Journal
AVIAN CONSERVATION AND ECOLOGY
Volume 7, Issue 2, Pages -Publisher
RESILIENCE ALLIANCE
DOI: 10.5751/ACE-00534-070206
Keywords
Chestnut-collared Longspur; edge effects; fragmentation; mixed-grass prairie; nonlinear regression; road ecology; Sprague 's Pipit
Categories
Funding
- Ducks Unlimited Canada Brooks office
- North American Waterfowl Management Plan
- Alberta Sport, Recreation, Parks and Wildlife Foundation
- Antelope Creek Habitat Development Area
- Science Horizons and Summer Career Placements (Environment Canada)
- Natural Sciences and Engineering Research Council
- John and Patricia Schlosser Environment Scholarship
- Izaak Walton Killam Memorial Scholarship
- Bill Shostak Wildlife Award
- Richard H.G. Bonnycastle Graduate Fellowship (Institute for Wetland and Waterfowl Research, Ducks Unlimited)
- Margaret (Peg) Brown Award in Environmental Studies and Wildlife Resources
- Ralph Steinhauer Award
- University of Alberta Walter H. Johns Graduate Fellowship
- Manitoba Graduate Scholarship
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One possible factor that may have contributed to the decline of grassland bird populations is edge avoidance. In the mixed-grass prairie, habitat fragmentation is often caused by juxtaposition of habitats with vegetation that is structurally similar to prairie, making it difficult to understand why birds avoid habitat edges. We hypothesized that display height or resource-use strategy, i.e., the degree to which a species depends on grassland habitat, might explain variation in sensitivity to habitat edges among different species of grassland birds. To test our hypotheses, we used data on the abundance of grassland birds in native mixed-grass prairie fields in southern Alberta, Canada, from 2000 to 2002. Point counts were conducted up to 4.1 km from croplands, 2.2 km from roads, and 1.8 km from wetlands. We used nonlinear regression models to determine the distance at which relative abundance of 12 bird species changed in response to edge, and linear regression to determine if display height or resource-use strategy explained variation in response to different types of edges. Variation in response to edge was not explained by display height or resource-use strategy. However, six species avoided wetland edges, two avoided roads, and four avoided cropland. Two species of conservation concern, Chestnut-collared Longspurs (Calcarius ornatus) and Sprague's Pipits (Anthus spragueii), declined in abundance by 25% or more within 1.95 km and 0.91 km, respectively, of cropland edges. Because Chestnut-collared Longspurs avoided croplands to at least 1.95 km, it will be important to prevent further fragmentation of mixed-grass prairies by agriculture.
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