Research Article

Landscape Ecology

, Volume 24, Issue 3, pp 351-360

First online:

Relative importance of habitat area and isolation for bird occurrence patterns in a naturally patchy landscape

  • Tammy L. WilsonAffiliated withDepartment of Wildland Resources, College of Natural Resources, Utah State University Email author 
  • , Elizabeth J. JohnsonAffiliated withArea Ecology Program, Deschutes National Forest
  • , John A. BissonetteAffiliated withUS Geological Survey Utah Cooperative Fish & Wildlife Research Unit, College of Natural Resources, Utah State University

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There is debate among ecologists about whether total habitat area or patch arrangement contributes most to population and/or community responses to fragmented or patchy landscapes. We tested the relative effects of patch area and isolation for predicting bird occurrence in a naturally patchy landscape in the Bear River Mountains of Northern Utah, USA. We selected focal patches (mountain meadows) ranging in elevation from 1,920 to 2,860 m and in size from 0.6 to 182 ha. Breeding birds were sampled in each focal meadow during the summers of 2003 and 2004 using variable-distance point transects. Logistic regression and likelihood-based model selection were used to determine the relationship between likelihood of occurrence of three bird species (Brewer’s sparrow, vesper sparrow, and white-crowned sparrow) and area, isolation, and proximity metrics. We used model weights and model-averaged confidence intervals to assess the importance of each predictor variable. Plots of area versus isolation were used to evaluate complex relationships between the variables. We found that meadow area was the most important variable for explaining occurrence for two species, and that isolation was the most important for the other. We also found that the absolute distance was more appropriate for evaluating isolation responses than was the species-specific proximity metric. Our findings add clarity to the debate between ecologists regarding the relative importance of area and isolation in species responses to patchy landscapes.


Breeding bird Fragmentation Metapopulation dynamics Sagebrush obligate Mountain meadow Utah USA