Population Dynamics of California Quail Related to Meteorological Conditions

Abstract

Demographic responses of California quail (Callipepla californica) to precipitation-related variables vary among locations with different mean rainfall. With 23 years of data from a California quail population in a semiarid region, we determined a positive response of reproductive success (juv/ad) to precipitation during the previous winter. Computed correlations with soil moisture content and actual evapotranspiration were significant but not as high as with precipitation. Correlations with mean monthly temperature, days/month 38 C were not significant. Attempts to account for possible lower reproductive capability of first-year breeders did not improve statistical relationships. The number of adults each year was positively correlated with the number of juveniles in the previous year. The number of juveniles produced each year was correlated with the number of adults in that year only when the effect of precipitation was removed; the relationship was then linear. The interannual fluctuations in population numbers resulted from low adult survival and the influence of precipitation on recruitment through unknown mechanisms. J. WILDL. MANAGE. 52(3):469-477 The distribution of California quail was originally limited to California and Baja California, Mexico. The species now inhabits areas with a wide range of climatic conditions and has proven adaptable in introductions into many western states and several other countries (Leopold 1977). Population numbers appear to depend on weather conditions. However, weather influences different populations in different ways. On the Modoc Plateau of northern California populations appear to be adversely affected by Present address: School of Fisheries, University of Washington, WH-10, Seattle, WA 98195. This content downloaded from 157.55.39.201 on Tue, 24 May 2016 05:03:17 UTC All use subject to http://about.jstor.org/terms 470 CALIFORNIA QUAIL DYNAMICS * Botsford et al. J. Wildl. Manage. 52(3):1988 early summer rains that destroy nests and chicks (Savage 1974). In a coastal population near Berkeley, California, young chicks apparently died after getting wet during spring rains, fog, and summer drizzles (Raitt and Genelly 1964). In contrast, high winter and spring rainfall is associated with high reproduction in a semiarid region near Shandon, California (McMillan 1964, Erwin 1975). For the Shandon population, Francis (1967) developed a multiple regression of annual reproductive success (juv/ad in fall harvest) on soil moisture at the end of April (83.1% of the variance), the ratio of juveniles to adults in the preceding year (12.4%), and the total seasonal precipitation at the end of April (3.3%). The model developed by Francis (1967) fit the data on which it was based but not population data for earlier and subsequent years (Francis 1970, Leopold 1977). We present a new set of data from a different semiarid site and further evaluate precipitation, temperature, and population density as determinants of California quail population levels in semiarid regions. We thank J. G. Brittnacher for computational assistance and comments. This study was funded by the California Department of Fish and Game and by federal funds administered through the Agricultural Experiment Station as Hatch Projects 3222, 3915, and 4071.