Cactus Ferruginous Pymgy-Owl

CFPO 1The cactus ferruginous pygmy-owl (Glaucidium brasilianum cactorum) is a small bird, measuring just 16.5 cm in length and 70 g in weight. The species is known to occur in far southern Arizona and south Texas, as well as into Mexico, Central, and South America. The historic range of the species included much of the lower Gila River basin; however, current known populations in southern Arizona are constrained to Organ Pipe Cactus National Monument in the west, across the Tohono O’odham Nation, to the Altar Valley in the east. Pygmy-owls commonly nest along heavily wooded xeroriparian washes with large Saguaro cacti or trees with suitable nesting cavities within Sonoran desert scrub and semi-desert grassland communities.

The Arizona population of the pygmy-owl was listed as Endangered under the Endangered Species Act in 1997 by the U.S. Fish and Wildlife Service, however was de-listed in 2006. The species was originally listed due to threats from loss of riparian habitat, increasing prevalence of disease and predation, and increasing frequency of wildfire due to non-native plants. Arizona populations of pygmy-owls have been decreasing since approximately 1990; however, since the species was delisted limited monitoring has completed to track large-scale population trends. Additionally, many of the threats the owl faced when listed are still present, especially riparian habitat loss due to development and groundwater pumping.

Pima County has a storied history with the cactus ferruginous pygmy-owl, in fact it was the species that spurred the initiation of the interagency Sonoran Desert Conservation Plan planning process in 1997. Rapid development in the Tucson basin as the time was heavily impacting the limited remaining pygmy-owl habitat in the area, leading to the U.S. Fish and Wildlife Service stepping in to halt multiple projects all together. The County convened numerous stakeholders, including the research, conservation, and development communities, to determine a way forward by which to protect the pygmy-owl and allow for responsible development.

CFPO 2The County is working closely with staff from the U.S. Fish and Wildlife Service and Dr. Aaron Flesch of the University of Arizona to document and monitor pygmy-owl populations on County conservation lands. Our first round of monitoring in 2017 demonstrated the importance of County conservation lands for conserving pygmy-owl habitat as we found numerous previously unidentified nesting locations. The next round of pygmy-owl monitoring will occur in 2020, and will include both continued monitoring of previously identified territories and inventories of areas not surveyed in 2017.

Photos by Aaron Flesch / University of Arizona