
[1] - https://www.goodreads.com/book/show/77166.A_Year_in_the_Main... [2] - https://www.goodreads.com/book/show/254704.Mind_of_the_Raven [3] - https://www.goodreads.com/book/show/122665.Ravens_in_Winter [4] - https://www.audubon.org/news/how-tell-raven-crow
Great book on the subject: http://www.goodreads.com/book/show/122665.Ravens_in_Winter
