The narrow bottom is preferred by Bluebirds, and helps to discourage birds with large broods. Houses need not be painted, but should remain light in color for less heat absorbtion. Light gray, green or beige stain may also be used. However, the landowner's permission must always be obtained first, and is usually given with enthusiasm and cooperation when the benefits of a Bluebird trail are explained. With proper placement of the recommended Bluebird houses and careful control of starlings and housesparrows, you should have reasonable success with your Bluebird trail and be able to send back increasingly enthusiastic reports.
Sparrow eggs are cream colored with brown specks.
A beneficial bird, the house wren, will take up residence in a Bluebird house if it is near undergrowth and bushes. The fiercely competitive wrens can carry out a whole Bluebird egg, but more often will pierce the eggs and start filling the box to the top with sticks. A male wren will put sticks in several boxes to attract his mate to choose, so these sticks should be quickly removed. We recommend putting wren houses in bushy areas that wrens prefer, to lure them away from the Bluebird boxes. Wren eggs are small, pale pink flecked with reddish brown.