Lifetime use of individual tree cavities in temperate and subtropical forest ecosystems in the Americas

TRZCINSKI, M. KURTIS; WIEBE, KAREN L.; COCKLE, KRISTINA L; MARTIN, KATHY; EDWORTHY, AMANDA B.

Tucson

Congreso; American Ornithological Society 2018 Meeting; 2018

Over 18% of birds globally use tree cavities, a multiannual resource that varies in quality and abundance based on the rate of cavity creation and loss. We analyzed factors influencing occupancy patterns (species richness, number of nests) over the lifetime of individual cavities for temperate and subtropical forest ecosystems that differ in species richness, and cavity formation processes. The temperate mixed forest in British Columbia, Canada had 31 cavity-nesting species and 95% of nests were in excavated cavities (1995-2016) whereas the subtropical Atlantic forest in Argentina had 72 species and 83% of cavities were decay-formed (2006-2016). In B.C., 88% of cavities were used by 1-2 species and only 3% were occupied by 4-6 species. In Argentina, 77% of cavities were used by 1-2 species, while 13% were occupied by 4-13 species. In B.C., species richness was highest in cavities excavated by small and medium-sized woodpeckers, and lowest in decay-formed cavities, but the agent of cavity formation had little effect on the number of nests over the cavity lifespan. In Argentina, species richness and the number of nests were higher in decay-formed cavities in Cedrela and Apuleia trees that were healthy. Generally, the highest value cavities were in live trees with decay in both forest ecosystems, but key factors to maintain the full biodiversity varied. Dead trees provided a critical resource for a few species, and cavity trees with a diversity of characteristics are needed to maintain complex cavity-nesting communities.