Journal of Ornithology

, Volume 148, Supplement 2, pp 425–434 | Cite as

The importance of excavators in hole-nesting communities: availability and use of natural tree holes in old mixed forests of western Canada

  • Kathryn E. H. Aitken
  • Kathy Martin


Nest-holes created by woodpeckers or natural decay processes are an essential commodity for secondary hole-nesting species. Hole-making agents may strongly influence the richness and abundance of species in hole-nester communities. However, few studies have examined the characteristics and relative importance of naturally occurring holes for hole-nesters. Between 1995 and 2006, we examined 1371 excavated and non-excavated holes used by 29 bird and mammal species in central British Columbia, Canada. Excavated holes were much more abundant (85%) than non-excavated holes (15%). Red-naped sapsucker (Sphyrapicus nuchalis) and northern flicker (Colaptes auratus) excavated 52% of the holes monitored. At the community level, non-excavated holes were used for nesting less than expected based on their availability (6% of total nests), particularly among woodpeckers (2% of nests). However, secondary hole-nesters used non-excavated holes roughly in proportion to their availability (10% of nests), and some excavators used non-excavated holes for nesting (flicker and red-breasted nuthatch, Sitta canadensis, 4% of nests each; black-capped chickadee, Poecile atricapillus, 13% of nests). Although nests in non-excavated holes tended to be lower on the tree, larger internally and with larger entrances, only European starling (Sturnus vulgaris) appeared to select non-excavated holes with characteristics most similar to their preferred excavated holes. Non-excavated holes may be an alternate nesting resource for secondary hole-nesters that cannot acquire an excavated hole and, occasionally, for excavators. The use of non-excavated holes may provide an advantage for secondary hole-nesters by releasing them from the constraints of excavator nest-site preferences.


Hole-nesting birds and mammals Importance of excavators Keystone excavators Natural holes Secondary hole-nesters 



We acknowledge our excellent field technicians including D. Gunawardana, M. Mossop, A. Newbury, A. Norris, T. Sutherland, R. Wilds and many others. This project was supported by research grants to K. Martin from the Natural Sciences and Engineering Research Council of Canada (NSERC, University of B.C.), the Canadian Wildlife Service (Environment Canada), Forest Renewal British Columbia (with F. Cooke, Simon Fraser University) and Lignum Limited. K. E. H. Aitken was supported by NSERC (Industrial Post-graduate Scholarship sponsored by Lignum Ltd.; Doctoral Post-graduate Scholarship), Science Council of British Columbia GREAT scholarship, Van Dusen Graduate Fellowship in Forestry, Canfor Corporation Fellowship in Forest Ecosystem Management, Bert Hoffmeister Scholarship in Forest Wildlife, University of B.C. University Graduate Fellowship, and by grants from the North American Bluebird Society and Brink/McLean Grassland Conservation Fund.


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2007

Authors and Affiliations

  1. 1.Centre for Applied Conservation Research, Faculty of ForestryUniversity of British ColumbiaVancouverCanada
  2. 2.Canadian Wildlife ServiceDeltaCanada

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