the odds that at least one young will survive to adulthood. If the supply of small rodents is plentiful, all of the young owls may survive to fledging. However, if the parents are unable to find enough food for all of the youngsters, younger nestlings cannot compete with older, stronger siblings for food and will die. Weakened or dead young may even be cannibalized by siblings.
Unless the rodent population completely crashes or a predator discovers the nest, at least one of the owlets is likely to survive. However, if rodent populations are low, barn owls may skip a breeding season.
Although barn owls are birds of prey, they still fall prey to other predators. Raccoons, black rat snakes, house cats and other nest predators readily consume barn owl eggs and young. Great horned owls are probably the most common predator of adult barn owls.
Lifespans of barn owls are rather short, believed to be 5 to 11 years in the wild. To compensate for this short lifespan, barn owls rely on their unique reproductive potential to perpetuate the species.
Researchers have found that barn owls are capable of catching prey using only their hearing to direct their attack. They placed owls in completely dark rooms and used sophisticated equipment to broadcast the minute sounds of a mouse going through its nightly business from different locations in the room.
With amazing accuracy, the owls repeatedly struck the exact locations from which the sounds were emitted. Not only were the owls able to locate the sources of the sounds, they were able to calculate the direction and speed of movement to strike a moving target.
This type of ability requires specialized hearing equipment. The large, heart-shaped face of barn owls serves as the equivalent of the outer ears of mammals. Short feathers on the face and side of the head form a groove that funnels sound waves into the ear openings.
A moveable flap of skin at the front of the ear opening may be raised to assist in catching sound coming from behind. This flap also may be closed to protect the sensitive inner ear parts. The right and left ear openings are shaped differently and occur at different heights on the sides of the head.
This lopsided arrangement allows owls to receive the sound from slightly different perspectives and helps them pinpoint the origin of sounds. The inner ear parts of owls also relay sound stimuli up to 10 times faster than human ears.
Barn owls not only are oddities among the bird world but also are unusual finds in Missouri. Listed as state endangered, barn owls have declined with the loss of open grasslands and nesting sites. Because their survival and reproduction is closely linked with their food supply, declines in rodent populations also seriously impact barn owls. Pesticides, passed along and concentrated in the food chain, harm barn owls by causing thin eggshells and reducing prey populations.
Because of the rarity of this species, the Conservation Department tracks barn owl nest locations to monitor population trends. The Conservation Department also works cooperatively with landowners to protect and encourage nesting pairs. Landowners with barn owls nearby receive bonus points when applying for CRP and other Farm Bill assistance programs.
Because barn owls readily use human-made structures for nesting, landowners can do something to help this beneficial, unique inhabitant of Missouri. Landowners who find barn owls on their property or wish to attract them can install nest boxes. Barn owls will nest in a simple box placed in a barn loft or other suitable man-made structure. One or two inches of wood shavings or hay provide a cushion for the eggs and young owls.
Once a pair of barn owls selects the nest box, they often will use the structure yearly. Nesting boxes installed in a building already being used by barn owls will help contain the litter of pellets and provide a safer place for raising young.
People who have barn owls nesting nearby are fortunate to have the opportunity of watching these champion hunters raise their families. They may see the young birds line up to be fed and eventually fly and begin to hunt for the first time. They also reap the benefits of having one of the most efficient mousetraps available.