Learning to identify birds similar to one another is a challenge to novice and experienced birders alike. In this case, it is important to remember that “in the field of observation, chance favors the prepared mind,” as Louis Pasteur once said.

Being prepared entails keeping your mind open to other possibilities, and not, for instance, becoming preoccupied with finding the snowy owl rumored to be hanging around. This type of tunnel vision effectively blinds you to obvious details when other opportunities present themselves-and leads to misidentification.

This is exactly what happened to me as I searched for the above-mentioned snowy owl last week. I saw no snowy, but hundreds of bohemian waxwings converging on the fruit trees of the University of Maine ornamental gardens. These western-breeding birds, which are rare winter visitors to the northeast, are very similar to the resident, more common cedar waxwings. However, I identified them as cedars to some people I know. It wasn’t until afterward that I realized my mistake.

I realized there were several details about the bohemians’ plumage and voice that I had picked up on only subliminally. Plumage differences included the undertail coverts (the feathers on the underside of their tail), the wing patterns, the face pattern, size, and overall color.

Cedar waxwings have white undertail coverts, whereas bohemians’ are a deep chestnut. The wing patterns are more elaborate on the bohemians. Besides the namesake red, wax-like tips on the secondary feathers (which are also present on cedars), the primaries (the longest, outermost feathers of the wing), are edged with yellow. The tips of the primary coverts (short feathers that overlap the base of the primary feathers), and the area above the waxy red tips on the secondary feathers (these are the shorter flight feathers that are closest to the body), are white.

The facial pattern on both birds is distinctive. However, the bohemian sports a long black chin patch in addition to the elegant black mask.

Bohemians are larger than cedars and have a gray belly; cedars have a yellow belly.

Telling them apart by voice is somewhat harder, but it was one of the characteristics that stuck with me that day. The bohemian’s call is a longer, louder, and lower-pitched call than the cedar’s high, lisping seeee.

First-year birds can be distinguished from adults by the absence of the waxy red wing tips. Incidentally, an explanation for these unusual structures is that they serve to protect the feather shafts of the secondaries from wear. They may also be an important signal of status in mate selection.

Bohemians and cedars will sometimes flock together, affording the perfect opportunity to compare characteristics, but don’t be afraid to make mistakes – this only speeds the learning process along.

Chris Corio’s column on birds is published each Saturday. Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com