Many bird species participate in mobbing in which individuals approach a predator while producing conspicuous vocalizations (Magrath et al. 2014). Mobbing is interesting to behavioral ecologists because of the complex array of costs of benefits. Costs range from the obvious risk of approaching a predator while drawing that predator’s attention to the more mundane opportunity costs of taking time away from other activities, such as foraging. Benefits may involve driving the predator to leave, teaching relatives to recognize predators, signaling quality to conspecifics, or others. An added layer of complexity in this system comes from the inter-specific interactions that often occur among different mobbing species (Magrath et al. 2014).
This study by Salis et al. (2023) explored the responses of a local bird community to mobbing calls produced by individuals of two common mobbing species in European forests, coal tits, and crested tits. Not only did they compare responses to these two different species, they assessed the impact of the number of mobbing individuals on the stimulus recordings, and they did so at two very different times of the year with different social contexts for the birds involved, winter (non-breeding) and spring (breeding). The experiment was well-designed and highly powered, and the authors tested and confirmed an important assumption of their design, and thus the results are convincing. It is clear that members of the local bird community responded differently to the two different species, and this result raises interesting questions about why these species differed in their tendency to attract additional mobbers. For instance, are species that recruit more co-mobbers more effective at recruiting because they are more reliable in their mobbing behavior (Magrath et al. 2014), more likely to reciprocate (Krams and Krama, 2002), or for some other reason? Hopefully this system, now of proven utility thanks to the current study, will be useful for following up on hypotheses such as these. Other convincing results, such as the higher rate of mobbing response in winter than in spring, also merit following up with further work.
Finally, their observation that playback of vocalizations of multiple individuals often elicited a more mobbing response that the playback of vocalizations of a single individual are interesting and consistent with other recent work indicating that groups of mobbers recruit more additional mobbers than do single mobbers (Dutour et al. 2021). However, as acknowledged in the manuscript, the design of the current study did not allow a distinction between the effect of multiple individuals signaling versus an effect of a stronger stimulus. Thus, this last result leaves the question of the effect of mobbing group size in these species open to further study.
REFERENCES
Dutour M, Kalb N, Salis A, Randler C (2021) Number of callers may affect the response to conspecific mobbing calls in great tits (Parus major). Behavioral Ecology and Sociobiology, 75, 29. https://doi.org/10.1007/s00265-021-02969-7
Krams I, Krama T (2002) Interspecific reciprocity explains mobbing behaviour of the breeding chaffinches, Fringilla coelebs. Proceedings of the Royal Society of London. Series B: Biological Sciences, 269, 2345–2350. https://doi.org/10.1098/rspb.2002.2155
Magrath RD, Haff TM, Fallow PM, Radford AN (2015) Eavesdropping on heterospecific alarm calls: from mechanisms to consequences. Biological Reviews, 90, 560–586. https://doi.org/10.1111/brv.12122
Salis A, Lena JP, Lengagne T (2023) Acoustic cues and season affect mobbing responses in a bird community. bioRxiv, 2022.05.05.490715, ver. 5 peer-reviewed and recommended by Peer Community in Ecology. https://doi.org/10.1101/2022.05.05.490715
DOI or URL of the preprint: https://www.biorxiv.org/content/10.1101/2022.05.05.490715v4
Version of the preprint: 4
Dear recommender,
Please find the manuscript with a formatting helping scientific readers. We changed the word '15' to 'fifteen'. Thank you again for all the advice given to improve this manuscript.
Dear Ambre Salis,
Thank you for your revisions. As soon as you post your re-submission, I will recommend this preprint.
I have one small editorial request - on line 282, please change “15” to “Fifteen” because it is the start of a sentence.
Sincerely,
Tim Parker
DOI or URL of the preprint: https://doi.org/10.1101/2022.05.05.490715
Version of the preprint: 3
Dear Ambre Salis,
Thank you for your revision. I am prepared to recommend this pre-print after you make a few small edits to improve clarity.
I look forward to seeing the final manuscript.
My suggestions follow by line number:
103: “playbacks” should be “playback”
also, “is” should be “in”
113: insert “)” after “hops”
250: This statement “The two main species, apart from coal and crested tits, were…” is, to me, misleading, since it suggests that both coal and crested tits responded more often than goldcrests, but from fig 1A, it seems that only crested tits were more common responders than goldcrests.
251: Here and elsewhere, I encourage consistency with bird name capitalizations. Given that you do not capitalize coal tit or crested tit, I suggest you not capitalize goldcrest, marsh tit, or others.
283: could you state the rates of occurrence at playback of coal tits and crested tits relative to goldcrests and chaffinches.
Also, I am confused – given the number of crested tits responding was higher than the number of goldcrests (according to Fig 1B), how is it that goldcrests responded 24% of the time and fewer than 25% of trials had any response? This suggests that goldcrests responded in (almost) every case where there was any response from any species – is that correct? Also, does this mean that most of the trials with crested tits responding had multiple individuals responding, and so the percent of trials with crested tits responding was not higher than the percent of trials with goldcrests, even though the total number of trials with goldcrests responding was higher than (or as high as) the number with crested tits?
319: change “per treatment” to “across treatments”
334: change to “middle graphs are responses”
380: change “modulates” to “modulate”
Also, I don’t think we have sampled widely enough across birds to say “usually” here. Maybe say “often”. Or maybe say something like “Where it has been studies, birds usually …”
427: insert “a” before “’community’”
443: change “explore” to “explored”
483: insert “support for” so that this reads “we found support for different models”
Sincerely,
Tim Parker
DOI or URL of the preprint: https://doi.org/10.1101/2022.05.05.490715
Version of the preprint: 2
DOI or URL of the preprint: https://doi.org/10.1101/2022.05.05.490715
Version of the preprint: 1
Dear Ambre Salis,
I apologize for the delay in providing these comments. By the time I received the second review, I had left on holiday for much of July.
Two independent reviewers and I have read your manuscript (Acoustic cues and season affect mobbing responses in a bird community). The reviewers and I all see value in this study. I appreciate the use of a thorough design to simultaneously evaluation multiple potential influences on the response to mobbing calls, the large sample of trials, and the evaluation of an important assumption of your experiment. However, we also all identified some important areas where improvements are merited. I have provided some detailed comments below and both reviewers provided detailed suggestions as well. Please carefully consider all these suggestions and either implement the suggestions or explain why you have not done so if you chose to resubmit a revised manuscript.
Before providing my detailed comments and those of the reviewers, I want to call attention to several points that are particularly important.
Both reviewers noted that group size may not be expected to correlate with the reliability of mobbing calls. I encourage you to explore the literature on this subject further, and to update your discussion of this topic.
Reviewer 1 and I both felt that your explanation in the main text of the supplementary experiment (done to assess the likelihood of overlapping responses between playback locations) is insufficient. I encourage you to either bring this experiment to the main document, or at least to provide more details in the main document.
Reviewer 1 and I also wanted to see more information about the 3-bird playback stimuli. Besides addressing the questions of Reviewer 1, I encourage to consider adding the stimuli and the sound spectrograms of the stimuli to your supplement.
On a related topic, both reviewers and I share the concern about your interpretation of the 3-bird stimulus due differences in duty cycle between the treatments.
Reviewer 2 identified several important issues related to your statistical analyses, including a model convergence error (which I also replicated when I ran your code). I do not believe there is only a single correct way to analyze a dataset, but I would like you to seriously consider Reviewer 2’s recommendations and concerns.
Sincerely,
Tim Parker
What follows are some specific concerns that I noted as I read the manuscript (organized by line number):
41: “We therefore confirm the hypothesis” – should be something like “We therefore find support for the hypothesis”
161-162: when a bird was detected in the area, what was your protocol? Did you wait for it to leave or move to another location?
113: How did you determine the order in which you visited survey locations?
159: How did you resolve differences in observations between observers?
174: please explicitly state that you excluded cases of zero detections from the intensity analyses
177: which versions of the lme4 R package? Also, please cite the package (e.g., ‘Bates et al….’ for lme4).
179: if you decide to remain with analyses using Poisson error (instead of taking the suggestions of reviewer 2), you should report the details of your test for overdispersion.
183-185: This sort of step-wise procedure can lead to biased model estimates (see Forstmeier and Schielzeth. 2011. Behav Ecol Sociobiol 65:47–55). Given that you present full models, it is not clear to me why you were using a step-wise procedure.
189: again, more information needed about packages
Table 1 vs. Table 2. The first table in the text is labeled ‘Table 2’, but presumably it should be labeled ‘Table 1’ – it seems that when you cite Table 1 in the text, you are referring to the table currently labeled ‘Table 2’
Table 2 (as currently labeled): Why do you not present number of mobbers results for coal and crested tits? You seem to have that information in another form in Figure 2.
Table 1 (as currently labeled): The heading says “propensity and intensity”, but the content of the table looks like only one or the other, but definitely not both.
Table 1 and Table 2/ Figure 2: You currently only present the estimates in graphical form. It would be useful to present the actual numbers (either in an expanded form of Tables 1 and 2, or maybe in a table in the supplement).
Table 2: ‘NB’ should be defined in the heading
338: You should more explicitly acknowledge the limitations of your experiment here (duty cycle not standardized).
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