Ferruginous Pygmy-Owl Glaucidium brasilianum

  • Order: Strigiformes
  • Family: Strigidae
  • Polytypic: 13 subspecies
  • Authors: Ray Larsen

Demography and Populations

Little information is available regarding life span, survivorship, reproductive success and population density throughout the owl’s range. Populations have been shrinking in most of Arizona and Texas since the 1920’s (Flesch and Steidl 2006; Flesch and Steidl 2007; Johnson et al. 2003; Proudfoot et al. 2006b), particularly along the peripheries of habitation, and populations may be experiencing similar decline more recently in northern Mexico (Sonoma) (Flesch and Steidl 2006; Johnson et al. 2003; Flesch and Steidl 2010), although research is needed. Some data exist on current population densities in Arizona and Texas, but historical accounts of Ferruginous populations are dominated by anecdotal evidence, so the rates of population shrinkages are difficult to calculate. In 1999, 99 nests were recorded in Kennedy County, Texas, and 16 nests in the Tuscon Basin of Arizona (Proudfoot and Johnson 2000). Proudfoot et al. (2006) estimated the population size of all owls in Arizona at 13-117 individuals (Proudfoot et al. 2006). In the south of Mexico through its range in Central and South America, the species is considered common, although population estimates are unavailable. The main cause of mortality in fledgling and adult Ferruginous Pygmy-Owls is predation, most notably by raccoons (Procyon lotor), Great Horned Owls (Bubo virginianus), Cooper’s Hawks (Accipiter cooperii), Harris’s Hawks (Parabuteo unicinctus) and other mammalian and avian predators (Proudfoot and Johnson 2000). Starvation is also a documented cause but accounts for few deaths (Proudfoot and Johnson 2000). Several body parasites have also been identified in fledglings, but their overall affect on Ferruginous health is unknown. Among them are Philornis mimicola and Ornithodoros concanensis in Texas populations (Proudfoot et al. 2006), and Protocalliphora sialia and Hesperocimex sonorensis in Arizona (Proudfoot et al. 2005). Known health consequences include blood loss and anemia (Proudfoot et al. 2006). Ferruginous Pygmy-Owls court and nest in their first year (Proudfoot and Johnson 2000).

Recommended Citation

Larsen, R. (2012). Ferruginous Pygmy-Owl (Glaucidium brasilianum), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.fepowl.01