222 PROPAGATION OF WILD BIRDS 



Following is a list of species using boxes, classified as the 

 proper sizes of the diameter of the entrance-hole which they 

 require. Where two figures are given they represent the 

 maximum and minimum sizes which are proper : 



(a) if -inch: house wren, Bewick's wren, Carolina wren, 

 chickadee. 



(b) ij-inch: white-breasted nuthatch, tufted titmouse. 



(c) ij to if -inch: bluebird, downy woodpecker, crested 

 flycatcher, tree swallow, violet-green swallow. 



(d) ij to 2 inches: red-headed woodpecker, hairy wood- 

 pecker. 



(e) i\ inches: flicker, saw- whet owl, purple martin. 



(f) 3 inches: screech owl, sparrow hawk. 



(g) 4^ inches: barn owl, wood duck. 



On estates where other ducks are bred and the wood-duck 

 boxes are accessible for pinioned stock, the opening should 

 not be larger than 4^ inches to keep other larger ducks 

 from interfering. 



Size of Chamber. In deciding the size of the nesting- 

 chamber, the principle to go on is to make it just large 

 enough to contain the nest that the species would normally 

 build, or if, as with the woodpeckers, no nest is constructed, 

 large enough for the bird to sit comfortably. For upright 

 boxes the chamber will naturally be round or square. The 

 height of the passage should be at least twice the diameter 

 of the chamber. The following dimensions, taken from 

 the Government Bulletin mentioned above, I should con- 

 sider about right. In the list of species just cited in refer- 

 ence to size of aperture, for groups (a) and (b) the diameter 

 of the chamber may be 4 inches; group (c) 5 inches; group 

 (d), including also the purple martin and saw-whet owl 



