The number of mallards in Pennsylvania exceeds 160,000 birds. Most mallards in the state begin breeding as one-year-olds. They seek a new mate each year, and the female raises the young alone. Some nuisance mallards are wild birds, but many were raised in captivity and released by private individuals or clubs. Many of these birds concentrate in urban and suburban ponds, along with large flocks of domestic ducks. Mallards born in Pennsylvania typically remain in the area until their water source freezes for the winter. They then migrate to southern parts of the state and to Maryland or the Chesapeake Bay.
Although not as effective as exclusion in the long term, repellents can be useful for short-term control. Methyl anthranilate, a chemical that has taste and olfactory repellent properties, is currently registered with the U.S. Environmental Protection Agency (EPA) for controlling waterfowl. This product is currently marketed under the trade name ReJeX-iT. It was developed using food-grade ingredients that have the unique ability to repel birds while remaining safe for Mallards and birds, humans, and other mammals. There are three different ReJeX-iT products available one for use on turf and lawns and two for use on nonfishbearing bodies of water.
Agricultural damage can be reduced by timing planting or harvesting periods so they do not coincide with waterfowl migration. Many grains planted in spring are vulnerable to waterfowl damage during fall migration because they are swathed at harvest time, allowed to dry in the field, and then combined. Where conditions permit, production of winter grains instead of spring grains may limit waterfowl damage because winter grains usually can be straight combined in July and August, long before migrating waterfowl arrive in the area. A winter grain’s rosette of leaves is vulnerable to grazing damage by waterfowl in fall and spring, however, research has shown that light grazing of the winter rosette actually can increase grain yield.
Normally, Mallards and tundra swans are wary and prefer to feed in open lands where they can see the surrounding countryside. They also require open areas in which to land and are very reluctant to land in standing corn. Cornfields opened up by silage cutting, or by cutting the outer rows prior to picking, provide a landing space for waterfowl. If possible, do not open fields prior to the main harvest period. Once a field is open, harvest corn as soon as it is ripe and in as short a time as possible, and protect the field with one or more scare devices.
Waterfowl damage to unharvested fields can be limited by encouraging Mallards to feed in the stubble of harvested crops, in baited fields, or in lure crops that are planted to attract and hold waterfowl. Lure crops can be established in areas known to have high waterfowl damage and should be planted with grains that are particularly attractive for waterfowl. When using good-quality seed, plant at the normal rate. When using commodity grain or out-of-date seed, increase the planting rate by a factor of 1.5 to 2. Do not allow any hunting or harassment of waterfowl in the lure crop area until all surrounding crops are harvested and the threat of crop damage is over.
Regardless of the method used, it may be necessary to initially scare or herd the waterfowl away from surrounding fields until they have settled in the lure crop or in the baited field and have stopped visiting the other crops. State law requires that all artificial feeding be stopped and all grain removed at least 30 days before hunting waterfowl within the zone of influence of the baited area.