A nest box occupied by a Eurasian scops owl might seem an unlikely place to find a live snake, yet that is exactly what researchers repeatedly encountered in central Türkiye. Across six breeding seasons, they inspected 109 owl nests and found the small worm snake Xerotyphlops vermicularis in 44% of them. The reptiles were not simply turning up in empty boxes. They occurred only in nests occupied by scops owls, and observations suggested that the owls were carrying the snakes inside while they were still alive. What happened next is less clear. The worm snakes, which feed on tiny invertebrates, were found moving through the nesting material, where ants and fly larvae can occur.The young owls also appeared to fare better in nests containing snakes: 61% of hatched chicks fledged, compared with 29% where snakes were absent. The figures raise the possibility of an unusual relationship, but they do not yet prove one.
An unexpected role for worm snakes inside scops owl nests
The species involved was the Eurasian scops owl, Otus scops, a small nocturnal owl that breeds across much of Europe and parts of Asia. The study published in Ornithology, titled ‘Association of nesting Otus scops (Eurasian Scops Owl) with Xerotyphlops vermicularis (worm snake) in Türkiye’ reveals the snake Xerotyphlops vermicularis, commonly known as the worm snake, a burrowing species with a diet centred on small invertebrates.During repeated nest-box inspections, the snakes appeared only in boxes occupied by scops owls. That pattern mattered because it made a simple explanation such as an accidental entry less convincing. The snakes were being found in active owl nests, including among the material used to line the nesting space.The observations also indicated that the owls were bringing the reptiles in while they were still alive. That is an unusual behaviour in itself. Owls commonly carry prey back to a nest for their young, but these snakes did not appear to be serving as food. Instead, the reptiles were left in the nest environment.
The surprising link between snakes and owl nest survival
The worm snake’s lifestyle offers a possible clue. It is an insect-eating, burrowing animal, and the material surrounding a bird nest can contain plenty of tiny creatures. Ants and fly larvae, for example, may live or develop in nesting material.A live snake moving through that material could therefore affect the small invertebrate community inside the nest. The researchers observed snakes both on the surface and within the nesting material, where they could encounter the insects and other organisms living there.That raises an intriguing possibility: the owls may gain something from having the snakes around.The nest data provide some support for that idea. There was no meaningful difference in clutch size or brood size between nests where snakes were present and those where they were absent. The difference appeared later, when the young had to survive long enough to leave the nest.
The snake-filled nests had a striking survival advantage
Among the young that hatched, 61% eventually fledged from nests containing snakes. In nests without snakes, the corresponding figure was 29%.The result does not establish that the snakes caused the higher fledging rate. The researchers were careful to leave that question open. There could be other differences between nests that were not captured by the observations, and the presence of snakes might itself be linked to some aspect of owl behaviour or nest conditions.Still, the contrast is large enough to make the snake’s role difficult to ignore.If the reptiles are consuming insects living in the nest, they could potentially reduce organisms that compete with, irritate or otherwise affect developing owl chicks. Some insects may also exploit the food and waste associated with a bird nest. Removing them could change conditions for the young without the snake needing to interact directly with the owls.
The mystery of why owls carry live snakes remains
The snakes could benefit simply from being carried into a warm, food-rich environment, while any advantage to the owls might be incidental. There is also the possibility that the owls sometimes select snakes as prey but fail to consume them, leaving them alive in the nest. The researchers describe several possible explanations rather than treating one as settled.This distinction matters because a mutualistic relationship requires benefits to both sides, not just an unusual association. The observations suggest that something interesting is happening, but they do not yet reveal exactly why the owls carry the snakes into their nest boxes.
The unusual behaviour has been spotted around the world
The finding also fits into a broader set of observations involving owls and blind snakes in different parts of the world. In several cases, birds have been observed bringing live, non-venomous snakes into nesting sites, even though the reptiles are not eaten.Taken together, such reports have raised questions about whether bird behaviour can sometimes create unexpected ecological partnerships. A predator does not necessarily have to consume an animal it captures. In some circumstances, bringing a particular species into a nest could produce an indirect benefit.For the central Turkish scops owls, selective predation could theoretically have played a role over evolutionary time. If owls that happened to carry these snakes into nests gained a small advantage because fewer nest insects survived, that behaviour could potentially persist and become more common. But that remains a hypothesis rather than an established explanation.