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Dear Dr. Blanco,
Thank you for your submission to PeerJ.
I am writing to inform you that your manuscript - Effects of a recent volcanic eruption on the isolated population of the iconic Red-billed chough in La Palma, Canary Islands - has been Accepted for publication. Congratulations!
[# PeerJ Staff Note - this decision was reviewed and approved by Patricia Gandini, a PeerJ Section Editor covering this Section #]
Dear Dr. Blanco,
Thank you for submitting the revised manuscript. The reviewers were satisfied with the efforts made to revise it. There are still a few suggestions made by reviewers that were not addressed in the revision. Please consider minor suggestions made by reviewers and submit the revised manuscript.
I congratulate the authors on their major revision. In particular, the authors have strengthened the introduction and included some modifications to the statistical analyses part of the methods. The manuscript is much improved, and I appreciate the authors’ responses to my questions, comments, and concerns. I have a couple follow up questions about the statistical analyses, results, and Figure 2 that I have included below.
I thank the authors for their changes as well as the addition of an explicit hypothesis tested in their investigation, and the authors are cautious in their interpretation of unclear results. My questions regarding the statistical analyses part of the methods have been addressed, but I have a couple follow up questions on this part.
Comment 1: I thank the authors for their response about my question regarding model overparameterization. However, I would still like some additional clarification about some of the variables included (are altitude and distance to the volcano continuous variables?) and how the authors chose to treat each variable as either categorical or continuous. Please include this information in the statistical analyses part of the methods to clarify this aspect of the models to readers.
Comment 2: I appreciate the additional information on the ash accumulation radii, but it is still unclear to me what the authors mean by “alternatively including” the orographic barriers and accumulated ash. Do the authors mean that either one or the other was included? Please clarify.
Comment 3: I thank the authors for their response about why they analyzed both the change in number of birds/breeding pairs as well as the total numbers after the eruption, but I have a follow up question. Based on the authors’ hypothesis, I believe that the former (change in number of birds/breeding pairs) helps to respond to this hypothesis, but I don’t understand how analyzing the total number only after the eruption helps to address the hypothesis, and I have some concerns about whether this method of analysis could be misleading. For example, if the total number at a particular site was very high before the eruption but decreased to a moderately high number, it could appear that the number of birds/breeding pairs was still high in an area when, in fact, it was severely impacted by the eruption. Please provide clarification about the justification on why the number after the eruption was included.
I thank the authors for their response to my comment about including additional detail (which is already included in the tables) in the results section and I respect their decision not to do so. However, I still cannot find information about the floater populations in the results section or tables of the manuscript. Please include these results in either the results or tables, or remove the discussions about floaters from the manuscript (this could be preferable since the “before eruption” measurement of these birds was many years before the eruption so the change could be related to many variables other than the eruption).
Figure 2: I thank the authors for modifying the legend names so that they are in English, but I still see no description of the m.a.s.l. abbreviation. Please indicate this in the legend or on the figure.
The revised version of the manuscript entitled “Effects of a recent volcanic eruption on the isolated population of the iconic red-billed chough in La Palma, Canary Islands” (#100926) addresses most of the questions and comments suggested by the referees. Overall, the manuscript now has a clearer structure, providing valuable information especially in the introduction and methods.
However, the hypothesis of the work still needs to be clarified:
Lines 113-115: The authors propose the hypothesis that the eruption would have directly affected the Red-billed chough populations if lava flows destroyed nesting, feeding or roosting areas. Only the locations of roosts prior to the eruption are shown in Figure 2. However, it is not indicated that there were roosts in the areas later affected by the lava flows prior to the eruption. Additionally, there is no mention of the previous presence of nests or the species' feeding areas in these locations before the eruption. Please clarify this point.
In addition, the authors should be careful with the references section (recommendation already suggested previously but not fully corrected).
The authors have provided extra information in the methods section that helps understand the study.
No comment
The results of this work contribute to research in volcanic ecology. Additionally, the study of population dynamics in an island bird, such as the Red-billed chough, provides valuable information for future research aimed at understanding the ecology and evolution of the restricted-range species, with important implications for their conservation.
Dear Dr. Blanco,
This paper was evaluated by three experts in the field who appreciated the study and suggested it should be published. At the same time, they raised several well-informed comments that must be taken into consideration in a revision. These comments are either requests for more clarity on methods and hypotheses or more clarity on the introduction. All these comments are very clearly presented and require no additional explanation. Please revise the manuscript considering all the suggestions given by all three reviewers.
This article is well written and the text is easy to follow. Many relevant references are included, but some could be expanded upon or added in order to strengthen the manuscript (see major and minor comments below). In particular, the introduction is lacking in some detail to fully understand the context and relevance of the manuscript. The structure is clear and includes all necessary sections, and figures and tables are generally clear and have detailed descriptions (although see some small recommendations in minor comments below). The results section requires some significant modifications in order to work with the other parts of the article (e.g., methods, discussion, tables). Details about my concerns and suggested modifications are detailed below in major and minor comments.
This is original primary research that falls within the scope of PeerJ. The research question is well defined and relevant, although some minor modifications to the introduction would make it stronger (see major and minor comments below). The investigation is of a high standard although I encourage the authors to be cautious in interpretation of some results (e.g., changes in floating individuals before and after the infection, additional details in major and minor comments below). Methods are well described and in good detail, but I have a few minor comments below to strengthen and clarify some parts.
The study provides meaningful and useful results concerning the effects of volcanic eruptions on an isolated island population. However, the results section is brief and I believe requires some major modifications before it is ready for publication (see major and minor comments below). Data have been provided and metadata are understandable. Some conclusions are well stated but others could be strengthened and/or clarified once the results section is modified (see minor comments below).
This was an interesting and well written paper that would make a constructive contribution to the scientific literature thanks to its findings regarding the effects of volcanic eruptions on an isolated vertebrate population. It was surprising that proximity to the eruption and ash did not appear to greatly influence the distribution or density of chough on La Palma, and these results could help to guide future studies on the effect of eruptions on vulnerable vertebrate populations. It was also interesting that the number of choughs and breeding pairs increased in the southern part of the island compared to the central and northern parts. I have provided a number of major and minor comments below that I hope will clarify certain aspects of the study and help to produce a stronger overall manuscript.
Major Comments:
Main comment 1: The introduction is well-written and direct, which I greatly appreciated. However, it was also lacking in some key information that could help to support and strengthen the relevance and importance of the present study. For example, the authors mention that eruptions and gasses/ash can influence populations, but they do not describe any examples of this. Providing additional detail would make it clearer as to why this study is particularly important for conservation purposes. In addition, the authors do not detail any predictions and/or hypotheses about the effects of the eruption. The fact that an eruption would have negative effects on a population is implied, but the authors conduct analyses that are much more precise that simply a negative, positive, or no effect of the eruption. I suggest that in the introduction, the authors discuss the main variables they consider in their analyses and their predictions related to these variables. I believe this approach would help prepare readers for the subsequent results and discussion sections of the paper.
Main comment 2: While some parts of the statistical analyses section were clear and straightforward, others were a bit confusing and lacking some justification. First, I would have chosen to use a Poisson distribution given that these are count data. Please clarify why a log transformation was chosen and provide justification (references or other) for this approach. Second, for a relatively small sample size of roosting sites (N = 24 to 25), the authors include 5 different fixed variables in their models, many of which are categorical variables with multiple levels. Based on my limited knowledge of the field sites and dataset, I believe the full models could be overparameterized. However, the authors may have very good justifications for including all of these variables and the levels of these variables. I suggest the authors either clarify their choices (which variables they included and how they chose to treat each variable as categorical/continuous) in greater detail, providing justifications from the literature if applicable, or reconsider the number of variables included in their models. Third, the authors indicate that the presence of orographic barriers or accumulated ash is included, and that they were alternatively included in models, but this is unclear to me. What does this mean that they were alternatively included? Were all models tested with both? If they were correlated, would it not be more appropriate to choose the most appropriate variable of the two and test the effect of that chosen variable? I also don’t understand why ash at particular altitudes were considered as separate models. Please provide further clarification on these points. Fourth, the authors discuss confidence intervals in the statistical analyses part of their paper but then present p values in the results section or in their tables. Either approach is appropriate, but please ensure that the methods presented in the statistical analyses are those that are then applied in the results section. Finally, the authors model both the change in the number of total individuals as well as the number of total individuals after the eruption. I believe that either of these approaches could be appropriate, but given that the two are intrinsically related and are based on the same data, I do not understand the justification for including both. Please describe this justification, including relevant references, or select only one of these two analyses to present that data.
Main comment 3: I believe the results section requires some additional detail. Much of the results section includes data related to changes in percentages of numbers of individuals at particular roosting areas before and after the eruption. This is useful, but it would also be helpful to have descriptions of the supported models and outputs in the text of the results, even if they are available in Table 1. The authors don’t need to report all outputs, but given that they specifically discuss trending results, it could be helpful to include those values in the text itself to facilitate evaluation of the results and their significance. The authors should also include more information than simply the p value (e.g., degrees of freedom, estimates, and/or confidence intervals, depending on their approach). This information will provide important additional context to evaluate the p values. I also noticed that the authors did not discuss the floater populations in their results nor in any of the tables in the main manuscript or supplementary materials, although they did speak about them in the methods and discussion. I suggest the authors remove these parts from their manuscript entirely, particularly since the “before eruption” measurement was many years before the eruption. Alternatively, they could include the results in the results section and full data in a table, but in this case I encourage the authors to use caution in interpretation of the results given the difference in timing of data collection compared to the total population and pair analyses.
Minor comments:
L32: Authors could include a brief description of the direction of those results.
L50-56: I suggest the authors expand upon some of the examples of how eruptions can lead to extinctions and how gases/ash can influence species. This would provide stronger justification for the present study.
L56-62: This sentence seems of two minds. First the authors state that effects are documented in different ways (what ways? please explain), then the authors state that the effects are largely unknown. Consider reworking this sentence to make the purpose clearer.
L65-66: How could the most recent eruption have occurred in 2021 but then was reported upon in 2008 (Carracedo 2008)? Please explain or revise accordingly.
L70-77: The authors indicate that ash fell on some neighboring islands, but it is unclear if the ash affected the La Palma. Where is the impact being analyzed by multidisciplinary teams? Across all islands or neighboring islands? Studies have focused on the impact on what area? Please clarify.
L80-81: This sentence is a bit unclear. How do the areas directly affected by ash differ from the content of the present study? Please further explain how the present study differs from other studies, and please cite the other studies that have been conducted that did study direct effects of lava and ash on vertebrates.
L85: Evocative power is a strange wording. Please revise.
L90-91: Please provide additional explanation and corresponding references as to why this is important to the species conservation. Is it a very active volcano? Are eruptions frequent and/or powerful? Or is it due to the proximity of the volcano to the isolated population?
L94-98: These two sentences seem to repeat the same information. In addition, it is unusual to provide information about results at the end of the introduction. Consider revising or removing these sentences.
L108-110: Please provide a citation.
L115-116: Please briefly describe the evidence that supports that it is an isolated population.
L121: Suggest revising persecution word choice.
L123: Suggest briefly describing the relevance of roosting sites to chough natural history.
L135-137: Please provide a citation.
L144-146: Were winter counts conducted as part of this study as well? Please clarify.
L154: Please briefly describe these methods.
L155: Please indicate what proportion of the monitoring season consisted of bad weather days when monitoring did not occur.
L156-157: Did these counts only occur in a single year? Why did they only occur in April (if breeding occurs in May as well)?
L165-170: Perhaps it is because I do not study communally roosting species, but I was not able to follow this part. How were isolated pairs identified as isolated and not part of the flock if they roosted in the same location as the roosting flock? How does this then relate to uncounted sites, if they are roosting with communally roosting flocks? Also, please provide the quantification of the number of isolated pairs in the population identified by the present or previous studies.
L171: It could be misleading to call these changes “post-eruption” because although the authors clarify that this is not assumed to be volcano induced, the name in and of itself implies the effects of eruption on the count. Please reword the name of this count in order to make it crystal clear to readers that counts of the floating population were not along the same time frame as the breeding pair and total population counts.
L183: Please specify what about the volcano. The center of the volcano? The leading edge of the lava flow? Please also provide justification for the relevancy of the chosen point of the volcano.
L186: Please provide justification for this measure. Is there support that the altitudinal distance is a good estimate of exposure to emissions? The authors discussed trade winds earlier in their article, and I imagine this could have a significant effect on exposure (or lack thereof), potentially much greater than the altitudinal distance.
L186-188: Is there support for using this type of measure to quantify ash exposure? Also, please clarify when this quantification occurred with respect to the eruption and why this timeframe was chosen.
L254: The wording is confusing here. Therefore implies that determining the impact is a challenge because of the impacts of volcanic eruptions (previous sentence), but then the authors go on to explain why determining the impact is challenging in the sentence L254-256. Please revise.
L257: Did the authors truly test the size of the overall population? My understanding is that the authors tested how the eruption affected particular roosting sites of a population. Please clarify here.
L264-266: I encourage the authors to include this information in the introduction as well, as it was unclear whether and how much ash fell on La Palma itself.
L278-280: It is unclear to me how traveling long distances to feed, roosting sites, and the effects of the eruption are related to one another. Please provide a little additional detail to clarify this point.
L283-284: Please clarify what the authors mean by “most” and “least” affected (e.g., what specific results does this conclusion refer back to).
L285-294: I think this is an interesting point, but given that the authors do not have the necessary information or data to test this hypothesis, I suggest removing it from the discussion.
L295-318: I suggest greatly reducing this section due to the fact that it is very difficult to relate any population changes in floating individuals to the eruption, since the “before” eruption counts date to many years before the eruption.
L326: Generally, sentinel species have low mobility, thus causing them to be a good indicator of local conditions since they are unable to move much. I would revise this sentence to clarify or remove it.
Figure 1: For part (c), I suggest the authors make it clear on the figure when the pre eruption measurement was collected for the floaters.
Figure 2: For part (a), please modify the legend names so that all are in English and state what m.a.s.l. stands for in the figure description.
Figure 3: These data should be included in the results section and potentially in the form of a table if the authors wish to keep the data in their paper.
This paper investigated the effects of a recent volcanic eruption (Tajogaite, island of La Palma) on the population structure of a native corvid species (Red-billed chough, Pyrrhocorax pyrrhocorax). The manuscript is clear, easy to read, and well-structured. Furthermore, its objectives focus on answering an interesting question: how a geological event of such magnitude affected the population dynamics of an island bird.
1. However, I would suggest including a hypothesis stating the authors’ expectations for the results based on the environmental variables considered, as well as on their prior research and knowledge about the species. In this sense, some additional information from volcano ecology conducted on birds (e.g. Williams et al. 2010; Alarcón et al. 2016) could help to better understand the context behind the study.
2. Authors must have a scrupulous care to format the references fully to Peer J. style. Further, you should be sure that all papers in the References are cited in the text (eg. Alarcón et al. 2016; Bonadonna et al. 2022; Mann et al. 2021, among others), and vice versa (eg. Cade 2015; Banner and Higgs, 2017; Mollie et al. 2017).
3. All figures must be appropriately labelled in the text.
Fig. 1d is Fig. 2a (Line 125).
Fig.1c is not cited in the text. Authors could consider to include it as an additional figure.
This work contributes to the knowledge of the short term effects of the volcanic impact on the populations of an island species, analysing data from pre- and post-eruption censuses, as well as different environmental variables, to assess the distribution and number of chough individuals through linear model analysis.
1. I would suggest providing additional details so that readers clearly understand the approach and assumptions of the analysis used (eg. type/s of linear model, distribution of the response variable, model validation methods, etc.)
The discussion clearly reflects the difficulty of studying the population dynamics of a species taking into account the critical moment of an eventual volcanic eruption.
1. I suggest adding some comments about the difficulties of undertaking this type of study at the time the eruption occurs (see Nogales et al. 2022). This reference also provides some observations on the behaviour of the species under study during the Tajogaite eruption that could be cited.
The authors also highlight the logical limitations of their results and provide suggestions for future studies addressing the long-term effect of volcanic impacts on island biotas.
This work contributes to research in volcanic ecology, with clear objectives. The fact that the volcanic eruption had no apparent effects on chough populations is a very interesting result, given that it is an island species with limited territory and resources.
1. However, some aspects must be clarified: a defined hypothesis and a more detailed description of the statistical analyses used. On the other hand, the authors are missing providing any progress on behavioural data (dietary, social, etc.) from field observations carried out during the time of the eruption. In any case, it would be interesting to provide information on the limitations of field research.
no comment
no comment
no comment
The manuscript “Effects of a recent volcanic eruption on the isolated population of the iconic Red-billed Chough in La Palma, Canary Islands” by Blanco et al presents the results of before and after surveys of the chough following a volcanic event in the winter of 2021.
I think the paper makes a good contribution to our knowledge of how birds can react to volcanic eruptions, especially on islands where dispersal is limited. Although no known roosts were destroyed by lava flows, the authors assessed the potential indirect effects of ash fall and fumes. Ultimately, the authors did not find any significant effect from the eruption, which is a valuable finding for the overall conservation of island bird species.
My largest comment is I found the Methods for the surveys difficult to follow. See my comments below. I think the authors can provide more details and better structure the methods to make their field methods clearer to the reader.
Line 140: you say non-breeders were surveyed during the breeding season (April-early May): I assume that very short period of time is when the surveys were conducted, not the length of the breeding season? What is the core breeding season date?
Line 147: Authors state that communal roosts can shift locations each year, which could have a significant impact on the findings of this study. Methods describe counts at known sites, but the previous count had been 2-3 years earlier. Would be nice to have a little more detail and assurances that the majority of roosts were found.
Line 156: “A sample of cliffs used as communal roosts…” I am not sure how these surveys fall in with the other. In the previous paragraph, that authors said it was necessary to locate all roosts, but here you talk about “a sample”(assuming some subset of all). You then mention a territory was considered occupied by a breeding pair if breeding behavior was observed, but there is no indication of home much time went into observations and if systematic across sites.
Lines165-170: Sounds like some pairs near roosts were not counted during winter counts, but not clear why not counted and how consistent that was recognized. Next sentence says isolated pairs represent a small portion of wintering population, but I thought the winter counts were to count all birds. Why exclude these pairs?
Lines 173-174: Here you say the pre-eruption breeding season count was conducted in 2004, but figure 1c seems to indicate the pre-eruption survey to have occurred in 2019?? Or is the figure referring to the cliff surveys (April 2019), but then I am confused on
Line 221: I cannot find in the results the use of the cliff roosting data.
Other comments:
Line 85, “evocative power” is an unusual term, perhaps trying a different phrase
Line 214: I did not do a literature check, but these 2 citations (Cade 2015, Banner and Higgs 2017) were not in the lit cited section
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