The Short-Eared Owl, Asio flammeus, is a bird of prey with one of the most extensive global distributions, found across North and South America, Eurasia, and numerous oceanic islands. Unlike many of its relatives, this medium-sized owl species prefers vast, open environments, including tundra, grasslands, prairies, and coastal marshes. This preference for treeless terrain directly shapes its feeding ecology and hunting habits, making it a highly specialized predator. The Short-Eared Owl is also a nomadic species, frequently moving great distances in search of areas where its preferred food source is most abundant.
Core Diet: Micro-Mammal Staples
The Short-Eared Owl’s diet consists overwhelmingly of micro-mammals, primarily voles (Microtus species). Voles form such a dominant part of their intake—often constituting 80 to over 95% of prey—that the owl’s entire life cycle, including nomadic movements and breeding success, is intimately tied to the cyclical rise and fall of vole populations.
When local vole densities are high, the owls congregate in large numbers, and females may lay larger clutches of eggs, sometimes up to 14, to capitalize on the abundant food supply. This specialization makes the Short-Eared Owl an extremely effective biological control agent for rodent populations in agricultural and grassland ecosystems. The owls also regularly consume other small, ground-dwelling mammals, which serve as secondary staples.
Secondary prey items include various species of shrews and mice, such as deer mice and wood mice, which are readily available in open habitats. Lemmings are also a significant part of the diet in the northern reaches of the owl’s range, particularly in tundra environments. The nutritional density and easy accessibility of these small rodents make them the most energetically efficient food source for the Short-Eared Owl.
Dietary Flexibility and Supplemental Prey
Although highly specialized, the Short-Eared Owl’s diet demonstrates considerable flexibility when primary prey is scarce. This opportunistic behavior allows the owl to persist in diverse environments or during seasonal changes. During periods of low vole abundance, the owl expands its hunting efforts to include a wider variety of animals.
Birds become a more prominent supplemental prey source, especially in coastal or marshy habitats, where the owls hunt small birds, including ground-roosting species, shorebirds, gulls, and terns. In some specific coastal studies, avian prey has been found to represent a majority of the diet by weight, demonstrating a significant shift from the typical mammal-heavy intake.
The supplemental diet also includes slightly larger mammals, such as young rabbits and gophers, though taken less frequently. Additionally, the owls will consume insects like grasshoppers and large beetles, which provide a less substantial but readily available source of protein during warmer months.
Hunting Strategy and Habitat Influence
The Short-Eared Owl’s hunting method is adapted to its open-country habitat, differing from the ambush tactics of forest-dwelling owls. It acquires food by flying low, typically just a few feet above the ground, in a characteristic buoyant, moth-like flight pattern. The owl systematically “quarters” the field, meaning it flies back and forth over an area in a grid-like search pattern.
This method allows the owl to cover large expanses of grassland, marsh, or tundra efficiently, often making it visible during daylight hours. While primarily crepuscular, hunting most actively at dawn and dusk, the need to feed young or food scarcity can prompt it to hunt throughout the day. The owl may briefly hover in place before dropping suddenly onto detected prey hidden in the dense vegetation below.
The open habitat allows the owl to utilize its exceptional sense of hearing to locate prey. The owl’s facial disc channels sound waves toward its asymmetrically placed ear openings, enabling it to pinpoint the exact location of a scurrying vole or mouse beneath a layer of snow or thick grass. This combination of low-altitude visual scanning and precise auditory location secures its micro-mammal diet.
The Role of Owl Pellets in Diet Study
Owl pellets are an invaluable resource for determining the Short-Eared Owl’s feeding habits. These pellets are masses of indigestible material, such as fur, bones, and feathers, which the owl regurgitates several hours after consuming its prey whole. The owl’s digestive system separates the soft tissue from the hard, non-digestible remains, which are then compacted into an oval pellet.
By collecting and analyzing the contents of these pellets, researchers can identify the species and number of individual animals consumed over a specific time period. The presence of numerous tiny skulls and jawbones from voles and shrews provides concrete evidence that confirms the high percentage of micro-mammals in the owl’s diet.