Providing evidence to improve practice

Individual study: Effects of nest-box design on the breeding success of eastern bluebirds Sialia sialis near Green Bay, Wisconsin, USA

Published source details

Radunzel L.A., Muschitz D.M., Bauldry V.M. & Arcese P. (1997) A long-term study of the breeding success of eastern bluebirds by year and cavity type. Journal of Field Ornithology, 68, 7-18


This study investigated the effects of nest-box design on the clutch size, hatching success, chick survival and predation rate of eastern bluebirds Sialia sialis breeding in artificial cavities in Brown and Oconto counties, near Green Bay, Wisconsin, north–central USA.



Between 1968 and 1994, around 500–700 nest boxes were erected near houses or on fences adjacent to fields, pastures or orchards. Boxes were of four designs: i) 10 × 10 × 29 cm, with a 9 cm diameter (screened) opening in the roof (‘open top’); ii) 10 × 13 × 18–21 cm, most with a sloping roof (‘standard’); iii) one gallon (around 3.8 litre) can, placed horizontally, with one end replaced with a wooden front (‘tin can’); iv) large post with a 10 cm diameter hole drilled out of the centre, to a depth of 36 cm, and the top left open / unscreened (‘hollow post’). Open-top and standard boxes were used in all 27 years of the study, whereas tin-can and hollow-post cavity were used in only 15 years.

From mid-March, boxes were checked for occupancy every 7–10 days, and more frequently after eggs were laid to collect data on clutch size, the proportion of eggs surviving to hatching (‘hatching success’), the proportion of chicks surviving from hatching to ringing/banding (at around 10 days old; ‘chick survival’), and the proportion of eggs that survived to ringing age (‘overall survival’).



Average clutch size (roughly 4.4 versus 4.3; n = 27 years), hatching success (82% versus 72%), chick survival (93% versus 87%) and overall survival (76% versus 62%) were all significantly higher in open-top than in standard boxes, but were not significantly different to those in tin-can or hollow-post cavities.

Although a roughly similar proportion of nests in all four cavity types suffered from partial loss eggs or chicks, the overall proportion that failed entirely (at the egg or the chick stage) was significantly lower in open-top boxes (16%; n = 1,506 nesting attempts) than in standard (28%; n = 1,066), tin-can (33%; n = 36) or hollow-post (31%; n = 29) boxes.

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