BUILDING THE "NB-COMPACT" TRAP

Part 2

The first order of business is to locate the coffee can you intend to use because the length of the can determines the front to back (depth) dimension of the trap. I used a large "Folgers" can. The label reads " 2 lb 2 1/2 ounce or 34 1/2 ounce". The can measures 6 1/8" in diameter and is 6 5/8" long, probably a common size nationwide. Remove both ends from the can and spray the inside of it flat black, the darker the cavity the more Starlings like it.

Now it's on to the main that is nothing more than a box made from plywood. I made mine from 1/4" which is on the verge of being too thin, it was what I had at the time. I would recommend 3/8" or even regular 3/4" lumber. Since everyone may be using wood of different thicknesses I won't bother giving the outside dimensions of the box, it's the INSIDE size that really matters anyway. The inside dimensions should be 15 1/2" wide, 9 1/4" tall and 7" deep. The critical one is the depth ( 7"). That's only 3/8" more than the length of the can and for the trap to work properly and not bind up this dimension must be adhered to. Now glue and nail this whole thing together. DO NOT PUT A ROOF ON IT YET. The roof must be cut a little larger to provide some overhang on all 4 sides, something along the order of 12x20 would be fine. Attatch the roof with screws so that you can remove it easily. You need easy access to the inner workings of the trap so that you can "tune" the mechanism and being able to remove the roof is the most logical way to do this. Make the roof from wood, sheet metal or whatever you like.

At this point you could cut the entrance and exit holes but I would wait until you complete the counterbalance and the inner workings. If you are like me you might like to deviate from the plan alittle and do some "customizing" here. I am not a mechanical engineer so you may have a greater knowledge of balance points and so forth, this may effect the placement of these holes in the final analysis. Lets move on to the "guts" of the trap first. The following design has worked very well for me.

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The two drawings show the setup in such detail that I doubt there will be a problem for you, it's very basic construction. Still there may be some question about the counterbalance weights and the point where the 1"x 2" ("B" on the plan) attaches to the coffee can so I'll touch on those points.

Cut a small 2"x 2" plate from a piece of 1/4" plywood then glue and screw it to one end of "B" (see drawing). This gives you a larger surface and makes attaching the can easier. Drill through the 2"x 2" plate, and the can, at four points and secure the plate to the can with bolts. Use some wood shims at the top and bottom of the plate because the curvature of the can will leave gaps. At the other end of "B"is where the counterbalance weight will go ("D" on drawing ). I used a short piece of 3/16" thick "flat bar" steel. I trimmed it till it was just a bit too light and used washers to make up the difference in weight. On the original model I mounted a small bottle and filled it with lead shot, adding or taking away the lead BB's made tuning the balance a breeze, you might give that a try or come up with your own counterbalance.

At this point it's time to put the whole thing together. Start by drilling two small holes for the pivet points as shown on the plans...one in the front panel and one in the back. Use two small finishing nails for the pivots. They'll go through the holes and into the ends of "C". By the way, the whole thing works alot smoother if you bevel the ends of "C". Check to be sure the mechanism can go through it's full motion up and down without binding. If the coffee can rubs on either side you may have to reposition the pivot holes to adjust the path of the can.

Now would be a good time to cut the entrance and exit holes. Both are 2 1/4" holes and can be cut with a hole saw or a sabre saw. By now you have a good idea of how this whole thing functions so positioning the holes should be easy. Facing the front of the trap, locate a point 3 3/4" from the left inside wall and 1 5/8" down from the underside of the roof. This point will be the center of your entrance hole. Now turn the trap around so you're looking at the back and remember that everything that WAS on the left is now on the right. The center of the exit hole will be 4" from the inside of the right wall and 1 1/4" up from the floor. This puts the exit hole right at floor level. BEFORE YOU CUT...you might DRAW the holes, mount the mechanism, then be sure the holes will be in the right locations as you move the can down and back up. On the photo you'll notice a piece of wood located below the porch. That wood covers up one of MY mistakes...I cut both holes on the same panel!!! That's what I get for discussing my son's curve ball with him while using power tools. Be sure you get it right.

Well you're almost done. All you need to do now is paint the exterior, balance the mechanism and get this thing up in the air. This one was painted with white exterior enamel and the interior was given a squirt of flat black inside on both walls near the can. As with any birdhouse a light color contrasts the dark entrance hole and makes it more noticeable to the birds.

Tuning the balance can be done by adding or taking off a few washers (see assembly "D" on the drawing). My neighbor said to "go shoot a Starling and use him to test the balance!" (No animals were harmed in the making of this motion picture). The best method is to reach in your pocket or go out to the dashboard of your car and get 4 quarters. Throw a couple of them in the coffee can and it should lower about an inch or so. A third quarter should drop the can to within an inch of the floor and when you pitch in the forth one the can should drop down to the floor of the trap. This setting has successfully worked on Starlings and the much lighter House Sparrow yet it's heavy enough to hold the can motionless even as heavy winds blow. All that's left now is to mount the trap and attach the "transport pipe" which gets the captured bird from the trap down to the holding cage. We'll cover that next.

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