Delaware Division of Fish and Wildlife biologists are banding barn owls during their annual checking and cleaning of barn owl nesting boxes, including 17 boxes in state wildlife areas and eight boxes in Bombay Hook National Wildlife Refuge. Banding provides valuable information on life span, home range, nest site fidelity, and migratory patterns, and in estimating population size.
Since 1996, Delaware biologists have banded 598 barn owls, including young from 128 broods and 32 adults. In addition, biologists in Delaware have captured previously banded birds from as far away as Blackwater National Wildlife Refuge near Cambridge, Md. Birds banded in Delaware also have been captured regularly in New Jersey.
Barn owls are an asset to farms and other rural properties. A single nesting pair of owls with a brood of young can eat more than a thousand rats, mice and voles during one nesting season. They primarily nest along the coastal marshes, where the availability of their favorite food, meadow voles, is the highest.
Barn owls will use a variety of natural cavities for nesting, such as hollow trees. However, if these owls do not find a suitable natural cavity near a good food source, they will choose non-natural structures that offer cavity-like shelter such as agricultural buildings or spaces under bridges. Nest boxes in areas where their preferred food is readily available provide another option for barn owls.
Construction and placement of nesting boxes began in 1990.
Barn owl nest sites should not be disturbed during courtship, incubation and early hatchling stages, when the birds are likely to abandon their nests. Also, disturbance of nest sites during early fledgling stage will often cause young to leave the nest prematurely, before they have the capability to fly back. Biologists monitor the nest sites closely and know the exact time each nest site can be approached safely, without causing undo disturbance.
Barn owls are protected by federal regulations under the Migratory Bird Treaty Act and by Delaware code protecting all non-game birds. They are not listed as endangered, but are considered a “species of greatest conservation need,” identified in the Delaware Wildlife Action Plan.
The Delaware Breeding Bird Atlas has also found that this species has declined considerably in the past 25 years. During the first atlas (1983-87), barn owls were found in 41 atlas blocks (approximately 10 square miles). However, in the current atlas, the distribution of barn owls has decreased nearly 70 percent to only 14 blocks.
Reasons for this decline are most likely associated with losses of suitable nesting sites, such as older buildings being replaced with newer, less barn owl-friendly structures. Tracking barn owls and installation and maintenance of barn owl boxes are an important part of the Division of Fish and Wildlife’s barn owl conservation efforts.
For more information on banding screech owls and barn owls, contact Wayne Lehman, Division of Fish and Wildlife, at 302-284-1077.