Owls are nocturnal birds of prey found across nearly every continent. While many species rely primarily on small mammals like voles and mice, their diet is diverse and frequently includes other birds. The inclusion of avian prey shifts based on the specific owl species, the available environment, and the season. Understanding what birds owls consume depends on the vulnerability of the prey and the capability of the predator.
General Categories of Avian Prey
The most common avian targets for owls are small, perch-dwelling birds known as passerines, which are often found roosting in dense cover at night. Species such as House Sparrows, Starlings, and various thrushes are frequently identified in owl dietary analyses. These small birds are particularly vulnerable due to their communal roosting habits, allowing an owl to ambush multiple individuals from a single hunting location.
Ground-feeding birds are targeted by owls that hunt close to the ground, such as the Little Owl. Examples include ground-nesting game chicks and small passerines that forage on the soil surface, making them accessible to a silent aerial strike. In areas near wetlands, owls may prey upon water-dependent species such as rails and various types of ducks.
Inexperienced juveniles and fledglings are easier to capture than adult birds. Studies on the Northern Pygmy Owl show that the proportion of small birds in their diet almost doubles from spring to summer, coinciding with the fledging period. This influx of young, less-aware birds makes them an abundant, low-effort food source during the late summer and autumn months.
The Influence of Owl Species Size on Bird Selection
The size of the owl is a major determining factor in the size and type of bird it selects as prey. Smaller owl species, such as the Eastern Screech Owl or the Northern Pygmy Owl, restrict their avian diet to very small birds. These species predominantly consume passerines, with many individuals weighing less than 30 grams.
Medium-sized owls, like the Tawny Owl and Long-eared Owl, consume a greater variety of avian prey than smaller species. They often take larger passerines and small game birds but avoid prey close to their own body weight. The Tawny Owl, for example, may shift from small mammal prey to small birds during its breeding season when feeding young.
Conversely, the largest owls, such as the Great Horned Owl and the Eurasian Eagle-Owl, are capable of tackling substantial avian quarry. The Great Horned Owl has been documented preying on adult ducks, grouse, pheasants, and even other raptors, including Ospreys and smaller hawks. The physical strength and powerful talons of these larger species allow them to subdue birds impossible for their smaller relatives to capture.
Seasonal Shifts and Opportunistic Bird Predation
Birds become a more substantial component of an owl’s diet when the primary food source becomes scarce. This dietary shift often occurs in winter when snow makes hunting small mammals challenging or when rodent populations naturally decline. Under these conditions, the energetic cost of hunting birds is lower than searching for concealed mammals, making avian prey a reliable alternative.
Seasonal changes in bird behavior also create opportunities for predation. Migratory periods can concentrate large numbers of birds in specific areas, increasing their availability to resident owls. Additionally, the vulnerability of birds near human habitation increases during periods of food stress.
Owls demonstrate opportunistic feeding behavior, exploiting predictable food sources. For instance, an owl may regularly target birds that gather at backyard feeders or those that use a communal roosting site. This situational hunting allows owls to conserve energy by focusing on areas where the density of potential prey is temporarily high.