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 offee, and at the start of bee) were obtained from the songs of a large sample of chickadees (n = 15 1) 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.

Chickadee Song Structure is Individually Distinctive Over Long Broadcast Distances

“…It was also the only feature under analysis that remained unaffected by transmission degradation for broadcast distances of up to 80 m and individually distinctive as long as songs were audible. The interval ratio (as well as the fee ratio) have been implicated as cues to species recognition for chickadees (Weisman & Ratcliffe, 1989;Shackleton et al, 1992). The remarkable stereotypy of these two features (showing less than 2% variation) across most of the species' range (Kroodsma et al, 1999) and within our Eastern Ontario population lends support to this notion.…”

“…1). These were song length (seconds), the relative length of the fee note (fee length = percentage of song length), the relative loudness of the fee note (relative fee loudness = the logarithmic root mean squared measure (RMS) of the amplitude of the fee note (V Fee ) expressed in decibels relative to the RMS value for the song (V Song )), the frequency ratios of the fee note (glissando ratio = frequency at fee start /frequency at fee end ) and the internote interval (interval ratio = frequency at fee end /frequency at bee start ) (see Weisman et al, 1990). The amplitude measure for the note and the song was determined using Avisoft software's 'copy RMS of marked section' analysis tool and the ratio in dB was calculated as 20 log V Fee /V Song .…”

Chickadee songs provide hidden clues to singers’ locations

“…Interestingly, the peak frequencies of fee and bee notes fall within the region of greatest auditory sensitivity in chickadees (Wong & Gall, 2015), and the spacing between these two peaks matches the width of auditory filters in a listening chickadee's peripheral auditory system ( Figure 2C; Henry & Lucas, 2010). Because singing chickadees maintain a relatively fixed frequency ratio between the two notes when they shift their songs up or down in frequency (Weisman & Ratcliffe, 1989, 2004Weisman, Ratcliffe, Johnsrude, & Hurly, 1990), the relationship between peak frequency spacing and auditory filter bandwidth holds true for all fee-bee songs. This correspondence between peak frequency spacing and auditory resolution suggests that the acoustic structure of the fee-bee song may facilitate discrimination of coincident reverberation cues by listening birds.…”

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla)

“…The prototypes for our simulations were the songs of eight freeliving male black-capped chickadees recorded in the wild at the Queen's University Biology Station (see Weisman, Ratcliffe, Johnsrude, & Hurley, 1990) and the distance calls of eight free-living female zebra finches recorded in the wild at Alice Springs and northern Victoria, Australia. The birds in the experiment had no previous experience with any of the vocalizations used here.…”

“…The fee-bee song is highly tonal and similar in acoustic structure among birds (Weisman et al, 1990). It could be that other chickadee vocalizations are easier to use to discriminate among individuals (e.g., "chick-a-dee" calls; Nowicki, 1989).…”