Nest Box Use by Cavity-nesting Birds

Abstract

Nest boxes were investigated for use by cavity-nesting birds at the Carey Run Sanctuary, Garrett Co., Maryland. These boxes provided nesting sites for the eastern bluebird (Sialia sialis), house wren (Troglodytes aedon) and tree swallow (Iridoprocne bicolor). Boxes at the Beltsville Agricultural Research Center, Prince Georges Co., Maryland, provided sites for the eastern bluebird, house sparrow (Passer domesticus) and tufted titmouse (Parus bicolor). Twenty-four box and habitat variables were measured at each location. Six variables were used in discriminant function analysis to segregate the boxes used by the three bird species at Carey Run. Bluebirds tended to use boxes where herb height was less than at boxes used by house wrens or tree swallows. Distance to nearest tree, sapling and shrub, and distance and dbh of the nearest tree in front of the box were least at boxes used by house wrens and greatest at tree swallow boxes. Bluebird boxes were intermediate. A discriminant function model developed for Carey Run was used to classify nest boxes at Beltsville. About 81 % of the eastern bluebird nest boxes, the species common to both sites, were classified correctly at Beltsville. Use of nest boxes by the eastern bluebird can be enhanced by placing them in the correct habitat configuration. Discriminant function analysis could be a useful management tool for evaluating nest box locations prior to undertaking an extensive nest box program. INTRODUCTION The eastern bluebird (Sialia sialis), a cavity nester, relies on woodpeckers and natural forces to create its nest cavities (Zeleny, 1976). The supply of nest sites available to bluebirds has declined owing to snag removal during agricultural and silvicultural practices, to use of treated fence posts that do not develop cavities, and to competition with introduced species, e.g., the starling (Sturnus vulgaris) and the house sparrow (Passer domesticus). The loss of nest sites has drastically reduced bluebird populations (Zeleny, 1976). To encourage bluebird nesting, nest boxes have been constructed and placed in open and semi-open areas, forming bluebird trails. Bluebirds and other cavity nesters have successfully used these boxes to raise and fledge young; however, little quantitative information is available on the influence of location on use of boxes by different cavity nesters. The objectives of this study were (1) to determine what differences exist between nest boxes and habitat used by cavity nesters, and (2) to evaluate the ability of a multivariate statistical model developed from data collected in one physiographic region to predict box use in another physiographic region. STUDY AREA We studied nest boxes on trails located in two physiographic provinces of Maryland, the Allegheny Plateau and the Piedmont. One trail was located at the Carey Run Sanctuary on the Allegheny Plateau in rural eastern Garrett Co. (39037'N, 79008 'W, elevation 756 m). The Sanctuary is composed of 65.6 ha of abandoned fields and pastures, orchards, pine (Pinus strobus, P. resinosa) plantings and mixed hardwoods. Forest species include white (Quercus alba) and red (Q. rubra) oak, sugar maple (Acer saccharum) and some hemlock (Tsuga canadensis). Hawthorn (Crataegus sp.) shrubs and black locust (Robinia pseudoacacia) saplings are scattered throughout open areas. The sample at Carey Run consisted of 51 nest boxes erected in the early 1960s in open fields 1 Contribution No. 1355-AEL, Center for Environmental and Estuarine Studies, University of Maryland.