This is a smaller bird than Dryobates scalaris eremicus from the northern half of Baja California; both upper and lower surfaces are lighter in color, with the white bars on the back broader and with the sides of the breast spotted. Mr. Brewster (1902) writes:
All the characters which have been proposed for this Woodpecker are shown by the large series before me to be subject to much variation, but this, as in the case of Melanerpes angustifrons, is confined within limits which do not overlap, if, indeed, they quite reach those of the bird’s nearest allies. The restriction of the black on the outer tail feathers is perhaps its best distinguishing feature, although this is not at all uniform, for many of my specimens have three complete dark bars crossing both webs of the outer tail feathers, while in one a fourth bar is only broken by a small space near the middle of the feather. The width of the dark bars on the back is also variable, although these bars are usually wider than in any of the allied forms. The feet average larger than those of bairdi, but they are by no means always larger. A difference which I do not find mentioned in descriptions, but which is shown by my series to be quite as constant as most of the characters that have been proposed, is that the white spots on the top of the head are much larger and more numerous than in bairdi, while the red is less vivid and more nearly restricted to the crown and occiput.
Griffing Bancroft (1930) writes of this woodpecker, in central Lower California, near the northern limit of its supposed range:
This little denizen of brush and thick undergrowth requires a heavy stand of low cactuses in which to feed and rest. It occurs from the shores of the Gulf to the mouth of José María Cañon. Though the rarest of the resident Picidae it is still fairly common. Its nesting instincts are quite distinct from other Dryobates scalaris. They, similarly situated, would utilize sahuaro, it is true, but they would also be prone to add such substitutes as dry mescal stalks, telephone poles, tree yucca and mesquite and would, more often than not, chose one of these other sites by preference. But lucasanus confines itself to the cardón, at least in the district we were studying, selecting a single-stalked giant cactus and drilling its hole very near the top of the plant. As a result the nest-cavity is rather uniformly twenty feet above ground. The entrance hole is at the top of a cavity typically five inches in diameter by fifteen in depth. No foreign material is brought in for a nest. The eggs lie on the chips that fall in the process of excavating.
The number of eggs in a clutch is two, three, or rarely four. The first two weeks in May find almost all the San Lucas Woodpeckers at the peak of laying. After the middle of the month nests with young may be expected. The parent bird will ordinarily flush, especially if the cardón be tapped, but it is not very nervous about its home. It is too busy with family duties to waste much attention on strangers.
The eggs are similar to those of the other subspecies. Bancroft (1930) gives the average measurements of 23 eggs as 22.9 by 18.1 millimeters. The measurements of 10 other eggs average 21.30 by 16.61 millimeters; the eggs, in this series, showing the four extremes measure 24.40 by 18.70, 23.70 by 18.80, 19.50 by 16.80, and 21.43 by 15.42 millimeters.
DRYOBATES SCALARIS CACTOPHILUS Oberholser
CACTUS WOODPECKER
HABITS
The ladder-backed woodpeckers are quite widely distributed in the Southwestern United States and in nearly all Mexico and in British Honduras, chiefly in the Lower Austral and Tropical Zones. When Dr. Harry C. Oberholser (1911b) wrote his revision of this group, he split the species Dryobates scalaris into 15 subspecies, 9 of which he described and named as new subspecies. Only two of these subspecies are found within the limits of the United States, and only two in Baja California, giving us four on our Check-List.