Nest webs: A community-wide approach to the management and conservation of cavity-nesting forest birds Kathy Martin a,* , John M. Eadie b a Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada, V6T 1Z4 b Department of Wildlife, Fish and Conservation Biology, University of California, 1053 Academic Surge, Davis, CA 95616, USA Abstract We propose that cavity-nesting bird communities are structured in nest webs analogous to food webs, where interspeci®c and intraspeci®c interactions are centered around nest site availability. Our sites of mixed deciduous coniferous forest in north- central BC, Canada, support a rich diversity of eight species of primary cavity nesters (PCNs) (woodpeckers), four species of weak cavity nesters (nuthatch, chickadees) and 20 secondary cavity-nesting species (ducks, passerines and birds of prey). Richness varied across forest-types with some plots being `hotspots' and others being depauperate. Across a range of forest- types, we measured species richness and abundance of birds and squirrels using point count census techniques, playbacks of taped calls of woodpeckers and owls, and by searching for active nests. We also measured resource use (trees able to support cavities, or existing cavities) in relation to availability (tree species, abundance and habitat characteristics such as edge-type and degree of fragmentation). In both 1995 and 1996, we found signi®cant positive correlations between the abundance of primary and secondary cavity-nesting birds, and negative correlations between both of these groups and weak cavity excavators. None of the three cavity-nesting groups was positively correlated with open-nesting (non-cavity) forest birds, rejecting our null hypothesis of common habitat quality. In contrast, the abundance of secondary cavity-nesting species was signi®cantly negatively correlated with non-cavity species, possibly because these species compete for resources other than nest sites, such as invertebrate prey. Using these data, we construct a nest web for the cavity-nesting community in north- central British Columbia. This approach demonstrated strong and weak links among species in the web and identi®ed key species whose presence may be critical to the integrity of the community. We plan to test how nest web structure shifts in response to different forest-cutting regimes, and whether changes in species richness and abundance can be ameliorated with selective harvesting. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Nest webs; Cavity-nesting birds; Community structure; Forestry operations; Bird±habitat interactions; Guild structure 1. Introduction Cavity-nesting birds comprise a major component of many forest bird communities. Primary cavity- nesting species (e.g. woodpeckers) excavate cavities used by a large number of avian and mammalian species. Weak cavity excavators (e.g. chickadees, nuthatches) use cavities produced by primary cavity excavators, but also create cavities of their own. Secondary cavity nesters (SCNs, e.g. tree swallows, bluebirds, ducks) rely primarily on the cavities created by the ®rst two guilds or on a limited number of natural holes. Accordingly, cavity-nesting bird com- Forest Ecology and Management 115 (1999) 243±257 *Corresponding author. Tel.: +1-604-822-9695; fax: +1-604- 822-5410; e-mail: kmartin@unixg.ubc.ca 0378-1127/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S0378-1127(98)00403-4