60 



the bill doubtless occurs about April l." The notes on the specimens 

 enumerated in the tables closing the accounts of the species will fur- 

 ther explain the time during which this change is made. 



INDIVIDUAL VARIATION. 



There is no noticeable range of individual variation among typical 

 examples of any form, and it is only the transitional specimens couuect- 

 iug two races of one species that vary at all from the normal standard. 

 A series of this nature connects var. tephrocotis with var. littoraUs, 

 difl'erent specimens exhibiting different degrees of relationship to the 

 two forms. The L. cirnqjestris of Baird (see Ornithology of Califor- 

 nia, I, 1870, 163) is of this character. The amount of individual va- 

 riation in size is shown by the tables of measurements annexed to the 

 account of each species. 



SEXUAL DIFFERENCES. 



The American species of this genus fall into two distinct groups, 

 according as the sexes do or do not dilier in appearance. In L. tephro- 

 cotis — in all its forms — there is not the slightest sexual difference j but in 

 L. atrata and L. austmlis,. the distinction is very marked. 



As a rule, the female is very slightly smaller than the male ; but that 

 she is not constantly so is clearly shown by the following tables of the 

 averages of the measurements of large series of each form : 



L. ATRATA. 



Botli sexes . . . 



Male 



Female 



L. TEPHROCOTIS. 



Both sexes 



Male 



Female 



L. LITTORAMS. 



Both sexes. 



Male 



Female 



L. GRISEIXl'tTlA. 



Both sexes 



Male 



Female 



L. .AUSTRALIS. 



Boih sexes .w. 



Male 



Female -.;.,' 



Wini 



4t) 



48 

 48 



Tail. 



.95 



,08 

 , 08 



Culmeu. 



43 

 ,43 

 ,44 



,56 



,45 

 , 45 

 .47 



Tarsus. 



,T9 



79 

 70 

 70 



,79 



,70 



,95 



,08 

 ,05 



76 



Middle 

 toe. 



No of 

 specimens. 



,50 



,58 

 ,60 



,57 

 ,59 



.58 



,71 

 .70 

 .73 



,57 



,58- 

 ,57 



155 



34 



48 

 7 



46 

 27 

 13 



106 

 69' 

 36 



