Barn owls, members of the family Tytonidae, are unmistakable nocturnal birds of prey. Their ghostly appearance and blood-curdling shriek have led to their incorporation into folklore and myth and have earned these birds a variety of nicknames, including "ghost owl" and "monkey-faced owl." Thirty-six subspecies have been identified worldwide. The subspecies that lives in North America is called Tyto alba pratincola.
Barn owls have a white or tan underside with black spotting. Males tend to be whiter and have less speckling than females (Figure 1). The wings are long and ornately colored with shades of brown, tan, black and white. Barn owls have a distinctly heart-shaped, white facial disk and lack ear tufts that are characteristic of many other owl species. Their eyes are dark and relatively small when compared to other owls. They have long legs that are easily seen when they are roosting or flying overhead. Female barn owls tend to be slightly larger than males. On average, females measure 34–40 cm (13.4–15.7 inches) in length and weigh 570 g (1.3 lbs), and males are 32-38 cm (12.6–15.0 inches) long and weigh 470 g (1.0 lbs).
Hunting and Diet
Barn owls hunt using their excellent low-light vision and hearing. Their facial disk funnels sound into their ear holes, which are located beneath the feathers on each side of their face. These openings are slightly lopsided from each another. This allows the owls to sense how far away a sound is from them. Barn owls are so good at locating prey by sound that they can do so even when the prey is completely hidden from view.
Small mammals are the primary food of barn owls. Voles (Microtus sp.) are the most common prey in northern North America and Europe, although mice, shrews and moles also are eaten. In southern Florida, where no voles and few mice occur, larger rats, such as cotton rats (Sigmodon hispidus), roof rats (Rattus rattus), and rice rats (Oryzomys palustris) are eaten, along with small marsh rabbits (Sylvilagus palustris) and round-tailed muskrats (Neofiber alleni). Non-mammalian prey, including birds, amphibians, reptiles and large insects are occasionally consumed. Prey usually are swallowed whole, although large items are sometimes torn into smaller pieces before being eaten. Indigestible bones and fur are later regurgitated in the form of an "owl pellet." The diets of barn owls can be analyzed by examining the contents of these pellets.
Habitat and Nest Sites
Barn owls inhabit open areas, including agricultural fields, grasslands and marshes. They nest in hollow trees and in buildings where there is not much human activity. Barn owls also will use artificial nest boxes. Nests typically are located on the floor of the natural tree cavity or building (Figure 2). They are made with broken-down bits of old owl pellets. Nest sites are commonly reused by the original occupants or other pairs of owls. The availability of potential nesting sites limits barn owl abundance in some areas.
Barn owls have a global distribution. They are absent only from parts of the West Indies, Indonesia, and New Zealand, and seldom occur at extreme northern latitudes. Estimates of individual home ranges, which vary greatly, have been as large as 3174 ha (12.3 sq mi) and as small as 151 ha (0.6 sq mi). This variation probably is due to differences in habitat and prey availability. For example, if food is scarce in a particular area, an owl may have to travel long distances to get the amount of food that it needs to survive. It would have to hunt over a much smaller area if food is plentiful. The home ranges of neighboring barn owls can overlap significantly.
Behavior and Sociality
These owls are strictly nocturnal predators and spend the daylight hours resting, or "roosting," in quiet protected areas. Members of a pair frequently roost together. They usually do not actively defend their foraging territories from other owls, but they will defend the area immediately around their nests. If food resources are abundant, barn owls sometimes nest in close proximity to each other. For example, at least