Nest defense behaviors of native cavity-nesting birds to European Starlings

Abstract

We used behavioral experiments to evaluate competition for nest sites and the extent to which European Starlings (Sturnus vulgaris) are seen as a threat by native bird species at the San Joaquin Experimental Range, Madera County, CA. We quantified the level of aggressive behavior of four species of native cavity-nesting birds to starlings at active nests in trees and nest boxes. In 2000, we presented a life-like model of a starling at active nests of native cavity-nesting species, placed in front of the nest opening. In 2001, a House Sparrow (Passer domesticus) model was used as a control, with both species presented at nests. Models were mounted on a piece of wood and placed on top of the nest box. Responses were coded as sporadic scolding, continuous scolding, aggressive flight, and attack. Placement of the starling model in front of the cavity elicited a relatively more aggressive response than that elicited by a model placed on top of the nest box. Oak Titmouse (Baeolophus inornatus) responses consisted entirely of scolding except for one aggressive flight toward the model, but Western Bluebird (Sialia mexicana), Ash-throated Flycatcher (Myiarchus cinerascens), and Acorn Woodpecker (Melanerpes formicivorus) responses included physical attacks on the starling model. The starling model elicited a significantly stronger response from Oak Titmice and Western Bluebirds than the sparrow model. Although sample sizes were small, Ash-throated Flycatcher responses to the starling model included both aggressive flights and attacks, while neither behavior was seen in response to the sparrow model. Acorn Woodpecker response to the starling model at three nests tested was strong, consisting of attacks on the model by up to seven members of the group. Over the two years of the study, we observed nest usurpation and/or depredation by starlings at seven nests of five species. Our results show that Western Bluebirds, Oak Titmice, Ash-throated Flycatchers, and Acorn Woodpeckers recognize starlings as potential aggressors. We recommend the use of nest boxes to reduce the potential for nest-site competition between starlings and some native cavity-nesting species.

Parent Publication

• Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities

Citation

Olsen, Rodney G.; Purcell, Kathryn L.; Grubbs, David. 2008. Nest defense behaviors of native cavity-nesting birds to European Starlings. In: Merenlender, Adina; McCreary, Douglas; Purcell, Kathryn L., tech. eds. 2008. Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: pp. 457-470.