I love birding but it has its frustrating moments. Like when you get a good look at an unfamiliar bird, notice all the field marks you can, then run to your field guide to look it up, only to discover that the bird you thought would be a cinch to identify is not in the book anywhere. It’s frustrating, especially if you are hoping to add a new species to your life list, and happens more often than you might think. There are lots of reasons why you might not find the bird in the book, but I think the real reason is quite simple: the boxes we make to categorize things are artificial.
Sometimes, I can’t find the bird in the guide is because I didn’t see what I thought I saw. When I am lucky enough to have a photo to refer to later, my mistake becomes apparent, and I am humbled once again by how my brain can completely misinterpret what it sees in the moment. Another cause for trouble is not knowing about all the types of birds there are in the area. When this happens, the bird is in the book, I just didn’t look in the right section, because I didn’t know, for example, that what I thought was a warbler was actually a vireo. But I think the most common reason for a bird not to be in the book is because the book can’t show all the variation that exists in the world.
When I was on a road trip a few years ago, I took my pocket edition of Sibley’s Field Guide to Birds of Western North America because it was easier to carry. At a rest stop, I spotted a bright yellow bird with a black head and back, and knew I had something new for my life list. I went through the guide page-by-page and still couldn’t find what I considered a distinctive bird. It wasn’t until I got home and was able to look in my big Sibley’s that I discovered that my yellow bird was a lesser goldfinch as seen in Texas (although I was in Kansas).
In making a guide, an author must choose how to represent each species of bird, what field marks to highlight, and how variations need to be addressed. What they really are doing is building boxes that we all use to sort the birds we see. We categorize them as raptors or ducks or flycatchers or herons, then zone in on exactly which heron we saw by using the definitions given to us. But ultimately, these definitions are artificial.

Birds, and in fact all life forms, show a wide range of variations. The visible traits we focus on — like shape, color, specific markings — can vary with time of year (breeding, non-breeding, in between), diet (which can make a usually orange bird red or even yellow), region (example: red-tailed hawks; scroll through the photos at the top of this page to see some of the different variations), and genetics.
The world is wildly complicated and wonderfully varied. While the difference between the individual bird and the image in the field guide can keep me from knowing exactly what I saw, I still revel in seeing that bird. She is literally one of a kind.
How about you? Do you struggle to find the bird in your guide?