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Distribution, abundance, and habitat characteristics of Coastal Cactus Wrens ( Campylorhynchus brunneicapillus ) in San Diego County, California—2025 data summary

Alexandra Houston·Suellen Lynn·Barbara E. Kus
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Abstract

Executive Summary We surveyed for coastal Cactus Wren ( Campylorhynchus brunneicapillus ) in 498 established plots in San Diego County, California, in 2025, encompassing 4 genetic clusters (Otay, Lake Jennings, Sweetwater/Encanto, and San Pasqual). Of the 498 plots, 372 have been surveyed every year starting in 2020. Two surveys were completed at each plot between March 1 and July 31. Cactus Wrens were detected in 220 plots (44 percent of plots). In plots that have been consistently surveyed since 2020, Cactus Wrens were detected in 35 percent of plots, similar to 2024 (34 percent), 2021 (35 percent), and 2020 (35 percent), and higher than in 2023 (26 percent) and 2022 (30 percent). Across all survey plots we detected 184 Cactus Wren territories in 2025. We documented 107 territories in plots that have been consistently surveyed since 2020, which is similar to the number of territories in 2024 (106) and 2020 (108), more than we documented in 2022 (93) and 2023 (85), but slightly less than the peak in 2021 (113). Across all survey plots the number of territories increased from 2024 to 2025 in the San Pasqual genetic cluster, increased slightly in the Lake Jennings cluster, decreased slightly in the Sweetwater/Encanto genetic cluster and remained the same in the Otay genetic cluster. At least 83 percent of Cactus Wren territories were occupied by pairs, and 100 fledglings were observed in 2025. We observed three banded Cactus Wrens in 2025. Adult birds ranged from 6 to 9 years old and occupied the same territories as in previous years. Banding of Cactus Wrens ceased in 2019 and as a result we have a very low number of banded wrens remaining in the population, which makes it difficult to detect movement of wrens between genetic clusters. We detected no movement of banded Cactus Wrens between genetic clusters in 2025. Vegetation at Cactus Wren survey plots was dominated by coastal sage scrub shrubs, such as California sagebrush ( Artemisia californica ), California buckwheat ( Eriogonum fasciculatum ), and lemonade berry ( Rhus integrifolia ). Cactus Wrens preferentially selected plots dominated by California buckwheat in the Otay genetic cluster and avoided plots dominated by lemonade berry and jojoba ( Simmondsia chinensis ). Cactus Wrens also appeared to prefer plots dominated by broom baccharis ( Baccharis sarothroides ) while avoiding plots dominated by California sagebrush in the Lake Jennings cluster. No definitive signs of fungal pathogens were observed on cactus within and around survey plots. Blue elderberry ( Sambucus mexicana ) was detected at 43 percent of plots, and Cactus Wrens preferentially occupied more plots with elderberry than were available. Very little dead or unhealthy cactus was observed within all survey plots, and Cactus Wrens preferentially occupied plots with less dead cactus while occupying plots with unhealthy cactus in proportion to its availability. Eighty-nine percent of plots had more than 5 percent of cactus crowded or overtopped by vines and shrubs, and Cactus Wren occupied plots in proportion to the degree of shrub and vine crowding or overtopping. Just over half of the plots had greater than 5 percent non-native annual cover, with Cactus Wrens preferentially occupying plots with less non-native cover.

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Alexandra Houston, Suellen Lynn, Barbara E. Kus. 2026-10-30. Distribution, abundance, and habitat characteristics of Coastal Cactus Wrens ( Campylorhynchus brunneicapillus ) in San Diego County, California—2025 data summary. https://doi.org/10.3133/dr1232

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