eWestern Birds

Use of Nest Boxes by Cactus Wrens in Orange County, California

Robert A. Hamilton, Jutta C. Burger, and Susan H. Anon

ABSTRACT: Responding to studies identifying an apparent lack of suitable natural nesting sites for the Cactus Wren (Campylorhynchus brunneicapillus) in coastal southern California, we designed “cactus-like” nesting structures and nest boxes (1) to determine whether this wren would use such structures or boxes and (2) to assess the efficacy of different construction designs. Out of 32 nest boxes deployed, two supported Cactus Wren nests that successfully fledged young—one in 2010 and another in a different location in 2011. In fall 2010, another box in yet a third location was used for a brood nest. In contrast, we observed no nesting in the 13 cactus-like structures over three years of study. Our results provide “proof of concept” that Cactus Wrens will select and successfully use nest boxes even in areas of mature cactus scrub. Furthermore, all three boxes used by Cactus Wrens were mounted in a tilted position, in which the nest box was angled up to 45°, rather than level. In the summer of 2011, we retrieved the artificial structures and weathering nest boxes and mounted 21 new boxes in the tilted position and with a level floor inserted to prevent eggs from falling into the bottom. We expect that this and future experiments will evaluate the potential conservation value of nest boxes for Cactus Wrens in areas recovering from wildfire and at sites of cactus restoration.

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