Song plasticity over time and vocal learning in clay-colored thrushes

Songbirds have been traditionally classified into close-ended or open-ended learning species according to the length of the sensitive period during which birds are able to memorize new vocalizations. Closed-ended learners are generally not capable of changing their song after the first year of life, while open-ended learners show song plasticity as adults. A few Turdus species have been sug- gested to be open-ended learners, but no long-term study has been conducted to investigate their song plasticity over time. We analyzed the songs of clay-colored thrushes, T. grayi, over four successive breeding seasons to assess song plasticity in their syllable repertoires within and between breeding seasons. A total of 16,262 syllables were classi- fied through visual inspection of spectrograms and multi- dimensional scaling analysis based on spectrogram correlations. On average, 563 ± 153 (SD) syllables per male per breeding season were analyzed. Male repertoire size was 9–20 syllable types. Males were capable of modifying their syllable repertoire between the initial and final periods of the breeding season. Song plasticity within breeding seasons may be associated with imitation between neighboring males, suggesting song learning in males that were C2 years old. This short-term plasticity is not enough, however, to explain the high proportion of change (mean = 65 % syllable types) in repertoire composition between breeding seasons in adult males. Song plasticity resulting from annual changes in repertoire composition could be explained by open-ended learning, but another mechanism, extended memory and re-expression, could also explain long-term plasticity. Experimental studies controlling the acoustic environment are needed to determine which mechanism is responsible for such a high level of song plasticity.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Song learning in male and female Uraeginthus cyanocephalus, a tropical songbird species

International audienc

Long-time storage of song types in birds: evidence from interactive playbacks.

In studies of birdsong learning, imitation-based assays of stimulus memorization do not take into account that tutored song types may have been stored, but were not retrieved from memory. Such a 'silent' reservoir of song material could be used later in the bird's life, e.g. during vocal interactions. We examined this possibility in hand-reared nightingales during their second year. The males had been exposed to songs, both as fledglings and later, during their first full song period in an interactive playback design. Our design allowed us to compare the performance of imitations from the following categories: (i) songs only experienced during the early tutoring; (ii) songs experienced both during early tutoring and interactive playbacks; and (iii) novel songs experienced only during the simulated interactions. In their second year, birds imitated song types from each category, including those from categories (i) and (ii) which they had failed to imitate before. In addition, the performance of these song types was different (category (ii) > category (i)) and more pronounced than for category (iii) songs. Our results demonstrate 'silent' song storage in nightingales and point to a graded influence of the time and the social context of experience on subsequent vocal imitation

Bird song and anthropogenic noise: Vocal constraints may explain why birds sing higher-frequency songs in cities

When animals live in cities, they have to adjust their behaviour and life histories to novel environments. Noise pollution puts a severe constraint on vocal communication by interfering with the detection of acoustic signals. Recent studies show that city birds sing higher-frequency songs than their conspecifics in non-urban habitats. This has been interpreted as an adaptation to counteract masking by traffic noise. However, this notion is debated, for the observed frequency shifts seem to be less efficient at mitigating noise than singing louder, and it has been suggested that city birds might use particularly high-frequency song elements because they can be produced at higher amplitudes. Here, we present the first phonetogram for a songbird, which shows that frequency and amplitude are strongly positively correlated in the common blackbird (Turdus merula), a successful urban colonizer. Moreover, city blackbirds preferentially sang higher-frequency elements that can be produced at higher intensities and, at the same time, happen to be less masked in low-frequency traffic noise