JTOODPECEEBS 331 



Williamson Sapsucker. Sphyrapicus thyroideus thyroideus (Cassin) 



Field characters. — A woodpecker, in size slightly smaller than robin. Male: Black, 

 with rump and large patch on fore part of wing white. (See pi. 6.) Female: General 

 color tone pale ; head light brown, nmip white ; plumage elsewhere narrowly barred 

 with black and light brown. A bird of notably qniet demeanor. Voice (not often 

 heard) ; A weak wheezy whang or whether. 



Occurrence. — Common resident of Hudsoniau and upper Canadian zones on both 

 slopes of Sierra Nevada. Observed from near Chinquapin eastward to Walker Lake. 

 One record for floor of Yosemite Valley: December 29, 1914. Restricted closely to 

 lodgepole pine belt. 



The distribution of the Williamson 8apsucker in the Yosemite region 

 is complementary to that of the Sierra Red-breasted Sapsucker ; in other 

 words the two birds do not overlap in range to any important extent. 

 The present species is a high mountain bird, being found only in the 

 upper Canadian and the Hudsonian life zones. It is non-migratory ; only 

 rarely is an individual detected in lower zones and then only during the 

 midwinter months. The Williamson Sapsucker is, like its relative of 

 lower altitudes, a quiet bird, rarely uttering its weak note, and never, so 

 far as known to us, drumming in the noisy manner so characteristic of 

 certain other woodpeckers. 



Of all species of North American woodpeckers, the AVilliamson Sap- 

 sucker is the most remarkable because of the striking differences in plumage 

 between males and females, and between adults and young. (See pi. 6.) 

 The only color mark of the species common to both sexes, at all ages, is 

 the white rump. Otherwise, males are chiefly black, with a large white 

 patch on the fore part of the wing (and not across the flight feathers as 

 in the California and White-headed woodpeckers). There is also a white 

 stripe backward from the bill across the cheek, and another behind the 

 eye. The black of the adult male plumage has a slight greenish iridescence, 

 while that of the young male is more sooty and of a softer texture. The 

 young have the chin white, this white being replaced by red in the adult 

 plumage. 



Females are entirely different. They are narrowly barred with black 

 and light brown or white on the back, wings, sides of body and tail, 

 and the head is uniformly light brown. Old adult females have a spot 

 of solid black on the breast, which the younger birds lack. Adults of 

 both sexes have the middle of the belly bright yellow, whereas in the j^oung 

 of either sex this area is chiefly white. Thus, in each sex, the young is most 

 nearly like the adult of that sex : the young' male does not at all resemble 

 the adult female, a condition contrary to rule among other birds the adults 

 of which are of different coloration. Young males acquire the adult 



