References

Johnsgard, P.1975. Waterfowl of North America. Fitzhenry and Whiteside Limited, Don Mills, Ontario.

BirdLife International 2012. Aythya americana. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 09 April 2013.

Hoak, E. 2003. "Aythya americana" (On-line), Animal Diversity Web. Accessed April 09, 2013 at http://animaldiversity.ummz.umich.edu/accounts/Aythya_americana/

Reiger,G. 2003. National Geographic Reference Atlas to the Birds of North America. National Geographic Society Washington, D.C., USA.

Ehrlich, P.R.,D.S. Dobkin and D. Wheye.1988.The Birder’s Handbook: A field guide to the naturl history of north american birds.Simon and Schuster Inc., New York, New York, USA.

Floyd,T.2008.Smithsonian Field Guide to the Birds of North America. HarperCollins Publishers New York, New York, USA.

Baldassarre, G., E. Bolen. 1994. Waterfowl Ecology and Management. New York: John Wiley & Sons, Inc..

Bellrose, F. 1976. Ducks, Geese and Swans of North America. Harrisburg: Stackpole Books.

Johnsgard, P. 1992. Ducks in the Wild: Conserving Waterfowl and Their Habitats. New York: Prentice Hall General Reference.

Kortright, F. 1942. The Ducks, Geese and Swans of North America. Washington, D. C.: The American Wildlife Institute.

Phillips, J., F. Lincoln. 1930. American Waterfowl: Their Present Situation and the Outlook for their Future. Boston: Houghton Mifflin Company.

Todd, F. 1979. Waterfowl: Ducks, Geese & Swans fo the World. New York: Sea World Press.