Protecting red-cockaded woodpecker cavity trees predisposed to fire-induced mortality

Published source details Williams B.W., Moser E.B., Hiers J.K., Gault K. & Thurber D.K (2006) Protecting red-cockaded woodpecker cavity trees predisposed to fire-induced mortality. Journal of Wildlife Management, 70, 702-707.
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Summary

From the mid-1990s onward, construction of artificial cavities and rotational burning to maintain longleaf pine Pinus palustris habitat are amongst measure that have enabled red-cockaded woodpecker Picoides borealis numbers to increase on Eglin Air Force Base, Florida (southeast USA). However, about 28% of natural cavity trees (6,226) surveyed since 1995 are dead, fire being responsible for 26% of deaths. Measures to reduce fire-induced mortality of longleaf cavity trees (used by woodpeckers) as a result of prescribed burns were assessed.

Prior to the 2001 burning season, 800 active and inactive cavity trees had one of six protection treatments applied: 1) clearing with hand tools and light raking; 2) mechanical clearing (using a mower); 3) mechanical clearing and light raking; 4) mechanical clearing and raking to mineral soil; 5) burning out from tree base prior to the actual burn; and 6) control (no treatment).

Treatments were assigned randomly but followed U.S. Fish and Wildlife Service recommendations such that active trees received only treatments 1, 3 and 5, and treatment 2 was applied only to trees with large, long-inactive cavities. Trees were monitored for post-burn survival after 1 year, and data collected on a range of characteristics useful in determining cavity tree predisposition to fire-induced mortality.

Protected tree mortality (2.6%) was significantly lower than that of unprotected trees (6.2%). Protection method did not differ in effectiveness at preventing mortality. Bark char was also significantly less on protected trees (again, no differences apparent among protection treatments). Extent of truck charring, needle scorch, sap cover, and whether the cavity burned were the characteristics most closely related to tree deaths.

The authors recommend that for greatest efficacy, percent of the bole covered in sap (sap being prone to ignition) and cavity height should be considered when deciding whether or not to implement protective measures. Mechanical clearing was the most efficient (least amount of time and resources) preparation method.

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