First, crows are a protected species under the North America Migratory Bird Act. Any type of lethal control requires appropriate permits available from state and federal agencies. Trapping is often less attractive than other techniques because of the wide-ranging movements of crows, the time necessary to maintain and manage traps, and the number of crows that can be captured compared to the total number in the area. Trapping and removing crows, however, can be a successful method of control at locations where a small resident population is causing damage or where other techniques cannot be used. Examples include trapping damage-causing crows near a high-value crop or in an area where nesting waterfowl are highly concentrated.
Two types of traps can be used to successfully capture crows. First, individual crows may be captured uninjured with No. 0 or No. 1 steel traps that have the jaws wrapped with cloth or rubber. These sets are most successful if placed at vantage points in areas habitually used by crows or if baited with a dummy nest containing a few eggs. Check such traps at least twice daily. Crows captured in this way might be used, if necessary, as initial decoys in the Australian crow trap described below, but the small number of captures is otherwise unlikely to affect a damage situation.
A second and more commonly used trap for crows is the Australian crow trap, a type of decoy trap. These traps are most successful if used during the winter when food is scarce. Australian crow traps should be at least 8 to 10 feet (2.4 to 3 m) square and 5 to 6 feet (1.5 to 1.8 m) high. If desired, construct the sides and top in panels to facilitate transportation and storage. Place the trap where crows are likely to congregate. The most attractive bait is meat (such as slaughterhouse offal, small animal carcasses) or eggs. Whole kernel corn, milo heads, watermelon, and poultry feed may also work and may be preferred where carnivores such as feral dogs might be attracted to the trap. Place the bait under the ladder portion of the trap. Also provide water. After the first baiting, the trap should not be visited for 24 hours. Once the birds begin to enter the trap, it should be cared for daily. Replace the bait as soon as it loses its fresh appearance. Remove all crows captured except for about five to be left in the trap as decoys. Remove captured crows after sunset when they are calm (to facilitate handling).
Should any nontarget birds be captured, release them unharmed immediately. Euthanize captured crows humanely by carbon dioxide exposure or cervical dislocation.
A well-maintained decoy trap can capture a number of crows each day, depending on its size and location, the time of year, and how well the trap is maintained.
A recent study in Israel of hooded crows (Corvus corone), which are about the same size as American crows, indicated that decoy crows were more important than bait to trap success. Using one hooded crow decoy bird, however, appeared to be as effective as using three to four, and fleshy baits did increase success in some cases. To prevent hooded crow escape, the ladder gap width of the American model was reduced from 18 to 12 inches (45 to 30 cm), and 1.5 x 0.8-inch (4 x 2-cm) square rungs were used instead of 3-inch (8-cm) diameter metal rods. The potential response of American crows to such trap modifications is unknown but merits study.
Resources: (online)
Crows
