One day, just as I had passed the tree in which the cavity was placed, I heard the wren scream desperately; turning, I saw the little vagabond fall into the grass with the wrathful bluebird fairly upon him; the latter had returned just in time to catch him, and was evidently bent on punishing him well. But in the squabble in the grass the wren escaped and took refuge in the friendly evergreen. The bluebird paused for a moment with outstretched wings looking for the fugitive, then flew away. A score of times during the month of June did I see the wren taxing every energy to get away from the bluebird. He would dart into the stone wall, under the floor of the summer-house, into the weeds,—anywhere to hide his diminished head. The bluebird, with his bright coat, looked like an officer in uniform in pursuit of some wicked, rusty little street gamin. Generally the favorite house of refuge of the wrens was the little spruce, into which their pursuer made no attempt to follow them. The female would sit concealed amid the branches, chattering in a scolding, fretful way, while the male with his eye upon his tormentor would perch on the topmost shoot and sing. Why he sang at such times, whether in triumph and derision, or to keep his courage up and reassure his mate, I could not make out. When his song was suddenly cut short, and I glanced to see him dart down into the spruce, my eye usually caught a twinkle of blue wings hovering near. The wrens finally gave up the fight, and their enemies reared their second brood in peace. That the wren should use such coarse, refractory materials, especially since it builds in holes where twigs are so awkward to carry and adjust, is curious enough. All its congeners, the marsh wrens, the Carolina wren, the winter wren, build of soft flexible materials. The nest of the winter wren, and of the English "Jenny Wren," is mainly of moss, and is a marvel of softness and warmth.