(473) 7:20 P.M. Regular shifts were maintained during the afternoon with nothing special to note until about 5:30 About 5:30 I sat in the glade; there was a loud burst of song at the nest. Soon Brownie came and was about to get a worm, when Greenie scripped, having followed from the nest apparently. Brownie immediately ran off full speed, there was a haih in the bushes, a few pit-yurkis and peet-byouicks and I hurried to the nest, but Brownie and Greenie were both headed for it too. B stopped and G went up into it. It seemed to me that G had left when she should not have done so and that B went to remonstrate and persuaded her to return. This, of course, may not be the true explanation. About 5:45 they changed shifts, Greenie flying towards her tree. I waited quietly. Soon G came back and went to the nest, but B did not come out, neither did G, but a Crowned Sparrow and a Brown Towhee did. (Ejected by G?). I waited until about 6, then got a flash light and climbed up very quietly on to the platform, then turned the light on to the nest about 18 inches away. Only one bird, where I had fully expected to find 2! As far as I could see, this bird did not even wink. I do not know which one it was. I stayed there (about the center of the tree, which is a small one) and turned the light in all directions, reducing the aperture of the lens by holding my hand over it and allowing but a small beam to pass, in this way reducing the glare reflected back to me, thereby allowing the pupils of my eyes to expand. When I turned the beam on Room B (See p. 408), there was the other thrasher, all settled and comfort- able, absolutely motionless . 11:13 P.M. The thrasher is still there. (Temp.62) So now they are both in the same tree. Why this change of habit as soon as the nest is occupied at night? Do they change shifts at night? Is it to make this safer and more convenient? Or is to give additional protection to the nest? Is this an instinctive act or is it an in-