This summer I devised but have NOT YET TESTED a conventional bottomless nest box trap
with a simulated nest with artificial eggs. The idea of the artificial nest is to entice timid starlings and house sparrows to enter the box. House sparrows are especially cautious and some people report that they do not enter their bottomless traps. This type of trap is simply a bottomless nest box mounted on top of a pipe and the entire interior painted flat black so the starling cannot see that there is no bottom. I used both 6" and 4" pvc drain pipe on my two prototypes. Both have an artificial nest mounted behind a lexan window. The trick is to provide enough light for the bird to see the eggs, but not to reveal that there is no bottom. These two traps are in place under the starling trees, but at the moment we have no starlings. We never have enough house sparrows to do an adequate test, but some starlings will likely return with cold weather. I often see 30 or more jabbing for grubs in our neighbor's short grass lawn.
Like all automatic traps, these black hole traps must be frequently monitored when in use. Each is fitted with a hole cover which I can close to inactivate the trap when not in use. An elbow at the bottom of the pvc tube prevents light from entering the tube and leads to a holding cage. The design of the cage depends on the intended use. If starlings are to be removed very quickly, a small wire cage is fine. At the other extreme, a large roofed aviary can comfortably house a colony of starlings (if you have some need to do so).
artificial nest in 4" pvc black hole trap
artificial nest for 6" pvc black hole trap The black painted top half prevents the bird at the entrance hole from seeing its reflection.
the 2x8's shaped for assembly of the 4" nest box cover
a small cage on the 4" trap with pivoting hand hole cover
Painting PVC pipe
PVC pipe has an oily residue on its surface which must be washed off. The surface should then be lightly scuffed with medium sandpaper. I use a flexible sanding block on a stick to reach the interior of 5' lengths (working from each end requires only a 30" reach). The pipe is never round, especially the thin walled 4" pipe, so a solid round sanding block that just fits inside the pipe does not work, as I learned in my first attempt. Next, a good quality latex primer designed for use on smooth surfaces should be applied, followed by a coat of flat black latex paint. I modified a paint roller for this purpose and use a foam brush attached to a stick for the inevitable touch up work. It's important that the couplings are painted where they will be exposed, but be careful to not get too much paint on the ends of the pipe and coupling and elbow or they won't slide together.
the modified paint roller with 4' handle for painting 4" and 6" pvc
the foam brush for touching up 6" pvc interior
May 2003 update - The black hole traps have not performed well this year, compared to the tipping can devices. Several starlings were caught in the 6" trap and none in the 4" model over winter. It may be that too much light is entering. Any debris that accumulates on the black painted elbow at the bottom of the tube reflects light from the cage. I have replaced these traps with more tipping bucket models placed on outbuilding walls.
