THE MALE RUBY-THROAT. 147 
been near by. After this I went to the edge 
of the wood, where I could keep an eye 
upon both trees without being myself con- 
spicuous. The sentinel spent most of his 
time in the ash, visiting the apple-tree but 
once, and then for a few minutes only. I 
stayed an hour and a half, and came away 
no wiser than before. The nest, if nest 
there was, must be elsewhere, I believed. 
But where? And what was the object of 
the male’s watch ? 
My curiosity was fully roused. I had 
never seen or heard of such conduct on the 
part of any bird, and the next forenoon I 
spent another hour and a half in the clear- 
ing. The hummer was at his post, as he 
always was. Wehad never to wait for him. 
Soon after my arrival he flew to the apple- 
tree, the action seeming to have no con- 
nection with my presence. Presently he 
went back to the ash, and drove out of it 
two intruding birds. A moment later two 
humming-birds were there, and in another 
moment they flew away in a direction op- 
posite to the apple-tree. Here, then, was 
a real clue. The birds were probably our 
sentinel and his mate. I made after them 
