Magna, mexicana, meridionalis and hippocrepis, are most similar in coloration; neglecta is most dissimilar compared with any of the others. Though each possesses peculiar characters, they are only of degree; for in the most widely different forms (neglecta and mexicana) there is not the slightest departure from the pattern of coloration; it is only a matter of extension or restriction of the several colors, or a certain one of them, that produces the differences.
Each modification of plumage is attended by a still greater one of proportions, as will be seen from the diagnoses; thus, though neglecta is the largest of the group, it has actually the smallest legs and feet; with nearly the same general proportions, magna exceeds it in the latter respects (especially in the bill), while mexicana, a very much smaller bird than either, has disproportionally and absolutely larger legs and feet united with the smallest size otherwise in the whole series. Meridionalis presents no differences from the last, except in proportions of bill and feet; for while the latter is the smallest of the series, next to neglecta, it has a bill much exceeding that of any other.
The markings of the upper plumage of the young or even winter birds are different in pattern from those of the adult; the tendency being toward the peculiar features of the adult neglecta; the various species in these stages being readily distinguishable, however, by the general characters assigned. Mexicana and neglecta are both in proportions and colors the
most widely different in the whole series; hippocrepis and neglecta the most similar. The relation of the several races to each other is about as follows:—
A. Yellow of throat confined within maxillæ.
Crown with black streaks predominating.
Smallest species, with reddish tints, and maximum amount of black.
Largest bill … meridionalis.
Smallest bill; largest feet … mexicana.
Next largest species, with less reddish tints, and smaller amount of black. Bill and feet the standard of comparison … magna