than one would probably assume off-hand. The factors influencing his choice of notes are as follows:
(1) Persistency of the sounds in the imitator's environment. Such persistency determined by:
(a) Seasonal status of "subjects" of imitation. All transients and irregulars would be eliminated since their notes would not persist in the imitator's environment for a sufficient number of weeks nor would they persist during the imitator's impressionable period.
(b) Associational preferences of subjects. Those of extremely local or restricted range w?ould be eliminated. This counts out the Bell Sparrow (which I found only on the sagey west slope of Chalk Peak); the Western Bluebird, the Pine Siskin and the Linnet (which showed a decided preference for the west slopes down toward the Redwoods); and the Violet-green Swallow and Martin (whose aerial habits kept them a good part of the time out of hearing of our imitator).
(c) Numerical distribution of subjects. Those of rare or occasional occurrence would be eliminated, namely, the Slender-billed Nuthatch, the Cabanis Woodpecker, the Nuttall Woodpecker, Western Kingbird, the California Thrasher, the Cassin Vireo, the Lawrence Goldfinch, the Black-throated Gray Warbler, the Western Gnatcatcher, the Point Pinos Junco, Mountain quail, the Tawny Creeper, Mourning Dove, Audubon Warbler.
(d) Time of activity of the subjects during the twenty-four hours. Birds of nocturnal or crepuscular habits would be eliminated, namely, the Poor-will and any owls that might inhabit the region.
(e) General vocal strength of subjects. The following weak-voiced birds are eliminated: Creeper, Pygmy Nuthatch, Bush-tit, Bluebird, Siskin, Anna Hummingbird, Allen Hummingbird, Western Gnatcatcher.
(f) General vociferousness of subjects. The Buzzard is eliminated as being silent.
(g) Uniformity of utterance on the part of the subject. The Plain Titmouse is too versatile; does not stick long to any one note. The Thrasher, Black-headed Grosbeak and Purple Finch (whose persistent utterances are their songs) sing in a manner too long, "diffuse" and variable to allow any one sound to outstand.
(2) Physiological conditions connected with the peculiar nature of the syrinx and other vocal apparatus of the imitator. Obviously certain types of sound could not be managed by the comparatively unelastic and unpracticed syringeal membrane of the Brown Towhee. Thus at least two classes of sound would be physiologically unmanageable:
(a) Too voluminous sounds, such as those of the California Quail, Band-tailed Pigeon, and California and Crested Jays (heavy chup-chup-chup notes of each, and the common zhrae of the former).
(b) Too low sounds, such as those of the Mourning Dove and Band-tailed Pigeon.
Applying the above tests to all of the birds recorded by me during my stay in the Santa Lucia Mountains, I find that I have eliminated all but nine. These nine represent birds which have one or two utterances to be heard persistently all day long every day during the summer months. Following is a list of the birds and their notes:
| California Woodpecker | "yarcob" and "cracker" |
| Red-shafted Flicker | "klee-yuh" |
| Ash-throated Flycatcher | "kippy" and "kip-preer" |
| Olive-sided Flycatcher | "peevue" and "pulp-pulp-pulp" |
| Western Wood Pewee | "beeeezzzz" |
| Spurred Towhee | "thwaaaa" and song |
| Western Tanager | song |
| Western House Wren | song |
| Wren-tit | common "tattoo" call |
