SWIFTS. 



437 



palatines of the young, as pointed out by Parker, who says that in the young hum- 

 ming-birds they agree in general with young Pusseres, " but in particular with both 

 young and adult of that family of birds which has most similarity to them in general 

 bodily structure, namely, swifts." 



In view of the extreme external ' isomorphism ' of the swifts and the swallows, 

 and the remarkable tenacity with which ornithologists have stuck to arrangements 

 based chiefly upon the external appearance, the comparatively early recognition 

 of their being totally different on account of their internal structure would be some- 

 what surprising but for the fact that there are also a number of easy external charac- 

 ters by which they are at once separated. The swifts, or MICKOPODID^E, and the swal- 

 lows are, indeed, "only 'second cousins,' and more alike 

 in their habits and mode of dress than in their real nature," 

 as will be apparent by the following juxtaposition of their 

 differences. Externally they may be easily distinguished ; 

 the swifts by having ten primaries, not more than seven 

 secondaries, and only ten tail-feathers, while the swallows 

 have but nine primaries, at least nine secondaries, and 

 twelve tail-feathers. The swifts have also the dorsal tract 

 bifurcate between the shoulders, while in the swallows it 

 is simple. Internally they differ in a great number of 

 points, but we shall only mention that the swifts have a 

 pointed manubrial process and no posterior notches to the 

 sternum, while the swallows have the manubrium bifur- 

 cate, and the posterior border deeply two-notched ; the 

 former have amyological formula A^-, the latter AXY^-; 

 the former are synpelmous, the latter are schizopelmous ; 

 the former have a peculiar arrangement of the tensor patagii brevis, the latter have 

 the general arrangement of the Passeres, to be explained in the introduction to that 

 order; the former have a simple syrinx without intrinsic muscles, the latter have a 

 very specialized syrinx ; the former are without caaca, the swallows possess them, etc., 

 the total effect being that the swifts are Picarians, and the swallows are Passeres. 



^j ' 



The swifts are found all over the globe, except in the extreme cold regions and in 

 New Zealand, being most abundant in the tropics of America and the Oriental region, 

 considerably over fifty species being known altogether. The peculiar structure of the 

 feet furnishes excellent characters for subdividing the family in two minor groups or 

 sub-families, the Micropodinse and the Chasturinae. The latter have the feet nor- 

 mally constructed with the usual number of phalanges, viz., 2, 3, 4 arid 5, while the 

 true swifts have the number of phalanges of the third and fourth toes reduced to 

 three, the formula, consequently, being 2, 3, 3, 3. At the same time the first toe is 

 directed more or less forwards or inwards ; in other words, the true swifts are pampro- 

 dactylous. Another feature is that their tarsi are feathered, while the Chagturinae have 

 them bare. 



Regarding the Chaaturinae as the more generalized type, we are at once confronted 

 with the pretty tree-swifts (Dendrochelidoti) from India and the Malay Archipelago, 

 which are provided with a feather-crest on the head, and very lengthened outer tail- 

 feathers. In the same regions, and also in many of the Polynesian islands (one species 

 even in Madagascar), are found the pigmies of the family, the so-called swiftlets ( C'ol- 

 localia), inconspicuous looking, dusky-colored birds, but famous as the manufacturers 



FIG. 219. Diagram of tho elbow- 



muscles in a humming-bird 



f/onn i/it/ns); muscles with longitudi- 

 nal, tendons with transverse lines ; 

 emrl, extensor metacarpi radialis 

 longns ; h, huinerus ; sr, secondary 

 remiges ; t, triceps ; tpb, tensor 

 patagii brevis ; tpl, tensor patagii 

 longus. 



