 five pairs are known to nest regularly in a single barn in south Florida. When cornered, barn owls exhibit a variety of threat displays including wing spreading, head waggling, hissing, and bill snapping.
Reproduction and Development
Barn owls usually are monogamous and often remain with the same partner for several consecutive breeding seasons. Eggs are laid between February and June, depending on locality and climate. In Florida, eggs are usually laid in February. In subtropical and tropical areas, including southern Florida, a second set of offspring are produced in the late summer or fall. The average number of eggs produced is 4–6, but extremes of more than 10 eggs in a single nest have been observed. Eggs are laid 2 or 3 days apart and hatch in that same sequence. As a result, there is always an age difference of a few days between each chick (Figure 3). This ensures that at least a few of the chicks, because they are older and stronger, will always be fed if food becomes scarce. If food is plentiful, all of the chicks will be able to eat. Chicks grow rapidly, achieving adult weight and feathering in 8–9 weeks (Figure 4). At this point they roost near the nest while learning to fly and hunt. Their parents still bring food to them for another few weeks until they become fully independent.
Barn owl populations are stable in some parts of their range, including Florida, but seven midwestern states list barn owls as threatened or endangered. Nine other states classify them as a species of concern. Population declines also have been noted in Europe. The most often cited cause of these declines has been the loss of nesting and roosting sites resulting from changing agricultural practices and urbanization. As agriculture has increased in scale and modern farming techniques implemented, many open-air barns and other farm buildings have disappeared from the landscape. Rows of trees that were once a common feature in small-scale agriculture also have been removed, further degrading barn owl habitat. Additionally, the expansion of urban areas into pastoral countrysides has destroyed owl hunting and nesting habitat. The use of pesticides may have impacted many owl populations by indirectly poisoning them or by killing off their food source. The relative importance of these factors in the overall decline of the species is unknown.
The loss of nesting sites may be offset by installing artificial nest boxes (Figure 5). Barn owls will readily occupy these structures if they are provided. The preservation of large trees and the maintenance of open, grassy areas also would be beneficial for these owls. Furthermore, reduced use of pesticides would minimize the risk of accidental poisoning of barn owls.
Florida Fish and Wildlife Conservation Commission. 2003. Florida's Breeding Bird Atlas: A Collaborative Study of Florida's Birdlife. http://www.wildflorida.org/bba
Lee, C.H. 1997. Barn owl for field rat control in cocoa. Journal of Tropical Agriculture and Food Science 25(1):43–54.
Marti, C.D. 1992. Barn owl. In The Birds of North America – Life Histories for the 21st Century (A.F. Poole, P. Stettenheim and F.B. Gill, eds.). The American Ornithologists Union and The Academy of Natural Sciences of Philadelphia, Washington, D.C. and Philadelphia. Pp. 5–15
Taylor, I. 1994. Barn Owls: Predator-Prey Relationships and Conservation. Cambridge: University Press. 304 p.
Van Vuren, D.; Moore, T.G.; and Ingels, C.A. 1998. Prey selection by barn owls using artficial nest boxes. California Fish and Game 84(3):127–132.