Chickadee Song Structure is Individually Distinctive Over Long Broadcast Distances

Abstract

SummaryThe two-note fee-bee song of male black-capped chickadees functions during the dawn chorus, in part, as a sexual signal across large distances. How song structure might encode information about male quality, however, remains unclear.We studied the availability of cues to male social rank (a proxy indicator of male quality), within the acoustic structure of dawn chorus songs of male chickadees whose ock dominance status we determined the previous winter. We used analysis of variance and discriminant function analysis to demonstrate that ve temporal, frequency or relative amplitude features of song can predict individual identity but not the category of social rank (dominant versus subordinate) to which individuals belong.After transmitting chickadee songs through the forest and re-recording them at four broadcast distances, we found that song structure continued to effectively predict singer identity by our statistical methods despite signi cant acoustic degradation for as long as songs remained audible (up to 80 m).In particular, the relative frequency interval between the two notes is both the most invariant between-male measure and among the most individually distinctive.

Stereotypy and variation of the mating call in the Lusitanian toadfish, Halobatrachus didactylus

“…The ratio CV b / CV w was then calculated to obtain a measure of relative between-male variability for each boatwhistle feature. When this ratio is larger than one, it suggests that the acoustic parameter is more variable between individuals relative to its variability within individuals and could be used as a cue for individual discrimination (Christie et al 2004). KruskalWallis tests were computed to compare differences among males for each acoustic feature in the two time frames.…”

Chickadee songs provide hidden clues to singers’ locations

“…However, in highly reverberant habitats, such as those frequented by black-capped chickadees (Smith, 1991), constructive and destructive interference can introduce fluctuations in frequency attenuation that confound interpretation of variations in the spectra of received songs. Using acoustic transmission studies, Fotheringham and Ratcliffe (1995) found that differential frequency attenuation in fee-bee songs did not reliably indicate source distance (however, see Christie et al, 2004a). Figure 2. (A) Spectral peaks are evident both from the directly received bee note and from the reverberant tail of the preceding fee note (feeR) after a song has traveled 80 m (FFT = 2048; 98% overlap; 250 ms Hanning window).…”

Black-capped chickadees categorize songs based on features that vary geographically

“…bee), and this frequency relationship between the two notes remains relatively consistent across song bouts (Horn et al, 1992;Weisman et al, 1990). Fee-bee songs contain acoustic features indicating individual identity (Christie et al, 2004a;Hahn et al, 2013b), and field (Wilson & Mennill, 2010) and laboratory (Phillmore et al, 2002) studies have demonstrated that chickadees can discriminate among individuals based on their songs. Although the black-capped chickadees' range extends across most of North America (Smith, 1991), little geographical variation has been described in this song (although, variation has been found in geographically isolated populations of chickadees, where some animals produce unusual songs; see Gammon & Baker, 2004;Kroodsma et al, 1999).…”