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Summer 2004
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Audubon Uses GIS to Identify Important Bird Areas in New York State

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Potential habitat patches unfragmented by major and minor roads in the Catskill Mountains ecoregion.

Audubon New York is a nonprofit organization that conserves birds, other wildlife, and their habitats through education and advocacy, based on sound science. A major component of Audubon's efforts is the identification, protection, and proper management of Important Bird Areas (IBAs).

Important Bird Areas represent critical habitats for the survival and conservation of birds. An IBA is a site that provides essential breeding and/or nonbreeding habitat for bird species or group of species of conservation concern. To be designated an IBA, a site must meet at least one of several criteria relating to its significance for threatened bird species, congregations of birds, and/or habitats important to assemblages of birds for which New York State has conservation responsibility.

The IBA program began in Europe in the mid-1980s. Today, IBA programs are underway on six continents and in 146 countries. In 1996, New York became the second U.S. state to initiate an IBA program. Sites were nominated from a broad audience of interested individuals, and today there are 127 IBAs recognized in New York, representing more than 800,000 hectares of critical nesting, breeding, and foraging habitat.

However, the original nomination process relied solely on the observations of birders and ornithologists. Though birdwatchers in New York are very knowledgeable, there are large areas of viable habitat that birders do not visit. This is evident because many IBAs were clustered in areas of high population. Audubon conservation staff saw a critical need to reassess the IBA nomination process by incorporating a landscape analysis of bird habitat variables across New York.

To address this need, in 2003 they expanded the IBA site identification process to include analysis of spatial habitat data at a landscape scale using GIS. Jillian Liner, Audubon New York IBA coordinator, notes, "The use of GIS and spatial analysis has been a crucial component in identifying IBAs in an unbiased manner; it has allowed us to comprehensively assess the state to identify the most critical areas for birds." Computer equipment and GIS software were acquired by Audubon New York in 2001 through a grant from the Conservation Technology Support Program.

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Blocks of land unfragmented by major roads within the Appalachian forest bird conservation region, across New York's ecoregions.

Audubon New York's GIS analysis targets habitat of forest, shrub, and grassland species assemblages for which New York has a high conservation responsibility. Species under New York's conservation responsibility were identified using the Partners in Flight species assessment process and include species with a large proportion of their populations found within the North American Bird Conservation Initiative's Bird Conservation Regions (BCRs) that make up New York. The IBA program does not identify every site where a species under conservation responsibility breeds as an IBA, because these species tend to be fairly common. Rather, taking a reserve system approach, it sought to identify the most important 10 percent of habitat for each assemblage.

"Most important" habitat was defined as the largest, least fragmented patches of habitat supporting the highest richness of species comprising each assemblage, with the greatest chance of long-term protection. Habitat identification was stratified across New York's BCRs and ecoregions to capture important ecological variation and ensure that potential IBAs were not clustered in one part of the state.

The Audubon New York staff built its analysis on land cover data, species predicted breeding habitat distributions, and stewardship lands from the New York Gap Analysis Program. Ancillary data included major and minor roads from the New York Department of Transportation. Using ArcView Spatial Analyst, the staff developed habitat and species richness indexes at multiple scales and created spatial models to integrate these indexes.

At a landscape scale, Audubon New York developed a data set of focus areas (referred to as habitat blocks) by combining relevant land cover data and predicted bird distributions to describe the character of habitat and bird richness within lands unfragmented by major roads. For each assemblage, three habitat variables (total area of habitat, percent of habitat area, and density of habitat patches) and one species distribution variable (area-weighted mean species richness) were calculated for each habitat block. The staff combined these variables in a spatial model using the ArcView Spatial Analyst Map Calculator to derive an index value for each habitat block. It then ranked the resulting block data set with the ArcView Legend Editor, using a quantile classification scheme with 10 classes. The top three to five classes became focus areas for further analysis at the patch scale.

At a patch scale, Audubon New York sought to identify the areas with the greatest chance of long-term protection and demonstrated avian significance as potential IBAs. Patch variable attributes included patch size, distance to stewardship lands, and distance to existing IBAs. Again using the ArcView Spatial Analyst Map Calculator, a spatial model was constructed that combined these variables in order to rank patches. Patches exhibiting a high score were considered potential IBAs and targeted for ground-truthing.

Bird presence was ground-truthed by utilizing data from the New York Breeding Bird Atlas (BBA) and via field surveys. BBA provides recent (2000-2003) data on the presence of breeding birds in 5 km x 5 km squares across the state. IBAs not adequately covered or surveyed by BBA were targeted for field surveys that were conducted by Audubon staff and qualified volunteers.

For more information, contact Jillian Liner, Audubon New York IBA coordinator (tel.: 607-254-2437, e-mail: jliner@audubon.org).

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