March 1998
Kevin Janni
Professor and Extension Engineer
Department of Biosystems and Agricultural Engineering
University of Minnesota
Many dairy producers complain about the mess and noise that sparrows, grackles and starlings make in naturally ventilated dairy facilities. The birds eat a lot of feed, defecate in the feed and on the cows, foul truss members, and peck at insulation. Severe bird infestations can be a significant nuisance. Birds can also transmit disease from farm to farm.
Dairy producers have tried many commercial and home-remedies to get rid of pesky birds. Subscribers to Dairy-L, a listserve on the World Wide Web, have reported trying plastic owls, noise makers, guns, balloons with predator eyes, caustic pastes on trusses, poisons and other practices with varied but usually no long term success. Two producers reported that bird problems were reduced when either an owl or a sparrow hawk moved into the area.
Wild bird hunting and poisoning is regulated. All wild birds, except sparrows, starlings and pigeons, are protected by Federal statutes. Dairy producers cannot hunt or poison grackles and black birds without a permit. This means that a natural biological control approach is needed by dairy producers.
Several years ago Dr. Gary Duke and Dr. David Halvorson, professors in the Veterinary Pathobiology Department and avian enthusiasts, recommended that poultry producers install nest boxes and perches to attract American Kestrels (Falco sparverius) or "Sparrow hawks" to help control starling, blackbird, and sparrow numbers around poultry houses. Dr. Duke received numerous letters from people who reported success attracting Kestrels and who enjoyed watching the attractive birds prowl the sky.
The American Kestrel is a small falcon, the smallest in the U.S., about the size of a jay or robin (9 to 12 inches tall) that feeds mainly on small birds, large insects, and mice. The males, slightly smaller than the females, over winter in Minnesota while the females migrate further south. Kestrels have reddish or rust colored backs and tails and black and white facial markings. The males have blue-gray wings.
Kestrels tolerate human activity fairly well. They are found in a variety of habitats including open fields and forest edges. They can also be found nesting along highways and in cities. Some states and counties erect nest boxes for Kestrels on the back of highway signs. A pair have nested on buildings on the University of Minnesota - St. Paul campus for many years. In 1992, several nest boxes were erected around field plots north of campus and perches were placed within the plots; at least two pairs nested there. The birds regularly "cruised" above the plots seeking prey or rested on the perches and scanned the ground for prey. It was generally concluded that the small falcons were helping control the large numbers of seed-eating blackbirds and sparrows that fed in the plots. The seed-eaters were frequently flushed or discouraged from settling in the plots altogether by the Kestrels' presence and activity.
Kestrels nest in woodpecker holes and cavities in dead trees, artificial nest boxes (See Fig. 2), or small niches in buildings. To attract American Kestrels, a nest box should be installed about 15 feet above ground on the north side of a tree or utility pole about 200 yards from the dairy barn(s). Line the nest with wood chips or coarse wood shavings because a Kestrel will not line its own nest. If the nest is placed in a tree, make sure that the nest entrance is clear of branches. Nests should not be near regular human and equipment activity. Too much human activity may dissuade Kestrels from nesting. Nests should be located where they can be observed and maintained periodically. Dead trees are a natural nesting place. Seldomly used buildings are another option. Light poles are not recommended for nesting boxes.
Kestrels use perches to scan for prey. They will use dead tree branches, poles, power and telephone lines, and artificial perches. To attract Kestrels, several perches should be placed 75 to 100 yards from the dairy barn(s). Artificial perches should be 12 to 15 feet tall with a 1 foot "Tee" on top made with half-inch diameter PVC pipe.
It may take a year or two to attract a nesting pair of Kestrels. They tend to be suspicious of new nest boxes. A male will find a nest site and take over the territory before finding a female partner. Other birds, blue birds or even pesky grackles and sparrows, may use the nest the first year. Producers may want to clean out the nest when undesirable birds inhabit the nesting box. Even after a Kestrel has been attracted, it may be necessary to empty the nest in late March or early April if a grackle or sparrow has set up residence before a Kestrel nests. Kestrels nest in spring from April to early June.
A nest box can be made out of single piece of lumber (1" x 10" x 8') or several pieces of scrap wood. (See Fig. 2.)
Figure 1. Example Kestrel perches on posts 12 to 15 feet tall.
Figure 2. Kestrel nest box plan.
For more information about Kestrels, their habits, and to report on your success in attracting them, check out The Raptor Center web site at http://www.raptor.cvm.umn.edu/ or contact:
Dr. Gary Duke
The Raptor Center
1920 Fitch Ave.
University of Minnesota St. Paul, MN 55108
(612) 624-4702
