ON THE SONG OF FEMALE BIRDS. XXIX. 



helmets read helmet. — 390, line 11, for Plantan read Plantain. 

 — 399, line 8 from the bottom dele the article a. 



In addition to what is stated by Mr. Sweet in page 73, con- 

 cerning the singing of birds, that gentleman has favoured me 

 with the following particulars : " When you called on me last 

 year, at Chelsea, I had several female birds which never at- 

 tempted to sing: but now I have two that sing frequently ; one 

 is a female Black-cap ; she sings a note peculiar to herself, and 

 not the least like the male or any other bird with which I am 

 acquainted; I kept her several years before she began to sing. 

 I have also a female Willow-wren that sings nearly as much as 

 the cock ; this bird was bred up from the nest, and did not sing 

 at all the first year ; her note is quite different from the male's, 

 but resembles it sufficiently to indicate that it belongs to the 

 same species. The females of the Larger Pettychaps, and the 

 Larger W hit e thro at , which I have had for several years, never 

 attempt to sing. The following are the migratory birds which 

 I now have. Wheatear, Whinchat, Stonechat, Redstart, Nightin- 

 gale, Larger, and Lesser Whitethroat , Black-cap, Greater Petty- 

 chaps, and Willow-wren ; I had also, till lately, the Wood-wren. — 

 R. Sweet, Chelsea, Oct. 26, 1827." 



The Willow-wren, Mr. Sweet informs me, sings also at night 

 when there is a light in the room. 



Page 49. That birds are rendered more buoyant by having 

 the cells in their bodies filled with air, as well as also the 

 bones, there is no reason whatever to doubt ; but in what 

 manner their increased buoyancy is produced does not seem 

 well ascertained. Whether by -condensation of atmos- 

 pheric air similar to that produced in a strongly inflated 

 bladder, by which its elasticity is considerably increased, or 

 whether by some other air specifically lighter than that of the 

 atmosphere? — The first appears the most probable reason. 



