A History of North American Birds, Land Birds. Volume 2. Robert Ridgway

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      The colors vary; the upper parts are generally uniform black or brown, sometimes olive; the under white or brown; no central streaks on the feathers. The hood sometimes differently colored.

      In the large number of species or races included in this genus by authors, there are certain differences of form, such as varying graduation of tail, length of claw, etc., but scarcely sufficient to warrant its further subdivision. In coloration, however, we find several different styles, which furnish a convenient method of arrangement into groups.

      Few genera in birds exhibit such constancy in trifling variations of form and color, and as these are closely connected with geographical distribution, it seems reasonable to reduce many of the so-called species to a lower rank. In the following synopsis, we arrange the whole of North American and Mexican Pipilos into four sections, with their more positive species, and in the subsequent discussion of the sections separately we shall give what appear to be the varieties.

      After a careful study of the very large collection of Black-headed Pipilos (leaving for the present the consideration of those with olive-green bodies) in the Smithsonian Museum, we have come finally to the conclusion that all the species described as having the scapulars and wing-coverts spotted with white—as arcticus, oregonus, and megalonyx, and even including the differently colored P. maculatus of Mexico—are probably only geographical races of one species, representing in the trans-Missouri region the P. erythrophthalmus of the eastern division of the continent. It is true that specimens may be selected of the four races capable of accurate definition, but the transition from one to the other is so gradual that a considerable percentage of the collection can scarcely be assigned satisfactorily; and even if this were possible, the differences after all are only such as are caused by a slight change in the proportion of black, and the varying development of feet and wings.

      Taking maculatus as it occurs in the central portion of its wide field of distribution, with wing-spots of average size, we find these spots slightly bordered, or at least often, with black, and the primaries edged externally with white only towards the end. The exterior web of lateral tail-feather is edged mostly with white; the terminal white patches of outer feather about an inch long; that of inner web usually separated from the outer by a black shaft-streak. In more northern specimens the legs are more dusky than usual. The tail is variable, but longer generally than in the other races. The claws are enormously large in many, but not in all specimens, varying considerably; and the fourth primary is usually longest, the first equal to or shorter than the secondaries. This is the race described as P. megalonyx, and characterizes the Middle Province, between the Sierra Nevada of California and the eastern Rocky Mountains, or the great interior basin of the continent; it occurs also near the head of the Rio Grande.

      On the Pacific slope of California, as we proceed westward, we find a change in the species, the divergence increasing still more as we proceed northward, until in Oregon and Washington the extreme of range and alteration is seen in P. oregonus. Here the claws are much smaller, the white markings restricted in extent so as to form quite small spots bordered externally by black; the spots on the inner webs of tail much smaller, and even bordered along the shaft with black, and the outer web of the lateral entirely black, or with only a faint white edging. The concealed white of the head and neck has disappeared also.

      Proceeding eastward, on the other hand, from our starting-point, we find another race, in P. arcticus, occupying the western slope of the Missouri Valley and the basin of the Saskatchewan, in which, on the contrary, the white increases in quantity, and more and more to its eastern limit. The black borders of the wing-patches disappear, leaving them white externally; and decided white edgings are seen for the first time at the bases of primaries, as well as near their ends, the two sometimes confluent. The terminal tail-patches are larger, the outer web of the exterior feather is entirely white except toward the very base, and we thus have the opposite extreme to P. oregonus. The wings are longer; the third primary longest; the first usually longer than the secondaries or the ninth quill.

      Finally, proceeding southward along the table-lands of Mexico, and especially on their western slope, we find P. maculatus (the first described of all) colored much like the females of the more northern races, except that the head and neck are black, in decided contrast to the more olivaceous back. The wing formula and pattern of markings are much like megalonyx, the claws more like arcticus. Even in specimens of megalonyx, from the southern portion of its area of distribution, we find a tendency to an ashy or brownish tinge on the rump, extending more or less along the back; few, if any indeed, being uniformly black.

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