Read the SURBFIRDS Review of Bird Coloration here
Author Geoff Hill of National Geographic's new Bird Coloration book took a few moments to sit with Surfbirds and answer some questions.
Surfbirds: One of the reasons many people get in to birding is the fascinating variety of species and the multitude of colors these species come in. However, we tend to leave it at that. Blue Jays are blue and Cardinals are red. Your book gives us context behind some of these avian colors. It's a fascinating topic. Have you been studying bird coloration for your whole career?
My first research project as a master’s student at the University of New Mexico in the early 1980s was on the function of delayed plumage maturation in male Black-headed Grosbeaks. Plumage color was also the focus of my doctoral research at the University of Michigan, my postdoctoral research at Queen’s University in Canada, and it remains a primary focus of my lab group at Auburn University. So “yes” I’ve been studying bird coloration for my entire career. When I first started presenting my work on color at national and international meetings in the mid-1980s, there were few other researchers studying color with only one or a few talks on color out of hundreds of talks presented. Now it is not uncommon for a big international meeting to have dozens of talks on bird coloration. It has been exciting to see the field expand and advance so rapidly in the past couple of decades.
Surfbirds: Was it a challenge to take on a scientific topic such as this and make it accessible to amateur birders and non-scientists?
Explaining the mechanisms by which bird colors are produced and how they function and evolve proved more challenging than I anticipated when I started the project. It was especially difficult for me to break free from the jargon and technical writing style that are required for journal articles. When readers skilled at non-technical writing reviewed early drafts of the book, they advised me to soften the text. I thought I had written the chapters in plain language, but these outside readers could point to section after section that would not be easily comprehended by nonscientists. The real challenge was to remove the jargon and make explanations clear without dumbing down the text. The final text was created with a lot of rewriting and with a constant focus on making broadly accessible explanations. I hope that readers find the final text challenging with regard conceptual issues but written in a style that is easy to follow.
Humans are visual animals, and color and pattern are typically the most conspicuous visual aspects of birds. I think an initial focus on color for bird identification is natural and appropriate. Skilled birders, however, certainly rely on much more than color. Size, shape, and especially behavior are key to identifying many species from flycatchers to storm petrels. So, I think it is just the opposite of what you propose: use coloration and pattern as a first sort and then focus on structure and behavior—exactly what most birders do.
Surfbirds: There seem to be a lot of unanswered questions in the world of bird color science. Could there be lots of discoveries to come and do you feel the advent of new technology could shepherd those in? Perhaps, even a practical application for birders in the field?
No doubt there are major discoveries to be made regarding bird coloration. It seems almost certain that new pigments as well as new forms of microstructures that create structural coloration will be discovered. We still have much to learn about the functions of coloration, and new discoveries for how bird colors function are appearing in journals each month. Studies addressing the evolution of coloration and why birds look the way they do are really just getting started, and I anticipate many advances along this line of research in years to come. These lines of investigation will improve basic understanding of coloration, but none will significantly impact bird identification.
I think the lines of scientific investigation that are most likely to impact bird identification and birding as a listing sport relate to the genetic control of coloration and the exchange of genetic material between species. The new genetic tools that are being created by biologists are revolutionizing our understanding of how organisms evolve including how color differences among populations relate to genetic distinctiveness. Such genetic studies are going to change what are viewed as species-level differences among populations.
Surfbirds: Lastly, a question I've pondered being an avid pelagic birder. In your book, you have a photo of juvenile Sabine's Gull and its distinctive upperwing pattern. Quite a few seabirds have a distinctive dark W or M pattern on their upperwing such as Kittiwakes and gadfly petrels. Is there an answer for this?
To my knowledge, the function of such distinctive and flashy wing patterns has never been studied. However, my grad student, Rusty Ligon, and I recently studied the bold and distinctive juvenal plumage of Eastern Bluebirds. We showed that the spotty breasts of young bluebirds deflect the aggression of adults, and it seems that this spotty plumage is a signal of immaturity. Science is founded on the premise that once we gain a general understanding of a natural phenomenon, we can extrapolate such understanding to novel circumstances. So, I would speculate the bold wing patterns of young Sabine’s Gull and other seabirds is an honest signal of immaturity that enables them to escape aggression from older birds.
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