Comparison of Campephilus and Dryocopus:

The four photos used in this collage are:
Top left: Pale-billed Woodpecker (Campephilus guatemalensis), female, Bahía Drake, Costa Rica.
Top right: Pale-billed Woodpecker (Campephilus guatemalensis), female, Playa de Oro, Colima, Mexico.
Bottom left: Lineated Woodpecker (Dryocopus lineatus), male, Río Lagartos, Yucatán, Mexico.
Bottom right: Lineated Woodpecker (Dryocopus lineatus), male, Chaparri, Lambayeque, Peru.

I have posted previously about the differences in toe structure and perching posture of woodpeckers (see: http://artusobirds.blogspot.ca/2015/01/why-woodpecker-lost-toe.html); however a recent photo opportunity in Costa Rica reminded me that I now have a chance to comment further on the postural differences between two of the largest woodpecker genera: Campephilus and Dryocopus.

Pale-billed Woodpecker and Lineated Woodpecker are quite similar in appearance and most people look to the facial markings to distinguish them. If the head is turned away or you don’t have a good look at the facial markings there is one quick aspect of GISS (general impression, shape and size) that helps distinguish them and it relates to a major difference between the Campephilus and Dryocopus woodpeckers (and one that helps us understand why such similar looking woodpeckers belong to different genera).

The Campephilus woodpeckers include many of the world’s largest woodpecker species and they have a neat trick to support their weight and large bodies. In addition to gripping with their toes and stiffened tail feathers, they also spread their trasometatarsus wide with the joint resting against the trunk as an extra support. The top two photos of a Pale-billed Woodpecker shows how this works on a vertical trunk (top left) and an angled branch (top right). Notice how the tarsus and “joint” rest against the trunk such that the bird appears to be resting on them (which many of us might think of this joint as a bird’s knee but it is technically the ankle). Even though the Dryocopus woodpeckers are almost as large, they perch in a more “normal” woodpecker fashion, gripping with their toes and using their tail as a brace as these Lineated Woodpeckers show on a vertical trunk (bottom left) and on an angled branch (bottom right). In each case, notice how the joint does not touch the tree and the tarsi are held at more of a 45 degree angle to the body and to the surface they are resting on (as opposed to resting on the surface as in the Pale-billed Woodpecker examples). This difference is visible from a distance and can be a useful identification clue in situations where lighting or distance makes it hard to observe plumage details with clarity.

To give a more complete, broader picture, following IOC taxonomy, there are six Dryocopus species: Black-bodied Woodpecker, Lineated Woodpecker, Pileated Woodpecker, White-bellied Woodpecker, Andaman Woodpecker and Black Woodpecker. There are 11 Campephilus species (all confined to the Americas), with the two largest presumed extinct: Powerful Woodpecker, Crimson-bellied Woodpecker, Red-necked Woodpecker, Robust Woodpecker, Crimson-crested Woodpecker, Pale-billed Woodpecker, Guayaquil Woodpecker, Cream-backed Woodpecker, Magellanic Woodpecker, Ivory-billed Woodpecker (presumed extinct) and Imperial Woodpecker (presumed extinct). Note that Helmeted Woodpecker has now been moved to the genus Celeus.