FOREST f AND STREAM 



88 



PTERYLOSIS 



HARRIS'S WOODPECKER. 



Fis. 1.— Loft lateral view of a plucked specimen of Harris's woodpecker (D. v. harrisii); adult male; d, upper part of the "inferior space" fj.pt. mesogastrmi); 7c, the uropygial gland of the left side; I, its 

 external papilla with opening at its summit, which is also "tufted." Fig. 2.— Dorsal aspect of the Same specimen; b, capital apterium; c, the median (at the point indicated) elevation of the 

 skin caused hy the epihranchials of the hvoidean apparatus beneath it; g. spinal tract; /, inner humeral tract; e, humeral tract; ft, lower dilation of spinal tract (the saddle); j, lower part of 

 spinal tract (rump tract); i, crural tract; o, femoral tract (very faintly seen m a woodpecker); p, caudal tract; q, alar tract. > ig. 3.— Anterior or ventral aspect of the same specimen, with its 

 head turned to the left; a, capital tract; n, the ventral tract, and m, its external branch. All the figures drawn by the author from the specimen. 



as a narrow, median, longitudinal strip, which dilates at 

 the middle of the back as a bifurcated "saddle-tract" 

 (Fig. 2, g and 7i); then occurs an interruption when a rump 

 division of the spinal-tract commences and extends down 

 over the tufted oil-gland (j), while that part which is 

 carried over the caudal region (the true tail of a bird) is 

 designated as the caudal-tract. Turning to Sphyrapicus 

 we note that there is no interruption in the spinal-tract, 



FiQ. i.— Ventral view of a plucked specimen of the red-naped 

 woodpecker (Sphyrapicus v. nuchalis), showing its pterylosis or 

 feather-tracts. (Life size, by the author from nature.) 

 and that the "saddle portion" is a lozenge-shaped area, as 

 shown in Fig. 5. This is particularly interesting when 

 taken in connection with the condition of the hyoid in 

 this bird, for the arrangement is quite similar to the 

 spinal-tract as it is found in passerine birds generally. 

 Birds also show a great variation in their spinal tracts, 

 and I hope some of the readers of Forest and Stream 

 will demonstrate this to their own satisfaction. 



Still referring to Figure 2, we note that the humeral 

 region of each arm is obliquely crossed by a narrow 

 feather strip (e), which is known as the humeral-tract (the 

 single long bone of the arm is the humerus), while in 

 our woodpeckers we see a character quite peculiar to 

 them, being present in both of our specimens, and shown 

 at/, a little separate tract, called the inner humeraMract. 

 Nitzsch found only one woodpecker that lacked this char- 

 acteristic feature, a Sumatran type (P. luridus). Such 

 feathering as a wing may show, aside from the flight 

 feathers, is collectively spoken of as the alar tract (Fig. 

 2, q). 



Over the region of the thigh there is a tract known as 

 the femoral tract (Fig. 2, o), which is but very faintly 

 indicated in woodpeckers, not noticeable at all in most 

 specimens and species. 



Then across the leg there is a well defined strip which 

 we call the crural tract, shown in Fig. 2 at i, and is 

 even more conspicuously seen in Sphyrapicus (Fig. 5). 



We may also see from these figures that the apteria, or 

 naked spaces, are sparsely covered over in r.ome places 

 by small, downy feathers of an elementary character. 



Turning next to Figures 3 and 4, we are enabled to study 

 the feather-tracts as they are found to occur upon the 

 ventral aspect of the body — and here again we note that 

 no little difference obtains between our two specimens of 

 woodpeckers. 



Most often the ventral-tract is a single broad one, ex- 

 tending from the region of the shoulder in front down to 

 the vent, being Eituated about half way between the 

 middle line of the body and the side, and not so Well 

 marked for its lower moiety as it is above (Fig. 3, m and 

 n). In these woodpeckers, however, the upper part of 

 this ventral-tract bifurcates, giving rise to an external 

 tract seen at m and of quite a different form in Dryobates 

 and Sphyrapicus. 



A circlet of feathers usually surrounds the vent, and in 

 Harris's woodpecker there extends down over the ante- 

 rior aspect of the coccygeal region, from this point, on 

 either side, a narrow feather tract, which, taken in con- 

 nection with a median line over the same part, we might 

 collectively name the postventral-tract, in the absence 

 of any other designation known to me for it. 



We have, then, the following feather tracts to study 

 and compare in birds with the view of assisting us in our 

 classification of this group of vertebrates, viz. : 



1. The spinal-tract (Pteryla spinalis). 



2. The humeral-tract (Pteryla humeralis). 



3. The femoral or lumbar-tract (Pteryla femoralis seu 

 lunibalis). 



4. The ventral-tract (Pteryla gastroei). 



5. The lateral neck-tract (Pteryla colli lateralis). 



6. The head-tract (Pteryla capitis). 



7. The wing-tract (Pteryla alaris). 



8. The crural-tract (Pteryla cruralis). 



9. The caudal-tract (Pteryla caudalis). 



10. The postventral-tract (Pteryla postventralis). 



There will, too, of course, be some anomalies to be on 

 the lookout for, as we see in the "internal humeral tract" 

 and such others like it. 



This chapter will not have been contributed in vain if 

 it but prove to be the means of inciting even one careful 

 observer to enter upon this very fruitful field of research. 



As for myself, I was never so fully impressed with the 

 value of pterylography as an aid to correct taxonomy in 

 birds, as I was when I came to investigate this character 

 and compare it in the swifts and hummingbirds, forms 

 hitherto supposed to be related to each, sufficiently so at 



least, to place them in the same order. I found the 

 pterylosis in a swift widely different from the pterylosis 

 in a hummingbird, a fact which further supports a former 

 proposition of mine, elsewhere published, to the effect 



Fig. 5.— Dorsal aspect of the same specimen of Sphyrapicus, shown 

 in Fig. 4, designed to illustrate its pterylosis. (Life size, by the 

 author.) 



that these birds belong in entirely different groups, they 

 not having any special affinity whatever, as any one may 

 see who has ever taken the trouble to fully investigate 

 their structure. 



obt Wing ate, N. M., Aug. i. 



