%0 Journal Article
%T Sustaining Cavity-Using Species: Patterns of Cavity Use and Implications to Forest Management
%A Fred L. Bunnell
%J ISRN Forestry
%D 2013
%R 10.1155/2013/457698
%X Many bird and mammal species rely on cavities in trees to rear their young or roost. Favourable cavity sites are usually created by fungi, so they are more common in older, dying trees that are incompatible with intensive fiber production. Forestry has reduced amounts of such trees to the extent that many cavity-using vertebrates are now designated ¡°at risk.¡± The simple model of cavity use presented helps unite research findings, explain patterns of use, and clarify trade-offs that can, or cannot, be made in snag management. Predictions generated are tested using data from over 300 studies. Implications to forest management are derived from the tests, including the following: ensure sustained provision of dying and dead trees, retain both conifers and hardwoods and a range of size and age classes, sustain a range of decay classes, ensure that some large trees or snags are retained, promote both aggregated and dispersed retention of dead and dying trees, meet dead wood requirements for larger species where intensive fibre production is not emphasized, do not do the same thing everywhere, and limit salvage logging after tree mortality. The paper focuses on species breeding in the Pacific Northwest, but draws on data from throughout those species¡¯ ranges. 1. Introduction Most cavities in trees begin with fungi. Because trees resist decay, it takes time for fungi to soften wood enough that cavity excavation by birds is possible. By that time, trees are often old and beginning to die. Old and dying trees reduce economic efficiencies within managed forests, so for decades we have sought to remove them. Our actions were successful, and cavity sites have been much reduced [1¨C3]. I focus on the Pacific Northwest of North America (PNW), here defined as Alaska, Yukon Territory, Alberta, British Columbia, Washington, Oregon, Idaho, Montana and northern Nevada, and California. Of the 67 vertebrate species commonly using cavities in the PNW, 20 (30%) are designated ¡°at risk¡± or ¡°potentially at risk.¡± Where forestry has been practiced longer, the proportion of cavity users among forest-dwelling vertebrates designated ¡°at risk¡± is higher [4]. I review kinds of cavity use, present a general framework of cavity use in the PNW, review key factors influencing cavity use, and interpret those in terms of management implications. Focus is on primary excavators, but all birds and mammals commonly using cavities are included. Summary tables and figures highlight regional differences: coastal forests (under maritime influence), subboreal plus boreal forest, and inland (all other
%U http://www.hindawi.com/journals/isrn.forestry/2013/457698/