EXTERNAL PARTES OF BIRDS. — TOFOGBAl'HY. 99 



bare in many birds, as the vulturine hawlts, and some pigeons; species of grouse liave a liare 

 warty supra-orbital space. Amtjng water-birds particuLirly, more or less of the interi-ainal space 

 is almost always unfeathered ; the nakedness always pro(.-eeds from before backwards. With 

 the rare exceptions of a narrow frontal line, and a little space about the angle of the moutli, no 

 other special parts (jf the head than those above given are naked in any Ncjith American bird, 

 unless associated with general baldness. 



The opposite condition, that of redundant feathering, gives rise to all the varicjus crests 

 (Lat., pi. crista) that form such striking ornaments of many birds. Crests proper belong to 

 the top of the head, but may be also held to include those growths on its side ; these together 

 being called crests in distinction to the ruffs, ruffles, beard, etc., of gula or mentum. Crests 

 may be di\'ided into two kinds : 1, where the feathers are simply lengthened or otherwise 

 (inlarged ; and 2, where the texture, and sometimes even the structure, is altered. Nearly all 

 birds possess the power of mo-idng and elevating the feathers on the head, simulating a slight 

 crest in moments (jf excitement. The general form of a crest is a full, soft elongation of thf; 

 coronal feathers collectively ; when perfect, such a crest is (/lobular, as in the genus I'yro- 

 cephaliis ; generally, however, the feathers lengthen (jn the occiput more than cjn the vertex 

 (jr front, and this gives us the simplest and commtmest form. Such crests, when more par- 

 ticularly occipital, are usually connected with lengthening of nuchal feathers, and are likely 

 to be of a thin, pointed shape, as weU shown in the kingfisher. Ccjronal or vertical crests 

 proper are apt to be rather different in coloration than in specially marked elongation of the 

 feathers ; they are perfectly illustrated in the king-bird, and other species of the genus Ti/ran- 

 niis. Frontal crests are the most elegant of all ; they generally rise as a pyramid from tlie 

 fjrehead, as excellently shown in th(; blue jay, cardinal bird, tufted titm(>use, and others. All 

 tlie foregoing crests are generally single, but sometimes double; as shown in the two lateral 

 occipital tufts of the " horned " lark, in all the tufted or " horned " owls, and in a few cormo- 

 rants. Lateral crests are, of course, always double, one on each side of tlie head ; they are of 

 various shapes, but need not be ])articularized here, especially since they mostly bidong to tlie 

 second class of crests, — those consisting of texturally xnodified feathers. It is a general, though 

 not exclusive, character of these last that they are temporary ; while the other kind is only 

 changed with the general moult, these are assumed for a short period only, the breeding season ; 

 and, furthcruiore, they are often distinctive of sex. Occurring on the top of the head, they 

 furnish the most remarkable ornaments of birds. I need only instance the elegant helmet-like 

 Ijhnnes of the partridges of the genus Lopihortyx ; the graceful flowing train of Oreortyx ; the 

 somewhat similar plumes of the night and other herons. The majority of the cormorants, and 

 many of the auks, possess lateral plumes of similar description ; these, and those (if the herons, 

 are proliably — in most cases certainly — deciduous ; while those of the partridges above men- 

 tioned last as long as the general plumage. These lateral plumes, in many birds, espectially 

 among grebes, are associated with, and, in fact, coalesce with, the ruffs, whicli are singular 

 lengthening and modifying in different ways of feathers of auriculars, genaj and gula ; and are 

 almost always temporary. Beards, or special lengthening of the mental feathers alone, are 

 comparatively rare ; we have no good example among our birds, but a European vulture, 

 Gypaiitus harhatus, is one. The feathers sometimes become scaly {squa)nous), forming, for 

 instance, the exquisite gorgelets or frfintlets of humming-birds. They are often hristhj (.seta- 

 ceous), as about the lores of nearly all luiwks, the forehead of the dabchick, meadow-lark, 

 etc. A particular set of bristles, which grow in single series along the gape of many birds, 

 are called rictal bristles or vibrissa;. These occur in greater or less development in most small 

 insectivorous birds ; they are large and stiff and higlily characteristic of the fiimily Tyrannidx, 

 or flycatchers; while in some of the goatsuckers (Caprimulgida;) they are jirodigiously long, 

 and in one species of that family (Antrostomus carolinensis) they have lateral filaments. While 

 usually all the unlengthened head-feathers point backward, they are sometimes erect, forming 



