This is the definitive study of the ivory billed woodpecker. Tanner spent many months in the fast-disappearing Southern old-growth forests in the 30s, and probably saw more ivory-bills than anyone in the 20th century. He describes their feeding, mating, etc., habits and regional differences.
The sad thing here is that Tanner was well-aware that the birds were on the verge of extinction, and the tone of the book is quite poignant.
I just wish this edition had more material on how the book affected later researchers and some updated material on the possible rediscovery of the bird.