No one ever said birding is easy. With 10,000 bird species in the world, one inevitably encounters groups of birds that are difficult to distinguish.

Hummingbirds in the New World tropics, sandpipers and sparrows are great examples. It’s easy to identify a bird as a hummingbird but which of the 340 species is zooming around you?

Gulls are another group of challenging birds. Any school kid can identify a seagull but identifying the species can be perplexing. Which of the 16 gull species in Maine are we seeing?

The difficulty of gull identification stems in part from the fact that gulls pass through a bewildering series of plumages. Most gull species molt at least some of their feathers twice a year, changing their appearance. To confound matters further, the timing of the molts differs among individuals so birds that are the same age may look strikingly different.

Gulls may take up to four years to acquire their adult plumage, called the definitive plumage in ornithology-speak. Smaller gulls like Bonaparte’s gull require only two years to get to their definitive plumage while our larger gulls, like the herring gull and great black-backed gull, take four years to reach adulthood. That’s a lot of plumages to keep track of.

To be sure, some birders delight in the challenges of gull identification. Poring through flocks of hundreds of gulls to find an uncommon gull like a lesser black-backed gull, black-headed gull, little gull or Sabine’s gull is a joy to gull enthusiasts.

That level of skill is tough to come by. But a book from Princeton University Press – “Gulls Simplified: A Comparative Approach to Identification” by Pete Dunne and Kevin Karlson – may be a gateway to allow you to identify gulls in a different way. Yes, I am aware that the phrase “gulls simplified” seems like a contradiction, but the phrase fits this book.

Who knows? Maybe your improved gull identification skills will allow you to be the person who finds a slaty-billed gull among the hundreds of gulls at the Hatch Hill Dump in Augusta.

Dunne and Karlson are highly skilled birders and popular tour leaders. But neither has a particular passion for gulls. The authors argue their level of interest is perfect for a book that aims to fill a need for a gull identification guide that’s welcoming to any birder.

The distinctive feature of this guide is that identifications are based more on general shape, size, behavior, general color patterns, habitat and comparisons to other known birds in the area. The guide downplays the feather-centered approach that gull nerds use to identify the age and species of a particular gull.

The authors rightly claim that most birders don’t care whether the Herring gull they are looking at is 1, 2 or 3 years old. It’s more important to know it’s a Herring Gull. Dunne notes that it’s easier for him to identify a lesser black-billed Gull at 200 feet than at 20 feet if he relies on general impressions rather than plumage.

Dunne and Karlson are pioneers in promoting bird identification by impression, having produced identification guides for hawks and shorebirds that use this technique. The approach works for gulls, too.

The book is packed with excellent color photographs, mostly taken by Karlson. Detailed legends for each photograph describe important characteristics for identification. I counted 46 photos for the Herring gull. There are several photo quizzes, as well.

The guide covers the 20 regularly occurring species in North America as well as five rare gulls. A section on hybrids is illuminating.

“Gulls Simplified” is a great addition to the wealth of bird guides.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at

whwilson@colby.edu