Holding cage modification for nest box traps
for starlings and house sparrows

All but one of the starling traps in my yard had been fitted with simple holding cages made from a 4" cylinder of hardware cloth attached to the bottom of the 4" pvc downtube. It was noted that sounds made by trapped birds in the holding cage traveled up the pvc tube to the trap, much as if it were a giant ear trumpet. This included the sounds of scratching on the wire cage or the bottom of the pvc tube as well as a variety of vocalizations. Video cameras were installed at the entrance to several tipping can traps, recording each visit to the entrance perch by starlings. The first video tapes revealed that after a starling was trapped and held in the cage, subsequent visitors were more likely to quickly leave instead of enter the trap. A microphone was then fitted to the pvc pipe just above the holding cage to determine if the trapped bird was vocalizing or scratching the hardware cloth or pvc when another starling landed on the perch and either flew off or entered the trap. Limited data suggested that starlings would not enter the trap when they could hear a trapped bird in the cage.

One of the holding cages was then modified to limit sound transmission up the pvc pipe. A large aviary replaced the cylinder cage and the plywood top of the cage was isolated from the pvc pipe with a 1/4" gap between the pipe and the plywood. Perches were provided well off to the side so that the trapped bird would not be directly below the pvc tube. In addition to less sound transmission up the tube, trapped birds were quieter in the large aviary.

Trap data was then compared for this trap before and after the change in holding cage. The data for the modified cage was also compared to two other traps with the cylinder cages for the same time period.

The SW aviary, NW cage and NE cage data are for the same time period, from March 25 to June 1, 2004. The SW cage data is for the time period of 3/3 to 3/24, the day before the aviary was installed. The dramatic increase in multiple catch days to 75 percent was quite a surprise. It looks like all of my traps will have to be fitted with large cages isolated from the downpipe. Sound absorbing material would also help, although it would be hard to keep clean. And, perhaps, a 2 part cage with a funnel exit between the two parts would move the birds off to the side as well as a larger cage. But, making the bird comfortable may play the most important role by keeping it quiet.

The first year of trapping resulted in many multiple catch days, but, there were many resident starlings in the yard that year. If I had videotaped the entrance perch then, I would likely have seen many more visits than catches. This year there are often only one or two visits per morning at a trap.

Even though the downtube of this trap extends down through two floors and the wire cage is outside, under the overhang of an open forebay bank barn, the sound of the caged bird still travels up the pvc tube as if it were only several feet away. Isolating the pvc tube with an air gap or non-sound conducting material and moving the bird away from the area directly below the tube is necessary, no matter how long the downpipe.

2004 nest box trap research - modifications and location

A new nest box trap design

Tipping can nest box traps

Use of nest boxes and nest box traps by starlings and house sparrows

remote operated nest box starling and house sparrow trap

artificial nest black hole traps

The house sparrow in America

The house sparrow in 19th C. America

Species of interest in our yard - photos and articles
barn owl American kestrel purple martin barn swallow Eastern bluebird
tufted titmouse Eastern phoebe yellow shafted flicker tree swallow chimney swift
house wren big brown bat Carolina wren brown thrasher catbird
Eastern wood-pewee cedar waxwing Northern mockingbird Turkey vulture

© 2004 - 2009, American Artifacts and Richard Van Vleck, Taneytown, Maryland.