Butler, Christopher J., Jeffrey B. Tibbits, and Katrina Hucks. 2013. Status of 10 Bird Species of Conservation Concern in U.S. Fish and Wildlife Service Region 6. Edmond: University of Central Oklahoma. http://www.fws.gov/mountain-prairie/migbirds/pdf/Status_of_10_Bird_Species_of_Conservation_Concern_Final_report_Mar_6_2013_v2.pdf