I devoted much of the last three decades of my career before retirement to studying a naturally occurring hybrid zone between two species of woodpeckers, the Red-shafted and Yellow-shafted Flickers. The hybrid zone served as a natural experiment and model for studying how ecology, natural selection and genetics interact to split an ancestral species into two new species.

Plate 494 from Audubon's Octavo Edition of The Birds of America depicts the "Missouri Red mustached woodpecker." Probably unbeknownst to Audubon, this is actually a hybrid between a Red- and Yellow-shafted Flicker. If, as the title suggests, this specimen was collected in Missouri, it was probably collected in the winter because Missouri is well east of the hybrid zone, but hybrids occasionally meander to the central Great Plains in the winter.

My interest in flickers evolved into a broader interest in the evolution of woodpeckers, which is reflected in most of my papers published towards the end of my career. As with hybrid zones, the evolutionary radiation of woodpeckers served as a model for studying the diversification of a group of animals across much of the face of the earth. Some of my final papers were developed as a member of a team working on "Early Bird," a project designed to determine the early evolution of birds.