EXTERNAL PARTS OF BIRDS. — TOPOGRAPHY. 99 



tai-e in many birds, as the vulturine hawks, and some pigeons ; species of grouse have a bare 

 "warty supra-orbital space. Among water-birds partieulai'ly, more or less of the interramal space 

 is almost always unfeathered ; the nakedness always proceeds from before backwards. With 

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

 other special parts of the head than those above given are naked in any North American bird, 

 unless associated with general baldness. 



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

 {Lat., pi. cristcE) that form sueli 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 divided into two kinds : 1, where the feathers are simply lengthened or otherwise 

 •enlarged ; and 2, where the texture, and sometimes even the structure, is altered. Nearly all 

 birds possess the power of moving and elevating the feathers on the head, simulating a slight 

 crest in moments of excitement. The general form of a crest is a full, soft elongation of the 

 coronal feathers collectively; when perfect, such a crest is gloiular, as in the genus Pyro- 

 ■cephalus ; generally, however, the feathers lengthen on the occiput more than on the vertex 

 or front, and this gives us the simplest and commonest form. Such crests, when more par- 

 ticularly occipital, are usually connected with lengthening of nuchal feather's, and are likely 

 to be of a thin, pointed shape, as well shown in the kingfisher. Coronal 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 Tyran- 

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

 forehead, as excellently shown in the blue jay, cardinal bird, tufted titmouse, and others. All 

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

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

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

 various shapes, but need not be particularized here, especially since they mostly belong to the 

 second class of crests, — those consisting of texturaUy modified 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, furthermore, 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 

 plumes of the partridges of the genus Lophortyx ; the graceful flowing train of Oreortyx ; the 

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

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

 are probably — in most, eases certainly — deciduous ; while those of the partridges above men- 

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

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

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

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

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

 Gypaetus barbatus, is one. The feathers sometimes become scaly (squamous), forming, for 

 instance, the exquisite gorgelets or frontlets of humming-birds. They are often bristh/ (seta- 

 ceous), as about the lores of nearly all hawks, 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 vibrissas. These occur in greater or less development in most small 

 insectivorous birds ; they are large and stiff and highly characteristic of the family Tymnnidas, 

 or flycatchers; while in some of the goatsuckers (Caprinmlgidce) they are prodigiously long, 

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

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



