Title
Nest-site selection by old boreal forest cavity excavators as a basis for structural retention guidelines in spatially-aggregated harvests
Author(s)
Cooke, H. A.;Hannon, S. J.
Published
2012
Publisher
Forest Ecology and Management
Abstract
Cavity excavators (woodpeckers, chickadees, nuthatches) are vulnerable to loss of old forest associated with traditional harvest practices. In the boreal plains of Canada, old forest excavators are retained in the short term in small (<100 ha) and large (1000s ha) harvests with residual trees and patches. Information on habitat selection can be used to guide "what, where, and how much" structure to retain and ensure excavators, and the secondary species that use their cavities, are conserved in harvests in the short term. We examined multi-scale nest-site use and selection by excavators in intact old upland forest and spatially-aggregated harvests with structural retention and developed guidelines for the types and spatial arrangement of trees, patches, and stands retained during forest planning (i.e. planned residuals) and harvesting (i.e. operator residuals). In both intact and harvest landscapes, live large (>35 cm) and tall (>25 m) trembling aspen (Populus tremuloides) with multiple (similar to 20) conks of a heartrot fungus (Phellinus tremulae) were the preferred cavity trees for yellow-bellied sapsucker (Sphyrapicus varius), hairy woodpecker (Picoides villosus), and pileated woodpecker (Dryocopus pileatus). Short (similar to 10 m), broken-top aspen snags of medium (>20 cm) and large (>35 cm) diameter were preferred by black-capped chickadees (Poecile atricapillus) and northern flickers (Colaptes auratus), respectively. In the harvests, sapsuckers, hairy woodpeckers, and flickers selected cavity trees in clumps with other medium- and large-diameter aspen with conks. Black-capped chickadees selected trees with no live large conifers within similar to 10 m. Sapsuckers selected old aspen and mixedwood stands in intact landscapes. In harvest landscapes, sapsuckers selected trees in or near planned patches greater than 5 ha and composed of mature and old aspen and mixedwood stands. Sapsuckers tended to nest in areas with similar to 50% residual forest cover whereas flickers selected open areas of cutblocks away from planned patches. We recommend harvest operators retain several live, large (>35 cm dbh) aspen with numerous (similar to 20) fungal conks in clumps that are adjacent to or near (<60 m) large (>5 ha) patches. Planned patches should have one to two thirds of their area derived from mature and old aspen and mixedwood stands and should be at least 5 ha, with most greater than 15 ha. These prescriptions will facilitate retention of the cavity-using assemblage of old upland forest in aggregated harvests in the short term. However, regional strategies for old forest conservation may be necessary to conserve cavity users in managed forest landscapes over the long term. (C) 2012 Elsevier B.V. All rights reserved.
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