Automated doors for waterfowl banding traps

Abstract

Improving trapping techniques is of continual interest to waterfowl biologists (Burtch 1918, Wainright 1957, Mauser and Mensik 1992). The most common trap for several decades has been the baited swim-in funnel trap with modifications to increase catches (Dumbell 1987, Spitzkeit et al. 1987) and decrease depredation (Godfrey and Fedynich 1986). This style of trap, while effective, can be further improved by attaching an automated door to the funnel entrance. We developed an automated door to reduce depredation of trapped waterfowl and allow greater flexibility of banding times. It may also increase catches of ducks. Without a door mechanism, a funnel trap is always open, and if precautions are not taken, large numbers of waterfowl are often caught in the evening and held in the trap overnight. This makes them vulnerable to depredation and harassment by such predators as raccoons (Procyon rotor) and mink (Mustella vison). To reduce depredation of trapped waterfowl, banders often capture and remove predators near trap sites, erect electric fencing to discourage predators, check traps in the evening to process captured waterfowl, or block the trap entrances after the morning banding period and reopen them once the birds have left the area in the evening. This extra effort significantly increases the time and expense required to operate a banding station. Automated doors prevent birds from being held in the trap overnight by opening during the pre-dawn hours and closing a few hours later, reducing the time birds are held in the trap and reducing their vulnerability to predators. Typically, we programmed the door to open at 5 a.m., before the birds arrived at the trap site, and close 1/2 to 1 hour after sunrise, before the birds began leaving the site. An automated door also allows for greater flexibility of work schedules. Sometimes a trap can not be operated on a particular day and the entrance must be sealed or the top removed to prevent birds from being trapped for extended periods. Consequently, no birds can be caught the next banding day because the trap must be reset. By programming the door to open the morning of the first working day, no days are lost to resetting the trap. Automated doors may also increase catches by closing the trap before birds attempt to exit. Some species adept at navigating narrow openings, such as wood ducks (Aix sponsa), often exit bait traps. We have watched >40 wood ducks enter and exit a clover-leaf trap in <1 hour. By observing feeding behavior, the door can be timed to close before the end of the feeding period when the birds begin to look for an exit. To build the door assembly we used an automobile antenna controlled by a DC timer to raise and lower a wire mesh door along a tubular frame.The 152 x 12-cm frame was constructed from 12.7-mm copper pipe (Figure 1). Parallel to this frame we attached a 152-cm length of pipe along each side using 4 copper elbows and 4 tees. We placed 4 19.0-mm copper pipe unions cut in half lengthwise (19.0 x 19.0 mm to reduce weight) over the slides, 2 on each side, to act as guides and mounts for the wire mesh door. We constructed the door from a piece of 16-gauge 2.5-cm x 2.5-cm wire mesh (12 x 82 cm) and attached it to the mounts 10 cm from each corner using cable ties. This allowed the door to slide freely up and down the slides. Another