CONICET | Buscador de Institutos y Recursos Humanos

In tropical and subtropical forestecosystems, decay-formed cavities are a key andscarce resource for secondary cavity-nesting birds ? agroup which is highlysensitive to logging. The Piedmont forest of northwestern Argentina is acomplexecosystem with 113 tree and 120 bird species. It has high logging pressure onthefew, well conserved remnants, complicating the delineation of sustainablemanagement guidelines for each tree or bird species in a short period of time.Ourobjective was to reduce the complexity of subtropical forests by grouping treespecies according to the characteristics used by secondary cavity-nestingbirds. Inthe Piedmont forest, 50 plots of 0.25 ha were sampled to record cavity treesandcavity characteristics. These were then used in cluster analysis to form treegroups. Additionally, cavity searches were conducted to identify the birdspeciesusing the secondary cavity-nests. A total of 187 cavity trees of 23 treespecieswere recorded and these formed four tree groups or clusters. We recorded 86cavities that were used by secondary cavity-nesting bird species. The four treegroups were unequally used by secondary cavity nesters. The tree group thatincluded valuable timber species (Myroxylon peruiferum, Anadenantheracolubrineand Calycophyllum multiflorum) and had the greatest cavity availabilityhad 71% oftotal cavity use. A subsequent tree group had valuable timber species (Cedrelabalansae and Amburana cearensis), measured >73 cm DBH and>21 m height,had cavity entrances measuring >0.10 cm2; and it had 14% of all cavity usebybirds. A third group had no highly economically valuable tree species, includedthesnag category and had 15% of cavity use. The fourth tree group had DBH <0.40cm and only one highly economically valuable tree species (Cordia trichotoma).This group supported no cavity use. The clustering of assemblages ofsub-tropicaltrees into tree groups can reduce the complexity of subtropical forests, henceeasing their management by focusing on trees with similar characteristics (e.g.thetree groups) and on trees that provide suitable nesting sites for secondarycavity-nesting birds

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