Meeting Abstract

P1.112  Jan. 4  Flexible breeding in a Sonoran Desert songbird is associated with El Ni�o-Southern Oscillation (ENSO) weather patterns SMALL, T.W.*; DEVICHE, P.; Arizona State University; Arizona State University tsmall@asu.edu

Inter-annual variation in weather conditions and resource availability can influence the timing of reproduction in animals. In arid environments, flexible breeding patterns are more commonly observed than in more seasonal temperate environments because many species breed in close association with temporally variable rainfall. The Rufous-winged Sparrow, Aimophila carpalis, is a Sonoran Desert resident that normally breeds after summer rains (July/Aug) but also breeds in the spring of some years. We studied Rufous-winged Sparrow breeding records for Southern Arizona between 1940 and 1975 to identify proximate environmental factors that may stimulate spring breeding events. In all years when spring breeding was observed (n=6), nesting was initiated in April. Total rainfall in the fall (Sept-Dec) and winter (Jan-March) prior to spring breeding events was approximately three times greater compared to years when early breeding was not observed (n=8) and compared to all other years between 1940 and 1975 with reliable climatic records but with no published breeding records (n=14). Temperature did not differ in any season between early breeding years and the other years. The Southern Oscillation Index, a measure of the El Ni�o-Southern Oscillation (ENSO), was significantly lower in the fall and winter prior to spring breeding compared to other years, indicating that spring breeding was correlated with warm water currents in the eastern Pacific Ocean. The North Atlantic Oscillation Index did not differ between early breeding and other years. We conclude that the environmental conditions stimulating spring breeding in Rufous-winged Sparrows may be caused by ENSO driven weather patterns.