Proceedings of the Vertebrate Pest Conference
Linnets, horned larks, crowned sparrows, and woodpeckers
- Author(s): Koehler, James W.
- et al.
Damage to orchard crops and field crops in California by several species of native birds is described, covering biology, behavior, and typical damage caused by linnets (house finches), horned larks, crowned sparrows, and woodpeckers. The legal status of this birds is unique in California, as these migratory birds may be controlled under the authority of the California Department of Agriculture and their associated County Agricultural Commissioners. Bird exclusion, frightening, or other deterrent techniques should be tried first, and only when these are ineffective or impractical should lethal methods be used. Specific bait formulas and toxicants for bird control are under the authority of the state and are not provided here. Control of house finches in agricultural crops typically involved use of prebait followed by toxic bait exposed in orchards in bait troughs; trough design, placement, and use are discussed. For horned larks, lethal control is best accomplished by closely observing feeding behavior, and then exposing prebait followed by toxic bait in furrows, trails, or other similar depressions in the soil within crop fields. Frightening has also worked well, using carbide exploders, the “stake and flag” method, or “continuous string flagging,” especially when these scare tactics are installed in advance of or at the first sign of horned lark damage. Crowned sparrows prefer dense vegetation, so habitat management to remove such cover (including weedy borders along fields or fence rows) near crops or orchards can entirely prevent damage. In smaller plantings, wire frames to exclude crowned sparrows or dense flagging can prevent damage. Where lethal control is needed, prebait and then toxic bait is exposed in shallow v-shaped troughs 2 to 3 feet above ground level, alternately throughout the period of crop damage. Woodpecker damage can be a serious problem in walnut and almond orchards, or they can damage wooden structures. Selective shooting can be effective, as can application of chemical repellent materials on areas that are being damaged or adjacent ledges. Occasionally, woodpeckers have been successfully removed by use of Victor rat traps, or use of toxic baits in holes where woodpeckers store acorns.