Using Acoustic Data Repositories to Study Vocal Responses to Playback in a Neotropical Songbird

Round 1

Reviewer 1 Report

This is an interesting work that takes advantage of the acoustic repositories to assess behavioral responses in a Neotropical songbird by the comparison of spontaneous and post-playback vocalizations. The authors found differences in the duration of songs but not in the spectro-temporal attributes of songs. The relevance and value of the acoustic repositories are shown and evident in this work. However, the limitations of a well-structured protocol of playback and the lack of metadata may reduce the certainty of the analysis and its interpretation.  Sometimes is not totally clear the direction of the study when the discussion focuses on the use of acoustic datasets or their limitations versus the changes in the acoustic properties of songs by the effect of playback stimulation.

 

My main concern is that the title and focus of the manuscript provide an idea that is not totally congruent with the analysis and the objectives of the study. The authors seem to want to note that this is a work of a citizen science initiative (such as a tool in this study). However, the fact is that analyses come from a dataset repository but not from a direct exercise of citizen science. This should be clarified in the title and the body of the manuscript. (e.g., “using citizen science data to study…” or “using acoustic libraries database to study…”. On the other side, the records in repositories such as Xeno-Canto o Macaulay are not totally products of citizen science, some records come from well-structured methodologies as a part of research projects with established protocols. Despite this, most recent acoustics records uploaded may come from citizen science activities organized or just occasional birding without any protocol. In fact, Xeno-Canto may involve records from citizen science projects (see https://xeno-canto.org/article/195).

To consider the real value of these practices and the acoustic material obtained from them, the records should be preselected in a well-described protocol to consider this approximation or the source of the data.

Another alternative may be to use the data analyzed but discuss more than from citizen science in the value of the acoustic repositories independent if they are from academia o citizen science initiatives, adding comments on the value of citizen science in the increasing of acoustic repositories and the need to establish protocols for the value of the data.

On the other hand, I still feel confused about the effect of geographic distance in the analysis, since is not clear which was the scale of the analysis.

Here I present specific comments on the text.

 

Line 35
I am not confident with using the “playback experiment” keyword since experimentation does not take place in the framework of the paper nor do the authors know if playbacks come from a standardized playback protocol. I suggest using only “playback”.

 

Line 42
In citation #2, use a broader reference to support the idea. The citation is specific to a single species, explore some book on animal communication or a complete review of the topic.

 

Line 45
Unformatted citation style. Do not use textual citation (Bailey et al., 1993), use numbers instead.

 

Line 46
Check citation #6. This is about the sexual-conflict hypothesis. Does this behavior present in the C.  gujanensis? If not use other approximations to talk about social pressures in the plasticity of songs.

 

Line 55
I do not find citation #12 necessary.

 

Lines 60 – 63
I do not find these lines supportive; the cited studies involve factors not assessed in your study (e.g., age, stress).

 

Line 67
Reconsider using citation #21 here (is broader). Retain citations #22 and #23.

 

Lines 69 – 70
I recommend revising the paper () that explore the relationship between acoustic parameter (Lowest peak frequency) and body size and territoriality in Oropendolas displays.

 

Lines 72 – 81
This paragraph is totally disconnected from the previous texts. Use connectors and rewrite ideas at the end of the previous paragraph and the start of this paragraph to provide more continuity in the reading. Anyway, consider my first comment about the real value of “citizen science” in your study. This paragraph requires a reorganization to justify this focus in your work.

 

Line 82
Reconsider (or explain) the term “citizen scientist” in this line. Are all birders making playback citizen scientists?

 

Line 95
which was the geographic scale of the study? The complete distribution of the specie? Only some regions (which)?

 

Line 96
If your objective is to note the role of citizen science in this research, you should define which records come from citizen science activities and which from other sources (research projects not involving citizen science). Not all records in the libraries come from citizen science. However, Xeno-Canto may involve records from citizen science projects (see https://xeno-canto.org/article/195)

 

Lines 101-103
How was the protocol to select this quality (low signal-to-noise ratio)? Do you perform measurements or indexes on the distribution of energy in the frequencies in the sample? Please explain.

You should provide details about post-playback recordings selection criteria. Do you inspect the metadata? what happens with “pishing” (there are not included?). Please give many details as possible of the process of selection of post-playback recordings.

 

Line 105
Explain why you choose <300 km

 

Lines 115-116
The recordings represent a unique individual (88 recordings = 88 birds ?), right? Please clarify.

 

Lines 127-129
The redaction of the idea looks confusing: “We did not calculate the song rate for 4 recordings that were composed of two or more recordings of the same bird separated by silent periods.”. To calculate the song rate do you need several songs from the same individual, I interpret this sentence as contradictory.

 

Line 131
Rewrite the sentence, it is confusing: "19 pairs of post-playback recordings" or "19 pairs of ONE post-playback recording?"

 

Line 132 - Figure 1
Add the power spectrum.

Secure the time includes the complete signal in the spectrogram, there is a fragment of the last note out of 1.5 s.

Use the same scale: 0.5 s instead of 500 ms.

 

Line 139-140
Unnecessary and confusing. Why highlight that duration and median frequency were measured for all recordings? Does that mean that the remaining variables were measured only for a subset of recordings? Please clarify.

 

Line 143
Citation is needed for the explanation of variables.

 

Lines 147-148
So, do you perform an analysis for time (duration) using 256 and for frequency measurements a window of 1024? please provide more details of this method.

 

Lines 165-166
Is not clear why you performed two analyses for the same approach (testing for differences in frequency measurements among post-playback and spontaneous song). Even the results end with the same conclusion (no differences). The multivariate approach is interesting when you have several response variables since you perform individual paired comparisons (t-test) you increase the error acceptance in each analysis. Another approximation is to select the most important (biological) variables for a follow-up individually paired t-test.

 

Line 164
Please, provide a more detailed explanation of the analysis. Since is not provided information on the geographic range of the data, it is still unclear to me if you consider the distances within all or within the same region/locality. Geographic variation may be masking differences. As I understand you corrected the effect of geographic distance, but this applies only to each paired recording (spontaneous vs post-playback). However, when you get the mean of each group do you consider the geographic distances among each paired block? If not, you need to include the effect of geographic distance in your analysis.

 

Line 182
Did you want to say, “amplitude threshold-based frequency”?

 

Line 185
Write the results of song duration before presenting the follow-up analysis (sound density and silence).

 

Lines 185-188
I recommend plotting these follow-up analyses also (sound density and silence).

 

Lines 191-192
Move statistic results to the main text and prefer to use symbols (letters or asterisks) to indicate the differences among groups in the figure.

 

Lines 207-209
To secure this affirmation you should perform an analysis of the feasibility of the data, test quality, and detailed description of the data. For example, compare several datasets, compare between platforms, and compare among regions (there are not the same policies of motivation to perform citizen science. Then, your assumptions come from the anecdotic experience to use this set of data instead of an analytical quality of data. Your work is important and shows some difficulties but is not an analysis of the use of the data. You need to reconsider the discussion about this point.

 

Line 229-231
What is in the metadata about the habitat of each recording? could you see a relationship with this to support your point?

 

Line 261
You are using data from the repository (not necessarily all data come from Citizen Science activities). Despite your found limitations, the discussion should be supported with an analytical approach, where you compare a test the value and factors and the quality of the data. However, your work does not explore that dimension and much of your discussions on the aggression results may have several connotations based on the unstandardized protocols of playback procedures and the lack of metadata associated and a solid foundation based on methodological issues.

I recommend broadly refocusing the discussion, is not clear what you want to show if differences between spontaneous and post-playback songs or the limitless use of data from repositories in studies of playback.

 

Line 293
Homogenization of bibliography. Some journals are presented as abbreviations others as complete names.

Scientific names in italics

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting manuscript on the possibility of use citizen science approach as a source of data for showing how playback (used for recording stimulated birds) affects the response of birds, by the meaning of changes in their song characteristics. 

 

The topic is interesting and also controversial. Firstly, I am basically against using playback for recording birds, especially by amateurs. We do not know for the majority of bird species how the playback influences their normal singing activity. We may extrapolate knowledge from other species, but ... how many bird species were already tested with any playback under scientific rigour, 2-5%? Recordings after the playback without a rigorous methodological approach could be useless. For example, if we do not know what and how in the signal encodes aggressive motivation.

Secondly, it is well known that even short playback may affect birds' behaviour by meaning hormonal changes etc. Recording with the use of playback could be as harmful as sitting two meters from the nest to take a snapshot of parents feeding nestlings.

I appreciate this manuscript, but I would suggest strengthening the message that it would be better not to affect birds by playback before recording!

 

According to the chosen species and discussion on the results... I like it. Interpretation of the results is reasonable, Authors are aware of the limitations of the methodology, and cited papers are well selected and reflect the state of knowledge. What I can suggest changing (or rather develop) is the issue of "changing frequency of song in response" to a rival. It is likely not a prevailing response pattern in most birds tested. Alternatively, it could be an overlooked phenomenon, as in a majority of playback experiments, researchers tended to focus on song rate, duration etc.

On the other hand, birds with discrete repertoires often produce song types which strongly differ in frequency. Hence, it seems that within some bandwidth, it is not a challenge to them (at least for many songbirds). Instead of changing song frequency, they may simply respond with a lower song type... if it mater. This manuscript came to me just after I conducted with my colleagues experiment in which we tested responses to lowered and increased frequency songs (within species' natural limits). I may say that we have got great results suggesting that in most cases, responding males did not approach the "larger" (low frequency) and did approach and respond quickly "smaller" (higher frequency) intruder. In a few cases, we observed attempts to lower song frequency which resulted in producing bizarre songs, probably due to the inability to lower frequency without changing other aspects of the songs. This was a non-learners, but anyway, these results show some limitations. Coming back to the results presented in this manuscript... we know nothing about playback used for forcing birds to respond, how long it was, what was the quality, was the song used derived from an aggressive or submissive individual etc. Therefore, interpretation of such recordings is really like guessing what has happened.

 

105 - "Nearby" city with a distance up to 300 km is quite a lot. Please, comment on the possible geographic variation in the song of this species. Are there any dialects or any other form of spatial variation in signal?

 

166-167 - Why didn't you use a mixed model with all raw measurements and male identity included as a random factor? According to the analysis, I would probably choose a different way. Firstly, I would check correlations between different measures of the song, then I would use principal component analysis... if possible, and then mixed model:

song parameter ~ [spontaneous vs post-playback] + time (of the year) + time (of the day) | (1- identity of paired recording).

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thanks to the authors to follow the suggestions. I am pleased with the response to my questions and their justification. I found a significant improvement in the manuscript.

The correction of the sense in the focus of citizen science let me comfortable.

I appreciate the inclusion of a new figure (Figure 1) to show the geographic scale of the study.

I consider this a novel study that lets us rethink the value of acoustic libraries in the study of animal behavior.

Just one suggested adjustment: In the legend of figure 3, indicate what each letter refers to.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

I can't see changes relevant to my opinion about the manuscript. So it is hard for me to assess how it was improved. if I am right... it was simply not improved. However, even in case my remarks were not convincing authors... they should respond. Otherwise, reviewing makes no sense.
I agree that this is an interesting topic to present, but I do not think that the method presented is the right way to collect data on birds' behavior in general or even in a wider scale.

Author Response

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Author Response File: Author Response.docx