Absolute and Relative Pitch Production in the Song of the Black-Capped Chickadee

Abstract

Black-capped Chickadee (Parus atricapillus) song consists of two notes, termed fee and bee. Frequency measures at three key points (at the start and end of fee, and at the start of bee) were obtained from the songs of a large sample of chickadees (n = 151) in the wild. In this sample, 19 birds produced songs shifted downward in frequency as well as their normal songs. Analysis of normal song revealed that fee declines in frequency in a glissando of nearly pure tone, then continues at greatly reduced amplitude at the start of bee; whereas bee, also a nearly pure tone, is always lower in frequency than either the start or end offee. The absolute pitches (frequencies) of these measures vary substantially among birds, but much less within individuals. In contrast, pitch intervals (ratios of higher to lower frequencies) for frequency changes among the three measures are highly invariant among birds. Moreover, chickadees with normal and frequency-shifted songs maintain virtually the same pitch intervals in both. This analysis suggests that the absolute and relative pitch constancies in chickadee song production may provide information for individual and species recognition, respectively.