OBJECTIVE

The Eastern Bluebird is one of many species of cavity-nesting songbirds native to the Upper Midwestern United States. It nests in natural cavities in trees near open, grassy fields. As humans encroached on bluebird habitat, nesting sites were reduced and competition among all cavity-nesters for remaining sites intensified. Eastern Bluebird populations declined drastically in response to this increased competition from native cavity-nesters and the exploding populations of non-native cavity nesters (e.g., House Sparrow, European Starling) that thrived around human habitats.

Conservationists throughout eastern North America responded to the declines in Eastern Bluebirds by developing and placing artificial nest boxes designed specifically for bluebirds. Numerous designs have been used and the programs have met with tremendous success, with Eastern Bluebird populations now considered "healthy". Hundreds of thousands of nest boxes currently are being maintained for the benefit of bluebirds. This exercise will familiarize you with the use of nest boxes to enhance Eastern Bluebird populations, acquaint you with potential nest box competitors, and examine whether bluebirds prefer to use either wood or PVC nest boxes.


HYPOTHESIS

Eastern Bluebirds prefer to nest in PVC nest boxes.


METHODOLOGY

Eastern Bluebird nest boxes in Winona's Valley Oaks Subdivision will be monitored during the spring months of the 2007 nesting season. Nest boxes in this area were constructed and erected several years ago with funding provided by the Bluebird Recovery Program sponsored by the Audubon Society. Nest boxes were erected in pairs (one wood box and one PVC box) throughout a residential/rural valley bordered by wooded bluffs. Students will be assigned to monitor each pair of boxes weekly throughout March and April for nesting activity by Eastern Bluebirds or their competitors.

Eastern Bluebirds and their competitors each construct unique nests that are easily recognized. Bluebirds construct a simple, unlined bowl nest made exclusively from clean, dry grasses. Tree Swallows construct a similar nest, but line it with large feathers. House Sparrows build a nest mostly of dry grasses, but include lots of other "stuff" such as string, cloth, insulation, paper, plastic, and many other materials gleaned from human habitats. A complete sparrow nest also usually has an arched top with a single entrance hole into the nest. House Wrens build a nest of small twigs, filling the entire nest cavity from top to bottom except for a small central chamber and a small entry. The central cavity is eventually lined with fine grasses.

During the first week, all nest boxes will be cleaned and prepared for use by birds. Each subsequent week, any nesting activities (nest constructed, eggs present, adult birds present, and so on) by any species (keep track of which one!) will be recorded (use the special data sheet). Nests of house sparrows will be removed as they are discovered, but nests of other species will be allowed to remain. Federal law protects the nests of native species, but not those of introduced species such as House Sparrows. Since House Sparrows are known to destroy bluebird nests, eggs, young, and even kill adult bluebirds, most people who monitor bluebird nest boxes remove sparrow nests.


ANALYSIS

After data are collected, display the results in table form (nesting activity by bluebirds and other species in the two types of nest boxes). Compare nest box use for each individual species with simple Chi-square tests (Ecology lab manual).


EQUIPMENT

Brush
Data sheet
Ecology lab manual

___________________________________________________
Neal D. Mundahl
Department of Biology
Winona State University
Winona, Minnesota

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