12 Miscellaneous Circular 18, U.S. Dept. of Agriculture. 
the weight of the lightest bird will cause it to “ break,” thus releasing 
the wire loop and permitting the door to descend and close. , 
Traps of this type are well suited to use on window-feeding 
shelves, and they have also been successfully used on the ground, 
3 on roofs of porches, 
and in similar places. 
NEST-BOX TRAP. 
For the purpose of 
making detailed stud- 
ies of the nesting hab- 
its of many birds, the 
trap-door perch is most 
effective. (Fig. 12.) 
A small piece of sheet 
metal, such as tin or 
zinc, 1s so bent upon a 
piece of wire that it 
serves aS a perch or 
B 1643M 
IIe. 12.—Nest-box trap. A device used to capture adult platform. By torts 
ianly vulupblo asin adie ifenitoty mds (ho g¢ og ne peat eee 
sun by & Penta Be tL ek ube pacts aomeaicianee. 
the device may be fas- 
tened immediately beneath the entrance hole in a nest box or tree 
trunk, and caused to rise from a horizontal to a vertical position by 
pulling a string attached to the wire axle, which is extended and bent 
at right angles to form acrank. As shown in the illustration, the wire 
is also bent into a loop that serves as a bracket to keep the perch in 
FR EMT: LERTICAL 
LRONT” LLLELATIOW. LCTIONAL LIEV, 
ric. 13.—Details of construction of nest-box trap shown in Figure 12, 
a horizontal position when open. A small block of wood will answer 
just as well as the sheet-metal perch. 
When used on nest boxes, the front of the box should be built so 
that it may be opened in order to take out the captured bird. Figure 
13 illustrates the details of construction. The edges of the top of 
the front are rounded off, so that the whole section may be pulled 
