Running head: Florida scrub-jay source-sink dynamics

Breininger, David; Oddy, Donna

Investigation whether source-sink ideas could be applied to quantify how habitat potential (scrub oak ridges), population density (breeding pairs/40 ha), and fires (shrub height) influenced demography and dispersal within territories of the Florida Scrub Jay. Source-sink theory can be applied to quantify how habitat variation influences population dynamics, but there are few empirical examples. We investigated whether source-sink ideas could be applied to quantify how habitat potential (scrub oak ridges), population density (breeding pairs/40 ha), and fires (shrub height) influenced demography and dispersal within territories. We mapped territory boundaries and measured survival, recruitment, emigration, and immigration of color-branded Florida Scrub-Jays for 12 years. We classified territories as primary if they had well-drained scrub oak. We classified territories as secondary if they didn’t intercept well-drained scrub oak but intercepted poorly drained scrub ridges >0.4 ha. We classified territories as tertiary if they only intercepted poorly-drained scrub ridges <0.4 ha. Territories were further classified as “short” if scrub oaks were <120 cm tall or “optimal” if territories comprised a mosaic of oaks that were short and 120-170 cm tall. We observed that primary territories were sources, because their height was usually optimal, recruitment exceeded mortality, and emigration exceeded immigration. Secondary territories sometimes functioned as sources, but mortality often exceeded recruitment because their height was too short or they were influenced by density-dependent reductions in demographic success. Tertiary territories were usually sinks because mortality exceeded recruitment and immigration exceeded emigration regardless of population, density, and height. Applying source-sink ideas at the territory scale was useful to quantify spatial and temporal habitat variation at a scale relevant to population processes. The approach provides opportunities to partition landscapes into potential source and sink territories to optimize conservation reserve design.