SCOPE OF THE ACCOUNTS 41 



the external, macroscopic features of the animal that are set forth in the 

 paragraph on ''field characters." 



Field characters may consist in relative size, in proportions of parts,' 

 in general color tone, in pattern of contrasted markings, in peculiarities 

 of movement (flight, gait, mannerisms), in voice, and, with many mammals, 

 in 'sign' (foot-prints, tooth-marks, droppings). Measurements are given, 

 more especially with mammals, and are stated as a rule in both inches and 

 millimeters. Otherwise, size is indicated by comparison with some animal 

 commonly familiar. Since size impressions in the field are likely to asso- 

 ciate themselves in memory with the best known animals, comparisons 

 among birds are most often made with the robin; among mammals, with 

 the house mouse, house rat, or house cat. 



Our paragraph on "occurrence" relates explicitly to the Yosemite 

 section. The status we give of each species is as based on actual findings 

 in the Yosemite section, not upon inference from conditions in the sur- 

 rounding territory. It must not be supposed to apply to the Sierras gen- 

 erally or to any larger area. "Occurrence" is intended to cover concisely 

 the concepts: season, relative abundance, and distribution by geography, 

 life zones, and vegetational tracts. 



In the general, large-type account next following, there will often be 

 found one or more paragraphs discussing some or all of the field characters, 

 especially in comparison with similar species with which confusion in the 

 field might occur. In some cases, characters are discussed with relation 

 to the distinctive habits of the species in question ; in other words, corre- 

 lation of structure and function may be dealt with. 



But, let it be emphasized by repetition that, save for only occasional 

 general statements, each account is limited to what was found out by us 

 in the Yosemite region. This will explain the very uneven magnitude of 

 the accounts. Their relative degree of comprehensiveness merely reflects 

 our own varying opportunities of observation. A number of well-known 

 species of the Sierras at large are given but meager attention here because 

 opportunity did not present itself for studying them adequately in the 

 Yosemite 'section.' 



Each general account, where the facts have been fully available, has 

 been drawn up, with regard to its subject-matter, on a more or less definite 

 plan of presentation. An introductory paragraph gives local names, other 

 than the accepted vernacular, and an epitome of the leading facts about 

 the species. Comparisons with related species are then made. There 

 follows a discussion of its distribution in the Yosemite region and the 

 special nature of its habitat preferences. Then comes a description of the 

 animal 's behavior ; its voice ; nests, or dens ; eggs, or young ; care of young ; 

 and its feeding habits. We give as much as we have learned with respect 



