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THE CONDOR Vol. XXI after in gradually increased numbers until the maximum was reached about February 15, when there were at least six hundred birds inhabiting an area of approximately three square miles. At this time when bird-life was relatively scarce it was possible to devote much of my leisure to their study. There had been a heavy crop of yellow pine and Douglas fir seeds (these are the only conifers in this area) and possibly this might account for their unusual abundance and their long stay. During the cold weather of January and the early part of February, be- fore there was .any sign of mating, the'birds remained in flocks of from ten to thirty in the heavily foliaged conifers. As they were usually silent they would often have escaped notice had it not been for the presence of the w?nged seeds scattered broadcast on the snow, each with the kernel neatly cut out,. and for various methods used for exciting the birds. An imitation of the Pygmy Owl call brought them at once' and they would circle over the tree tops in their eagerness to locate their enemy. When the sound was located they would fly from tree top to tree top near the source of the sound, uttering their sharp alarm note until the calling ceased, when they would disappear into the forest again. Dissection of a series of males. collected on February 19, showed the sex organs to be in various stages of development from 1 mm. to 5 mm. in length. Males in the red, the yellow, and the mixed red and yelloxv plumages, were found to be in breeding condition, and others in similar plumage shot on the same day were undeveloped sexually, or nearly so. No evidence as to the age of the birds could be deduced from the sex organs then, nor did comparison of the Skull granulation help. While a discussion of moults will not be attempted in 'this paper it might be of interest to state that specimens were taken which plainly show a rever- sion to the yellow plumage from the red. The first mated birds and the first nuptial flight were seen on February 19. Four or five birds at a time were frequently seen after this, chasing one another in circles around the tree tops and singing on the wing. Their song came as a delightful surprise in the silent snow-clad woods. Heard through a medium of clear frosty winter air, the song seemed to have the same fine qual- ity as that of the Townsend Solitaire; a less.sustained effort and lighter in tone, but with.equal carrying power. As the mating season progressed, the song gained in volume and quality, until, by the end of March, it was common to hear the birds sing for twenty minutes at a time, I decided that it was the equal. in every way, of that of the solitaire, with all of the volume and sweetness of the latter's song. In March, the courtship period being over, there was non? of the chasing and singing on the wing observed in February. Solitary males sang from the topmost twig of the tallest tree, frequently a solitary yellow pine towering above the second growth firs. Often three or four birds could be heard at once --a most delightful chorus. In singing the bill is pointed straight up, chest ex- panded and breast, head, and flank feathers puffed out until' the singer looks much larger than he really is. In the early morning the birds sang continu- ously, evidently serenading their sitting mates, and the song could be clearly heard on a still day at two hundred yards. In searching for nests, it was soon found that the Pygmy O?vl call would be of no service as the males would come from any distance, up to a quarter