Brown-headed Nuthatch

The brown-headed nuthatch is a small songbird endemic to pine forests throughout the Southeastern United States. Genetic analyses indicated low differentiation between northern and southern populations in Florida, but the study also found lower genetic diversity among south Florida populations that may be a result of the increased habitat fragmentation that was documented. The Bahama nuthatch was formerly considered a subspecies (S. p. insularis), but has since been reclassified as its own separate species. Two recent studies assessing vocalizations in Bahama and continental nuthatch populations found important differences. One of the studies also demonstrated that continental and Bahama populations did not respond aggressively to calls of the other population. This type of call-response study is often used to help define cryptic species.

Source: Wikipedia