With continuing research and greatly improved digital photography, modern field guides provide a wealth of detail that 20th century field guides simply couldn't. While biological knowledge continues to increase, there is a limit to how much detailed identification information can be included before we end up with a no longer field-worthy book. This contributes to the proliferation of guides to specific avian families. Whether it be gulls, shorebirds, hawks or hummingbirds, in any avian family guide there's room for a deep dive into all the delicious little details that won't fit in a standard field guide.
Among the more challenging groups are the flycatchers. When they are singing in the proper habitat in their normal range and season, even the toughest empids aren't a problem. But migrants and vagrants can show up almost anywhere, and they are often silent in such non-breeding situations.
Often, you'll get too fleeting a glimpse to name every bird, and that's never going to change. But is there anything more frustrating than a lingering, cooperative bird with a look in its beady little eyes that seems to say, "Give up?" Some of the guides to advanced birding of the 1980's brought a new focus on Giss or gestalt to this group, but not enough was known to bring frequent certainty. I can vouch that they stimulated many, mmm. err, "discussions", among birding friends.
Professor Cin-Ty Lee and artist Andrew Birch have produced a compact volume brimming with fine details, hints and tips. The numerous line drawings and paintings ask you to attend to things such as crown shape, forehead angle, bill length, lower mandible color, tail length and width, primary projection, wing bar and wing panel contrast, upper/under part contrast, eye ring, and behavior. Additional detailed drawings help birders assess each feature.
That's an almost overwhelming list of features to attend to, and the author concedes that no single field mark is typically diagnostic. But if you can assess several of them, you quickly go from ten empids to two or even one. The marks are summarized in a "field mark matrix", which will help guide the observer to the best answer. Spring and fall migration timing maps and detailed descriptions of vocalizations further refine the identification.
A good way to start would be with singing birds on territory. You know it's an Acadian Flycatcher (or whichever) before you even see it. Compare the features shown in the matrix and drawings with your bird, so you can get a handle on how to judge the features, and the range of variation.
Neither the author nor artist assert that the "Field Guide to Flycatchers of North America: Empidonax and Pewees" will let you ID every bird with ease and certainty. But it will certainly raise the odds in your favor. Consider it the syllabus for a course; the semester begins with spring migration and continues through late fall. The more classes you make, the faster you'll learn!
If it does no more than increase your appreciation for the finer details of these subtly attractive birds, the author and artist are to be applauded. I'm looking forward to May 2024, when their second volume covering Kingbirds and Myiarchus flycatchers is due to be published.