Predator in Action: New Records of Predation by Guira Cuckoo (Guira guira Gmelin, 1788)
By analyzing thousands of citizen science photographs and new observations, this study reveals that the Guira Cuckoo is a highly opportunistic generalist predator with a broader diet than previously recognized, including significant predation on diverse vertebrate taxa such as amphibians, reptiles, birds, mammals, and fish.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
To understand how animals survive, scientists often look at what they eat. This field, known as trophic ecology, helps researchers map out the complex web of life, showing who eats whom and how species adapt to their surroundings. For many birds, diet is a matter of specialization; some eat only seeds, while others hunt specific insects. However, some birds are generalists, capable of switching their menu based on what is available in their environment. The Guira Cuckoo, a bird with yellowish-white feathers and a distinctive orange beak found across South America, has long been thought to be such a generalist. Traditionally, scientists believed its diet consisted mostly of insects, with the occasional meal of a small lizard or frog being a rare treat. But this view relied on limited observations, often missing the full picture of the bird's hunting habits. Understanding the true scope of what these birds eat is important because it reveals how they interact with their ecosystem, potentially controlling populations of insects and small animals, and how they might be affected by changes in their habitat.
A team of researchers set out to rewrite this story by looking at a massive collection of photographs taken by birdwatchers across Brazil. Instead of relying on a few scientists watching a few birds for a short time, they turned to a citizen science platform called WikiAves, which hosts millions of photos uploaded by the public. They systematically reviewed nearly 3,000 images that showed Guira Cuckoos in the act of eating between 2009 and 2025. By examining these snapshots, the researchers could identify the prey in the birds' beaks, ranging from common insects to various vertebrates. The results were striking. While insects remained the most common food source, the study revealed that the birds eat vertebrates far more often than previously realized. The photographs documented the crows eating hundreds of frogs, scores of lizards, dozens of other birds, and even small mammals and fish. This suggests that the Guira Cuckoo is not just an occasional predator of small animals, but a highly opportunistic hunter that takes advantage of whatever prey is abundant and easy to catch in its environment.
Among the most significant findings were records of the birds eating specific types of animals that had never been documented as prey before. The researchers captured images of a Guira Cuckoo eating a young toad, a small snake, and a tree frog. In one detailed observation, a bird was seen catching a toad, striking it against a rock to subdue it, and then swallowing it whole. In another instance, a bird struggled for a moment to swallow a small snake before succeeding. These records are not just about adding new items to a list; they show the bird's ability to handle different types of prey. The study also found that the birds frequently eat the eggs and young of other birds, including their own kind, a behavior known as cannibalism. While this might seem unusual, the researchers noted that it is a known strategy for some birds, though the specific reasons for it in the Guira Cuckoo remain unclear.
The sheer volume of data provided by the public was crucial to these discoveries. The researchers found that the birds had eaten 404 amphibians, 312 reptiles, 116 birds, 25 mammals, and eight fish. This number of vertebrate prey records was surprisingly high, challenging the old idea that such meals were rare exceptions. The study also highlighted that the birds seem to target animals that are common in open areas or places modified by humans, such as grasslands and agricultural fields. This adaptability allows the Guira Cuckoo to thrive in changing landscapes. The researchers also noted that the birds can eat insects with stinging hairs, like certain caterpillars, without getting hurt, thanks to a special ability to shed the lining of their stomachs. This physical adaptation, combined with their willingness to eat a wide variety of animals, paints a picture of a bird that is incredibly flexible in its feeding habits.
This work demonstrates the power of citizen science in uncovering details of nature that are difficult to find through traditional methods. By pooling together thousands of photos from across the country, the researchers were able to see patterns that would have been invisible to a single observer. The study confirms that the Guira Cuckoo is a highly adaptable predator, capable of shifting its diet to include a wide range of prey depending on what is available. While insects remain the main course, the bird's appetite for small vertebrates is much more significant than previously thought. This flexibility likely helps the species survive and flourish in diverse environments, from natural grasslands to human-altered landscapes. The findings serve as a reminder that even well-studied animals can hold new secrets, waiting to be discovered by those who look closely at the world around them.
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