Mexican spotted owl (Strix occidentalis) population dynamics:: Influence of climatic variation on survival and reproduction

Understanding the mechanisms causing temporal variability in demographic parameters is essential to understanding fluctuations in populations. As part of a long-term demographic study, we evaluated influence of climate on Mexican Spotted Owl (Strix occidentalis lucida) annual survival and reproduction in two study areas, one in Arizona and one in New Mexico. Spotted Owl survival in New Mexico and reproductive output in both study areas were positively related to total amounts of precipitation from the previous year, previous winter, or monsoon season. For both study areas, temporal process variation in reproductive output (CV[R] = 51.2 and 75.2% for Arizona and New Mexico, respectively) was greater than that for survival (CV[phi] = 12.9 and 7.1% for Arizona and New Mexico, respectively). Precipitation from the previous year explained 73% of (sigma) over cap (2)(temporal) reproductive output for Arizona owls and precipitation from the previous monsoon explained 42% of (sigma) over cap (2)(temporal) in reproductive output for New Mexico owls. Precipitation from the previous monsoon season explained 53% of (sigma) over cap (2)(temporal) in Arizona owl survival and precipitation from the previous winter explained 56% of (sigma) over cap (2)(temporal) in New Mexico owl survival. The two populations of Spotted Owls we studied appeared to have the same life-history strategy hypothesized for a population of Northern Spotted Owls (S. o. caurina), although the Mexican subspecies apparently responded quite differently to climatic variation. Received 6 February 2001, accepted 29 October 2001.