Nov’, 1922 MUSICAL “PASTE” Ihe THE BROWN TOWHEE 199 
So far as appearances go this incorrigible mimic is easily holding his own 
in ‘‘the struggle for existence.’’ If his mimicry causes confusion among any of 
the species mimicked it apparently does not come back on him or his race. His 
mimicry, so far as I, myself, have ever observed, or read, or heard, does not cause 
confusion among his own kind. But I doubt if he gains anything beyond a 
certain ‘‘aesthetic pleasure’’—an emotion doubtless shared with his mate, but 
not otherwise having any ‘‘social’’ significance. 
It might be claimed, of course, that the Mockingbird ‘gets away with’’ his 
promiscuous mockery solely because of his pugnacious disposition and ability to 
take care of himself, whereas a less able bird, say a Goldfinch, might court death 
if it had the temerity to imitate a Sparrow Hawk or a Shrike. Personally, how- 
ever, I cannot easily picture a Goldfinch* (assuming it to be an imitative bird) 
meeting its death as the result of mocking a Shrike. The Shrike is not a gre- 
garious bird, and the only eall it might coneeivably respond to (that is, fly 
towards) would be the sex-eall of its kind. It would then respond in a wooing, 
not in a killing, mood. 
Let me concede the possibility, however, that it might, on discovering its 
mistake, change its mood, and kill the Goldfinch. Such events would tend to 
eliminate from the racial song of the Goldfinch any and all notes copied from 
birds that prey on the Goldfinch, since, in each case, the individual doing the 
imitating would perish. But even though this may be the case with some birds, 
it does not seem to be with the Mockingbird, whom we may observe imitating 
‘‘dangerous’’ birds with apparent impunity. | 
It seems to me utterly absurd that a Shrike should ‘‘imitate other birds for 
the purpose of attracting them within range of its attack’’—a habit that Yarrell, 
as quoted by Witchell (pp. 173-174), attributes to the Great Grey Shrike. It 
very well may be that the Great Grey Shrike has imitative powers; and undoubt- 
edly this bird is capable, in certain ways, of profiting by chance experience. 
But I cannot picture this as one of the ways: it is endowing the bird with too 
much intelligence. 
I do not believe, then, that practical or economical considerations enter into 
the choice of sounds to be imitated by the Mockingbird or by any bird. The 
behavior of imitating birds does not indicate such to be the ease. 
There are two main factors, however, that I believe to be reasonably borne 
out by observable facts, influencing the choice of sounds to be imitated. In dis- 
cussing these factors, let us return to the Brown Towhee as being a bird in the 
simpler and early stages of song evolution and as furnishing therefore a less 
complex ‘‘test case’’ for our purposes than the Mocker. To make our ease defi- 
nite let us keep in mind as our individual example the Brown Towhee of the 
Chalk Peak region of the Santa Lucias who imitated the Western House Wren. 
Let us make a note of the fact that he belongs to a non-migratory race. The 
association where I found him was arid Transition in the yellow pine belt. {t 
is assumed that a bird is most influenced by the sounds of its environment during 
its own song period, that is, during the spring and summer months. With these 
ideas in mind, it can be demonstrated, I believe, that the number of bird-notes 
available for imitation in the habitat of our Brown Towhee is far more limited 
Since there are no American birds besides the Mockingbird in the evolved stage 
of mimicry, I am forced to choose as my example a non-imitative bird. -In contrast to 
the derth of mimics in this country see Witchell’s enumeration of imitative British birds 
(pp. 190-229). 
