File:The Canadian bird book - illustrating in natural colors more than seven hundred north American birds, also several hundred photographs of their nests and eggs (1914) (14562285008).jpg - Wikimedia Commons

The Nests and Eggs of Birds Of the United States., by Thomas G. Gentry

The Project Gutenberg eBook of Color Key to North American Birds, by Frank M. Chapman.

Encyclopedia of Birds: 400 Species from Around the World by Per Christiansen, Paperback

Book of North American Birds: An Illustrated Guide to More Than 600 Species: Editors of Reader's Digest: 9798889770053: : Books

File:Birds and nature in natural colors - being a scientific and popular treatise on four hundred birds of the United States and Canada (1913) (14565635258).jpg - Wikimedia Commons

The Project Gutenberg eBook of Color Key to North American Birds, by Frank M. Chapman.

The Nests and Eggs of Birds Of the United States., by Thomas G. Gentry

File:Illustration from Birds of America (1827) by John James Audubon, digitally enhanced by rawpixel-com 194.jpg - Wikimedia Commons

The Project Gutenberg eBook of Color Key to North American Birds, by Frank M. Chapman.

Book of North American Birds: An Illustrated Guide to More Than 600 Species: Editors of Reader's Digest: 9798889770053: : Books