Wigwag Trap for Adults
A simple but effective nest box trap for breeding adults can be constructed using the design shown at left.
The advantage of this trap is that it can be installed on the box from the time the swallows first investigate the box. One can then trap the birds there without ever having to worry about them getting used to a new object near their box at trapping time.
The trap is activated by pulling on a long piece of monofilament fishing line attached to the ‘anchor’ staple by means of a snap-swivel. The line is attached only at the time of trapping, and may initially cause some hesitation by the birds. We typically watch from 15 - 20m away and vigorously pull on the fishing reel when the bird we are after enters the box. Note that there are two ‘keeper’ holes. When the trap is not in use, the right-most hole is used to hold the trap securely away from the hole. To set the trap the ‘keeper’ nail is moved to the left hole and the trap rests against this nail until pulled to capture the bird(s).
The ‘wigwag’ can be easily cut from standard lath material (roughly 1/4"-3/8" thick x 1.5" wide). The anchor staple and the trip line guide are heavy carpentry staples about 1cm long. For the pivot nail we use galvanized roofing nails that are short enough not to penetrate through to the inside of the box, with a large head that serves to stabilize the lath at its pivot. For the keeper nail we usually use "sinker nails" that are covered with a heat-sensitive glue. We never generate any heat by pounding these in, but the glue coating keeps the nails from rusting. And for the ‘catch’ nail we use a very large galvanized finishing nail.
Install these traps in the following way:
- Hammer a staple onto the lath about 1/2 way along its length. Be sure not to go through the lath, otherwise the staple points will snag on the box front.
- Place the lath over the box hole and the spot for the pivot (dashed ‘footprint’ in diagram - note angle). Drill a hole through the lath and into the box at the pivot, placing the hole off center on the lath so that more of the lath is below the pivot than above it. This encourages the lath to fall away from the box hole if anything goes wrong. At the same time, drill a pilot hole for the ‘catch nail’, just slightly to the right side of the lath. This pilot hole should be parallel to the ground, not all the way through the front of the box, and not too close to the size of the nail.
- Pound in the roofing nail to pivot the lath--we sometimes add a washer between the head of the nail and the lath to ensure that the lath can turn freely on the pivot. In any case, do not pound the nail in very tightly!
- Drill two holes, inclined downward, for the keeper nail. Drill one hole through the lath (this will hold the lath when not in use), and one hole directly to the left of the lath. These holes should allow the keeper nail to be inserted and removed easily, and it helps if the hole is not drilled all the way through the box wall (it might catch the swinging side).
- Pound in the long catch nail securely, but not through the box front. Swing the lath up against the catch nail (check to be sure the hole is covered - if not, the pilot hole may need to be re-drilled) and, holding the lath securely, bend the catch nail to the left across the edge of the lath to make a latch.
- Finally, nail in the trip line guide. Only drive this staple in far enough to hold firmly in the wood--you want to leave enough room for the snap swivel of your fishing line to pass easily through when setting and removing the trap line.