DF S EL BORNE. i^i 
whereas the bird you kept (pq[}h- torquatus Rati) abides all the year, 
and is a thick-billed bird. I queftion whether the latter be much 
of a fongfler ; but in this matter I want to be better informed^ 
The former has a variety of hurrying notes, and fings all night. 
Some part of the fong of the former, I fufpedt, is attributed to the 
latter. We have plenty of the foft-billed fort ; which Mr. Pennant 
had entirely left out of his BritiJJj Zoolog]', till I reminded him of 
his omiffion. See Britifi Zoology laft publifhed, p. 16 
I have fomewhat to advance on the different manners in which 
different birds fly and walk ; but as this is a fubjedt that I have not 
enough confidered, and is of fuch a nature as not to be contained 
in a fmall fpace, I fliall fay nothing further about it at prefent 
No doubt the reafon why the fex of birds in their firif plumage 
is fo difficult to be diftinguilhed is, as you fay, becaufe they 
" are not to pair and difcharge their parental funftions till the 
*^ enfuing fpring." As colours feem to be the chief external fexual 
diilinftion in many birds, thefe colours do not take place till 
fexual attachments begin to obtain. And the cafe is the fame in. 
quadrupeds ; among whom, in their younger days, the fexes dif- 
fer but little : but, as they advance to maturity, horns and lhaggy 
manes, beards and brawny necks, he. Src. ftrongly difcriminate 
the male from the female. We may inftance if ill farther in our 
own fpecies, where a beard and flronger features are ufually charac- 
teriitic of the male fex : but this fexual diverfity does not take 
place in earlier life ; for a beautiful youth fliall be fo like a beautiful 
girl that the difference fliall not be difcernible ; 
" Quern fi puellarum infereres choro, 
" Mire fagaces falleret hoipites 
" Difcrimen obfcurum, folutis 
" Crinibus, ambiguoqus vultu.'* Hor, 
« See letter xxv. to Mr. Pennant, X See letter xlii. toMt. Barrington. 
S LETTER 
