Unusual Dining Habits of Barn Owls in Hutton Buscel: A Cockchafer Feast
In the quiet countryside near Hutton Buscel, North Yorkshire, a surprising discovery has shed light on the adaptability of one of Britain’s most iconic birds: the barn owl Tyto alba. While undertaking ecological survey work on a local barn, I stumbled upon a barn owl roost, where I found numerous owl pellets packed with the remains of cockchafer beetles Melolontha melolontha. This is an unusual find, as barn owls are known for their preference for small mammals, particularly voles, and is the first time I have found beetles in any number within barn owl pellets. In this blog post, I’ll dive into this curious dietary shift, compare it to the typical barn owl diet, explore cockchafer phenology, and suggest possible reasons for this behaviour, drawing on scientific literature to ground our understanding.
Barn owl pellet containing remains of numerous cockchafers, one of a large quantity of pellets found.
The Typical Barn Owl Diet: A Mammal-Centric Menu
Barn owls are specialised predators, primarily feeding on small mammals. Studies across the UK consistently show that field voles Microtus agrestis dominate their diet, often making up 50–80% of prey items by number, followed by wood mice Apodemus sylvaticus and shrews Sorex spp. For example, a long-term study in the UK South Midlands found that field voles were the most common prey, with wood mice and common shrews as secondary choices. By weight, larger prey like brown rats Rattus norvegicus can also contribute significantly to their energy intake. Birds, amphibians, and invertebrates, however, are typically minor components, with invertebrates rarely exceeding 1–2% of the diet in most studies.
This mammal-centric diet is tied to the barn owl’s hunting strategy. Their silent flight and acute hearing allow them to pinpoint small mammals in grassy habitats like rough grassland and field margins, which are abundant in North Yorkshire’s patchwork farmland. The reliance on voles is so strong that barn owl breeding success often tracks vole population cycles, with poor breeding years coinciding with vole scarcity.
The Cockchafer Surprise: An Unusual Find
The pellets I found near Hutton Buscel told a different story. Dissecting them revealed a striking number of cockchafer beetle remains, shiny copper wing cases, thoraxes, and legs, far more than the occasional insect fragment one might expect. Cockchafers, also known as May bugs, are large beetles (20–30 mm long) belonging to the Scarabaeidae family. Their presence in such quantities in barn owl pellets is highly unusual, as insects are not a staple in the barn owl’s diet. While previous studies have noted occasional invertebrate consumption, such as dung beetles Geotrupes spp. or ground beetles in the UK, such instances are rare and typically involve single individuals, not a significant dietary component.
This discovery raises questions about why these barn owls were consuming cockchafers in such numbers. To understand this, let’s explore the phenology of cockchafers and the ecological context that might have driven this dietary shift.
Cockchafer Phenology: Timing and Abundance
Cockchafers have a fascinating life cycle that spans 3–4 years, most of which is spent underground as larvae feeding on plant roots. In late spring to early summer (typically May–June in the UK), adults emerge en masse to mate and feed on foliage, often appearing in large numbers during warm evenings. This synchronised emergence can lead to temporary abundance, making cockchafers a conspicuous presence in rural areas on some evenings.
In North Yorkshire, 2025 likely saw a peak in cockchafer emergence, as their multi-year cycle aligns with periodic population booms. Their large size (up to 10–15 g) and slow, buzzing flight make them an easy target for opportunistic predators. For barn owls, which typically hunt by swooping down on prey in open areas, cockchafers active at dusk or caught resting on vegetation could present a tempting, energy-rich snack, especially if more typical prey is scarce.
Why Cockchafers? Two Hypotheses
The prominence of cockchafers in these barn owl pellets could be explained by two main factors: their abundance and size, or a scarcity of the owls’ usual prey, such as voles. Let’s examine both possibilities.
Abundance and Size of Cockchafers
Cockchafers’ large size and periodic abundance make them an attractive prey item. A single cockchafer provides more biomass than smaller insects like moths or crickets, potentially offering a worthwhile energy return for the effort of capture. Barn owls are known to be opportunistic when prey availability shifts. For example, in parts of their global range, barn owls incorporated a wider range of prey, including reptiles, birds and insects, when small mammals were less abundant. The cockchafers’ emergence in May–June 2025 likely coincided with the owls’ breeding season, a time of high energy demand for provisioning nestlings. If cockchafers were swarming in the fields around Hutton Buscel, the owls may have capitalised on this temporary bounty.Vole Scarcity
Alternatively, the owls may have turned to cockchafers due to a shortage of their preferred prey. Field vole populations in the UK follow a 2–4-year cycle, with peaks followed by crashes. If 2023 (when I found the pellets) was a low point in the vole cycle in North Yorkshire, the owls may have struggled to find enough small mammals to sustain themselves and their young. During such times, barn owls are known to broaden their diet, incorporating birds or, in rare cases, invertebrates. A study in the Mediterranean noted that barn owls consumed more birds when small mammals were scarce, suggesting dietary flexibility in response to prey availability. The abundance of cockchafer remains in the pellets could indicate that the owls were compensating for a lack of voles by targeting these large, accessible beetles.
Ecological and Conservation Implications
This observation highlights the barn owl’s adaptability, a trait that has allowed it to thrive across diverse habitats worldwide. However, it also underscores the importance of monitoring prey populations and habitat quality. If vole scarcity drove this dietary shift, it could signal broader ecological changes, such as habitat loss or agricultural intensification reducing vole numbers in North Yorkshire. Rough grasslands, critical for supporting vole populations, are declining in many areas, and conservation efforts like agri-environment schemes promoting wildflower strips and extensive meadows could help stabilise prey availability.
The reliance on cockchafers also raises questions about the nutritional adequacy of such a diet. While cockchafers are biomass-rich, they lack the protein and fat content of mammals, potentially affecting owl health or breeding success if consumed over long periods.
Conclusion: A Window into Barn Owl Behavior
Finding barn owl pellets stuffed with cockchafer remains, was a rare glimpse into the flexibility of these silent hunters. While their typical diet revolves around voles and other small mammals, the abundance of cockchafers or a scarcity of voles likely prompted this unusual feast. Cockchafer phenology, with its periodic booms, aligns with this behavior, and scientific literature supports the idea that barn owls can shift their diet when needed. This discovery not only adds a quirky chapter to the story of North Yorkshire’s barn owls but also reminds us of the complex interplay between predators, prey, and their environment. Next time you’re out in the Yorkshire countryside, keep an eye out for those ghostly white shapes gliding over the fields—you never know what they might be dining on.
Another barn owl pellet filled with cockchafer remains.
References
Meek et al., 2012. The use of Barn Owl Tyto alba pellets to assess population change in small mammals.
The Barn Owl Trust, 2021. The Field Vole Cycle.
British Trust for Ornithology. Barn Owl.
Obuch et al., 2021. Large-scale spatial patterns of small-mammal communities in the Mediterranean region revealed by Barn owl diet.
Pavluvčík et al., 2015. Barn Owl Productivity Response to Variability of Vole Populations.
Charalambous et al., 2018. Spatial and temporal patterns in the diet of barn owl (Tyto alba) in Cyprus.
Séchaud et al., 2021. Behaviour-specific habitat selection patterns of breeding barn owls.
Rubolini et al., 2024. Collection methods of wild barn owl pellets at low environmental contamination.
Fara et al., 2024. Little owls (Athene noctua) shift their diet towards nocturnal beetles in an arid North African area.
Note: If you’d like to try pellet dissection yourself, always wear gloves and follow hygiene guidelines, as pellets can harbor pathogens. Happy owl-watching!
