While some species are easy to identify, many birds present challenges. Look-alike species such as scaups (below), sandpipers, gulls, and the notoriously difficult Empidonax flycatchers, are enough to keep birders working to improve their skills for years to come.

But as if that wasn’t hard enough, just as we begin to feel confident, fall arrives. Birds are migrating, males become drab and the world is flooded with a new crop of immature birds. It makes me feel like a beginner birder, all over again!

Bright feathers attract mates, but they also attract predators. By September, those beautiful colors are more of a liability than an asset. As a result, warblers molt out of their breeding plumage. All the ducks are hard-to-see brown. Finches lose their reds and yellows, opting instead for duller shades. The birds are harder to see, and harder to identify when we do.

Migrants add to the confusion. Instead of staying in their normal habitats—such as aptly named species like the Willow Flycatcher, Alder Flycatcher, and so forth—the birds are on the move. Often, they have to settle for substandard accommodations en route—any thicket will do. Some migrating birds, especially those new to the experience, end up far from their expected range, further confounding the birder. (Once identified, however, we delight in adding the rare-to-us bird to our lists.)

Not so long ago, the fields and forests were full of harried parents, exhausting themselves to keep their broods fed. Now, those nestlings have become still-immature juveniles. They’ve left the nest and are, for the most part, on their own. While I’m thrilled at a new generation of birds, these youngsters may or may not look like mom and dad. Some simply look like females, others have stripes or hues that disappear as they mature.

Take these White-crowned Sparrows, for example. Fledglings have striped chests, while adults do not. Immature birds have brown and white striped heads; adults’ heads are black and white:

For another example, Colorado’s Front Range typically sees four species of hummingbird—Broad-tailed, Black-chinned, Calliope, and Rufous. The adult males are easy to tell apart, but they’ve departed by late summer, leaving the females and juveniles. I’ve spent the last month trying fruitlessly to decide if the birds I was seeing were Broad-tails or Rufous. Maybe I’ll catch on next year.

There are approximately 750 to 800 “regularly occurring species” of birds on the ABA’s North American list.* But consider the many dimorphic species (those where the male and female look different, such as ducks, warblers, and many thrushes), along with those that take months—or even years—to achieve their adult plumage. Clearly, there are many more than that we need to learn to recognize.

As far as I can tell, all these birds are Common Yellowthroats. I think.

Winter is coming with its snow and ice, and fewer species to enjoy (while some species arrive from the north to winter here, many more head south). I should have plenty of time to focus on identifying all the mystery birds I photographed this month. Meanwhile, anyone want to write a book? I could use a Fall Field Guide to the Birds.

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*In this case, “North America” means only the U.S. and Canada, not including Hawaii or islands in the Caribbean.

The answer to last week’s quiz is Great-tailed Grackle (female)