Long-term efficacy of artificial cavities for red-cockaded woodpeckers: Lessons learned from hurricane Hugo
Between 1990 and 1992 an extensive artificial cavity installation program was conducted on the Francis Marion National Forest (FMNF) in coastal South Carolina where Hurricane Hugo had caused vast devastation. Four artificial cavity types were installed: drilled starts, drilled cavities, modified drilled cavities, and inserts. In 1998, we examined 443 of the artificial cavities (average age 8.5 years). Our objective was to determine the relative effectiveness of the 4 types of artificial cavities by comparing their use and durability as well as host tree mortality and reproductive success of red-cockaded woodpeckers (Picoides borealis) using the various types of artificial cavities. Per annum mortality rates for longleaf pines with drilled starts, drilled cavities, and modified drilled cavities did not vary, but the mortality rate of loblolly pines with inserts was 2.4 times greater than for longleaf pines with inserts. Drilled cavities had the highest usability of all cavity types whereas modified drilled cavities and inserts in loblolly pines had the lowest. Modified drilled cavities were more prone to structural damage than drilled cavities, and inserts and modified drilled cavities were more prone to flooding and enlargement than were drilled cavities. Each type was used successfully for nesting and the number of young fledged from artificial cavities did not differ significantly from the number of young fledged from natural cavities. However, red-cockaded woodpecker use of artificial cavities for nesting declined over time, and the long-term usability of drilled starts and drilled cavities for nesting was greater than that of modified drilled cavities and inserts. Although red-cockaded woodpeckers used all cavity types, drilled cavities and drilled starts tended to be the most effective over time. However, managers must weigh training time, tree characteristics, and long-term usability when deciding what types of artificial cavity to install.