That is how this book is. I have several different field guides and have never seen one like this. I would call it more of an encyclopedia...it has some really cool features like ~ an egg chart, drawing of different types of tails, bills and feet, a color key to water birds, land birds and warblers, a glossary plus all of the pictures and drawings. One of the things I like is that the pictures are a nice size and states the ''scale'' ~ like ½ natural size ~ which is very helpful and easier for me to actually visualize a bird's size for some reason.
So when the Western Scrub Jay was split into two different birds and named California and Woodhouse's I thought those were new names but according to this book that was their former names...there is so much fascinating info in this awesome book.