Chapter 3: Landscape Assessment and Siting Practices to Address Risk to Wildlife and Habitat

Documenting Wildlife and Habitat at a site

Updated December 27th, 2022

While preliminary site visits to a prospective wind energy site are predominantly qualitative (evaluating the overall picture of wildlife and natural resources), the next step in site assessment – pre-construction field studies – is designed to document wildlife and habitat at a site in scientifically rigorous, quantitative terms. The methods used to quantify the distribution, relative abundance, behavior, and site use by species of concern will depend on which species of concern have been identified as either being present or likely to use the site on a regular basis.

Measures of abundance and activity

The correct method to estimate the spatial distribution and relative abundance of wildlife depends on the type of species being documented.

  • For diurnal birds, methods include counts of birds seen or heard at specific survey points (point count) or along transects (transect surveys).
  • Raptor nest searches identify both the presence of breeding birds and specific locations within a project site where nests occur (many species of hawks and eagles re-use nests for multiple years). Data collected during these searches allow developers to avoid putting turbines and other infrastructure in areas that might disrupt nesting.
  • Prairie grouse are generally surveyed using lek counts (a count of the maximum number of males attending a mating ground, or lek) conducted during the breeding season.
  • Acoustic monitoring is often used to determine the presence of threatened, endangered, or otherwise rare species of bats throughout the stages of a proposed project. A similar method can also be used to help assess presence of nocturnally migrating birds. Radar can also be used to compliment this information.
  • Searches of roosts (the places bats sleep during the day) and roost exit counts may be used to confirm bat presence, composition, and colony size.

Learn more in the U.S. Fish & Wildlife Service Land Based Wind Energy Guidelines, Chapter 4.

The Service recommends consulting with state, Tribal, and federal agencies regarding specific survey protocols for locally listed species of concern.

Determining how species use the site

Field studies also need to look at whether there are species that use the site only during certain times of day or seasons. In addition to quantifying species’ relative abundance, site documentation gathers information about:

  • Temporal use (time of day/night, seasonal use)
  • Spatial use (flight height, specific breeding areas or nesting sites)
  • Life history use (foraging, migration, stopover, breeding, etc.)
  • Potential for habitat fragmentation

Utilizing site documentation

Merely establishing that a species is present or that a species is using a site prior to construction is not necessarily a predictor of post-construction risk. While there is a correlation between pre-construction raptor (and particularly eagle) abundance and post-construction fatalities, predicting bat fatalities from pre-construction acoustic monitoring data has not been effective. The identification of nesting or roost sites, or other features of the landscape that may increase collision risk for local species of concern, can be useful in designing a wind project to avoid or create a buffer around those features.

For sites that include habitat used by species particularly sensitive to habitat fragmentation, pre-construction field studies seek to identify the amount of habitat that could be impacted by the proposed wind energy facility. Again, the specific features documented by the field study – location within the project area of lek and nesting sites, existing instances of fragmentation (such as roads) versus intact areas of habitat – can be taken into account in the design of the project to minimize adverse impacts.

Finally, the data gathered during pre-construction field studies are used to determine whether there is a need for post-construction monitoring to document fatality rates or evidence of displacement.