In a study conducted by Daniel Twedt, Paul Hamel and Mark Woodrey, they compared two different survey methods for determining species richness as well as relative abundance of grassland bird populations.  Their study area included 23 different sites, 9 coastal pine savannas and 14 recently reforested areas.  The study is titled Winter Bird Population Studies and Project Prairie Birds for Surveying Grassland Birds.  The study compared two survey methods, the first called Winter Bird Population Studies, is a method which has been used for decades, which simply involves a single observer to methodically move through a search area and identify and count all birds detected.  The second method titled Project Prairie Birds involves three researchers, the observer and the two “flushers”, it was designed to better determine the population and abundance of secretive species.  The study found that the Winter Bird Population Study method tended to overestimate the species richness.  While the Project Prairie Bird tended to overestimate avian abundance.  They also concluded that both of these methods are ineffective and suggests that the use of distance-based survey methods would provide the most complete results.