The effects of cattle grazing on the breeding biology of riparian forest birds

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Holgate, Katheryn T.
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1999
Cattle grazing in riparian zones can have large impacts on vegetation characteristics and avian biodiversity. To assess these impacts in southern Alberta, vegetation and bird surveys were conducted in twelve riparian sites (four each in heavily grazed, moderately grazed, and ungrazed habitats) along the Oldman River. The shrub understory and bird species diversity and abundance declined significantly as grazing intensity increased. Settlement patterns, territory sizes, and food provisioning rates of some bird species were examined to assess the mechanisms behind this reduction. Five out of seven species settled earlier in ungrazed habitats, whereas two species did not show any discernable settlement pattern. The territory sizes of three species examined increased as grazing intensity increased. House wrens (Troglodytes aedon) brought more food and more food biomass to their nests in ungrazed habitats. These results indicate that available food biomass decreased as grazing intensity increased, and is an important factor in population dynamics of some species.
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Birds -- Effect of habitat modification on -- Alberta -- Oldman River Region , Dissertations, Academic , Birds -- Breeding -- Alberta -- Oldman River Region , Birds -- Habitat -- Alberta -- Oldman River Region , Grazing -- Alberta -- Oldman River Region