Spatio-Temporal Distribution Patterns and Determinant Factors of Wintering Hooded Cranes (Grus monacha) Population

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The Shengjin Lake and Caizi Lake are an internationally important wetland and an important waterfowl nature reserve in China. It is undoubtedly an ideal place to study the scientific aspects of the wintering habitat of marmots. In this study, the authors observed the spatial and temporal distribution of cranes and influencing factors. It is significant for the wintering behavior and protection research of cranes. So it is suitable for publication in the journal Diversity. In general, the article is well organized and has a good quality. The Abstract is well prepared and focuses on the main ideas developed in the article. The Introduction adequately justifies and highlights the importance of carrying out this study.

 

I only have a few minor comments that may help to improve the quality of the manuscript. 

 

1. The authors do not specify when the food measurements were carried out, only once, or once a month? It is not clear from the text.

2. It is recommended that the authors indicate the main types of food in the patch, e.g. which aquatic plants and benthic molluscs are present, preferably with pictures. Is the difference of food species in different habitats also a factor affecting crane abundance?

3. In the Figure 3, in the horizontal coordinates, the patch size and food biomass are missing measurement units (m² or km²; g or kg).

4. The author selected the food biomass, patch size, human disturbance and other factors to discuss the abundance of cranes. However, the author seems to ignore or fail to state clearly these issues: a. Whether other organisms (especially other waterfowl) in the habitat are disturbed; b. The author did not explain the reason why the spatial variation of crane abundance of migratory crane in different wintering periods, is the dynamic immigration of cranes? I think if the author measures the biomass of food in each quadrat every month, the change of the amount of food may also be one of the reasons.

Author Response

Dear reviewer

 

Thank you for your letter and the comments concerning our manuscript entitled “Spatio-temporal distribution patterns and influencing factors of hooded crane (Grus monacha) wintering population”. Those comments are valuable and very helpful. We have read through comments carefully and have made corrections. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript.

 

Comment 1: The authors do not specify when the food measurements were carried out, only once, or once a month? It is not clear from the text.

Response 1: We have described the details and frequency of biomass measurements. Revision positions are given at lines 124-129.

 

Comment 2: It is recommended that the authors indicate the main types of food in the patch, e.g. which aquatic plants and benthic molluscs are present, preferably with pictures. Is the difference of food species in different habitats also a factor affecting crane abundance?

Response 2: We have added a description of the main food resources of cranes in the patch. Revision positions are given at lines 130-132.

Due to the unique climate and geographical characteristics, specific food resources may often be concentrated in patches within certain periods. We did not take differences in food species into account.

 

Comment 3: In the Figure 3, in the horizontal coordinates, the patch size and food biomass are missing measurement units (m² or km²; g or kg).

Response 3: We add the units of the variables in the abscissa of the figure. Revision positions are given at figure 4.

 

Comment 4: Whether other organisms (especially other waterfowl) in the habitat are disturbed.

Response 4: The disturbance of other waterbirds has been discussed in our discussion. Revision positions are given at lines 233-239.

 

Comment 5: The author did not explain the reason why the spatial variation of crane abundance of migratory crane in different wintering periods, is the dynamic immigration of cranes?

Response 5: The crane survey in the two lakes were conducted simultaneously, and we think that the probability of crane migration between the two lakes is low. Although our study area is not the whole lake, the number of wintering hooded cranes in our study area accounts for the majority of the whole lake. The occasional discovery of a small number of cranes outside the study area is considered to have little impact on this study.

 

Comment 6: I think if the author measures the biomass of food in each quadrat every month, the change of the amount of food may also be one of the reasons.

Response 6: Cranes can well perceive the changes in food resources and flexibly select habitat patches with high food biomass in lakes. Cranes usually forage in flocks during the wintering period. They often collectively migrate to the patches which have more food resources when food resources decline. We measured food biomass in patches where cranes were present which reflects the survival strategies of cranes in fragmented habitats.

 

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

 

Sincerely,

Mr. Sun

Author Response File: Author Response.docx

Reviewer 2 Report

This study investigates the effects of food biomass, foraging area patch size, and an index of human disturbance (proximity to roads or settlements) on the relative abundance of hooded cranes during the winter at two sites in the Yangtze River floodplain. However, it is unclear what this study adds to the existing literature on Hooded Crane winter ecology, in part because the field and analytical methods are poorly explained, making it difficult for the reader to assess the validity of the methods or relevance of the results. The authors assert that this is the first paper to consider multiple factors simultaneously on hooded crane abundance/spatial distribution, but in a quick search I was able to find several studies that investigated multiple factors on occurrence or flock size (examples given below). The introduction and discussion sections contain many speculative statements and an over-simplified attempt to relate this study to optimal foraging theory. The revision should focus on providing missing details on field and analytical methods, careful consideration of what this study adds to the existing literature, and keeping the introduction and discussion sections within the (limited) scope of this study. Specific comments below:

 

Abstract

 

Lines 12-16: suggest narrowing the focus to hooded cranes rather than waterbirds generally.

 

“Previous studies [of waterbirds] focused on a single variable, and research considering multiple perspectives is lacking” – simply not true, especially as written, which implies that this is true for all waterbirds and not just hooded cranes.

 

 “The spatio-temporal distribution of the cranes differed at Shengjin Lake, but not at Caizi Lake in different wintering period.” – I do not follow. Does this mean abundance changed over time at Shengjin lake? Did the cranes use different areas? Statement needs to be more specific.

 

Introduction

 

Lines 51-52: This statement is a major oversimplification of optimal foraging theory, and is only supported by a reference with findings that geese preferred larger fields. Optimal foraging theory considers many more factors than just patch size.

 

Lines 75-77: see Cai et al. 2014. PLoS One - https://doi.org/10.1371/journal.pone.0089913 – their model of hooded crane occurrence included multiple variables related to habitat, food availability, and human presence. Also Hang et al. 2015 looked at both food abundance and human disturbance.

 

Lines 83-84 need revised for clarity

 

Methods

 

Lines 102-122. The description of survey methods is insufficient. Were there pre-defined sampling points that were set up and visited? If so, how many and how were they distributed across the study area? How many times were points visited throughout the season? As it written, it sounds more like observers must have searched the areas for cranes without any particular protocol and then mapped the location of flocks they found.

 

Line 114 – What was a “patch”? The description of food biomass sampling is also insufficient to fully understand/replicate what was done.

Line 122: “The thickness of straw covering the rice was considered as the burial depth of the food.”  I don’t understand this sentence, perhaps more context is needed. Was rice always covered in a layer of straw in the field?

 

Line 126: It’s not correct to say that calculating an average reduces the measurement error.

 

Line 129: How was distribution of food resources measured or characterized?

 

Lines 138-140: Distance to nearest road or settlement was used as a metric of human disturbance, rather than direct observations of human behavior and how it affected the birds. The limitations of this method should be discussed somewhere.

 

Lines 141-162: There is insufficient description to evaluate the statistical methods used. There is no information about model structure or the candidate model set, only how relative abundance per patch was calculated and how AIC was used for model selection. There is no information about sample sizes and it’s unclear whether there are multiple observations per “patch” at different time periods.

 

Results – The large standard error for the food biomass estimate is completely at odds with the reported P value and the narrow error bars in Figure 3b. Something looks amiss, but without more information on how the models were constructed and evaluated it’s hard to diagnose.

 

Discussion

Lines 201-202: I’m not sure this can be concluded. As far as I can tell, the study only looked at what was used, not what was available on the landscape.

 

Lines 202-205: Again, the link to optimal foraging theory is a stretch. Not sure where the purported link between patch size and habitat heterogeneity is coming from but that is certainly not uniformly true.

 

Lines 206-212: I fail to follow the logic here or to understand the relevance. Many of these statements are speculative, and if there is a clear link between water levels and patch size, it should be made clearer earlier in the manuscript.

 

Lines 231-238 – Further speculation

Comments for author File: Comments.pdf

Author Response

Dear reviewer

 

Thank you for your letter and the comments concerning our manuscript entitled “Spatio-temporal distribution patterns and influencing factors of hooded crane (Grus monacha) wintering population”. Those comments are valuable and very helpful. We have read through comments carefully and have made corrections. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript.

 

Abstract

Comment 1: Lines 12-16: suggest narrowing the focus to hooded cranes rather than waterbirds generally.

Response 1: We have changed the focus of the study to cranes, highlighted the significance of the study for crane conservation. Revision positions are given at lines 12-15.

 

Comment 2: “Previous studies [of waterbirds] focused on a single variable, and research considering multiple perspectives is lacking” – simply not true, especially as written, which implies that this is true for all waterbirds and not just hooded cranes.

Response 2: we corrected the ambiguity in the abstract. Revision positions are given at lines 16-18.

 

Comment 3: “The spatio-temporal distribution of the cranes differed at Shengjin Lake, but not at Caizi Lake in different wintering period.” – I do not follow. Does this mean abundance changed over time at Shengjin lake? Did the cranes use different areas? Statement needs to be more specific.

Response 3: we corrected the ambiguity in the abstract. Revision positions are given at lines 23-25.

 

Introduction

Comment 1: Lines 51-52: This statement is a major oversimplification of optimal foraging theory, and is only supported by a reference with findings that geese preferred larger fields. Optimal foraging theory considers many more factors than just patch size.

Response 1: We have modified this part. Revision positions are given at lines 54-55.

 

Comment 2: Line 75-77: see Cai et al. 2014. PLoS One - https://doi.org/10.1371/journal.pone.0089913 – their model of hooded crane occurrence included multiple variables related to habitat, food availability, and human presence. Also Hang et al. 2015 looked at both food abundance and human disturbance.

Lines 83-84 need revised for clarity.

Response 2: We corrected the ambiguity in this part, reviewed relevant literature, strengthened the understanding of crane overwintering ecology, and highlighted the important ecological significance of this study. Revision positions are given at lines 77-86, 90-92.

 

Method

Comment 1: Lines 102-122. The description of survey methods is insufficient. Were there pre-defined sampling points that were set up and visited? If so, how many and how were they distributed across the study area? How many times were points visited throughout the season? As it written, it sounds more like observers must have searched the areas for cranes without any particular protocol and then mapped the location of flocks they found.

Line 114 – What was a “patch”? The description of food biomass sampling is also insufficient to fully understand/replicate what was done.

Response 1: We add details on the frequency and methodology of food biomass sampling. Revision positions are given at lines 124-132.

 

Comment 2: Line 122: “The thickness of straw covering the rice was considered as the burial depth of the food.” I don’t understand this sentence, perhaps more context is needed. Was rice always covered in a layer of straw in the field?

Response 2: In autumn, after the rice harvest, there is a lot of straw left on the ground, which prevents the cranes from feeding on the rice grains in the paddy fields.

Comment 3: Line 126: It’s not correct to say that calculating an average reduces the measurement error.

Response 3: We have modified this part. Revision positions are given at lines 140-142.

 

Comment 4: Line 129: How was distribution of food resources measured or characterized?

Response 4: We further describe the method for determining patch size. Revision positions are given at lines 146-155.

 

Comment 5: Lines 138-140: Distance to nearest road or settlement was used as a metric of human disturbance, rather than direct observations of human behavior and how it affected the birds. The limitations of this method should be discussed somewhere.

Response 5: The limitations of different measures of human interference have been mentioned in the discussion. Revision positions are given at lines 257-261.

 

Comment 6: Lines 141-162: There is insufficient description to evaluate the statistical methods used. There is no information about model structure or the candidate model set, only how relative abundance per patch was calculated and how AIC was used for model selection. There is no information about sample sizes and it’s unclear whether there are multiple observations per “patch” at different time periods

Response 6: We added sample size information in Appendix B. We add details on the frequency and methodology of food biomass sampling and patch size determination. This also facilitates the understanding of analytical methods. Revision positions are given at lines 124-129, 146-155, 167-168.

 

Results

Comment: The large standard error for the food biomass estimate is completely at odds with the reported P value and the narrow error bars in Figure 3b. Something looks amiss, but without more information on how the models were constructed and evaluated it’s hard to diagnose.

Response: Due to the unique climate and geographical characteristics, food resources may often be concentrated in certain areas within certain time periods. The food biomass of resources was high in the meadow in November, the paddy fields after harvest in November, and the meadow in February and March of the following year. This results in a high standard error of food biomass.

 

Discussion

Comment: Lines 201-202: I’m not sure this can be concluded. As far as I can tell, the study only looked at what was used, not what was available on the landscape.

Lines 202-205: Again, the link to optimal foraging theory is a stretch. Not sure where the purported link between patch size and habitat heterogeneity is coming from but that is certainly not uniformly true.

Lines 206-212: I fail to follow the logic here or to understand the relevance. Many of these statements are speculative, and if there is a clear link between water levels and patch size, it should be made clearer earlier in the manuscript.

Lines 231-238 – Further speculation

Response: We have modified the description that is not completely accurate in the discussion to keep its content within the scope of this study. Revision positions are given at lines 229-233.

We have extended on the last part of our discussion. Revision positions are given at lines 253-276.

 

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

 

Sincerely,

Mr. Sun

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I think the authors have carefully accepted the comments of the reviewers, and the revised paper has been greatly improved. I think it is acceptable.

Author Response

Dear reviewer

 

Thank you for your letter and the comments concerning our manuscript entitled “Spatio-temporal distribution patterns and influencing factors of hooded crane (Grus monacha) wintering population”. Those comments are valuable and very helpful. We have read through comments carefully and have made corrections. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript.

  Thank you for your suggestions. According to your advice, this manuscript was edited for proper English language, grammar, punctuation, spelling, and overall style by a native English speaking editors. We have edited and proofread the manuscripts for submission. Please check our newly uploaded manuscript file.

 We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

 

 

Sincerely,

Mr. Sun

Author Response File: Author Response.docx