Some of my friends think marking up a book is tantamount to heresy. For me, a bird book is a tool with limitations dictated by publishing, printing, style, and space. Why not tailor it to work better? With judicious additions of notes, marks, colored dots, tabs (or whatever else you can think of), the book becomes more usable, and the birdwatcher more efficient. It is also a great study tool because when adding these notes, you are studying closely the differences in similar species.
I can’t count the number of times I’ve been distracted by a bright head pattern when it is the wing or tail features that clench the identification. Today several bird books follow the Peterson method and indicate important field marks with little black pointers and, or notes. I take a lesson from these experts by marking unadorned plates similarly. I find a few well-placed indicators can simplify a confusing group of birds, or remind me that the most obvious feature is not necessarily the discriminating one. More importantly, though, the act of adding the marks and studying the birds with them make it easier for me to remember key features when confronting a bird in the field. Not all birds will grant a leisurely audience where I can refer to the book and back to the bird, so the more I can recall without referring to the book, the better. Admittedly, sometimes memorizing field marks for each group of birds before a trip becomes overwhelming, so jotting a quick note saying “bill weight and call” serves as a reminder that in this group of honeyeaters, the heaviness of the bill and call differentiate species no matter how much I wish it was head pattern.
I employed another type of book mark in Robert Ridgely and Paul Greenfield’s indispensable book Birds of Ecuador (2001. vol. II) which places range maps in a separate area from the plates. To help me sort out species ranges without flipping from one part of the book to another, I added small spots with colored highlighters representing elevation and slope. Purple, blue, green, yellow, orange, pink, or red dots in the margins let me tell at a glance which hummingbirds were likely to occur below 1,000 meters on the eastern slope (red), and which were located in the central valleys (yellow). Relatively quick and easy to add, these dots saved me precious minutes in the field when confronted by a host of new species. Similarly, because authors include every bird ever seen in an area, a letter “R” or “V” next to a species name will indicate which birds are rare or vagrant and help narrow my choices.
I realize that not everyone’s brain functions the same way, so the cues that work for me may differ from the ones that help you. Some mistakes I’ve made were to use marks that were not waterproof and made a mess of my book when caught in a drippy fog-bank in Costa Rica. Also, once when applying a permanent felt pen, I moved from one plate to another too quickly and ended up leaving small black dots on the text side because the ink hadn’t dried. Now I stick mostly to soft pencil for my notes so that I can change them or delete them as needed. At the very least, I do write my email address in all bird books, notebooks, and other field books so if one falls out of your bag while, for example, searching for Beach Thickknee, it has a chance of getting home. (I dipped on the Thickknee in Australia, but was able to return the notebook to Texas).