Riebel, K. | Search bioRxiv

bioRxiv2021

An experimental test of chronic traffic noise exposure on parental behaviour and reproduction in zebra finches

Chronic traffic noise is increasingly recognised as a potential hazard to wildlife. Several songbird species have been shown to breed poorly in traffic noise exposed habitats. However, identifying whether noise is causal in this requires experimental approaches. We tested whether experimental exposure to chronic traffic noise affected parental behaviour and reproductive success in zebra finches (Taeniopygia guttata). In a counterbalanced repeated-measures design, breeding pairs were exposed to continuous playback of one of two types of highway noise previously shown to be either neutral (control) or aversive. Parental nest attendance positively correlated with feeding effort and was higher for the aversive than the control sound and this effect was more pronounced for parents attending larger broods. However, neither noise condition affected offspring number, growth or body mass. The absence of an effect held when we combined our data with data from two other comparable studies into a meta-analysis. We discuss whether the increased nest attendance could be a compensatory strategy that alleviated detrimental noise effects on the chicks, and whether it could be caused by impaired parent-offspring or within-pair communication. Future work should test these hypotheses and investigate potential long-term costs of increased parental engagement.

animal behavior and cognition↗

bioRxiv2021

Frequent female song in blue tits: behavioural context suggests a role in intrasexual competition

The blue tit (Cyanistes caeruleus) is an important avian model in evolutionary ecology (> 20,000 published scientific studies). Song, like in other songbird species, is generally described as a male trait and plays an important role in mate attraction and territory defence. Over the decades, there have been recurring reports of anecdotal female song but these have not led to any quantitative study of female song in blue tits. Our systematic sampling over three years revealed prolific female singing in a northern population of colour ringed blue tits. Daytime singing of females occurred throughout the breeding season during agonistic interactions, solo songs and alarm situations, and these contexts are similar to male song. Notably, female song was absent during the dawn chorus; the period around sunrise when males sing intensively just before mating. Female and male song overlapped substantially in acoustic structure (i.e. same song types, peak frequency or trill rates) but there were also significant differences in that females had smaller repertoires, shorter trills and lower vocal consistency. Differential selections pressures related with contextual (functional) differences in the role of male and female song could explain the observed differences in acoustic structure. The new finding of prolific female singing in such a well-studied species suggests we ought to revise our understanding of male and female vocal communication in this (and probably other) species. Identifying the selection pressures associated to the convergence versus divergence of male and female song may provide important insight in understanding birdsong evolution. Lay summaryFemale song has been anecdotally reported in blue tits but there are no quantitative studies of singing behaviour, song structure or context. Here, we report frequent female singing in blue tits, associated mostly with agonistic interactions and alarm situations. Importantly, female song was not observed during dawn chorus, the period around sunrise when males sing intensively just before mating. Female and male song overlapped substantially in acoustic structure (i.e. same song types) but there were also significant differences (i.e. females sang with lower vocal consistency). We speculate that differences in context (function) of male and female song could explain the observed differences in acoustic structure. The new finding of prolific female singing in such a well-studied species suggests we ought to revise our understanding of male and female vocal communication.

animal behavior and cognition↗