Differential geographic patterns in song components of male Albert’s lyrebirds

Abstract

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Higher-order sequences of vocal mimicry performed by male Albert's lyrebirds are socially transmitted and enhance acoustic contrast

“…For six birds, we used recordings from autonomous sound recorders set up 7-10 m from the display platform. Individuals were identified by location [40] and adult male plumage confirmed either in person or from camera trap footage from display platforms. Recordings were made using a hand-held Sennheiser ME 66/ K6 shotgun microphone and a Marantz PMD 661 with a 96 kHz sample rate and 24-bit depth, or a Swift (Terrestrial Passive Acoustic Recording Unit, developed by the Cornell Lab of Ornithology) with a 48 kHz sample rate, 16-bit depth and 33 dB gain.…”

“…Male Albert's lyrebirds have a varied but structured repertoire including species-specific 'whistle song' [40] and 'gronking' [38], as well as mimicry of heterospecific vocalizations and environmental sounds [37]. Here, we focus on the most common form of vocal mimicry ('sequential song' [38]), which royalsocietypublishing.org/journal/rspb Proc.…”

“…In Albert's lyrebirds, mimicked vocalizations appear to be learnt from both conspecific tutors and heterospecific models, although it is unclear how these two mechanisms interact [39]. Sequences of mimetic units in the recital mimicry are typically repeated multiple times without a break, sometimes interrupted at irregular intervals by speciesspecific whistle songs or introductory notes [40]. Sometimes recital mimicry transitions to a discrete specific-specific song known as 'gronking' [38] (F.B.…”

“…To apply the same treatment to all birds and avoid creating artificial differences between populations in sequence length, we split recorded bouts into sequences using the mimetic unit that had the most consistently high occurrence in all birds (satin bowerbird vocalization 'd' in figure 1; electronic supplementary material, appendix S2 and table S3 for details). Song bouts were subsequently split into sequences beginning with this mimetic unit using the strsplit function in R. Species-specific whistle songs are temporally discrete within singing bouts [40], and so whistle songs (n = 314), and solitary introductory elements normally associated with whistle songs (n = 14), were removed from these sequences. Removing whistle songs and introductory elements marginally increased similarities between sequences (electronic supplementary material, table S3), but this is unlikely to affect any conclusions from results.…”

“…To examine the effect of geographic separation on the degree of sequence sharing, we compared average similarities between pairs of individuals and populations with measures of geographic distance. For distances between populations, we used the length weighted by resistance of least cost paths calculated from a species distribution model (SDM) produced in a previous study [40]. As distances between individuals within populations were often smaller than the resolution of the SDM (range = 95-5927 m, mean = 1709 m), we used geodesic distances between individuals.…”