Barn Owls May Help Solve Everglades Rodent Problem

Researchers at the University of Florida's Institute of Food and Agricultural Sciences are hoping to increase the number of barn owls in south Florida to help rid the Everglades Agricultural Area (EAA) of destructive rodents.

Rodent pests, primarily cotton rats and marsh rabbits, can cause up to $30 million in damage annually to the area's 750,000 acres of sugarcane, rice and vegetable crops. In sugarcane fields, rodents cause a direct loss by devouring the millable portion of the plant, the stalk containing the desired sucrose. But indirect losses due to stand reductions and harvesting losses may be even more substantial, said Richard Raid, an associate professor of plant pathology at the UF/IFAS Everglades Research and Education Center in Belle Glade.

``In the past, growers relied principally on chemicals to control excessive rodent populations, but rodenticides are short-lived and have to be re-applied,'' Raid said. ``Rodents can also become bait shy, rendering chemicals less effective.''

With the current emphasis on ``sustainable agriculture,'' Raid has joined with Greg Hendricks, a wildlife biologist with the USDA Natural Resources Conservation Service (USDA/NRCS), to look for a more environmentally sound method of rodent control. Their cooperative efforts have focused on one of nature's most efficient rodent predators --- the barn owl.

``The indigenous barn owl is very effective in preying on such agricultural pests,'' Hendricks said, ``with a single nesting pair capable of eliminating more than 1,000 rodents per year. But barn owl populations in the EAA remain far below optimum because of a shortage of suitable nesting sites.''

Hendricks said that while barn owls readily accept man-made structures such as barns, silos, pole sheds and church steeples as nesting sites, urbanization, farm consolidation and building modernization have all taken a toll on historical barn owl nesting sites and natural habitat.

With the support of Florida's sugarcane industry, Raid and Hendricks are looking at the use of man-made nesting boxes as a way of enhancing barn owl populations. In a cooperative effort by IFAS, the USDA/NRCS and Wellington Community High School, studies have shown that barn owls will readily colonize one of several nesting box models selected by Raid and constructed by environmentally minded high school students.

``Perhaps even more importantly, our research has demonstrated that barn owls will colonize nesting boxes positioned on tall posts along drainage ditches and canals surrounding agricultural fields, in spite of the open exposure,'' Raid said. ``Since such terrain makes up the bulk of the EAA's acreage, such findings are extremely promising.''

Sylvia K. Beauchamp

photo by Thomas Wright

Barn owls, such as the one shown here with plant pathology Professor Richard Raid, are effective predators of agricultural pests like cotton rats and marsh rabbits, which can cause up to $30 million in damage annually to south Florida's sugarcane, rice and vegetable crops.