Dark Phased.

[PeteJ]

Wouldn't an immature Harlan's be considered to be in an imature color phase, not only does the color of their tail feathers change, they usually get darker after their first molt.

Without determining that the hawk in the picture is not a Harlan's, it is incorrect to classify it as a Dark Morph.

Morphs must occupy the same habitat at the same time: this would exclude geographical species such as the Harlan's

The term Morph in reference to color variation makes no sense as the bird is not going to morph into something else.

I think when they use the term 'morph' in this case it is short for morphology, in other words: 'One of various distinct forms of an organism or species.' And, regardless if it is a Harlan's or a RT, it is dark and therefore a dark morph. There are light morph Harlan's, although when I think of Harlan's I must admit to thinking that the normal plumage is dark and the lighter plumage is probably the lesser known. Much like the dark plumage is not average for an RT.