Pecking only in the pines

By BILL CHAISSON
Of a Feather
Friends of mine who winter on the Gulf Coast of Florida recently saw what they at first guessed was a red-cockaded woodpecker. It was small, black checked with white, with a small red spot on the head. As it happens this also meets the description of a downy woodpecker, which their photo revealed it to be. They now, however, are on the lookout for a real red-cockaded woodpecker. To see one, they will have to venture away from the slough where they usually walk and explore a different type of habitat, one that this species rarely leaves.

The red-cockaded woodpecker (Dryobates borealis) is a “southern pine specialist,” which is why it is a rare and declining species. Historically, it ranged from southern New Jersey and Maryland in a broad swathe across the Southeast through Kentucky and Missouri to eastern Texas and Oklahoma and south to the Gulf Coast. It now ranges north only to southern Virginia with an isolated population in Kentucky and others scattered through its former range. Its population at European settlement is estimated to have been about 1 million birds. There are now thought to be 12,500 left.

The habitat to which this species is largely confined consists of longleaf (Pinus palustris), loblolly (P. taeda), slash (P. elliottii), shortleaf (P. echinata), Virginia (P. virginiana), pond (P. serotina) and pitch (P. rigida) pines. The forests must be mature and the understory kept to a minimum by frequent fires (1-5 year intervals). This kind of forest once covered enormous areas of the Southeast, but its value to the forest-products industry has reduced its extent and transformed much of what remains into even-aged stands in which fire is suppressed. The woodpecker’s struggle with the timber industry has caused it to be dubbed “the spotted owl of the Southeast.”

The red-cockaded woodpecker is 7 to 9 inches long, larger than the downy (D. pubescens) and about the same size as the hairy (D. villosus). My Florida friends were not wayward in their confusion of the two species. Jerome A. Jackson believes D. borealis is descended from the habitat-generalist hairy. It is an evolution by vicariance hypothesis. During the previous interglacial interval sea level was higher than it is now, which made part of the Florida peninsula into a large flat island, presumably covered in pine forest and trapping populations of hairy woodpeckers for tens of thousands of years. During this time these small, isolated populations preserved mutations that caused them to look different and behave differently than their hairy ancestors.

Jackson’s evidence for his hypothesis includes the following: (1) hairy and red-cockaded woodpeckers are antagonistic toward one another and D. villosus is rare in the southeast; (2) in many hairy woodpeckers the central red nape spot is divided into two parts on each side of the nape and reduced in size; (3) some marginal populations of the hairy woodpecker have much more white on the sides of the head and neck; (4) barring in the white patch on the back is also seen in marginal hairy populations; and (5) in the Bahamas hairy woodpeckers are almost entirely restricted to pine forests.

Oddly, for this day and age, no molecular genetic work seems to have been done on the relatedness between these species. A 2011 paper by John Klicka (University of Nevada) and others examined the genetic diversity of hairy woodpecker populations. They found that populations in the west and southwest were quite genetically diverse and different from one another, while those in the East and North were neither. Klicka et al. suggested this was “a classic example of glacial effects on within-species biodiversity.” Any region recolonized after the glacial retreat had less diversity and was therefore less liable to produce new species. This implicitly gives support to Jackson’s hypothesis. It also should be noted that among the many subspecies of D. villosus, the eastern one, the purported ancestor, has the most white-checking on the wings.

Red-cockaded woodpeckers have evolved a way of raising their young that is quite distinct from any species thought to be closely related to them. These birds live in family groups that consist of a mated pair plus one to four male birds that are members of previous years’ broods. These “helper” birds take shifts incubating the eggs and also help to feed the brooding female. It is quite rare for these helpers to be female, except in Florida populations, where up to 30% may be.

While these woodpeckers do not migrate, they are also very reluctant to leave their breeding grounds, even as the forest transforms around them by succession. Family groups have been found living in areas where deciduous trees have begun growing in the understory (due to lack of natural wildfires) or even if much of the surrounding forest has been clear cut. This species is extremely attached to its nesting cavity, which is excavated with a great deal of labor and then used year after year. Jerome Jackson emphasizes that populations do not persist long-term in habitat like this.

The conservation status of the red-cockaded woodpecker is characterized as “near threatened” but there is no accepted federal plan for helping the species survive on federally protected lands, which are its last holdout. After the passage of the Endangered Species Act in 1973, private landowners in east Texas began cutting down longleaf pines to prevent the woodpeckers from making nesting cavities in them. Consequently, the Safe Harbors Agreements were developed to allow landowners more flexible management of their land if they preserved the pines.

It is so much work to build cavities that woodpeckers are reluctant to colonize new territory. In some areas without woodpeckers but with good habitat, wildlife biologists are creating artificial cavities. In Florida birds are released into protected areas with suitable habitat.

It’s hard to be a specialist.

Bill Chaisson has been a birdwatcher for over 50 years. He lives and works in Wilmot.