188 CALIFORNIA ACADEMY OF SCIENCES. 



this marking is associated with other head markingri, 

 or where it is present but not black in color. The fourth 

 type — the malar steak, represented by Cohipte.'^ aaratufi 

 in the plate, is less commonly met with alone; but type 

 5, Denchoicd vh'cns in the diagram, which is the throat 

 patch, is very common. There are only a few forms, 

 however, such as Dendroica occiJentalis and Ainj)liisj)iza 

 bUhi-cdta where it occurs as the only black patch upon 

 the head. 



The combinations of these five types follow next. Fig. 

 6 is Boulroicii tigriim, which presents. a combination, 

 not of types 1 and 2, but of 1 and modification a of type 

 '1. Fig. 7, Di'iidroica blackhmniuv, is a combination of 

 1 and 3, the black cap and ear covert. This is a very 

 common form, being presented with greater or less 

 deviation from the type by such forms as (S'(7/« cun- 

 (idens)s,CerthioIa bahamensiN and Pitiingus di'rbianvs. Fig. 

 .S is the combination of types 1 and 4, as shown in 

 ]>endrolcii siriuta. Fig. 9 is a combination of types 1 

 and 5 illustrated by ParuK utricapillufi. Fig. 10, of 

 AiJiprliN ccdroruin is eijuivalent to 2i( plus 5, and fig- 

 ure 11, Hel iniuthophila chrysojiii'va, equals o plus 5. 

 Fig. lOc, Parus lnulvonicvuj is a combination of types 

 1, 2 and 5; while fig. 11a, MnlotiltK varin, is a com- 

 bination of types 1, 3 and 5. 



There is little difficulty in understanding tJiese types 

 and their combinations as markings which have fol- 

 lowed the feathers along natural areas of the birds' 

 heads. They may thus be in part accounted for in ac- 

 cordance with the location of growth force along lines of 

 least resistence, although natural selection has played a 

 not unimportant part in shaping and defining them. 

 Upon leaving the types and considering the various 

 modifications, it becomes immediately evident that here 

 the part played by selection must have been a far more 



