The phrase ἄνθρακας πρινίνους (here in the genitive plural ἄνθρακων πρινίνων) refers to 'birch coals' or, more likely in this context, coals made from the wood of the birch tree (Betula), which were notoriously used in ancient comedy to represent the burning of a specific, often absurd, fuel source for magical or ritualistic purposes. The word φέψαλος is a hapax legomenon in the extant corpus of Aristophanes, appearing only here, and is generally understood as a type of small bird (perhaps a wren or a thrush) or, more plausibly in the context of the bird's frantic movement, a metaphorical or onomatopoeic term for a bird fluttering or twitching violently. The verb ἀνήλατ' (aorist of ἀνάλλω) is rare and specifically denotes the act of 'shaking off' or 'shaking oneself free' (often with a connotation of vigorous, almost convulsive movement), which is crucial for the comic imagery of the bird being goaded by the wind (οὐρίᾳ ῥιπίδι) into a frenzied state. The combination of these elements creates a vivid, albeit obscure, metaphor for the frantic, wind-driven movement of the character (or the chorus) that follows, relying on the specific, almost grotesque, imagery of a bird agitated by a birch-coal fire and a gust of wind.