By ALBERT ERVIN THOMPSON
Nature Magazine, September 1937
The nesting black swift pictured in the accompanying photograph was found on the nest near the western boundary of General Grant National Park in Fresno County, California, in the Transition Life Zone at an elevation of five thousand two hundred feet above sea level in the Sierra Nevada Mountains. The situation and the nest material used differ so much from those utilized by other members of the family that a brief description seems justified.
The narrow mountain gorge in which the nest was found is forested with tall sugar and yellow pines, white fir, incense cedar, and giant sequoia, and, because of a steep slope to the northwest, receives very little direct sunlight except during a brief portion of the afternoon. At other times only random shafts of light find their way among the trees.
THE BLACK SWIFT AT HOME
The nest was built in a hollow of a granite wall, sheltered by an overhanging projection of rock. It was about six feet above the bed of a mountain brook and not more than twelve feet removed from a rushing cascade that boiled down a chute from a cliff above. Because of the smoothness of the sheer face of the rock, the situation was inaccessible to snakes and small mammals. The nest was formed by moist mossy material, imbedded in a natural growth of the same plant. Seeping water and spray from the waterfall kept the site continually moist. For this reason the nest was at first mistaken for that of a water ousel. One egg was laid, but after it hatched the young bird mysteriously disappeared, perhaps devoured by an enemy.
The parent bird was brave and hard to flush, becoming quite used to the camera, but whenever it did leave the nest, it dropped quickly out of sight past the willows of the stream without uttering a sound, and would not return while visitors were present.
The picture was taken in the latter part of June, 1936. The incubation period of the egg could not be determined, as it was almost ready to hatch when first discovered.