114 The Natural History 



billed bird. I question whether the latter be much of a 

 songster; but in this matter I want to be better informed. 

 The former has a variety of hurrying notes, and sings all 

 night. Some part of the song of the former, I suspect, is 

 attributed to the latter. We have plenty of the soft- 

 billed sort ; which Mr. Pennant had entirely left out of 

 his British Zoolo^y^ till I reminded him of his omission. 

 See British Zoology last published, p. 16.^ 



I have somewhat to advance on the different manners 

 in which different birds fly and walk; but as this is a 

 subject that I have not enough considered, and is of such 

 a nature as not to be contained in a small space, I shall 

 say nothing farther about it at present.^ 



No doubt the reason why the sex of birds in their first 

 plumage is so difficult to be distinguished is, as you say, 

 *' because they are not to pair and discharge their parental 

 functions till the ensuing spring." As colours seem to 

 be the chief external sexual distinction in many birds, 

 these colours do not take place till sexual attachments 

 begin to obtain. And the case is the same in quadrupeds ; 

 among whom, in their younger days, the sexes differ but 

 little : but, as they advance to maturity, horns and 

 shaggy manes, beards and brawny necks, etc., etc., strongly 

 discriminate the male from the female. We may instance 

 still farther in our own species, where a beard and 

 stronger features are usually characteristic of the male 

 sex : but this sexual diversity does not take place in 

 earlier life ; for a beautiful youth shall be so like a 

 beautiful girl that the difference shall not be discernible : 



*' Qnem si puellaium insereres choro, 

 Mire sagaces falleret hospites 

 Discrimen obscurum, solutis 

 Crinibus, ambiguoque vultu." — HoR. 



* See Letter xxv. to Mr. Pennant. 

 ^ See Letter xlii. to Mr. Barringtoii. 



