I have been asked the question "do dark (rufous and dark-morph) Western Red-tailed Hawks always have multiple tail bands? The answer is no, and in fact, many lack multiple tail bands. The idea that dark birds seen on migration in the mid-west or eastern North America are actually Eastern (borealis) birds, has been tossed around. And one of the factors this thought was based on is that many lack multiple black bands on the tail as seen on Western birds. However, check out the Utah breeding birds in the photos below and note that they all lack obvious tail banding. And of course, Western light-morph adults lack tail bands quite often as well, and can have pale throats similar to Eastern (borealis) birds!
Just a note to clarify things, and hope you find this stuff as interesting as I do..."click" on photo to enlarge.