WHITE-EARED HUMMINGBIRD 459 



step on the rim before taking flight, but the hummingbirds showed 

 their mastery of the air by making their departure in a more direct 

 manner. Still sitting on the eggs, they spread and vibrated their 

 wings and rose directly into the air, with as little apparent effort as 

 if they were lighter than the atmosphere, and ascended because their 

 hidden moorings had been severed. Frequently they flew upward 

 and backward until they had cleared the nest, then quickly reversed 

 and darted forward and away. When they wished to turn their 

 eggs, they flew backward from the bowl onto the rim, alighted on 

 that portion that had been beneath the tail as they sat, bent down 

 the bill into the cup, and in an instant flew away. Of course, I could 

 not see the eggs or what was done to them, for the nests were above 

 the level of my eyes as I watched ; but this is the only significance I 

 can find in the oft-repeated act; and moreover, if the hummingbirds 

 did not turn their eggs on these occasions, they never turned them 

 at all. They never rose up while incubating to adjust their eggs 

 beneath them, as other birds do, doubtless because the length of the 

 bill, coupled with the narrowness of the bowl, would have made this 

 an awkward and difficult performance. 



During the morning hours the white-ears devoted much time to 

 seeking down and cobweb and bringing these materials to the nest. 

 The down was deposited inside the cup, the cobweb wiped from the 

 bill to the outer surface; and in addition an occasional lichen was 

 attached there. Since the nests had been completed before the eggs 

 were laid, these additions to its bulk appeared to be made from force 

 of habit rather than from necessity; and it was interesting to find 

 that the new materials were brought chiefly at the time of day when 

 the birds had built most actively. The daily application of fresh 

 cobweb was useful in that it served to prevent the binding of the 

 nest, and its attachment to the supporting twigs, losing their strength 

 with age. During the hours when the gathering of material claimed 

 their attention, the birds spent very brief periods on the eggs, often 

 only a minute and sometimes less; but in the afternoon, when they 

 brought nothing back with them on returning from their recesses, 

 they sometimes sat continuously for 20 or 30 minutes, rarely slightly 

 longer. During the course of an entire day the average period of 

 incubation of one white-ear was 9.7 minutes; her average recess was 

 five minutes. Her separate sessions on the eggs during the forenoon 

 ranged from less than 1 minute to 15 minutes, with an average of 

 7.4 minutes ; her recesses varied from 1 to 10 minutes, with an average 

 of 3.7 minutes. During the afternoon, when she sat more constantly, 

 her sessions varied from 7 to 24 minutes, with an average of 15 

 minutes, and her recesses were of 2 to 17 minutes' duration. From 

 her first departure in the morning until her final return in the eve- 



