It is a dark, wintry night and you are driving past an old cemetery.
Suddenly, from nowhere, a huge white form swoops across the road in front of you.
Your headlights pick up a ghostly face with dark, haunting eyes set deep within rimmed sockets.
When your heart stops pounding and you recover your breath, you realize what you have just seen -- a barn owl on its nocturnal flight.
If you've ever experienced such an encounter, you will understand perfectly why Europeans often refer to this bird as the "spirit owl" or "night-hag."
For all their mystery and spookiness, barn owls are a welcome guest to local farmers. A superb mouse-catcher, a barn owl feeding a brood of young may capture 50 or more mice in a single night.
One reason for the barn owl's success as a predator is its deep-set eyes, which allow it to detect prey in extremely low light. In addition, the owl possesses extraordinarily acute hearing that can pick up the sound of voles and mice running even when they are concealed by cover.
Glenn Therres, supervisor of the Maryland DNR's Non-Game and Urban Wildlife Project, has attempted to assess the status of Maryland's barn owl population during the past year.
"Unfortunately," Therres says, "a long-term set of clean data is not available. One of the few ongoing sources of information is the annual Christmas bird count conducted by the Audubon Society since the late 1940s."
He notes that barn owls are more difficult to count than most other birds due to their nocturnal habits and their tendency to vocalize less than other owls.
Additional information has been retrieved by duplicating surveys conducted in the 1950s and the 1970s with reference to barn owl nesting habitats in marsh areas of the bay. There, a plentiful supply of small animals has always attracted a large barn owl population.
Carroll County, of course, has no bay marshes. Before settlement, when our area was almost completely forested, barn owls were scarce. With the coming of agriculture, a habitat was created for the field mice -- scientifically known as "meadow voles" -- which constitute the main part of the owl's diet. Consequently, the owl population proliferated.
Now, Therres says, that trend is reversing. Changing agricultural practices -- fields are no longer left fallow between crops -- along with increasing urbanization have resulted in a shrinking barn owl population in the county.
Also, fewer abandoned barns and silos -- preferred barn owl nesting spots -- are to be found. It is possible, however, to attract barn owls with nesting boxes affixed to the outside of buildings. People who have installed nesting boxes often become quite fond of "their" barn owls and enjoy observing them, especially when the nests contain young.
Therres emphasizes that virtually all the research done on barn owls and other non-game species has been funded by the Chesapeake Bay and Endangered Species Fund, to which taxpayers can designate part of their tax dollars.
To obtain additional information about nesting boxes for barn owls, contact the Piney Run Nature Center, 30 Martz Road, Sykesville, Md. 21784; phone, 795-3274.
To support further barn owl research, check Line 63 -- Chesapeake Bay and Endangered Species Fund -- of your Maryland Personal Income Tax Form.