motionless and voiceless. A few minutes later he had taken up his undersong. At 1:20, after having annoyed another thrasher (Bb?) in a tree near the berry patch, just enough to make it leave, B again retired to his night roost for a rest of 20 minutes, during part of which time he sang slumber song. He then left for other enterprises. August 17th. A lot of full song up to about 7:30 A.M. At 8 the two young thrashers were at the oval lawn. In a few minutes Brownie joined them peacably. There was no sign of a chase. B came up to me in the upper garden when a thrasher was heard calling from near the glade. B answered each call with a chirp so soft that it could not be heard by human ears more than 2 or 3 yards away. If he was really answering instead of merely automatically reacting to the call, the question naturally arises as to whether the other bird could hear it, and if so does the hearing apparatus of birds respond to sounds of higher frequency than those perceptible to the human ear. 9:50 A.M. Brownie and Bb are in the upper garden (patio) just if appearances deceive not outside the window. Bb, at the moment, is trying to get Brownie to chase him! He hides under an azalea near which B is working and darts out at him suddenly, then retreats. He circles about him and makes dashes at him from various quarters. B responds mildly, but prefers to dig and sing half-song, which he has been singing for 15 minutes. I have been watching these two birds, especially, for 20 minutes. At 9:30 B was on the oval lawn, Bb in the driveway a few feet from him. Bb saw me arrive and sit on a bench and, without, invitation, ran to my feet where I dropped worms to him. B came, and Bb retreated about 6 feet. Each time B threatened mildly and ad- vanced on Bb, I spoke to him and he stopped and looked up at me making inarticulte interrogatory sounds. This was repeated 4 or 5 t