6 HABITS OF BIRDS. 



ders, may be considered as in some degree blameable 

 when they introduce into their enumeration circum- 

 stances that are vague and uncertain. Among such 

 doubtful things appears to be the opinion that the 

 feathers of birds require to be done over with a kind 

 of oil or grease, in order to cause the rain or other 

 water to run off without penetrating them, the unction, 

 when wanted, being supplied by the gland on the 

 rump. If those who adopt this opinion, plausible as 

 it seems to be, had taken the trouble to ascertain the 

 small quantity of fluid actually secreted by this gland 

 from day to day, and compared it with the proportional 

 extent of surface constituted by the assemblage of the 

 numberless feathers of any particular bird, not to speak 

 of the instrument with which the dressing is said to 

 be effected, they would have seen at once that the 

 theory is untenable, as the quantity secreted in one 

 day would scarcely suffice to anoint a single feather, 

 much less the whole. We have just squeezed out all 

 the oil contained in the double rump gland of a com- 

 mon wren, and found it impossible to make it go 

 over one of the tail feathers*. " One fact/' says M. 

 Le Vaillant, " is frequently sufficient to demolish a 

 theory t;" and the fact that the feathers of the 

 rumpless fowls which have no gland are as smooth 

 and proof against rain as those which possess the 

 gland, furnishes a striking illustration of the remark. 

 The fact, however, is unquestionable that birds 

 are sometimes seen pecking about the gland in 

 question. But the observing of a bird thus en- 

 gaged, so far from authorizing the received conclu- 

 sion, might have shown that the point of the bill 

 could never squeeze out enough of fluid for the pur- 

 pose alleged. The only legitimate inference would 

 have been that some slight pain or irritation had 

 caused the bird to peck the gland ; and every school- 

 * J, R. t Hist. Nat, des Perroouets, i. 20. 



