WHITE-EARED HUMMINGBIRD 463 



highlands, a bur-marigold {Bidens refracta), common in the open 

 oak woods, is one of their principal food plants. With great pa- 

 tience the hummingbird poises on vibrant wings before a yellow 

 flowerhead and rapidly moves its bill from floret to floret, an instant 

 in each, and usually probes many in each head, before flying on to 

 the next. Each tiny floret yields at best a minute quantity of nectar, 

 but there are so many in a flowerhead that in aggregate they must 

 supply a considerable amount. Later in the season, various species 

 of Salvia, in particular the red Salviaf cinnaharina, yield an abun- 

 dance of nectar, which is secreted as a single large drop at the base 

 of the corolla tube, and so is far more conveniently sipped than the 

 sweet secretions of the bur-marigold heads, divided among a multi- 

 tude of separate florets. Though usually the white-ear reaches the 

 nectar through the throat of the corolla, once I watched an eccentric 

 individual puncture the side of the tube of the lovely blue flowers of 

 Salvia cacalioefolia, easily pushing his sharp bill through the delicate 

 tissue of the corolla. 



Behavior. — In April 1938, in southeastern Sinaloa, Mr. Moore ob- 

 served four species of hummingbirds "feeding from the flowers of 

 one large shrub at an altitude of about 6,000 feet. Approaching the 

 proportions of a tree, this remarkable shrub, 20 feet in height and 

 of the same width, was completely covered with globelike clusters of 

 grayish-lavender blooms. At no time from sunrise to sunset were 

 there less than four hummingbirds in this tree. Often there were as 

 many as 20 of four different species, white-eared, broad-tailed, cal- 

 liope, and Margaret's hummingbirds. The white-ears, like irascible 

 knights of the air, were always ready to thrust lance at an assumed 

 affront. It made no difference whether it was the tiny Margaret's or 

 the larger broad-tailed, some white-ear would dive viciously at any 

 intruder that dared to approach too close. The broad-tailed hum- 

 mingbird, heavier and more powerful, would dart into the tree with 

 direct flight and pompous hum, but his assurance would be quickly 

 dispelled. A male white-ear would immediately launch an assault 

 and drive the larger bird up the mountainside in ignominious retreat. 



"The same dominance was exhibited on several afternoons in May 

 1937, when I visited the mammoth paintbrush beds on the slopes of 

 Mount Mohinora at the 10,000-foot level. Here the white-ears out- 

 numbered all the broad-billed, blue-throated, and Rivoli's together. 

 In one of these astounding fields of color, perhaps 100 yards long 

 and 100 feet wide, a dozen white-ears were feeding at one time. If 

 one of the other larger species dived into the flower masses, even if at 

 a point far removed from the nearest white-ear, one of the latter 

 would immediately whirl to the attack and drive the Rivoli's and 

 blue-throated hummingbirds, twice their size, into headlong flight. 



