The "twittering" in the title doubtless refers to the birds, while the "machine" is suggested by the hand crank. The two elements are, literally, a fusing of the natural with the industrial world. Each bird stands with beak open, poised as if to announce the moment when the misty cool blue of night gives way to the pink glow of dawn. The scene evokes an abbreviated pastoral—but the birds are shackled to their perch, which is in turn connected to the hand crank.
Upon closer inspection, however, an uneasy sensation of looming menace begins to manifest itself. Composed of a wiry, nervous line, these creatures bear a resemblance to birds only in their beaks and feathered silhouettes; they appear closer to deformations of nature. The hand crank conjures up the idea that this "machine" is a music box, where the birds function as bait to lure victims to the pit over which the machine hovers. We can imagine the fiendish cacophony made by the shrieking birds, their legs drawn thin and taut as they strain against the machine to which they are fused.