26 BIKDS. 



II. A decrease in the number of digitals may take place at distal end of wing. 



(a) A remicle may be lost, its principal coverts being retained (as in the 

 Turkeys, Grouse, etc.). 



(b) The remicle and its coverts may disappear, and, in addition, the next 

 predigital (2) may disappear also (as in "nine-primaried birds"), though generally 

 some trace of it may be found. Among Passeres almost every gradation in the 

 development of these feathers may be met with (Nat. Hist. Museum). 



The Arraryement of the Coverts. 



The coverts of the upper surface of the wing (Tectrices superiores) are divided 

 into Tectrices majores, T. medice, and T. minores. Those of the lower surface 

 are Tectrices inferiores. The relative development of these series of coverts 

 varies much in different groups of birds. 



The most important, or "Principal Coverts," are the Tectrices majores, consisting 

 of one row of upper coverts attached to the bases of the remiges, and a row of in- 

 ferior coverts attached in a similar way. Each remex has thus two principal coverts 

 in relation to it, one on its upper or dorsal, and one on its lower or ventral surface. 



The dorsal covert of the first metacarpal remex is generally rudimentary, in 

 compliance with mechanical requirements in the folding of the wing. 



Modifications of the Cubital or Secondary Remiges. 

 Beyond variation in number and form, the only important modification in this 

 series consists in the absence in many birds (Owls, Eagles, Geese, Ducks, Pigeons, 

 Grebes, etc.) of the fifth remex (counting from the carpal joint), the coverts being 

 retained. This condition is "Aquin cubitalism"; when the feather is present 

 the condition is called " Quin cubitalism." 



Wing Claws. 

 Horny claws of the same nature as those of mammals and reptiles are not un- 

 frequently present on the end of the first and sometimes the second digit, though 

 not found on the third in any existing birds. More often they are absent, or 

 occur only in an imperfect or rudimentary condition. Thus a claw is present on 

 the terminal phalanx of the first digit {jiollex, or bastard wing) of the Secretary 

 bird {Serpentarlus reptilivorus), and well-developed claws are seen on the end of 

 both the first and second digits in the wings of the Hoatzin (Opisthocomus 

 cristatus). 



Wing Spurs. 

 Wing Spurs are conical bony outgrowths (the spurcore) covered by a sharps 

 pointed horny sheath, and therefore closely resemble the horns of ruminants. 

 One or more may be present on the forelimbs of birds, being always placed on 

 the radial side either of the carpus or the metacarpus, and forming weapons for 

 fighting. They are not to be confounded with the claws which often ensheath 

 the terminal phalanges of the digits. Thus a long curved black spur is found on 

 the first metacarpal at the bend of the wing of the Indian Spur-winged Plover 

 (Hoplopterus ventralis), and a small tubercular spur in the same position on the 

 wing of the Bronze-winged Jagand {Melopidius indicus). A carpal spur is present 

 in the Spur-winged Goose {Plectropterus gambensis); while the Derbian Screamer 

 (Chauna derbiana) possesses two spurs, one on the first metacarpal and one on 

 the second metacarpal, as well as a claw at the end of the first digit. 



