The environmental impact assessment (EIA) has been a tool for decision makers since the enactment of the National Environmental Policy Act (NEPA). Since that time, few analyses have been performed to verify the quality of information and content within EIAs. High quality information within assessments is vital in order for decision makers, stake holders, and the public to understand the potential impact of proposed actions on the ecosystem and wildlife species. Low quality information has been a major cause for litigation and economic loss. Since 1999, wind energy development has seen an exponential growth with unknown levels of impact on wildlife species, in particular bird and bat species. The purpose of this article is to: (1) develop, validate, and apply a quantitative index to review avian/bat assessment quality for wind energy EIAs; and (2) assess the trends and status of avian/bat assessment quality in a sample of wind energy EIAs. This research presents the development and testing of the Avian and Bat Assessment Quality Index (ABAQI), a new approach to quantify information quality of ecological assessments within wind energy development EIAs in relation to avian and bat species based on review areas and factors derived from 23 state wind/wildlife siting guidance documents. The ABAQI was tested through a review of 49 publicly available EIA documents and validated by identifying high variation in avian and bat assessments quality for wind energy developments. Of all the reviewed EIAs, 66% failed to provide high levels of preconstruction avian and bat survey information, compared to recommended factors from state guidelines. This suggests the need for greater consistency from recommended guidelines by state, and mandatory compliance by EIA preparers to avoid possible habitat and species loss, wind energy development shut down, and future lawsuits.