Ixxxii 
IXTRODUCTIOiSr. 
Over quadrupeds many land birds possess another advantage, that o^ 
an harmonious voice ; by which they can express their passions and affec- 
tions, soothe the hours of incubation of their partners, and pour forth in 
concert the full tide of harmony. This power of song is almost confined 
to the Sparrow tribes, and in most species to the m.ale, and if the female 
sing, which is very rarely the case, her notes are far inferior to his. At 
the opening of Spring, when nature begins to attire herself in gaiety and 
splendour, the little warblers most exert themselves in song ; they then 
contend, in active rivalry, for the graces of some favourite fair, or strive 
to solace their partner during the period of incubation. But the song of 
Abirds is not merely the voice of love ; many of those that cease from their, 
strains in summer, when the young brood demand their utmost exertion, 
(for they all sing most earnestly when most idle,) in autumn, with the loss of 
their cares recover their song ; then their warblings are marked with 
softer modulations and sweeter cadency ; they are less broken and inter- 
rupted, though they no longer rise to that pitch of elevation occasioned by 
desire. The Redbreast, the Wren, the Thrush, the Linnet, the Skylark, 
the Woodlark, the Titlark, and the Goldfinch, warble on till the cold of 
winter makes their subsistence a work of toil ; and, as plenty is one of the 
stimulants of song, when that season passes away without its usual rigour, 
many of these resume their strains. And the Waterouzel, regardless of the 
frozen atmosphere, enlivens, with its delightful notes, the margins of the 
ice-bound streams. 
The lungs of birds, by their imbibing such a quantity of air, enable 
them to prolong their notes, which are modulated as well by the tongue as 
by the flexible muscles of the larynx. From the great quantity of air 
imbibed by their lungs, their voices are comparatively sonorous and loud. 
The neighing of the Horse is weaker than the scream of the Peacock ; the 
bellowing of the Ox than the boom of the Bittern ; the bleating of the 
Sheep than the cry of the Woodpecker ; and the full notes of the Night- 
ingale far exceed in strength the shrill squeak of the Hare ; the Goatsucker 
