One day, while staying at Buena Vista, Colorado, I hired a saddle-horse and rode to Cottonwood Lake, twelve miles away, among the rugged mountains. The valley is wide enough here to admit of a good deal of sunshine, and therefore flowers studded the ground in places. It was here I saw the only female broad-tailed hummer that was met with in my rambles in the Rockies. She was flitting among the flowers, and did not make the buzzing sound that the males produce wherever found. She was not clad so elegantly as were her masculine relatives, for the throat-patch was white instead of purple, and the green on her back did not gleam so brightly. But, oddly enough, her sides and under tail-coverts were stained with a rufous tint--a color that does not appear at all in the costume of the male. A curious habit of these hummers is worth describing. The males remain in the breeding haunts until the young are out of the nest and are beginning to be able to shift for themselves. Then the papas begin to disappear, and in about ten days all have gone, leaving the mothers and the youngsters to tarry about the summer home until the latter are strong enough to make the journey to some resort lower in the mountains or farther south. The reason the males do this is perhaps evident enough, for at a certain date the flowers upon whose sweets the birds largely subsist begin to grow scant, and so if they remained there would not be enough for all. In the San Francisco Mountains of Arizona, Doctor Merriam found the broad-tails very abundant in the balsam timber and the upper part of the pine belt, where they breed in the latter part of July; after which they remain in that region until the middle of September, even though the weather often becomes quite frosty at night. At break of day, in spite of the cold, they will gather in large flocks at some spring to drink and bathe. Doctor Merriam says about them at such times: "They were like swarms of bees, buzzing about one's head and darting to and fro in every direction. The air was full of them. They would drop down to the water, dip their feet and bellies, and rise and shoot away as if propelled by an unseen power. They would often dart at the face of an intruder as if bent on piercing the eye with their needle-like bills, and then poise for a moment almost within reach before turning, when they were again lost in the busy throng. Whether this act was prompted by curiosity or resentment I was not able to ascertain."