Demography of Mexican spotted owls in the Sacramento Mountains, New Mexico

• Published in: The Journal of wildlife management 2014-01, Vol.78 (1), p.42-49
• Main Authors: Ganey, Joseph L., White, Gary C., Ward Jr, James P., Kyle, Sean C., Apprill, Darrell L., Rawlinson, Todd A., Jonnes, Ryan S.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal populations; Animal, plant and microbial ecology; Applied ecology; Aves; Biogeography; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Demecology; Demography; Endangered & extinct species; Endangered species; fecundity; Forest service; Fundamental and applied biological sciences. Psychology; General aspects; Mexican spotted owl; Mountains; Owls; Parametric models; Population dynamics; Population Ecology; Population estimates; Population growth; population trend; Population trends; population viability; Pradel model; recruitment; reparameterized Jolly-Seber model; Strix occidentalis lucida; Survival; Threatened species; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Viability; vital rates; Wildlife management
• ISSN: 0022-541X; 1937-2817
• DOI: 10.1002/jwmg.642

Information on population dynamics is key to gauging the status of threatened or endangered species. We monitored demography of a population of threatened Mexican spotted owls (Strix occidentalis lucida) in the Sacramento Mountains, New Mexico from 2003 to 2011. We estimated reproductive output for territorial pairs of owls; used mark-recapture methodology and Pradel's reparameterized Jolly-Seber models to estimate annual apparent survival rates, recapture rates, recruitment rates, and annual rate of population change (λRJS) for 2005-2009; and used estimates of λRJS to assess short-term population viability. Reproductive output was highly variable for 2004-2011, whereas annual apparent survival and recapture rates were less variable among years. Annual rates of population change exceeded 1.0 for both sexes from 2005 to 2009, and empirical observations of numbers of territorial owls supported the model-based trend estimate. Abundance of territorial owls was strongly related to reproduction within the study area, suggesting that population change was driven largely by internal processes. Population viability analyses suggested that population growth was likely to continue in the short term if current conditions persist. The positive growth rates observed in our study populations are encouraging, and may indicate that current recommendations for recovering this owl are succeeding. However, our estimates of λRJS covered a very short time period, given both the potential lifespan of Mexican spotted owls and the extent of temporal variability in weather typical of the southwestern United States. Longer studies of owl demography than we present will be required to understand long-term population trends, and such studies should extend across the range of the subspecies. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.