TEBNS 251 



FoRSTER Tern. Sterna forsteri Nuttall 



Field charoetcrs. — Approaching pigeon in size; of slender build; tail deeply forked 

 and wings long and narrow. Head black capped; back lavender-gray; whole under sur- 

 face pure white. Flight airy and swallow-like; bill held pointing downward (nearly at 

 right angle to axis of body). 



Occurrence.- — Casual visitant to lowland waters. One seen over Tuolumne Eiver 2 

 miles southwest of Lagrange, May 6, 1919. Usually seen over open water. 



Only one Forster Tern was seen by us, as noted above. But the species 

 probably visits regularly, during migrations, the low country on both 

 sides of the mountains. The tern in question was flying along over the 

 Tuolumne River, maintaining a height of from 20 to 40 feet, its bill held 

 down, mosquito-like, as the bird watched for prey in the water beneath. 

 Once it saw something, hesitated a moment, and then went down in a spiral 

 course and splashed into the water after the object it sought, presumably 

 some small fish. 



Black Tern. Hydrochelidon nigra surinamensis (Gmelin) 



Field characters. — As small as Eobin; resembling a swallow in form and flight; 

 wings long and pointed, tail somewhat forked. Head and most of body (in summer 

 adults) black; back, tail, and wings, dark gray. Usually seen coursing over lakes or 

 smooth-running streams. Voice: A grating cry. 



Occurrence. — A transient through the region. Observed by us only at Mono Lake. 



The terns are mostly associated with the seashore, but this member of 

 the family is partial to inland waters. Black Terns were seen on two 

 occasions at Mono Lake in 1916. On May 6, six were observed foraging 

 about the marginal ponds near the mouth of Rush Creek. On June 3, one 

 was seen. The graceful aerial evolutions of the birds, which resemble those 

 of swallows, and the black and dark gray plumage and forked tail serve 

 easily to identify this species. 



Farallon Cormorant. Phalacrocorax auritus albociliatus Ridgway 



Field characters.— General appearance goose-like; neck long and slender, wings long 

 but narrow, tail narrow. Plumage wholly black in adults; in immatures, brownish 

 above, gray or whitish below. Bare skin on chin and throat (involving "gular sac") 

 yellowish orange. In flight, course direct, wing beats continuous, neck outstretched and 

 often crooked. 



Ocaiirrence. — Observed along Tuolumne Eiver below Lagrange, May 6 and 7, 1919. 

 One individual taken in Yosemite Valley (see below). Usually frequents vicinity of 

 lakes or reservoirs. 



