Activity and population characteristics of Andean Condors in southern Chile

Data were collected on general activity patterns and population characteris tics of free-ranging Andean Condors Vultur gryphus in Torres del Paine Nati onal Park, Chile from July 1992 to June 1994 during 3,680 h of observation. Seasonal differences were evident in relative abundance and activity patte rns. The mean number of condors sighted, observation significantly higher i n fall-winter than in spring-summer. There was a significant decrease from spring-summer to fall-winter in the percentage of observations during which we sighted solitary condors and a significant increase in the number of gr oups of condors. In addition, mean monthly maximum group size was significa ntly larger in fall-winter than spring-summer. The sex ratio (males:females ) of juveniles was significantly skewed in favor of females, and that of ad ults was significantly skewed in favor of males. The significantly differen t adult:juvenile ratio of condors visiting the park could have resulted fro m differences in distribution and habitat use and/or low breeding rates. Di fferential juvenile mortality and dispersal could also have produced skewed age and sex ratios, but more research is needed. Condor activity seemed re lated to wind speed. The greatest proportion of condors was observed flying in calm and low winds and less frequently in moderate to very strong winds . Temperature seemed to have an important effect on aerial activity because the greatest proportion of condors was sighted flying and soaring on warm days. Temperature and wind speed were weakly correlated.