Genes allow birds to keep the rhythm while singing

Researchers have linked 4 genes to birds’ innate rhythmic ability in song, according to a new study in Nature Communications.

Rhythm, which involves song elements being regularly distributed in time, is an essential component of communication that mediates key social behaviours, such as recognition of different individuals and mate selection.

Of the genes identified, 2 – NRXN1 and COQ8A – are also known to affect human speech and have been widely associated with speech impairment.

“Most genetic studies on bird song have so far focused on the genes implicated in song learning, thus leaving the molecular mechanisms underlying the temporal or spectral patterning of bird songs unexplored,” the authors write.

“Our study goes beyond what is known so far by identifying candidate genes underlying one of the fundamental characteristics of bird vocalisations: their rhythmic pattern.

“Of these, NRXN1 and COQ8A have both previously been associated with human speech disorders, and ENAH with hearing disabilities. MSH2 has yet to be associated with any vocal communication-related function.”

Photograph of a small light brown coloured bird with a bright orange spot of feathers on the front of its head
A yellow-fronted tinkerbird with deep orange forecrown photographed in October 2022 in Seringveld conservancy, northeast of Pretoria in Gauteng, South Africa. Credit: Matteo Sebastianelli

The research team measured the song rhythms of 2 species of African tinkerbirds across a region of Eswatini and South Africa where the 2 species have cross-bred, or hybridised. These species develop song innately, which removes the confounding effect of learned behaviour.

The authors describe their songs as comprising of “a repetitive series of pulses delivered at constant pitch and rate, with the latter differing subtly but unambiguously between Southern African populations of two species, yellow-fronted tinkerbird (Pogoniulus chrysoconus extoni) and red-fronted tinkerbird (Pogoniulus pusillus pusillus).”

Credit: Alex Kirschel
Credit: Sifiso Lukhele

Using a reference genome for P. pusillus, the team then investigated which areas of the genome are associated with variation in vocal rhythm.

They found that individuals with greater red-fronted tinkerbird ancestry at the candidate genes sing both faster and rhythmically more consistent, and thus more stable songs.

Photograph of a small light brown coloured bird sitting on a branch amongst the leaves. It has a bright red spot of feathers on the front of its head
A red-fronted tinkerbird photographed on 23 November 2021 in bushland west of Richard’s Bay, KwaZulu-Natal, South Africa. Credit: Alex Kirschel

The researchers say this suggest rhythm may play possible role in reproductive isolation, that red-fronted females may use this to choose mates of their own species and avoid hybridising with yellow-fronted birds.

“Because rhythm is omnipresent in animal communication, candidate genes identified here may shape vocal rhythm across birds and other vertebrates,” they write.

“We eagerly anticipate future studies into the genetics underlying rhythm-related behaviours across vocal non-learners and learners that may unveil the mechanisms of a potentially shared musical heritage with humans.”

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