Hybrid zones are regions where individuals with divergent genomes interact, resulting in offspring of mixed ancestry. These natural laboratories can be used to investigate the mechanisms that underlie reproductive isolation and the genetic bases of traits relevant to speciation. They can also be used to investigate species interactions and the influence of environmental change on these interactions and on species distributions. We have worked on a number of hybrid zones, including murres in the North Pacific, boobies off the northern coast of Peru, and both warblers and chickadees in eastern North America. Much of our hybridization research today is being done through the ºù«ÍÞÊÓƵ Chickadee Study, see below.