I have been much interested this spring at witnessing in two or three instances the tenacity with which the Marsh Titmouse sits on its nest. Being in a wood near my own house, I perceived a pair of these birds in one of the trees, and having seen them in the same place several times before, and being desirous of finding the nest, I sat down to watch their motions. After examining me on all sides with much chattering and many gesticulations, indicative of dislike and suspicion, the female flew to the root of a tree, three or four yards off, and disappeared, as she had gone to the opposite side of the tree to that on which I sat; and as there were several holes about the root I was at a loss to know in which the nest was built, and began to strike the root with a stick, expecting her to fly out, but nothing appeared. I then examined the holes one by one, and whilst doing so heard her hissing and puffing from within, in such a way that if I had not known she was there I should have thought it was a snake rather than a bird. However, as she would not come out, and the hole was so small that I could not get my hand in, I was obliged to raise the siege until next morning, when I returned armed with a hammer and chisel with which to storm her citadel. As the wood was sound, the hole small, and the nest six or eight inches within the tree, I was five or ten minutes before I could get to it, during which I gave her repeated opportunities of escaping if she chose; but she still sat on her nest, puffing and pecking at the stick that I thrust in in order to drive her off. She at last crept to the further edge of the nest, which I then took out, as I wanted it for one of my friends who is a collector of eggs, but on attempting to blow one I found they had been sat upon too long, and I then felt desirous of seeing whether the old bird would hatch them after having her nest torn from under her, and I turned back to the tree whence I had taken them, and found her still sitting in the hole where I had left her. I regret to add that the humane part of my experiment did not succeed, for although she remained after I had returned the nest to its place, she left it immediately after, and did not return to it again.