What actually counts as a learned rhythm?
The key distinction is between the sound an animal makes and the timing with which it makes it. Zebra finch males learn their song from a tutor, but the short calls produced by both males and females are not learned—their acoustic structure is innate [2]. Yet those same innate calls can be precisely coordinated between individuals, and the timing of when a bird answers a partner can be modified through experience [2]. That separation is useful: it shows that a fixed, built-in sound can still be delivered on a learned schedule.
A second, related ability is perceiving rhythm rather than producing it. Male zebra finches recognized a regular, evenly spaced pattern of sounds regardless of how fast or slow the sequence was played, even at speeds far from what they were trained on [1]. Pigeons and rats, which do not learn their vocalizations, appear much more limited in this respect and tend to lock onto absolute durations instead of the relationships between intervals [1]. This contrast is consistent with the idea that vocal-learning species process rhythm more flexibly, though it concerns perception rather than the birds' own vocal output.
The jamming experiment: learning to change *when* you call
The most direct demonstration of learned vocal timing comes from a setup in which a robotic bird exchanged calls with a real finch. Because birds answer with fairly stereotyped delays, the robot could be programmed to fire calls that would collide with—and mask—the bird's reply. Within minutes, birds adjusted the timing of their responses to dodge the interference, which is a learned change in when they vocalize [2].
Two details sharpen the picture. First, females adapted their timing more than males did, even though females only produce innate calls [2]. Second, when the birds faced more complex rhythms containing jamming elements, they adjusted their calls in anticipation of the disruption rather than only reacting after it [2]. Together these suggest that the plasticity is in the timing system, not in the call's acoustic form, and that it can be predictive rather than merely reactive.
Flipping the brain's song output off
If timing adjustments were purely a low-level reflex, interfering with the song system should not matter much. But blocking the cortical output of the song system dramatically reduced how precisely birds timed their responses and abolished their ability to avoid jamming—and this happened in both males and females [2]. The authors interpret this as evidence that descending forebrain projections, including the song-production pathway, act as a general-purpose sensorimotor communication system: for calls it enables plasticity in timing, while for songs it enables developmental changes in vocal structure [2].
That interpretation is a proposal about function, not a settled fact. What the experiment establishes is narrower but strong: the forebrain song system is required for flexible call timing in both sexes, which also indicates the female song system is functional rather than vestigial [2].
How far does this generalize, and what's still murky?
Zebra finches are not the only candidate. Harbor seals appear to have capacities for both vocal learning—learning sounds outside their natural repertoire—and rhythm processing, and some of the underlying building blocks seem to appear early in life [4]. That work is presented as data from roughly 15 studies spanning spontaneous recordings, playback, operant-conditioning learning experiments, and anatomy, and it supports the broader hypothesis that vocal learning and rhythm processing are linked across species [4]. It does not, on its own, cleanly separate learned rhythm from innate timing [4].
A wider review of timing in animal communication notes that learned signals such as birdsong and innate signals may share neural timing mechanisms, and argues that even innate signals can illuminate the neural oscillators animals use to track time [5]. It also raises a trade-off worth keeping in mind: greater timing precision may come at the cost of the range of intervals an animal can produce, so communication signals are a window onto the physiological limits of neural rhythms [5]. Classifying a behavior as learned vocalization at all depends on careful definitions—whether an animal learns sounds that match an auditory template versus relying on innate motor programs—which is why a formal taxonomy of vocal learning matters for interpreting these results [3].
Sources used in this answer
Vocal learning and flexible rhythm pattern perception are linked: evidence from songbirds (2021) PNAS - Supporting files
Male zebra finches recognized evenly spaced (isochronous) rhythmic patterns based on the relations between intervals rather than absolute durations, even at rates distant from training, unlike vocal non-learners such as pigeons and rats.
The Forebrain Song System Mediates Predictive Call Timing in Female and Male Zebra Finches.
Zebra finches learned within minutes to shift the timing of their innate calls to avoid jamming by a robotic bird, females showed greater timing plasticity than males, and blocking song-system cortical output reduced timing precision and abolished jamming avoidance in both sexes.
A taxonomy for vocal learning
A taxonomy of vocal learning distinguishes learning vocalizations to match auditory templates from innate motor programs, which is needed to classify whether a behavior counts as learned vocalization.
Vocal learning and rhythm processing in harbor seals
Harbor seals show evidence of both vocal learning and rhythm processing, with some building blocks appearing early in life, but the data do not clearly separate learned rhythms from innate timing.
Interval timing and animal communication.
Learned signals like birdsong and innate communication signals may share neural timing mechanisms, and timing precision in communication may trade off against the range of intervals an animal can produce.