Avian assemblages in natural and second-growth balsam fir forests in Western Newfoundland

Hogan, Holly A. (1997) Avian assemblages in natural and second-growth balsam fir forests in Western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Avian assemblages were investigated in natural (uncut) and mature second-growth balsam fir (Abies balsamea) forests in western Newfoundland. Within these forest classes, there were four forest types varying in site richness. Birds were studied to determine if assemblages differed between forest classes and among forest types, and to determine if differences in avian assemblages were associated with vegetation structure and composition. The IPA (lndice Ponctuel d'Abondance) version of the point-count method was used to census birds. -- The result indicated avian species richness, diversity and total abundance (IPA) did not differ between natural growth and second growth forest. Three species were more abundant in natural growth. Black-backed Woodpeckers (Picoides arcticus) were found exclusively in natural growth. Five species and one guild (seed-eating) were more abundant in second growth forests. -- A trend toward increased abundance with increased forest type richness was evident for Black-throated Green Warbler (Dendroica virens), Ovenbird (Seiurus aurocapillus) and Mourning Warblers (Oporomis philadelphia) and the seed-eating guild as well as for species richness and IPA. The foliage-gleaning guild was least abundant in moss forest types, where foliage height diversity and habitat diversity (Shannon-Wiener index) were lowest. -- Twelve bird species and three guilds had significant multiple regression models in the analyses using principal components from analyses of vegetation variables from all stands. Of these, Black-backed Woodpecker, Yellow-bellied Flycatcher (Empidonax minimus) and Yellow-romped Warbler (Dendroica coronata) and the flycatching guild were indicated to avoid dense fir with canopy cover and snags (PC1), while Boreal Chickadees (Parus hudsonicus) and Black-throated Green Warbler, and the generalists guild preferred such areas. Seven species and two guilds (foliage-gleaning and generalists) strongly preferred rich forests with ferns, and forbs (PC2). Seven species and one guild (flycatching) avoided older forests lacking deciduous litter (PC3). Deciduous litter was highly correlated with Ovenbird abundance. Principal Component 2 and PC3 explained most of the variance associated with species richness and IPA. Both second-growth and natural growth forests seemed to provide adequate breeding habitat for most species. It is important to maintain stand diversity in order to promote avian biodiversity and increased abundance. Important structural components to maintain are: snags, for bark foragers and cavity nesters, particularly Black-backed Woodpeckers; some deciduous trees, for some ground foraging species, especially Ovenbirds; and a portion of canopy trees, as a source for future snags.

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