DRAFT Corrected NAWCA shorebird priotiy polygons (2026)

These data depict areas of the United States where North American Wetlands Conservation Act (NAWCA) projects should be developed and favored based on benefits to wetland-associated shorebirds. The dataset represents a corrected and updated version of the NAWCA Shorebird Priority Landscapes layer and was developed to improve the accuracy of coastal boundaries while maintaining the biological intent and geographic extent of the original priority landscapes. The purpose of this update was not to identify new priority areas or substantially expand existing priority landscapes, but rather to modernize coastal boundaries using higher-resolution shoreline data and ensure that important coastal habitats remained represented in the dataset. The update focused first on shorebird priority polygons and may serve as a model for future revisions of other NAWCA bird conservation priority layers. Shorebirds include families of birds dependent on wetland, grassland, and beach habitats during portions of their life cycles, including (but not limited to) avocets and stilts, plovers, oystercatchers, sandpipers, and phalaropes. Technical Question #3 for the North American Wetlands Conservation Act (NAWCA) asks applicants to describe how proposed grant and match activities address national and continental geographic priorities for wetland habitat conservation as outlined in the major migratory bird conservation plans. This dataset supports that evaluation by identifying landscapes where habitat protection, restoration, enhancement, and management are expected to provide the greatest benefits for priority shorebird species. The original shorebird priority map was developed by the U.S. Shorebird Conservation Partnership in consultation with regional U.S. Fish and Wildlife Service Migratory Bird biologists, state shorebird biologists, nongovernmental organization shorebird experts, and Joint Venture staff. The original 2004 map depicted broad areas of national importance to shorebirds and focused on landscapes supporting large numbers of migrant shorebirds (>20,000 individuals) or high densities of breeding and wintering shorebirds. A 2012 revision refined these areas using a landscape-based approach and generally relied on EPA Level IV Ecoregion boundaries to better define priority landscapes. A subsequent 2024 update expanded coverage to include important shorebird areas in Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands. This corrected polygon layer preserves the conservation intent of previous versions while improving the spatial accuracy of coastal boundaries and associated marine and estuarine habitats. ## Data Development and Revision Process ### Coastal Boundary Update A higher-resolution coastal boundary dataset was identified and used to improve shoreline representation. The primary source was the United States State Boundaries layer derived from U.S. Census Bureau 2020 TIGER/Line geodatabases (National Sub-State Geography), published in June 2024. The layer was enhanced using TIGER hydrography data to provide more detailed coastline representation for cartographic and analytical purposes. Additional improvements to island representation in Alaska were incorporated using a supplemental ZIP Code boundary dataset that provided greater island detail than the Census-derived coastline. To update the shoreline geometry: 1. Original shorebird priority polygons were buffered outward by 50 kilometers. 2. The buffered polygons were merged with the original polygons using a union operation. 3. The resulting polygons were clipped using the updated national coastline dataset. 4. Interior landward boundaries created during processing were manually removed while preserving the original landward boundary of each priority landscape. 5. New seaward coastal buffers were generated from the updated shoreline boundaries to ensure complete inclusion of relevant coastal and estuarine habitats. ### Buffer Evaluation Process Multiple coastal buffer distances were developed and evaluated, including 1 km, 5 km, 10 km, and 20 km offshore extensions. These alternatives were reviewed by representatives from Joint Ventures, shorebird conservation partners, and other technical experts to determine an approach that best reflected shorebird habitat use while maintaining consistency across geographies. Following a series of technical review meetings, participants agreed to: * Update the coastline vector layer before applying any new coastal buffers. * Maintain the intent of the existing shorebird priority landscapes and avoid creating substantially new areas. * Apply a 5-kilometer coastal buffer to most U.S. shorelines. * Apply a 20-kilometer coastal buffer along the Gulf Coast to better reflect shorebird habitat use patterns and coastal ecology in this geography. * Clip all buffers at international boundaries. * Remove or correct terrestrial areas unintentionally included through the buffering process. ### Polygon Corrections Additional refinements were incorporated following review by Joint Venture and shorebird conservation representatives. #### Alaska Island Inclusion The coastline update process excluded certain islands that had been included in previous NAWCA shorebird priority landscapes. These islands were re-added to maintain consistency with prior conservation priorities and to ensure continuity of habitat representation. This correction affected Alaska only. #### Terrestrial Buffer Corrections For areas buffered by 5 kilometers, unintended terrestrial inclusions created by the buffering process were corrected by clipping buffers to follow the trajectory and intent of the original terrestrial boundary. This approach was reviewed using examples from the Atlantic Coast Joint Venture and subsequently adopted across all applicable geographies. For Gulf Coast polygons buffered by 20 kilometers, the review group determined that most terrestrial inclusions reflected the intended coastal landscape and should remain. The only modification applied was clipping the eastern edge of the large Gulf Coast polygon where buffering created an unintended extension. #### San Francisco Bay Revision Following consultation with representatives from the San Francisco Bay Joint Venture (SFBJV), San Joaquin Valley Joint Venture (SJV), and Central Coast Joint Venture (C3JV), the treatment of San Francisco Bay was revised. Reviewers noted that the entire Bay functions as an interconnected shorebird landscape whose ecological importance varies across years. Although the updated buffer methodology captured most of San Francisco Bay, reviewers recommended retaining the entire Bay within the corrected priority landscape. Based on this recommendation, the final corrected polygon includes all of San Francisco Bay, with the western boundary terminating at the mouth of the Bay just west of the Golden Gate Bridge. This adjustment was made to preserve the ecological integrity and conservation intent of the original priority landscape. ### Polygon Simplification The review group concluded that individual polygon names were not necessary for the intended NAWCA application. Where possible, adjacent polygons were dissolved into larger units to reduce complexity and improve usability within the NAWCA Mapper and related conservation planning tools. ## Attribute Information Attribute fields include 2020 total population values derived from U.S. Census Public Law 94-171 data and any legacy attributes retained from previous shorebird priority landscape datasets. ## Use Constraints These data are intended for conservation planning, prioritization, and evaluation of NAWCA proposals. The dataset identifies landscapes where habitat protection, restoration, enhancement, and management are expected to provide greater benefits for priority shorebird species relative to areas outside the mapped boundaries. The polygons represent conservation priority landscapes and should not be interpreted as precise habitat boundaries or regulatory designations.