Chapter 1: Regulatory Context, Study Methods, and Voluntary Development Guidelines

Voluntary Wind Energy Guidelines

Updated September 01, 2021

In 2012, the U.S. Fish & Wildlife Service issued voluntary Land-Based Wind Energy Guidelines (Guidelines). The Guidelines were a first for the Service, which saw an opportunity to engage with wind energy developers and other stakeholders to advance wildlife conservation and renewable energy goals beyond the confines of the regulatory context. Based on the consensus recommendations of a Federal Advisory Committee that included state and federal agencies, wind developers, conservation organizations, Tribes, and academics, the Guidelines provide a consistent framework to use in systematically considering and addressing wind-wildlife interactions. Most wind energy developers follow the Guidelines when siting new projects.

The structured, tiered, risk-based approach provided by the Guidelines was important because all wind projects are different – in size, location, and factors like the presence of species and habitats. The Guidelines’ decision tree draws on the logic of the mitigation hierarchy – first seek to avoid adverse impacts, minimize impacts that cannot be avoided, and offset or compensate for unavoidable impacts – and the methods and metrics described in the National Wind Coordinating Collaborative’s Comprehensive Guide to Studying Wind Energy/Wildlife Interactions. The Guidelines are designed to mirror and inform the decision-making process, beginning with wind energy project siting and development through operation. An underlying principle is a recognition that the level of due diligence and investment in studying and preventing impacts should be commensurate with the level of risk posed by a project.

The tiered approach helps wind developers make decisions about whether to proceed with or abandon the development of specific projects, and when and how to collect additional information. This approach embodies adaptive management by collecting increasingly detailed information used in decision-making as a developer moves through the tiers. It does not require that every tier, or every element within each tier, be implemented for every project; rather, it strives for efficient use of developer and wildlife agency resources with increasing levels of effort until sufficient information and the desired precision for the risk assessment is acquired.


During the pre-construction project planning and siting stages (Tiers 1-3), developers seek the best available science and coordinate with the Service to identify whether there are risks to wildlife as they make preliminary decisions about avoiding and minimizing risk.

Tier 1 – Preliminary, landscape-level screening. Sites or broad areas under consideration are screened for high potential risk to wildlife based on existing research, databases, and maps. Potential wildlife impacts are among of many site characteristics, including wind resource, land ownership, and access to transmission lines, that companies must consider when prospecting for potential project sites.

Tier 2 – Site characterization. Once the options have been narrowed to specific possible project sites, one or two in-person reconnaissance visits are made by trained wildlife biologists to further assess potential wildlife issues. The biologists look for evidence that known species of concern may use the site, either year-round or seasonally, based on site attributes or records indicating the presence of nesting sites, migration stopovers or corridors, leks, or other areas where species of concern congregate. Project developers also begin communication and coordination with the Service and state agencies to inform risk assessment and project planning, and this coordination continues throughout the tiered process. 

Learn more about how landscape level screening and site characterization studies are used during a project’s pre-construction stages to avoid collision and habitat impacts. 

Tier 3 – Detailed field studies. If warranted based on risks identified in Tiers 1 and 2, detailed field studies are conducted to document the relative abundance, behavior, and site use of species of concern, and quantify potential project impacts. Information gathered at this stage serves several purposes: (1) to enable a decision whether to proceed with or abandon site development; (2) to design a project that avoids or minimizes wildlife risk; (3) to establish a baseline against which to evaluate actual project impacts; and (4) to identify compensatory mitigation measures (if necessary) to offset projected unavoidable adverse impacts.

Learn more about how Tier 3 studies are used during the latter stages of siting and project design to document site wildlife and habitat resources and help avoid and minimize collision and habitat impacts.


During construction and operation of a wind energy project, developers assess whether their actions to avoid and minimize impacts are successful. The outcome of studies in Tiers 1, 2, and 3 are used to determine the duration and level of effort of post-construction studies.

Tier 4 – Fatality monitoring and habitat impact assessment. Post-construction fatality monitoring (PCM) studies (Tier 4a) involve searching for bird and bat carcasses beneath turbines to estimate the number and species composition of fatalities (see pages 34-39 of the Guidelines for a more detailed description of the questions to be answered and the methods and metrics to be used in PCM studies).

Learn more about how PCM results from individual wind projects are used to estimate collision risk and risk factors at operational wind energy projects.

Habitat studies involve application of GIS and use data collected in Tier 3 and Tier 4b, and/or published information. See the Service’s Land-based Wind Energy Guidelines, pp. 40-42, for a more detailed description of the questions to be answered and the methods and metrics to be used in assessing direct and indirect impacts of habitat loss, degradation, and fragmentation (Tier 4b studies).

Learn more about what we’ve learned about habitat-related risk and risk factors from wind energy development.

Tier 5 – Additional studies. If warranted based on Tier 4 study outcomes, additional studies may be performed to further understand any significant impacts, improve mitigation efforts, or assess potential population-level impacts. Most wind projects do not proceed to Tier 5 studies – instead, the Service may encourage developers to participate in non-project-specific collaborative research studies or studies on an experimental mitigation technique, such as differences in turbine cut-in speed to reduce bat fatalities, but this is beyond the scope of Tier 5 studies.

Learn more about the kind of research studies used to assess habitat impacts, and evaluate population-level impacts.