In 2007 blood samples from 52 adult Yellow-billed Cuckoos were sexed by Avian Biotech International lands in Florida. They were able to assign sex for 49 of the 52 birds in the sample. Banding, telemetry and call-response data from 2001-2005 were analyzed for sexually-based differences in behavior and morphology. There is no evidence of sexual dimorphism in Yellow-billed Cuckoos in behavior, vocalizations, tail spots, or morphology...Three rounds of surveys were conducted on the San Pedro River NCA [National Conservation Area] in 2006 and a single survey was conducted during the summer of 2007. The San Pedro population, which had been experiencing a marked decline from 2004-2006, has increased to one of the highest levels ever detected.