology, the global multi-species study was led by Dr. Rachael Miller while at Anglia Ruskin University (ARU) and the University of Cambridge, alongside a core leadership team from the .

Neophobia plays a crucial role in how animals balance risk and opportunity. While caution can protect individuals from potential threats, it can also limit their ability to adapt to new nesting sites, foods or changes in the environment.

The research involved 129 collaborators from 82 institutions. Testing, and other associated research tasks, took place in 24 countries across six continents—including lab, field and zoo sites—and investigated why some birds are more cautious than others when encountering unfamiliar objects when feeding.

Using standardized methods, in separate tests, each bird was presented with familiar, desirable food items, both alone and alongside a novel object. The novel objects were designed with consistent colors and textures, and scaled proportionally to the size of each species.

Researchers then measured the time taken to touch the food in both scenarios, with increased hesitation in the presence of the object interpreted as neophobia.

Grebes and flamingos exhibited the highest neophobia while falcons and pheasants were among the least neophobic species, approaching food quickly regardless of the unfamiliar item.

Overall, across all 1,439 birds and 136 species tested—representing 25 taxonomic orders from penguins to parrots—the study found that two ecological drivers strongly predicted neophobia: dietary specialization and migratory behavior.

Species with narrower diets may experience fewer variations in environmental stimuli and therefore may perceive changes as being more threatening than feeding generalists, which are typically faster to explore and exploit different food types.

Migratory species may face increased risks associated with interacting with a wide range of potentially dangerous novel items and environments, and neophobia may be evolutionarily beneficial for these species.

Individuals typically behaved consistently in their responses over time—a bird that was hesitant to approach novelty in one trial was similarly hesitant when tested again several weeks later—suggesting neophobia to be a stable trait.

Birds tested together were more neophobic than those tested alone, which is contrary to expectations that social presence might reduce fear through shared risk. Instead, individuals may be affected by other birds' fear cues or may wait to allow others to take the risk of approaching first.

Dr. Rachael Miller, who carried out the research at Anglia Ruskin University alongside Dr. Julia Mackenzie, currently has roles at both the University of Cambridge and the University of Exeter.

Dr. Miller said, "Neophobia comes with benefits and costs. Neophobic responses can protect an individual from potential risks, but may also decrease opportunities to exploit novel resources, such as unknown food or nesting sites.

"Neophobia plays an important role in assessing how species might respond to change. Species that are more wary of unfamiliar objects or situations may struggle to adapt to factors such as climate change or urbanization, while those with lower neophobia may be more flexible or resilient.

"Our study also highlights the power of big team science. Through the ManyBirds Project, we were able to pool data and expertise from across the globe, helping us to uncover the hidden rules shaping animal behavior on an evolutionary scale."

The ManyBirds Project was co-founded by Dr. Miller and Dr. Megan Lambert in February 2021. Dr. Lambert, of the University of Veterinary Medicine, Vienna, said, "Our findings have important implications, particularly for species experiencing habitat change or being reintroduced into the wild from captive breeding programs.

"By better understanding these behavioral tendencies, conservationists can tailor strategies to improve the chances of survival in at-risk species."