File:Red-billed and Alpine Choughs - Pyrrhocorax naumann 004.jpg

Summary
Painting of Red-billed and Alpine Choughs Publication information: Johann Friedrich Naumann (1780-1857), Naturgeschichte der Vögel Mitteleuropas, 2nd edition (1896-1905); originally published between 1820 and 1844 Band IV, Tafel 6 - Gera, 1901

This image comes from the book Naumann, Naturgeschichte der Vögel Mitteleuropas (Natural history of the birds of central Europe) of 1905 or his earlier works. The copyrights for those books have expired and this image is in the public domain.