Effects of nest-box design on the breeding success of eastern bluebirds Sialia sialis near Green Bay, Wisconsin, USA
This study is summarised as evidence for the following.
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Provide artificial nesting sites for songbirds
A replicated study between 1968 and 1994 in orchards and fields in Wisconsin, USA (Radunzel et al. 1997), found that eastern bluebirds Sialis sialis were less likely to suffer total clutch loss in nest boxes with screen openings in the roof than in three other designs (16% of 1,506 nesting attempts lost in open-top boxes vs. 28% of 1,066 in standard boxes, 33% of 36 in one gallon tin-cans and 31% of 29 in hollowed posts). In addition, clutches in open-top boxes were larger than those in standard boxes (4.4 eggs/clutch for open-top vs. 4.3 eggs/clutch for standard boxes) and had higher hatching success (82% vs. 72%), chick survival (93% vs. 87%) and overall survival (76% vs. 62%). Open-top boxes were 10 x 13 x 29 cm, with a 9 cm screened opening in the roof; standard boxes were 10 x 13 x 18-21 cm with no roof hole.