PONE-D-22-11852Interspecific synchrony on breeding performance and the role of anthropogenic food subsidies.PLOS ONE

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Reviewers' comments:

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1. Is the manuscript technically sound, and do the data support the conclusions?

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Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I’d like to thank the authors for creating this interesting article, that takes an original look at the phenomenon of anthropogenic food subsidies in vertebrate populations, adding the community aspect, which is rarely assessed in this context. I enjoyed reading it, it is well-written, and I believe the methods are sound. My main criticism would be that the time series is still too short to confirm certain trends that are suggested in the discussion. On the other hand, we can’t wait for decades to report on demographic monitoring trends when they concern aspects relating to the short and mid-term consequences of policy changes on wildlife. I refer to my detailed comments on the discussion for what I think might be a bit weak in terms of conclusions. I believe this manuscript is fit for publication after minor revision. I look forward to a revised version.

Detailed comments:

L46-67 This general introduction to synchrony, and its focus on intra-specific, inter-population synchrony, is a bit too long and far-reaching. Could the authors try to shorten it, perhaps into a single paragraph?

L68 replace “have” by “having” or “despite that”

L76 ‘considerably’

L78-79 I don't see how one follows the other: synchrony is a useful indicator of environment state because breeding parameters reflect environmental conditions?

L84 “These subsidies”

L89; 95-96 I suggest to avoid an ambiguous use of the words “nature” and “natural”

L92 perhaps replace “species” by “populations”?

L 97 The term "subsidy" has other connotations when used in combination with "EU" (i.e. economic incentives). How about replacing it by "waste" or "food waste"?

L101 “aiming for the termination”

L103 “a ban on fisheries discards”

L104 delete “experimentally”. Also “aim to modify”

L105 “of anthropogenic food subsidies for wildlife” Please be generous with the non-specialized reader

L111 “waste becoming inaccessible”

L124 sympatry: if the nesting grounds do not overlap, do the home ranges overlap? How much does the spatial niche of these species actually overlap?

L152 do we have any evidence for a relationship between maternal investment and breeding success in these species? If not, references to works on similar species may instead be cited

L158 replace ‘despite’ by ‘although’

L159 replace “necessary” by “necessarily”

L172 delete “we used we used the”

L181-183 do you mean by this that you included the interaction between NAO and your proxy for synchrony in the full model? Please state explicitly which interaction were included and to what end

L187; 206; 223 I’m afraid I’m misinterpreting the figure… but it seems like synchrony is observed only in 5 years after landfill closure? But you consistently mention a 7-year synchrony period throughout the manuscript. Can you please clarify this to me in the rebuttal letter?

L209 “decreased”

L210 replace “were” by “was”

L211 Perhaps be a bit more explicit on what this event was: "After closure of the open-air landfill, and consequent disappearance of a main local source of anthropogenic food subsidies, ..."

L213 – 214 ‘the foraging strategy of one species’: I’d rather explicitly say here “of the species so far relying on the disappeared subsidies”. I feel like the more interesting trends are here given by Lm, while the discussion is treating both species equally.

L214 “and/or”

L214-215 do the numbers (nLm and nCd) reported in Table A.1 reflect total population size of the study colonies? Are there discernible trends in these population sizes, particularly in relation to the closure of the landfill?

L223 ‘time associated with acquiring’

L224 so this reported synchrony is interpreted as symptomatic of a decreased efficiency in the use of the surrounding landscape by the Lm's nesting in Dragonera?

L231 so marine productivity increases under more positive NAO conditions? It would be helpful if either in the introduction or earlier in the discussion a short explanation is provided on what NAO is and what it most probably implies from the point of view of breeding seabirds.

L233 “carry-over”

L235 What would be the mechanism linking population size change to synchrony in maternal investment? I fail to understand how the latter would be a consequence of the former without more details. Is it that Lm reproductive individuals exploiting garbage migrate away from the population, with only those Lm individuals that respond in their reproductive performance similarly to Cd remaining in the colony? I feel like abstract terminology is sometimes getting in the way of the interpretation of results in this discussion.

L239 is there any reason to suspect a similar (interspecific interaction) mechanism to be at play in this context? If so, which one exactly? Feeding competition at sea?

L249 "non-linear dynamics": Please be more explicit on exactly what you claim to prove. Are you saying that we have evidence that the sudden disappearance of food subsidies induces in itself a response in population dynamics that would not be expressed if this disappearance had been gradual? What is this claim based on?

L252 Did we previously not think that anthropogenic food subsidies buffer natural variability in population dynamics of the species exploiting them? And that this had consequences on the community dynamics? In the introduction it was expected, based on previous knowledge, that the population so far relying on subsidies would respond to environmental fluctuations more similarly to a population that did not rely on subsidies, because these subsidies decouple population dynamics from non-anthropogenic environmental variation. I would rather argue that the results confirm this already existing theory from a novel point of view: they highlight its consequences

for phenomena of interspecific population dynamics such as synchrony in breeding performance.

L256 I would also add somewhere toward the end a caveat regarding the interplay between trends in (breeding) population size, breeding performance, and (anthropogenic and non-anthropogenic) resource availability, particularly in open populations where it is unclear whether fluctuations in resource availability translate more into shifts in species' range or population size.

Figure 1 the letters indicating the subsections of the figure (a;b;c) are not represented on the figure. The bird drawings in the legend are not very informative, especially for the reader unfamiliar with how these species look like, perhaps the species name could be added here?

Figure 2 please state what the line and greyed area represent

Table 1 I don't see “np” in the table, but the "df" field is not referred to in the caption. same comment applies to table C.1

Table A.1 So these are the same values represented in figure 1? Can you please provide the SE for egg volumes?

Table C.2 For Sync and NAO, would it be possible to report on estimated marginal means instead of estimated differences from the baseline values?

See https://cran.r-project.org/web/packages/emmeans/vignettes/models.html#I for compatibility with the used modelling procedure

I’d finally like to thank the authors for sharing the code for their analyses.

Reviewer #2: This study aims to look at the synchrony of breeding investment in two seabird species following a change in food subsidies. While the question is relevant and interesting to the field, the authors fail to clearly presents how the address the question and how they answer their hypothesis. I also have major concerns on the statistical analysis. I appreciated the supplementary material which were very informative, but I think some of this information has their place in the manuscript itself. I suggest the manuscripts needs major revisions prior to publication.

Major comments:

1. Authors brings this idea of subsidy-decoupling hypothesis, yet fail to address it in their own study hypothesis, and prediction but most especially in the discussion. Most importantly, they fail to clearly show how their analysis answers the hypothesis or research questions. Authors use a lot of scientific terms without defining them or giving concrete examples that could help an uninformed, novice and even experienced readers to understand the claims made in the study.

2. Authors use mean egg volume per year as their experimental unit, as a proxy to breeding investment. I think this is concerning in several ways:

a. Gulls lay three eggs. Therefore, those three eggs are not independent from each other, as they are part of the same breeding investment from the same gull pair. Not only this is a problem on itself, but the size of the egg may very with the order they are laid, most especially the third egg which is often smaller than the first two. This may lower the mean egg volume per year.

b. Shearwaters only lay one egg. Comparing the volume of that one egg with eggs produced within a clutch is not statistically correct as sampling units differ between species. You could use the volume of the largest egg per gull clutch or calculate a volume per nest (sum of all egg volumes?). These would be a comparable measures of breeding investment with the single shearwater egg.

c. By measuring only three egg clutches, you are not really quantifying the breeding investment of your population, just the ones of the individuals who invests the most. From year to year, the proportion of three versus two egg clutches may vary. To fully compare the breeding investment of gulls from year to year, variation in clutch size would also be indicative of breeding investment in your population.

d. While your best models (the linear model with WNAO) do not include year in the model, including year and species in the same model as seen in Table C.1 (where mean egg volume per year is your response variable) is pseudoreplication (1 measure of egg volume per year and per species) and therefore is not valid. I’m also wondering why you calculated a mean per year (thus using year as the experimental unit) instead of using the nest as your experimental unit.

Minor comments:

Abstract

Consider rewriting your abstract with statistical results and your hypothesis (and whether you validated them).

Introduction

Line 46-52: Not relevant information, especially to start your introduction

Line 53-67: You talked about what affect synchrony here, yet I still don’t know what you mean by synchrony (definition at line 106-107) or what studying synchrony really brings to understanding of population and interspecific dynamics. These answers come later in the intro, I suggest putting them earlier

Line 64: … density of individuals fluctuates indenpendantly … of what? Environment?

Line 75: Add examples of demographic parameters as opposed to just breeding parameters later in the paragraph

Line 81-82: Anthropogenic food subsidies shape communities … How?

Line 87-81: Sentence hard to read. Does give us concrete example on how the patterns are influenced or the expected effects on survival and reproductive parameters.

Line 94: You are referring here to Figure 1, which is part of your results, before even stating an hypothesis. Remove mention of figure 1.

Line 110 : suggest: two sympatric avian top predators

Line 113: Why shortening Yellow-legged gull to Lm rather than just gull and Scopoli’s shearwater to Cd instead of just shearwater? Seems like if we miss that part of the intro, the rest of the paper is confusing.

Line 137: increasing the degree of synchrony in egg volume relative to years with an active landfill. I would also had a prediction about environmental buffering, which you test with general linear model, but don’t mention here with your hypothesis.

Methods

Line 151-153: Using egg volume as a proxy to breeding investment should be clear in your hypothesis as well.

Line 155-164: I’d suggest beefing up this part a little bit with some of the information provided in the supplementary material. You explain what cross-correlation and State-based Markov Chain modelling work and are relevant in your study, but not really how you used them with your data or what measure you get out of it.

Line 167-170: This part should be in the introduction

Line 175: Where is the random effect of your mixed model? According to your supplementary material, it looks like a linear model without random effects.

Line 180-181: If two model had an ΔAIC < 4, which one did you choose ultimately as your best model? The most parsimonious? By looking at table C2, looks like you averaged the estimates of your candidate model (yet no mention of this in the methods). Yet again, Table 1 shows ‘ the best model’ in bold. What are your criteria, just the AIC?

Result

Line 185-186: Can you statistically test the difference between your CC? Is there an error associated with this measure?

Line 189: AIC or AICc? Methods doesn’t mention that you corrected for small sample size.

Lines 190-192: Indicate that the values in bracket are the confidence interval and that you considered a significant effect when CI did not cross 0 in your methods.

Discussion

Line 205: This is the first (and only) mention of entropy analysis in the manuscript (excluding supplementary material). Make sure to introduce the term earlier.

Line 208-210 : This is the only sentence discussing the environmental buffering tested with your linear model. Why is it due to low sample size? No other reasons? Maybe it is because you included shearwaters (which were not affected by landfill closure) instead of testing gulls by themselves?

Line 215: Reference?

Line 218: evidence for what?

Line 241: What in your result specifically indicates transient dynamics?

Line 245: What sis missing in your study to pin-down the factors responsible to synchronization? What would you suggest for further studies?

References

Lines 314-318: This paper seem duplicated.

Figure 1:

The different states are not described in the methods (only in the supplementary material). It needs to be described for better interpretation.

Why 1.96 SE instead of 95% CI ?

Figure 2:

This figure is misleading of results since WNOA was only significant as an additive effect, thus the curve should be all points, no separation by species or synchrony.

If kept as is, put a) and b) in the same panel and c) and d) in the same panel with different shades and point shapes. Put error of data points (since it’s the annual mean in egg volume).

Table 1 and Table C.1:

-Why is synchrony in the model and not landfill closure? I know you proved that synchrony is tied to landfill closure, but here, you want to test environmental buffering before and after landfill closure and it seems to me, this variable would be more representative (and informative) than just synchrony.

-Why include shearwaters if they were not affected landfill closure? Your question is whether environmental buffering was present during landfill closure (so the difference of the Vegg~WNAO curve before versus after landfill closure). This could be answered with a simple Vegg ~ WNAO*landfill closure using the gull data only.

-Seems like you just tested all combinations of variable without consideration for biological process and relevance. See my previous comment on pseudoreplication.

Table C.2:

Indicates what bold font means

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Reviewer #1: Yes: Alejandro Sotillo

Reviewer #2: No

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PONE-D-22-11852R1Interspecific synchrony on breeding performance and the role of anthropogenic food subsidies.PLOS ONE

Dear Dr. Payo Payo,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Oct 10 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Jose M. Riascos, Ph.D.

Academic Editor

PLOS ONE

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Main comments

I thank the authors for the care and seriousness they have shown in addressing every single comment that the reviewers made in the first round. I find that the manuscript has improved and the authors have addressed my concerns rather satisfactorily. The study appears now more transparent, and I get a better grasp of the hypotheses, results and conclusions. The methods section has greatly improved, but it is still missing some important information.

In relation with the comments by reviewer #2 about the quality of the analyses performed, it would illustrate the representativeness of the sample that was analyzed if yearly estimated nesting population size, number of sampled nests and proportion of these nests that contained 3 eggs were presented. Is there any tendency between years in clutch size? Were nests monitored once per year or several times? When exactly were they monitored? Is there any information on interannual variation in reproductive phenology (advanced/delayed – concentrated/spread out laying seasons)? If concepts such as synchrony, sympatry and interspecific competition are invoked, it should be clearly acknowledged that the temporal niche does not fully overlap (interspecific differences in laying phenology). What is the difference in median laying date between the 2 species? Did it vary between years?

I have answered "partly" to the question "2. Is the manuscript technically sound, and do the data support the conclusions?" because, regarding the message on environmental buffering by anthropogenic food subsidies, the results as they are now presented do not convey this idea just by themselves. I trust the authors’ claim, but it is just not very striking from the figures and tables that they show. I suggest the authors reconsider how they want to present their evidence for this important point they make in their paper. If evidence is weak, they might want to consider removing the focus from it.

Comments on the authors’ rebuttal

Reviewer 1 “L124 sympatry: the extent of home range overlap is not known” This is not necessarily a problem, but it would be good to state this clearly: that sympatry of these populations is assumed rather than well-documented.

Reviewer 1 “L214-215” Thank you for this information. Could this be made available in the supplementary material?

Reviewer 2 “2. Authors use mean egg volume per year as their experimental unit, as a proxy to breeding investment. I think this is concerning in several ways:” Thank you for this information. Could this be made available in the supplementary material? Also, if you have information on interannual variation of clutch sizes across the study period, please provide this in the sup mat. I understand that some of this information may be found in other publications based on the same data base, but such details in annex do help the present paper stand on its own.

Comments and suggestions on the revised manuscript:

L23 I'm not sure that metapopulations are relevant enough in this case to be mentioned in the abstract, I suggest removing “metapopulations persistence”.

L35 “environmental buffering…” I'm not convinced that sufficient evidence is provided to support this claim. If the authors believe there is, they should try to highlight it more in the results (see main comments as well as comments below).

L50 replace “the correlation” by “correlating”

L63 remove “- such as egg volume –“

L64 replace “so the” by “, making”. Remove “could be used as”

L66 remove “new”

L68 “competition and predator-prey interactions”

L69 “worldwide, and”

L71 remove “potentially”

L72 “and/or”

L78 “should” instead of “would”

L80;81 does it reveal dynamics that were otherwise hidden, or does it restore dynamics that had been altered through anthropogenic impact?

L85 “decades”

L86 I'm not sure that the subsidization of some wildlife populations had a very relevant part in motivating any of both directives. In my understanding, the landfill directive was responding to a concern about environmental pollution, while the discards ban was about tackling overfishing to retain only larger-sized fish, lack of selectivity in fishing methods and a pointless source of waste. I'd rather say that the reduction of this subsidization phenomenon was a positive side-effect. But please ignore this point if the cited legislation actually states it as a main motivation.

L90 replace “is a fantastic” by “provides an”

L91 replace “ultimately aim to” by “will”

L94 replace “changes” by “variability”

L97 remove the commas around “regularly”

L99 remove the comma before anthropogenic

L107 do you mean adult survival probability?

L108 and elsewhere: I'd be rather inclined to write "The Yellow-legged Gull", particularly when opening a sentence

L113 replace “have” by “having”

L117 remove “- until 2010 –“

L145 remove “traditionally used and”

L189-191 The interactions that were considered in models should be mentioned here. The authors need to justify the biological meaning of adding these interactions

L201-202 I gather that the possible min-max range of CC is -1 to 1. Stating this explicitly gives an idea on how important this increase is.

L214 I fail to see what figure 2 is telling about environmental buffering. The authors should be more explicit as to what they are interpreting to be "environmental buffering". Is it the beta estimates for an interaction? Which one exactly? Where can the reader find these figures (which table)?

Discussion general comment: Now that WNAO has been described in methods as "High positive WNAO values are associated with the intensification of upwelling and small pelagic fish availability thus higher food availability for seabirds." I am missing a broader discussion on how the proxy for reproductive output in both species appears to be negatively correlated to this index.

L231 Sorry I don’t get the ending of the sentence: what similar drivers? Similar to what?

L234 No need to refer to figures in the discussion

L260 “is that landfill”

L272 “longer time”

L273 replace “clarification to” by “light on”

L276 see comment on L80;81

L277;278 I don't think you add any extra evidence on the pervasiveness of the impact of anthropogenic food subsidies. I'd rather say that the impacts are shown to express themselves in more compound ecological metrics such as inter-specific synchrony in breeding parameters

L280 replace “such as” by “like the” to avoid redundancy

L281;282 “or from sudden population collapses resulting from current environmental change” I find this very vague, can you be a little more specific? Do you mean that opportunities to study fluctuations in synchrony should be sought in circumstances where accelerated environmental change is known to be taking place? Like in areas suffering desertification, receding permafrost, deforestation…?

Supplementary material main comment: could the code be provided separately as a ".R" file? This way any user could just load your file instead of copy/pasting the code

Figure 2 Is it possible to add an in-figure color legend?

I thank the authors for their excellent work, and trust that after this second revision round any relevant issues will have been fixed. I’m looking forward to a second revised version.

Reviewer #2: I would like to congratulate the authors for their hard work on improving this manuscript and addressing the reviewer’s comments. Most of my concerns were address by simply clarifying the method which was greatly appreciated. The paper has improved significantly, and I only have minor suggestions.

L44: add ‘a’ before pronounced.

L50-51: Sentence is unclear. Suggestion: Intra-specific synchrony is apparent a at large spatial scale from correlated environmental conditions, the so-called ‘Moran’s effect’. I’m not sure if this is what you were trying to say.

L63-65: I’m having trouble connecting the start and end of this sentence. I suggest making it into 2 sentences: Breeding parameter – such as egg volume- often reflect conditions in the ecosystems. Therefore, using inter-specific synchrony of breeding parameters could be a useful indicator of local environment state.

Line 67: Your discussion now clearly answers your hypothesis, but I would mention your subsidy-decoupling hypothesis somewhere in your discussion.

Line 83-84: I don’t think a subsection is necessary here.

Line 93-123: This paragraph is very long. I suggest merging line 93-96 to previous paragraph and splitting the paragraph by species for the remaining lines (splitting somewhere around 108).

Line 108: Does YLG always breed close by to shearwaters or is that inly in the Mallorca region?

Line 121-123: I appreciate the addition; however, I’m still craving for more detail. Suggestion: add ‘so that egg volume is higher when environmental stochasticity is removed’ at the end of the sentence.

Line 137-138: Thank you for clarifying that you calculated the mean of egg volume per clutch prior to calculating the annual mean. Maybe mean egg volume per clutch instead? Was the annual mean used for both the synchrony and the GLM? At line 190-191, you only refer to ‘mean egg volume’ which suggest to me that you used mean egg volume per clutch and not the annual mean (which is appropriate for the GLM). If so, the annual mean should only be mentioned in the synchrony part. If not correct line 190-191.

Line 204: Add a sentence precising that synchrony stopped after 2017. This is a big part of the discussion but was not apparent to me until then.

Line 222: Correlation? Why not the actual relationship with you B estimate? Do you have an actual value of R2 to add to the figure?

Line 228-252: Long paragraph and a little confusing. I would first split at line 236. Then I would reshuffle the sentences around: all sentence mentioning overlap first, then YLG foraging strategies. I can see where you are going with this, it just lacks a clear flow.

Line 229: add ‘s’ to ‘regulation’

Line 234: Not sure if I mentioned it in previous revision, I personally don’t think figures should be mentioned in a discussion if they are properly interpreted in the results.

Line 240: ‘…could be the result of changes in foraging strategies and behaviour…’

Line 245: Suggestion: Although evidence of increase diet overlap between the studied species is lacking…

Line 253: A second explanation for what?

Line 253-259: You described the drivers of breeding success for shearwaters but not for gulls. What would be the difference between shearwater and gulls that could explain the synchrony? or environmental buffering (see comment line 253).

Line 262-263: Say what was the change in population size (increase or decrease).

Line 265-268: I suggest splitting and rewriting the sentence like this: However, we argue that the mechanisms from transient dynamic do not explain the disappearance of synchrony after seven years, and that changes in interspecific competition at sea is likely the cause of this pattern.

Typos and double spaces: Lines 231; 238; 240; 246; 254; 261; 262; 266

Figure 2: Add the value of R2. Y-axis put ‘Annual mean egg volume per clutch’

I’m curious whether you tested the leverage of the data at WNao -5. I’m concerned that it’s driving the slope of your relationship, and it wouldn’t be significant otherwise.

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Reviewer #1: Yes: Alejandro Sotillo

Reviewer #2: No

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Interspecific synchrony on breeding performance and the role of anthropogenic food subsidies.

PONE-D-22-11852R2

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