Heartrot fungi's role in creating picid nesting sites in living aspen

Abstract

Abstract—To determine the number of cavity-containing aspens in old-growth (>80 years), we counted the number of stems containing cavities in 132 0.02-ha plots in Wyoming. There were 8.7 cavities/ha of aspen type. At least 84 % of the cavity stems were alive when the initial cavity was constructed; 60 % were alive when examined. Fruiting bodies and Phellinus tremulae (a heartrot fungus) were present on 71 % of all cavity-bearing stems but on only 9.6 % of all stems>15 cm d.b.h. Cavities were present in 7.7 % and 0.2 % of living stems with and without fruiting bodies, respectively. Average d.b.h. of cavity stems was 27.4 cm. During a 4-year interval, 74 of 226 snags>15 cm d.b.h. fell, giving an average instantaneous rate of snag loss of r = –0.099. Ninety-six new snags>15 cm d.b.h. were created during the 4-year study period. Our results indicate that some primary cavity-nesting birds in northwest Wyoming prefer-entially selected living aspens with heartrot as nest sites and that the average longevity of aspen snags>15 cm d.b.h. is about 10.7 years.