By Adam Sears, Natural Resource Biologist, R.O.W. Vegetation, Cerro Gordo County Conservation Board, 641-423-5309
The Cerro Gordo County Eastern bluebird population is in for quite a surprise when it returns home for the 2011 spring season. The county conservation staff constructed and installed fifty bluebird boxes this past winter hoping to increase nesting success.
Bluebirds migrate south for the winter months and then return in late February to mid-April. Young birds will often return to the general area where they hatched while adult birds may return to the same location that they successfully raised a family the year before.
Male bluebirds are territorial and defend an area several hundred feet wide in order to assure their mate and offspring adequate supplies of insect food. They prefer habitat that is open with a few scattered small trees like in wildlife areas and roadsides. Then in early-to-mid-April they begin to lay their first clutch of about five pale blue eggs.
The staff chose a bird box plan called the Peterson bluebird nest box – a slightly more complicated box to construct which has shown greater nest success than other boxes. Several comparison studies indicate that higher numbers of bluebirds will fledge per Peterson box which produces more bluebirds. The preferred wood material used for construction is cedar. Another feature worth noting with the Peterson bluebird box is that the roof is sloped to shield rain from the entrance and exit hole which will protect the birds and eggs resulting in higher offspring success. To obtain a blueprint with construction plans for a Peterson bluebird nest box contact or visit the Lime Creek Nature Center.
The staff has selected 25 sites in the roadside that will provide the best habitat for the bird boxes. The sites that were selected have been planted with a diverse mix of native grasses and wildflowers. These sites are generally larger than a standard roadside with most of them being triangles at curves in the road approximately 1 to 2 acres each.
The remainder of the bird boxes were installed at Lime Creek Conservation Area, some of these being new box sites and others replacing old worn out bird boxes. The conservation staff will monitor and record data to see the level of use and nesting success rates of the new bluebird boxes.