410 BIRDS. 



Befides thefe enumerated particulars, there are a few circumftances which deferve 

 notice, but are not common to' the whole clafs. Spines, fpinae, are a kind of offenfive 

 horny weapons, peculiar to fome birds, with which they can fight their enemies ; thefe 

 are fometimes fituated on the fore part of the wing, in the place of the thumb of hand- 

 ed quadrupeds, as in the Ofirich, Jacana, Screamer, Spur-winged Plover, and fome 

 fpecies of Ducks ; at other times they are placed on the heels, when they are called 

 Spurs, calcaria, as in the Peacock, Pheafant, and Grous ; in fome fpecies, as in the 

 Screamers, and Horned Tuvky, the fpine is fituated on the head, and is then named a 

 Horn, cornu. Wattles, palearia, are flefhy membranes which hang down from the 

 lower mandibles of the bills, as in the Wattle-bird, and Common Cock; and in the 

 latter animal, a Creft or Comb, crijia, of a fimilar flefhy fubllance, rifes from the crown 

 of the head. In the Ibis and Pelican, a Sac, facculut, compofed of a thin, tough, naked,, 

 and diflenfible membrane, hangs down from the lower mandibles, under the chin. 



Mofl birds are monogamous, or live in pairs of one male and one female during the 

 breeding feafon ; in fpring thefe choofe their mates, after which they exert their joint 

 induftry in conflrufting their nefts, and keep conflantly together until the cares of in- 

 cubation, and of rearing their young, are completed : Mofl of the Gallinaceous 

 order, and of the Duck tribe, are polygamous, at leaft in the domefticated (late ; the: 

 males of thefe neglect their young, and in fome cafes would even deftroy them if not 

 carefully concealed by the females. 



The nefts cf birds, which, may be confidered as ferving the purpofes of an uterus,, 

 are conftrucled with great care and wonderful artifice, though fome have no neft, or 

 hardly any ; fome of them are rudely conftrudled of flicks, but mod are lined with 

 foft materials ; fome are built on high inacceffible fummits of rocks and mountains ;-. 

 others in caverns, fhelves of the rocks, or burrows under ground ; fome on trees, in 

 fhrubs or bufhes, or in the hollows of trees ; fome in ruined walls ; fome in bufhes 

 and hedges ; fome among long grafs, or even on the bare ground. Of thefe nefts fome 

 are built of clay, curioufly knead and plaflered, as thofe of Swallows ; fome are built 

 with great ingenuity, fo as to hang from the ends of the flender branches of trees ; 

 fome are conftructed to float on the furface of the water ; fome have very artful 

 paffages contrived to them ;. and fome have many feparate chambers communicating; 

 with each other. 



The eggs of birds are very various in their numbers and appearance, though each 

 fpecies has an appropriate fhape and colour, and generally keep to a fixed number, or 



nearly 



