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Conserving Boreal Songbirds Using Variable Retention Forest Management Open Access


Other title
songbird conservation
forest harvest
variable retention management
emulation of natural disturbance
forest ecology
Type of item
Degree grantor
University of Alberta
Author or creator
Odsen, Sonya G.
Supervisor and department
Spence, John (Renewable Resources)
Acorn, John (Renewable Resources)
Examining committee member and department
Nielsen, Scott (Renewable Resources)
Pinzon, Jaime (Renewable Resources)
Schmiegelow, Fiona (Renewable Resources)
Department of Renewable Resources
Conservation Biology
Date accepted
Graduation date
Master of Science
Degree level
The Canadian boreal forest is vital breeding habitat for North American songbirds. Extensive anthropogenic disturbances within this biome are therefore of conservation concern. Using unharvested stands as controls, I examined the effects of variable retention management (VRM) relative to clear-cuts on songbird assemblages and individual species in a boreal mixedwood forest. Breeding season point count surveys were performed in 10-ha cutblocks applied across four dominant forest types (deciduous dominated, deciduous with spruce understory, mixedwood, and coniferous dominated), and harvested in winter 1998/99 to five retention levels (clear-cut (2%), 10%, 20%, 50%, and 75%), plus unharvested controls. Surveys were conducted prior to harvest in 1998, and subsequent to harvest in 1999, 2000, 2005, 2006, 2012, and 2013 at the Ecosystem Management by Emulating Natural Disturbance (EMEND) experiment in northwestern Alberta. In the first two post-harvest years, songbird assemblages in stands with less than 75% retention differed significantly from those in unharvested stands. After 14-15 years, assemblages in stands with 20% retention or higher no longer differed significantly from the controls, suggesting accelerated recovery within high retention stands. In the controls, however, species richness increased after 7-8 years, and species composition changed after 14-15 years, suggesting that c. 10-ha unharvested stands were too small to maintain unchanged songbird assemblages of undisturbed forest. Closer examination of six old forest-associated species – brown creeper (Certhia americana), winter wren (Troglodytes hiemalis), ovenbird (Seiurus aurocapilla), black-throated green warbler (Setophaga virens), Canada warbler (Cardellina canadensis), and western tanager (Piranga ludoviciana) - revealed that 20-75% retention prevented significant declines of all six species, and five of the six species increased significantly after 14-15 years. This suggests that variable retention management can be useful for conservation of songbird assemblages and species typical of unharvested forest. However, spatial trade-offs, lagged recovery in harvested stands, and assemblage changes in unharvested stands reinforce the importance of larger (> 10 ha) forest reserves in harvest planning.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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