Owls are captivating nocturnal predators and obligate carnivores, meaning their diet consists entirely of animal matter. These birds possess unique physical adaptations, such as silent flight and acute hearing, which make them highly efficient hunters.
The Natural Diet: Primary Prey Categories
The diet of an owl in the wild is determined primarily by its species, size, and geographic location, leading to highly varied prey selection.
Smaller owl species, such as the Flammulated Owl or the Elf Owl, are largely insectivores, consuming a high volume of moths, beetles, crickets, and grasshoppers. They may also take small invertebrates like earthworms or scorpions.
Medium-sized owls, including the Barn Owl and the Long-eared Owl, focus their hunting efforts on small mammals. Their diet is dominated by rodents such as mice, voles, and shrews, which they locate using their remarkable directional hearing. The slightly larger Screech Owls exhibit a more diverse diet, readily consuming small mammals, birds, reptiles, and amphibians.
The largest owls, such as the Eurasian Eagle-Owl and the Great Horned Owl, are powerful hunters capable of taking much larger prey. These apex predators can subdue hares, rats, skunks, and even other raptors or small foxes. Specialized species like the African Fishing Owls primarily hunt aquatic animals, including fish, frogs, and crayfish.
Unique Digestive Biology: The Role of Owl Pellets
A defining characteristic of owl feeding is the habit of swallowing small prey whole, or tearing larger prey into large, unchewed pieces. Owls lack a crop, the muscular pouch other birds use to store food, so food passes directly into the stomach.
The stomach is divided into two parts: the proventriculus, which secretes digestive acids, and the gizzard, a muscular second chamber. The digestive acids of the proventriculus are not powerful enough to dissolve dense materials like bone, fur, feathers, or teeth.
The gizzard acts as a filter, separating the digestible muscle and tissue from the indigestible components. These hard, undigested remnants are compressed into a compact mass that conforms to the gizzard’s shape, known as an owl pellet.
This pellet is moved from the gizzard back into the proventriculus, where it can remain for several hours. The presence of the pellet partially blocks the digestive tract, preventing the owl from eating again until it is regurgitated. Casting the pellet is a necessary physiological process that clears the digestive lining and indicates the owl is ready to hunt again.
Safe Feeding Practices in Captivity and Rehabilitation
For owls under human care, such as in rehabilitation centers or zoos, feeding must precisely replicate the natural whole-prey diet. The standard diet consists of frozen, commercially raised whole prey, primarily mice, rats, or day-old chicks, which are by-products of the poultry industry. This practice ensures the owl receives the necessary balance of protein, fat, and minerals found in a whole carcass.
The use of commercially raised prey is important because it mitigates the risk of transmitting diseases or parasites often carried by wild-caught animals. Prey must be completely thawed, preferably slowly in a refrigerator to prevent bacterial growth, and served at ambient room temperature. The prey must be offered whole to stimulate the formation and regurgitation of a pellet, which is essential for digestive health.
Feeding only lean meat without bone and fur creates a severe nutritional deficiency, particularly in calcium, as the calcium-to-phosphorus ratio becomes unbalanced. For very young owlets or birds with specific health needs, a veterinarian may recommend supplemental calcium or a balanced vitamin powder. In emergency situations, raw lean beef or chicken muscle may be provided temporarily, but this must not be a long-term diet, as it is nutritionally incomplete and prevents pellet formation.
Foods and Substances to Strictly Avoid
The most significant danger to an owl is the consumption of prey that has been poisoned by humans. Secondary poisoning occurs when an owl eats a rodent that has ingested an anticoagulant rodenticide.
Second-generation anticoagulant rodenticides (SGARs), such as brodifacoum and bromadiolone, are especially hazardous because they remain potent in the rodent’s tissue for a long time. Ingesting these poisoned rodents causes the owl to suffer from fatal internal hemorrhaging.
Owls must strictly avoid all processed human foods, including bread, dairy products, and cooked meats. Foods high in sugar, salt, or preservatives offer no nutritional value and can lead to health complications. Additionally, raw pork and lamb should not be fed due to potential disease transmission risks.