Importance of Spatial Scale to Habitat Use by Breeding Birds in Riparian Forests: A Hierarchical Analysis

Abstract

Patterns of habitat use by breeding birds were studied in cottonwood riparian forests along 100 km of the South Fork of the Snake River in southeastern Idaho, United States, from 1991 to 1994. A hierarchical approach was used to examine habitat use at three spatial scales: microhabitat (local vegetation characteristics), macrohabitat (cottonwood forest patch characteristics), and landscape (composition and patterning of surrounding [matrix] vegetation types and land uses). This paper addresses a series of predictions about species’ distributions that incorporate the different spatial scales. Bird distribution and abundance and vegetation data were collected on 57 cottonwood forest patches ranging in size from 0.40 ha to 205 ha. The surrounding landscape changed from a valley surrounded by mountains, on the upstream end of the study area, to a narrow canyon adjacent to natural upland vegetation in the middle section, and to a wide, open floodplain dominated by agriculture on the downstream end. The best predictors of high species richness (r2 = 0.71) were natural and heterogeneous landscapes, large cottonwood patches, close proximity to other cottonwood patches, and microhabitats with relatively open canopies. Distribution and frequency of occurrence were evaluated for 32 species of small land birds. The most frequent significant predictor of species occurrence was the landscape component: increases in upland natural vegetation with decreases in agriculture. Both interior and edge specialists were found in arid land, cottonwood riparian forests that are linear in nature, with large amounts of edge. Nest predators, brood parasites, and exotic species responded positively to human‐altered landscapes. Landscape patterns were the primary influence on distribution and occurrence of most bird species, whereas macrohabitat and microhabitat were of secondary importance. Thus, surrounding landscape (matrix) features should be a primary consideration for selecting riparian reserve areas.

Urban Bird Diversity and Landscape Complexity: Species-environment Associations Along a Multiscale Habitat Gradient

“…The reverse was also equally true, as local-level variables added significantly to the same number of models when we accounted for parks and surrounding forest cover. Other studies have demonstrated support for landscape-level effects on birds in urban areas and generally have concluded that urbanization around forest patches and riparian areas affects bird diversity and abundance within these areas (e.g., Munyenyembe et al 1989, Smith and Schaefer 1992, Bolger et al 1997, Germaine et al 1998, Saab 1999. However, results from multiple-scale studies have not consistently shown that these effects are significant (Berry andBock 1998, Clergeau et al 1998).…”

“…Thirdly, the distribution of birds in urban areas has been investigated using spatial-structuring theories of ecological communities in which local-scale habitat features are viewed in relation to the surrounding landscape features (e.g., Bolger et al 1997, Rottenborn 1999, Saab 1999, Odell and Knight 2001. Spatialstructuring studies have often indicated that the surrounding landscape characteristics (100 ha to <30,000 ha) provide significant additional information to local-scale bird habitat models that include only local, site-level (<3 ha) habitat characteristics (Smith and Schaefer 1992, Blair 1996, Bolger et al 1997, Germain et al 1998, Rottenborn 1999, Mörtberg 2001.…”

“…Urban gradient analysis attempts to capture this gradient of environmental variation and to examine the response of the biotic community (McDonnell and Pickett 1990). Although a few studies have examined the effects of surrounding urbanization on bird species richness in park and riparian fragments (e.g., Saab 1999, Sodhi et al 1999, Mörtberg 2001, Er 2002, none has looked at the reverse, that is, the effects of surrounding parks on the bird communities in residential areas. The occupancy of poor-quality or marginal areas by resident birds could be influenced by the surrounding landscape (regional parks vs. highdensity housing) because the surrounding habitats may act as resource areas for residential birds and as "source" areas for dispersing birds.…”

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“…Studies with birds have been rather equivocal. Several have found patch-level variables more important determining factors of species occupancy or abundance (e.g., Berry and Bock 1998, Estades 1999, Mortberg and Wallentinus 2000, Bajema and Lima 2001 while other studies have found landscape variables to be the primary explanatory factors (e.g., Jansson and Agelstam 1999, Saab 1999, Howell et al 2000, Loyn et al 2001). In addition, there are interspecific factors.…”

A Bayesian method for assessing multi-scale species-habitat relationships

“…Although there is presumably not a single 'best' spatial scale at which to associate species and their habitats for all species or ecological conditions, it is possible to reveal relevant ecological associations when the scale of analysis approaches the operational scale of the process of interest. Studies often use expert knowledge to set the scale of analysis, or in some cases use expert-informed designs to collect data at 'fine-' versus 'large-' spatial scales to compare their relative explanatory power (e.g., Saab 1999;Coppeto et al 2006;Cunningham et al 2014). Unfortunately, information regarding the ecological processes shaping the distribution or abundance of a species is often lacking, let alone the spatial scale at which these processes may act.…”