National Geographic : 1932 Jul
THE NATIONAL GEOGRAPHIC MAGAZINE rnotograpn by A. A. Allen A SPEAR OF TIMOTHY MAKES A PERCI FOR A HUMMER An existence of such a type is in strong contrast to that of the beautiful long-tailed Sappho hummer (Sappho sapho) that I found in the Andean foothills of western Argentina, living in open valleys grown with low creosote bush, where the birds were constantly in the open. THE HUMMER'S PLUMAGE UNDER A MICROSCOPE The majority of hummers are character ized by glittering reflections from their plumage, and as a general rule the males are more brilliant than the females. The hues of the plumage are iridescent and are caused by the refraction of light. On close examination of the feather of a bird, it is found to be composed of many fine filaments, which under the microscope are seen to be divided into still finer divi sions. In the shining feathers of hum mers, there is an abundance of dark pig ment in the tiny feather divisions known as barbules. The sheath overlying this pig ment is either smooth and highly polished or has many minute lines on or under its surface. This structure causes a reflection or a refraction of the light, according to the circumstance, making the brilliant hues found in these birds. The colors vary ac- cording to the angle of the light, changing in intensity and in hue as the bird shifts position. As for form, the variation among hum mers is truly astonishing. The smallest bird in the world is Helena's humming bird (Calypte helenae) of Cuba, from two and one-fourth to two and one-half inches or a trifle more in length, with the wing only one and one-third inches long or less and the bill less than half an inch long. This tiny sprite is sometimes called the fairy hummer. In contrast to it, there is the giant hummer of the central and south ern Andean mountains that is about eight and one-half inches in length and has a wing five inches long. This species is as large in body as a bluebird and is strong and powerful, resembling a large swift in general appearance. IIUMMERS WITH SICKLE-SHAPED BILLS Variations in details of form are as re markable as those in size. In one species of hummer, the sword-bearer (Docimastcs ensifera), the bill is nearly five inches long, being longer than the rest of the bird. An other (Ramphomicron microrhynchum) has the bill less than a quarter of an inch long.