I always keep two houses up for bluebirds, and several for wrens. It is pleasant to watch them make their choice, and after a fledging they can set up housekeeping again in the same house, or take another. My experience has been that birds become attached to a house where they have safely fledged a brood, and if it is promptly cleaned they will return to it, rather than try a new one. But I have known instances where a pair began a second nesting before the young of their first brood were fledged. In such a case an extra house is convenient.
MOTHER ORIOLE IN THE BATH
My bluebird house is five by seven inches,[3] and is so shaped as to afford depth. Sufficient height is secured by means of a gable roof; and a half-inch hole immediately under the roof affords ventilation.
The bluebird covers the floor of her house with grasses to the depth of about an inch and a half. Away back against the rear wall she makes the little hollow in which she lays her eggs. I make her entrance one inch and a half in diameter, and just below the middle front. While brooding she can look outside, and this affords her some diversion during that monotonous task. This certainly seemed to be what one bluebird aimed at who nested in Mrs. Daily’s wren house. The wad of grasses in that house reached clear up to the entrance, which was about four inches above the floor. Apparently this bird had tried to build her nest high enough so she could look outside.
Wrens always make a litter several inches high of twigs and other materials. In this litter they embed their nest of fine grasses and feathers. Hence I conclude that they want their entrance several inches above the floor, so that, on going in, they can walk over the litter and do not have to grope through it. Being small birds they need only a small house. After years of experimenting I have settled on five inches by seven for wrens also, but their house is so shaped as to afford height. The sides run up at the back to twelve inches. A half-inch hole high on each side affords ventilation. I make the entrance one inch and an eighth in diameter, just too small for the English sparrow, but large enough to serve some other small bird should no wrens come. A smaller entrance makes it difficult for wrens to get in their bulky nesting materials. My wrens raised three broods in their little house in the pear tree last summer.
A friend of mine bought a wren house which has a low entrance. Some wrens nested in it. One day Father Wren was very much excited, but no one could understand what was the trouble. The next day, believing that the wrens had fledged their young, my friend ordered the house to be cleaned. To her horror she found Mother Wren wedged in among the nesting, dead. The babies were dead in their nest. Evidently their increasing weight had settled the nesting materials so the mother could not get out any more and neither could Father Wren go in. Let this be a warning to all who make wren houses, to make the entrance several inches above the floor!
My houses for wrens and bluebirds are so made that they can be easily opened after use, and cleaned. The front on the wren house can be raised, that on the bluebird house lowered. By means of a screw eye, the front is securely closed while the house is in use.
SO MADE THAT THEY CAN BE EASILY OPENED AFTER USE AND CLEANED