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BFF (bird friendly fungus) for RCWs (red-cockaded woodpeckers)

Arkansas Natural Heritage Commission - Thursday, November 30, 2017

by Bill Holimon

Unlike most woodpeckers in our area that nest and roost in dead trees or the dead portions of trees, the endangered red-cockaded woodpecker (RCW, Picoides borealis) makes its home within live pine trees. The RCW meets the challenge of excavating cavities in live pines by preferentially selecting trees infected with red-heart fungus (Phellinus pini). The fungus helps decay the heartwood of pines, the central part of the tree that is no longer active or growing. This makes that dead tissue softer and more easily removed by RCWs for creating their cavity chamber.

RCWs are dependent on older pine trees because they have a higher frequency of red-heart fungus and are usually large enough for an RCW’s cavity chamber. Even though the red-heart fungus is typically hidden within the trees, RCWs have a knack for finding portions of the trees affected by the fungus. Sometimes though, as in the case of the image above, the RCW gets a very strong hint with the presence of a red-heart fungus fruiting body, also called a conk. This fruiting body releases spores which are dispersed by the wind. Some spores will land on large branch stubs, providing them an entry way to the heart of the pine tree. There, they germinate, slowly decaying the central heartwood, and after about a decade produce their own conk which will repeat the process. The ever-thankful (at least in this case) RCW is excavating a cavity just below the conk.

The RCW also preferentially selects pines or portions of pines where the live portion of the tree, the sapwood, is narrower. The sapwood is harder regardless of the presence of red-heart fungus and, not surprisingly, loaded with pine sap. So, in addition to being harder to chisel through, this portion will exude large amounts of sap when injured. The RCW typically abandons work for long periods when sap flow is high from its excavation, returning when the sap has hardened and it can resume work without danger of coating its feathers and causing issues with flying.

Because of these challenges, it typically takes a very long time for an RCW to create a new cavity, about 2-4 years in Arkansas and longer in other parts of its range. The cavity in the current photo has been under construction for nearly 2 years. RCWs could not complete many of these cavities without the help of its BFF (bird friendly fungus), another reflection of the importance of older pine woodlands to this endangered woodpecker.


Photo above:

A red-heart fungus (Phellinus pini) fruiting body (conk) in the upper portion of the above image. Below the conk is a red-cockaded woodpecker (RCW, Picoides borealis) cavity under construction. The RCW typically abandons work for long periods when sap flow is high from its excavation, returning when the sap has hardened and it can resume work without danger of coating its feathers and causing issues with flying (note the spider web across the cavity entrance as well as along the bottom of the conk). However, RCWs use sap flow to their advantage, intentionally wounding the tree to start resin flow. This makes it difficult for their primary predator, rat snakes (Elaphe spp.) to reach the cavity where they could devour eggs, nestlings, or even adults.



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