Evidence for Teaching in an Australian Songbird

Abstract

Song in oscine birds (as in human speech and song) relies upon the rare capacity of vocal learning. Transmission can be vertical, horizontal, or oblique. As a rule, memorization and production by a naïve bird are not simultaneous: the long-term storage of song phrases precedes their first vocal rehearsal by months. While a wealth of detail regarding songbird enculturation has been uncovered by focusing on the apprentice, whether observational learning can fully account for the ontogeny of birdsong, or whether there could also be an element of active teaching involved, has remained an open question. Given the paucity of knowledge on animal cultures, I argue for the utility of an inclusive definition of teaching that encourages data be collected across a wide range of taxa. Borrowing insights from musicology, I introduce the Australian pied butcherbird (Cracticus nigrogularis) into the debate surrounding mechanisms of cultural transmission. I probe the relevance and utility of mentalistic, culture-based, and functionalist approaches to teaching in this species. Sonographic analysis of birdsong recordings and observational data (including photographs) of pied butcherbird behavior at one field site provide evidence that I assess based on criteria laid down by Caro and Hauser, along with later refinements to their functionalist definition. The candidate case of teaching reviewed here adds to a limited but growing body of reports supporting the notion that teaching may be more widespread than is currently realized. Nonetheless, I describe the challenges of confirming that learning has occurred in songbird pupils, given the delay between vocal instruction and production, as well as the low status accorded to anecdote and other observational evidence commonly mustered in instances of purported teaching. As a corrective, I press for an emphasis on biodiversity that will guide the study of teaching beyond human accounts and intractable discipline-specific burdens of proof.

Syntactic modulation of rhythm in Australian pied butcherbird song

“…The song units (phrases and notes) of the pied butcherbird songs are first segmented computationally by a dynamic-threshold-based automatic segmenter [ 52 ]. We define pied butcherbird notes as discontinuous instances of acoustic events surrounded by silence [ 53 ], and pied butcherbird phrases to be 1–3 s of continuous singing surrounded by silence [ 28 ]. The resulting textgrid segmentations are then manually reviewed and adjusted for accuracy in Praat; the segmentation boundaries for notes are checked with both the waveform amplitude and the spectrogram of the song, and the segmentation boundaries for phrases are aligned with the onset and offset of the first and last note, respectively, of each phrase.…”

“…The rhythmic structures of formal songs at the note level are correspondingly dynamic and diverse, and are similar to rhythmic devices described by music theory [ 26 ]. Additionally, formal songs are performed with immediate variety (where syntactic transitions occur between individual notes) [ 28 ], which allows for comparable analysis between syntactic and rhythmic features at the note level.

Figure 1 Pied butcherbird nocturnal formal song hierarchy.

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Learning: An Evolutionary Perspective

“…-rather than being followed by chance when moving to a site of interest, the possessor of knowledge can ensure that it/he is followed by a naïve subject or subjects (in Temnothorax albipenni ants, tandems are thus observed where an informed subject leads a naïve subject to a food source, thus inducing learning) (Franks & Richardson, 2006); the dance of bees, which transforms ignorant bystanders into informed subjects of an interesting food location, seems to belong to the same category, a mix of genetically recorded mechanisms and induced learning; -rather than being inadvertently exposed to a relationship between two stimuli, the learner may be introduced to such a relationship through repetitions (blackbirds exposing chicks to the relationship between one type of call, the "purr" call, and food); -rather than simply being observed performing an action and subsequently imitated, the subject who is the repository of the skill may set itself up as a demonstrator (a bird singing longer than usual in front of an apprentice) (Beecher & Akçay, 2020;Taylor, 2021); -rather than unknowingly providing a learning opportunity, tutors can tailor their products to theirs students' learning capacities (meerkats, cats and cheetahs bring prey that is sometimes dead, sometimes injured, and sometimes intact back to their cubs, depending on the age of the young, thus providing opportunities for them to exercise their hunting dispositions).…”