Changing Habits of Vaux Swift and Western Martin

Abstract

Two broods are evidently raised, as an immature bird, in company with an adult, was flushed on August 9. The nighthawks were noticeably less numerous during the latter part of the summer, and it is possible that the males and the young of the first brood left in July or earlier. The flight of the Texas Nighthawk gives the impression of ease to a greater degree than that of any other of our smaller birds. While not slow, it appears leisurely and is frequently varied by periods of gliding. The large expanse of wing gives great buoyancy and the bird seems to float through the air almost without effort, while a turn of the wing serves to change its course at an abrupt angle The Texas Nighthawk flies at a much lower altitude than is the usual habit of swallows and swifts. While hunting it never ascends to any great height, and often skims close to the ground, passing among the vegetation. In the evening its activities begin about sunset or earlier, usually ceasing before dark, and in the morning it is apt to remain in the air for some time after sunrise. It may sometimes be seen hunting at mid-day, especially in cloudy weather. The nighthawk displays some curiosity and often swoops down within a few feet of one's head. Even at that distance the flight is entirely inaudible. In general the vocal utterances of the Texas Nighthawk are of three kinds: first, a low soft cluck, repeated slowly; second, a louder, querulous, nasal cry, repeated more rapidly and used when two or more of the birds are together; third, a series of throaty staccato notes delivered in monotone so rapidly as to be almost continuous, sustained for several seconds at a time and resumed after a short pause as if for breath. This trill is sometimes given from the ground, and very frequently while flying. It is used only when the birds are undisturbed and is not ordinarily heard at close range. While the tone is soft, the carrying power is great, and sometimes on summer evenings when several of the nighthawks are about, the air seems filled with an indefinable vibration.