A Brown-headed Nuthatch is truly elfin, weighing about ten grams and measuring only 4.5 inches. That's not much larger than a kinglet, and less than half the weight of a White-breasted Nuthatch.
Another interesting aspect of RCW nest cavities is the birds' propensity for drilling sap wells around the cavity's perimeter. By doing so, the woodpeckers trigger a sheet flow of gummy, sticky sap all around the nest site. The likely theory for this is that the tarry sap impedes the ability of predators such as high-climbing rat snakes to gain access to the hole. Plenty of viscous white pine sap is evident in the photo above.
The Red-cockaded Woodpecker was listed as an endangered species in 1970; thus it was among the first group of animals to gain protection under the federal Endangered Species Act with its passage in 1973. At that time, fewer than 10,000 RCW's existed. With protection of its habitat and management techniques, the woodpecker population has grown by one-third. That's still precious few birds. I certainly hope this iconic bird of the southern pinewoods never goes the way of its larger cousin, the now extinct Ivory-billed Woodpecker.