EXPLANATORY NOTES 



FOR purposes of defining ranges of birds, the term "North 

 America" is here applied to that part of the continent north of 

 the United States - Mexico boundary, and includes the peninsula 

 of Lower California; while Mexico and Central America, and 

 their islands, are collectively called Middle America. This con- 

 forms to the plan of the A.O.U. Check-List and to usage long 

 established among zoologists. 



Unless otherwise stated, plumage-descriptions refer to adult 

 males in spring, or breeding, dress. 



Terms describing relative numbers of a species, as " common," 

 "rare," etc., are exceedingly flexible and incapable of exact 

 definition. A species recorded only once or twice a year, in its 

 proper habitat, would be considered rare; if recorded daily, in 

 numbers, it would be called abundant; while the term "common" 

 generally means of regular occurrence in relatively small numbers. 

 Further, the meaning of these terms varies with the numerical 

 status of a species as a whole. Thus "abundant" applied to 

 Eagles might mean a half-dozen seen in a week; while the same 

 term applied to Red-winged Blackbirds would mean a score or a 

 hundred noted in a single day. 



Numbers preceding the scientific name are those of the A.O.U. 

 Check-List. Numbers following parentheses give lengths of birds 

 which are approximate only. 



Summer, or nesting, range is indicated on the small distribu- 

 tional maps by northeast and southwest lines; winter range by 

 lines northwest and southeast. Where these lines cross the species 

 is found throughout the year. 



ABBREVIATIONS USED IN TEXT 



Low. Son. Lower Sonoran. Mig. Migrant. 



Up. Son. Upper Sonoran. Res. Resident. 



Trans. Transition. S.V. Summer Visitant. 



Abun. Abundant. W.V. Winter Visitant. 

 Com. Common. 



