First off, I admit I haven't read most of this book, because I have a problem sticking with non-fiction from beginning to end, and hop around, like, um, a bird, while I read. I bought this for my Grandma Dory, because she loves birds. As far as I know, she's never kept one as a pet, but she's not the kind for that. She wasn't a farm girl, exactly, but growing up in a farming community makes her stance on pets pretty harsh. Animals stay out of the house; they belong in the barn, or in the wild. But she watches, and watches with the exacting eye of a naturalist. To this day, she has at least five different kinds of feeders outside her kitchen window, and the Audabon and Sibley guides in a little basket by the window frame. She can tell you how to squirrel proof anything.
Dad and other members of the family have started buying her books about birds - she stills reads, and a lot - and this is what the stack looks like:

Anyway, I got a letter from her last week, the third in which she wrote about how great this book is. Here's the text:
"Dear Ceridwen,
I am really enjoying "The Bird" It has so many interesting stories of the achievements of a whole series of birds across the years. I seem to fill the book with markers to share these stories with [Aunt] Kristen when she comes home. It's not one of those books to read and put on a shelf, but one to return to when I see a bird flash by my window. One can never feel alone when you can see birds outside the window."
So, the idea of birds outside my window is a little more creepy for me than for her, but I get her point, and I love this letter. The parts I read of this book, before I left it at her house, were crazy informative, getting into things like how birds fly, and what exact dinosaurs they evolved from, and how feathers are formed, the different kinds, taxonomy, other really technical stuff. It was not written to be opaque, and what I read I followed easily, despite my being sort of non-fictionally challenged. I spent most of my time in the section about the evolution of birds from dinosaurs, because I love dinosaurs, and Tudge had some really interesting things to say about how we class different species.
I'm not a big bird lover, but if you are, this is ranked by one of the most well-informed people I know on the subject as a great read. Five stars from Grandma Dory.