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Responses of bird communities inhabiting boreal plain riparian habitats to forestry and fire

Worldwide, riparian areas are considered among the most biologically productive and species-rich habitats on the landscape and provide important breeding areas for many bird species. In the Boreal Plain ecozone of western Canada, forests adjacent to riparian areas are generally protected from forest harvesting through the retention of treed buffer strips. <p>Riparian buffer strips are expected to provide habitat for wildlife including many passerine bird species. Recently, non-conventional methods of riparian management have been implemented in parts of the Boreal Plain with the intent of aligning forestry more closely with natural disturbance processes. How bird communities associated with these management scenarios diverge from natural disturbances and how riparian birds interact with disturbances in the adjacent upland habitat are key questions in the conservation of boreal riparian bird communities. To answer these questions, I surveyed birds inhabiting riparian areas with adjacent naturally disturbed (burned) and harvested forest to determine how bird communities differ early (1-5 years) post-disturbance and, separately, in a before-and-after harvesting study. <p>Riparian species associated with burned merchantable shoreline forests and riparian areas included Common Yellowthroat (<i>Geothlypis trichas</i>) and Eastern Kingbird (<i>Tyrannus tyrannus</i>). Le Contes Sparrow (<i>Ammodramus leconteii</i>) was associated with burned riparian habitats adjacent to non-merchantable forests (e.g., bog, fen), while Alder Flycatcher (<i>Empidonax alnorum</i>) and Wilsons Warbler (<i>Wilsonia pusilla</i>) were indicative of harvested sites with larger buffers (30 m). Riparian species richness was highest in burned non-merchantable sites. Multivariate Redundancy Analysis of post-disturbance bird communities showed greater divergence in overall (riparian and upland) community composition than one with only riparian species. This suggests reduced sensitivity of riparian birds to disturbances in forested areas compared to upland bird communities. However, a higher natural range of variability was exhibited in riparian bird community composition in post-fire sites than in post-harvested sites. This emphasizes that forest management practices do not currently fully approximate natural disturbance for boreal riparian birds. <p>To assess the response of bird communities in riparian habitats to forestry, I studied bird communities one year (2004) prior to forest harvest and two years (2005 and 2006) after harvest. One of three treatments, 1) 5-35% retention (0 m buffer), 2) 35-75% retention (10 m buffer with variable retention in the next 30 m), 3) 75-100% retention (50 m buffer) and unharvested reference sites, was randomly assigned to 34 wetlands. Treatments were designed to represent buffer management strategies currently applied in the Boreal Plain. Eight of 22 species showed a significant response (p<0.1) to treatment, year or year*treatment effects including two riparian species, the Common Yellowthroat and Song Sparrow (<i>Melospiza melodia</i>) that increased in abundance in harvested sites. Overall pre-disturbance communities diverged (p<0.05) over the three-year study period as shown using Multiple-response Permutation Procedures (MRPP). However, riparian bird communities did not diverge from pre-disturbance or from reference sites providing further evidence that riparian bird communities are less impacted by forestry in the adjacent upland habitats than overall bird communities. Therefore, alternative forest harvesting methods should be explored that encompass landscape-scale management including total buffer removal to maximize conservation objectives for boreal forest bird communities while attempting to maintain natural disturbance processes.

Identiferoai:union.ndltd.org:USASK/oai:usask.ca:etd-10222007-153141
Date31 October 2007
CreatorsKardynal, Kevin John
ContributorsVan Rees, Ken C. J., Hobson, Keith A., Hannon, Susan, Clark, Robert G., Chilton, Neil B.
PublisherUniversity of Saskatchewan
Source SetsUniversity of Saskatchewan Library
LanguageEnglish
Detected LanguageEnglish
Typetext
Formatapplication/pdf
Sourcehttp://library.usask.ca/theses/available/etd-10222007-153141/
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