Peer review of: Nuthatches vary their alarm calls based upon the source of the eavesdropped signals (2020)

Reviewers' Comments: 
 
Reviewer #1: 
Remarks to the Author: 
The paper represents a thorough and interesting aspect of heterospecific communications and graded 
responses according to information source. In most ways, I cannot fault the paper either in method or 
clarity of results. It is also carefully written and the paper requires very few corrections. For instance, 
very minor corrections are: 
Line 60 spelling error- very/vary: are known to vary their alarm calls; Line 192/3 double brackets-
remove one (preferably change bracket for comma in line 192) Line 482/3 incomplete citation --pls 
complete-(my copy says: Bates, D., Maechler, M., Bolker, B. and Walker, S., 2014. lme4: Linear 
mixed-effects models using Eigen and S4. R package version, 1(7), pp.1-23.) 
 
However, the paper suffers from a dated perspective and does not engage with recent and relevant 
literature in the field, not even with publications that have recently appeared in Nature 
communication. 
It seems that the paper stops in its own theoretical framework in 2014, except for inclusion of two 
titles that are later, and does not engage with recent findings. A period of five years is a long time in 
science, particularly in a field that is of continued interest and vibrant. I am thinking of Suzuki’s work 
et al. (2016, 2018) Magrath et al. -2015-2018, and Potvin et al. (2018) and various others. 
 
The literature has been quite rich and innovative in the field in which the authors present their findings 
and I firmly believe that it is essential that a paper is fully engaged in (or delineated from) current 
debates in the field and that such engagement is apparent in the introduction, possibly in the method 
and most definitely in the discussion. The paper consequently is not within a framework of current 
ideas and research findings. 
 
As a reader, one needs to be convinced that the paper is fresh and has something new to say that has 
not already been described or discovered or has been debated in the recent literature. If this is an old 
paper, then it needs to be updated (datedness also noticeable in the programs used in Raven and the. 
lme4: Linear mixed-effects models package- both have more recent versions). If it is a paper that has 
purposely omitted latest research findings, for whatever reason, one can only advise that this strategy 
does not work and would appear to me to run counter to the very raison d’être of research reporting. 
At the very least, it leaves the reader dissatisfied. 
 
 
 
Reviewer #2: 
Remarks to the Author: 
Review of NCOMMS-19-23668 
 
I have reviewed the paper “Nuthatches vary their alarm calls based upon the reliability of the 
eavesdropped signals”. 
 
 
This study focuses on the influence of direct vs. indirect information sources on the further 
propagation of predator-specific information in the alarm calls of red-breasted nuthatches. 
Through the implementation of a controlled playback experiment the authors show that when 
receiving direct information (i.e. predator vocalisations), red-breasted nuthatches reliably vary their 
alarm call structure to accurately communicate this threat. However, when receiving indirect 
information (i.e. through the alarm calls of chickadees responding to the same predators) they 

produce alarm calls that are more intermediate or “general” in structure. 
I thought the paper was very well written and the results interesting. Of particular relevance is the 
fact that the results speak against the popular theory in animal communication that information 
encoded in graded vocalisations varies systematically with arousal: although exposed to likely highly 
arousing chickadee alarm calls, this did not result in nuthatcher vocalisations of comparable structure. 
 
I think this paper will be of interest to researchers from a broad spectrum of disciplines, from animal 
communication, to behavioral ecology and comparative psychology. I have a few comments that the 
authors might want to consider when revising the MS. 
 
Specific comments: 
 
1. L82: Perhaps the authors could spell out the interaction effects more, which I feel would help the 
reader interpret the results more clearly. 
 
2. L84: From the results it seems that for call length there is not an interaction between predator 
threat and the source of information but it is generally discussed as if there is. I think it would be good 
for the authors to note that the interaction applied for 2 of the 3 acoustic variables measured. 
 
3. L96: Isn’t this the same result as on L82? It is not clear why the authors bring this up a second 
time rather than just discussing this is a trend when they first describe the results (L82). 
 
4. L210-214: This reads more like introduction than methods. 
 
5. L250-251: It is not really clear what the authors mean by “good playback characteristics” – please 
elaborate. 
 
L258: If the authors were not able to identify individuals, is it possible that the same individual 
contributed more than one call to the acoustic response data set? Is this problematic in terms of 
pseudoreplication? In line with this, can the authors add sample sizes of calls analysed to the results 
section (i.e. L81-99). 
 
6. L318: Wouldn’t Likelihood-ratio tests not have been more appropriate here? 
 
Minor points: 
 
L60: change “very” to “vary”. 
L293: Change to : “vary in the time they take to begin mobbing…”