The role of singing style in song adjustments to fluctuating sound conditions: A comparative study on Mexican birds.

Many bird species adjust their songs to noisy urban conditions by which they reduce masking and counteract the detrimental impact on signal efficiency. Different species vary in their response to level fluctuations of ambient noise, but it remains unclear why they vary. Here, we investigated whether noise-dependent flexibility may relate to singing style and signal function of the flexible acoustic trait. Species with highly variable songs may generally be more flexible and strongly repetitive singers may be more limited to stray from their stringent patterns. We exposed males of four passerine species with contrasting singing styles (repertoire size, immediate or eventual variety singing and syllable diversity) to three experimental sound conditions: 1) continuous urban noise; 2) intermittent white noise and 3) conspecific song playback. We found no spectral or temporal changes in response to experimental noise exposure in any of the four species, but significant temporal adjustment to conspecific playback in one of them. We argue that the consistency in song frequency and timing may have signal value, independent of singing style, and therefore be an explanation for the general lack of noise-dependent flexibility in the four species of the current study.

Bermúdez-Cuamatzin E ，López-Hernández M ，Campbell J ，Zuria I ，Slabbekoorn H ... -  《-》

Immediate spectral flexibility in singing chiffchaffs during experimental exposure to highway noise.

Verzijden MN ，Ripmeester EA ，Ohms VR ，Snelderwaard P ，Slabbekoorn H ... -  《-》

Signalling through acoustic windows: Nightingales avoid interspecific competition by short-term adjustment of song timing.

Brumm H 《JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY》

Timing vocal behavior: lack of temporal overlap avoidance to fluctuating noise levels in singing Eurasian wrens.

Many animals live in or near urban areas that have become increasingly widespread and noisy over the last century. Especially those species that rely heavily on acoustics for communication may be affected by these elevated anthropogenic noise levels. Many bird species that sing to defend their territories and to attract mates may have to exploit specific noise coping strategies to persist in such acoustically challenging conditions. Eurasian wrens (Troglodytes troglodytes), like several other bird species, have been shown in a previous experiment to time their vocalizations such that they avoid overlap with other singing birds. Here, we tested whether Eurasian wrens also time their songs to avoid overlap with fluctuating anthropogenic noise. However, we did not find any evidence in favor of this potential phenomenon. Territorial wrens persisted in singing without temporal adjustments in noisy territories with 'natural' fluctuations of traffic noise levels as well as during experimental exposure to intermittent white noise.

Yang XJ ，Slabbekoorn H 《-》

The learning advantage: bird species that learn their song show a tighter adjustment of song to noisy environments than those that do not learn.

Song learning has evolved within several avian groups. Although its evolutionary advantage is not clear, it has been proposed that song learning may be advantageous in allowing birds to adapt their songs to the local acoustic environment. To test this hypothesis, we analysed patterns of song adjustment to noisy environments and explored their possible link to song learning. Bird vocalizations can be masked by low-frequency noise, and birds respond to this by singing higher-pitched songs. Most reports of this strategy involve oscines, a group of birds with learning-based song variability, and it is doubtful whether species that lack song learning (e.g. suboscines) can adjust their songs to noisy environments. We address this question by comparing the degree of song adjustment to noise in a large sample of oscines (17 populations, 14 species) and suboscines (11 populations, 7 species), recorded in Brazil (Manaus, Brasilia and Curitiba) and Mexico City. We found a significantly stronger association between minimum song frequency and noise levels (effect size) in oscines than in suboscines, suggesting a tighter match in oscines between song transmission capacity and ambient acoustics. Suboscines may be more vulnerable to acoustic pollution than oscines and thus less capable of colonizing cities or acoustically novel habitats. Additionally, we found that species whose song frequency was more divergent between populations showed tighter noise-song frequency associations. Our results suggest that song learning and/or song plasticity allows adaptation to new habitats and that this selective advantage may be linked to the evolution of song learning and plasticity.

Ríos-Chelén AA ，Salaberria C ，Barbosa I ，Macías Garcia C ，Gil D ... -  《-》