We examined individual relatedness patterns and population genetic structure among gnatcatcher aggregations throughout coastal southern California from Ventura to San Diego Counties. To accomplish this goal, we developed a set of highly polymorphic microsatellite loci and sampled 268 individuals throughout the range. With genetic analyses we addressed the following questions:1) How many genetically distinguishable populations exist across the U.S. species range?2) Is genetic relatedness among individuals explained by the amount and distribution of suitable habitat?3) What is the range of dispersal distances between presumptive siblings and parents/offspring?4) What are the patterns of genetic diversity within aggregations across the U.S. range and what is the effective population size?5) How do these results impact future management and monitoring efforts aimed at species recovery?