Composition and conservation of riparian bird assemblages in a balsam fir ecosystem

Whitaker, Darroch M. (1997) Composition and conservation of riparian bird assemblages in a balsam fir ecosystem. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (9MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Undisturbed riparian zones are typically viewed as the highest quality habitat available to wildlife in forested landscapes and, in keeping with this, are seen as having the highest biodiversity. Riparian buffer strips are retained during clearcutting throughout most of the boreal forest, a practice promoted as a means to reduce the impact of harvesting on terrestrial fauna. Current perceptions of the importance of riparian zones to wildlife originated from studies in southwestern North America, yet their generalization to boreal forests remains relatively untested. Furthermore, little research has been conducted to quantify the extent to which buffer strips are used by wildlife. This study was designed to evaluate the relative importance of riparian habitat for breeding birds in a boreal forest ecosystem and to assess the conservation potential of riparian buffer strips in areas of extensive clearcutting. -- Breeding birds were surveyed in riparian edge, non-riparian edge (clearcut or access road), interior forest and buffer strip habitats in balsam fir (Abies balsamea) forests in western insular Newfoundland. Observations from riparian edge, non-riparian edge and interior forest transects were compared in order to describe the assemblages associated with each of these habitat types and to group species into habitat selection guilds. Several distinguishing species were associated with each of these habitat types, and five habitat guilds were differentiated. Total abundance and species richness did not differ between riparian and interior forest transects, but were significantly higher on non- riparian edge than riparian transects. Different habitat features lead to the development of distinct bird assemblages along the two edge types. Based on this and other recent studies, it is apparent that relatively high riparian biodiversity may be the exception for bird assemblages in coniferous and coniferous-deciduous mixed forests, where interior forest species form an important component of the avifauna. -- Comparisons were made between bird assemblages (grouped by habitat guild) observed along undisturbed shorelines and buffer strips. Total avian abundance was higher in buffer strips than riparian controls, largely due to significantly higher counts of birds from the ubiquitous and open/edge guilds. Abundance of forest generalise interior forest and riparian species were similar between the two shoreline types. Counts of riparian species did not increase in wider buffers, likely due to the association of these birds with habitat adjacent to the water, which does not increase in proportion to strip width. Riparian buffer strips did, however, provide habitat for a diverse avian assemblage, and retained many riparian and woodland species in areas of intensive clearcutting. Interior forest species, many of which are declining in northeastern North America, were more abundant in wider buffers. However, even in the widest strips (40-50 m) they were rare when compared to local interior forest habitat, and three of six species in the guild were not observed in any buffer strip. It is clear that separate (but complementary) conservation strategies are required to protect riparian and interior species. Interior species are likely not afforded adequate protection in boreal forests, where conservation efforts focus largely on preserving riparian habitat.

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