52 
THE CONDOR 
Vol. XVI 
Turner-Reich lens of eighteen-inch focns, stopping down to 64 U. S., and giving 
an exposure of ten seconds on a Seed number 30 plate, I secured a negative of 
her in this position wliich is the best one of all. Some idea of the value of a good 
convertible lens in this work may be secured by comparing the picture of the sit- 
ting bird with that of the nest and surrounding rocks (fig. 20), both taken from 
the same spot. The double combination of the lens of six and one-half inch 
focus Avas used in the latter picture. A slight movement of the focusing cloth 
after this exposure was too much for the nerves of the bird, and she was off 
like a Hash, but so quietly as to be unheard even at the short distance I was from 
the nest. 
Roth birds put in an appearance after the one left the nest, but beyond cat- 
Eig. 2.1. Pacific Horned Owls three weeks old; portion of rabbit 
IN foreground 
calling and ‘‘who-who"-ing around, made no disturbance. The mate of the sitting 
bird flew out from a small sumac bush on the steep hillside directly above. J 
had always supposed there was considerable difference in appearance between the 
male and the female birds, but T could not tell one from the other 
except for one having an unusually white feather in its “horn”. This feather 
sl’.ows up very plainly in the picture of the sitting bird. One was much wilder 
than the other and could not be approached very closely, indicating that they took 
turn about in the incubation of the eggs. 
The cause of the extreme bravery of the sitting bird was at once apparent 
upon looking into the nest. One owlet was out of the shell and the remaining 
egg' was pipped. This is conclusive evidence that the period of incubation is 
