Owl Box Installation in San Diego
Barn Owls are pale owls, 33–39 cm in length with an 80–95 cm wingspan. A barn owl has a heart shaped face and two-tone coloration. The head and back are buff, and the underparts are white. Sometimes people in San Diego called them Screech Owls because of their loud, shrill scream, which can be ear-shattering at close range. When cornered, the Barn Owl hisses like a snake, and will throw itself on its back and kick with its sharp-taloned feet for defense. Contrary to popular belief, it does not make the call "tu-whit to-whoo" (which is made by the Tawny Owl).
Barn Owl Food / Hunting
The Barn Owl primarily feeds on rodents, but also eats birds and reptiles. It also sometimes eats insects. A single Barn Owl will eat one or more rodents per night, a nesting pair and their young can eat more than 1000 rodents per year. Barn Owls fly silently; tiny serrations on the leading edges of its feathers break up the flow of air over its wings, reducing turbulence—and the noise that accompanies it. They hunt by flying low and slowly over an area of open ground, hovering over spots that conceal potential prey.
Barn Owls eat more than other owls of the same size. Pound for pound, Barn Owls consume more rodent pests than any other creature. This makes the Barn Owl one of the most economically valuable wildlife animals to those with rodent problems. Often times, these owls are more effective at killing rodents than poisons. The best way to encourage Barn Owls to stay around by providing nest sites in the form of Owl Boxes.
Barn Owl Boxes
The idea of harnessing barn owls in an attempt to control rodents is not a new one. The first introduction of this species for that purpose can be traced back to 1899 when seven birds were imported from London by the Otago Acclimatization Society and liberated at West Taieri in New Zealand. Barn owls are specialized rodent hunters. They are one of the few predatory species that have the ability to regulate their clutch size in a response to eruptions in the population of their prey.
When a rodent explosion occurs, barn owls are capable of producing "super clutches". The healthy condition of the female owl allows her to lay anything from 8-20 eggs. The relationship between predator and prey is always a complex one, in many cases it is not just predation that controls the prey but the behavioral adjustments required by the prey in order to co-exist with the predator. The control of rodent numbers by barn owls is not related as much to the number of rodents caught by the owls, but to the reduction of foraging freedom created by the presence and the potential threat of predation by the owls.
The presence of an occupied box prevents the rodents from straying too far from shelter in its foraging endeavors. This control reduces food availability and in turn reduces population. Barn owl projects have been implemented in many countries worldwide. The Malaysian palm grove projects were well documented in a doctorial thesis and dealt with the financial comparisons between baiting and owl boxes. Over a seven-year study it was found that 75% of the 275 owl boxes erected were utilized. The reduction in rodent damage was reduced by 62% and the use of poison practically eradicated.