Size Matters: Diversity and Abundance of Small Mammal Community Varies with the Size of Great Cormorant Colony
Round 1
Reviewer 1 Report
I have completed my review for ‘Size matters: response of small mammal community varies with the size of Great Cormorant colony’, which is currently under consideration for publication in Diversity. Here, the authors described the effects of the Great Cormorant colonies on the community of small mammals in Lithuania. Overall, there were differences among colony sites. For example, in the largest colony, the mammal community attributes were lower than those in the smaller colonies. And within the larger colony, there were differences among control, active, and abandoned zones. The authors concluded that up to a specific colony size, cormorant pressure is a driver of habitat succession and has similar effects on the small mammal community as other successions in disturbed habitats. I enjoyed reading the manuscript and believe it could be essential to the topic. However, the manuscript has some issues that need further clarification.
More information about the study sites is needed, for example, the area of the colony and distance to the control sites, and the size of active and control sites within each colony. Also, a description of the vegetation composition would be helpful. Although the authors gave a brief description (page 3, lines 95-100), more is needed to understand the design and differences within and among colonies clearly.
Similarly, more information about small mammal trapping efforts is needed. Although the authors mentioned that details could be found in previous studies, it is relevant to give more details about the design of the trapping effort. In particular, given that this study presents the results of 12, 9, and 7 years of effort at each colony site, it is essential to explain if the location of these snap trap line were within and among years.
The authors present the results for each colony (Tables 1-3). These are the total values. However, it would be more valuable if the authors showed the temporal information (among years). If the plots for the trapping efforts are the same, this could help to differentiate the added effect of time of the colony on the small mammals. So, it could be possible to test the effect of colony size and time.
Finally, some parts of the discussion are speculative. For example, on page 8, lines 254-272.
Author Response
Dear Reviewer,
Thank you for giving the opportunity to submit a revised draft of our manuscript titled “Size matters: response of small mammal community varies with the size of Great Cormorant colony” (diversity-2182000). We appreciate your time and valuable comments that have helped us improve the manuscript. Please find answers to responses to your comments.
Sincerely,
Marius Jasiulionis
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper is about changes in the small mammal community in breeding colonies of great cormorants in Lithuania. The AA reported data collected over 7-12 years in three colonies of different size, i.e. of colonies hosting a small or a large number of breeding pairs, showing differential effects on the small mammal assemblage in occupied vs abandoned nesting area and close not damaged habitats.
After having quickly discussed factors potentially involved in the observed community changes, the AA conclude that small mammals may quickly reoccupy abandoned cormorant nesting areas and that in small colonies moderate disturbance due cormorants may have a positive effect on the diversity of the small mammal community (and the converse for large occupied colonies).
Other than on small mammal communities in modified forest habitats, the paper gives new insights on a topic often debated among wildlife managers and conservationist who are worried about the potential detrimental effects of cormorant (and other fish-eating colonial waterbirds) colonies (and other communal aggregations such as night roosts) on the local fauna. The work is of more general interest and worth of be published.
Below I report some comments I hope could be useful to the Authors to further improve their paper.
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8 |
“Cormorant colonies are often viewed negatively … “ Although could be shared by a vast majority of people, a negative or positive view of the presence and effects of a cormorant colony will be different according to the attitude and involvement of people and stakeholders. I suggest to identify the stakeholder to which refers the adverb "often" (eg. wildlife manager, fishermen, ...) |
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31-37 |
Some of the cited references refer to more species of waterbirds and/or not only on cormorants ref. 9, 17) and the statement applies to all (fish-eating) bird aggregations . In the first sentence I suggest to add words such as “colonial waterbirds” or “waterbird colonies” or “piscivorous birds” |
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40 |
It is known the year of colony establishment ? If so, please add it |
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42 |
The active part of the colony was characterized It could be worth to specify that this is the area with occupied nests |
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49 |
In the paper, the size of the colony is represented by the number of nests or breeding pairs, while it would be relevant to have data about nest density. Considering the small mammal community and the population parameters will be influenced by the extension of the above areas, it would be useful to consider also nest densities and the land surface occupied by the active and abandoned parts of the colony as well as of the extension of the forest habitat (or the original habitat) surrounding the cormorant colony. |
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49 |
Cormorant numbers in Europe is constantly increasing … After a well-described population increase, from the 1980s to the mid 2000s, since then the population of Cormorants in Europe is clearly levelling off and in some regions even declining. This is due to the combined effects of environmental factors (see. https://drive.google.com/file/d/14YSTp8MMTvRRrPTyWu8Hb_HtgeGqsQb6/view) |
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74 and following along the paper |
hereafter referred as CC I find superfluous and a bit confusing add every time “CC” to the name of the colony; the name of the locality would be enough and less redundant (eg. “At Lukštas …” instead of “At Lukštas CC” …). |
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104 |
Every year trapping was done from September to November For non ornithologist readers, it would be worth to add the surveys were carried out after the breeding season and after cormorant (at least the great majority, I suppose being so North in the species range) left the colony/study areas. |
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122 |
based on the number of individuals trapped on the first day Not clear to me what it means “…on the first day” |
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137 |
…were captured in 3 … … were captured in the 3 … |
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144 |
If I correctly understand, in this section, the results report to the means and C.I.s calculated from the samples collected during the whole study (2011-2022): it would be more clear if stated to what sample or period of time they refer |
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155 |
Table 1 (and 2 and 3) reports the number of individuals of the different small mammal species collected during the several years of the study. Likely, the diversity and other community indices were different in the different sampling years/periods. It would be worth to report (perhaps as an appendix) the range of the value recorded in the different sampling seasons. |
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259 |
… Large cormorants can cause … AA refers to the birds or their nests/colonies/aggregations (eg. night roosts)? Something is missing ? |
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268 |
Migration is certainly a main driving factor for the prompt recolonization of the damaged area of the colony; for that It would be interesting to know about the surface ratio of the colonies and those occupied by the surrounding not damaged habitats |
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280 |
Also, some small mammal species can also feed on pellets, regurgitates and remain of fish prey dropped by cormorant nests, so cormorant may have a positive role in providing additional food. |
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288 |
“…Once the cormorants have left the nesting site …” So said it seems at the end of the breeding season while I understand the AA meant when the colony is abandoned. If so, I suggest to modify the sentence. |
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382 |
The link does not work properly Replace with (also check the length of underscore) https://nerija.lrv.lt/uploads/nerija/documents/files/Kormoranu_2017_ataskaita__red.pdf |
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Author Response
Dear Reviewer,
Thank you for giving the opportunity to submit a revised draft of our manuscript titled “Size matters: response of small mammal community varies with the size of Great Cormorant colony” (diversity-2182000). We appreciate your time and valuable comments that have helped us improve the manuscript. Please find answers to responses to your comments.
Sincerely,
Marius Jasiulionis
Author Response File: Author Response.pdf
Reviewer 3 Report
1. Title: “response” – can you be more specific? Community composition? Diversity? ….
2. Line 26. Drivers of what? Change “icthyophages” to “piscivorous” or “fish-eating”?
3. The entire Introduction paints cormorant colonies as somewhat unnatural when in fact they are a native species and they are a driver of ecosystem change along with many other natural disturbance regimes. Here and throughout, you need to get out of the language that these birds and their colonies are somehow an anomaly ……
4. Line 49. No, the populations are not “constantly increasing”. They have increased since whatever decade and in many cases have reached maximum population or are decreasing. Avian influenza virus along with many other factors are most certainly acting as a population regulation mechanism….
5. A weakness of the study is that it does not provide quantitative measures of vegetation differences across sites, it relies instead on fairly descriptive aspects (photos, degree of perceived cormorant impact….). Vegetation quadrats etc would have been useful..
6. Line 290-291. I think you need to remind the reader that cormorant colonies are part of the natural disturbance regime.
Author Response
Dear Reviewer,
thank you for your comments that have helped us to improve the manuscript (diversity-2182000). Please find answers to responses to your comments.
Sincerely,
Marius Jasiulionis
Author Response File: 
Author Response.docx
Round 2
Reviewer 1 Report
I have completed my review of the new version of the manuscript ‘Size matters: response of small mammal community varies with the size of Great Cormorant colony’, which is currently under consideration for publication in Diversity. I want to thank the authors for improving the manuscript. Although some English grammar and style need to be reviewed, this new version reads well. In addition, the study area and sampling effort are better described.
Author Response
Dear Reviewer,
thank you for your comments that have helped us to improve the manuscript (diversity-2182000). Please find answers to responses to your comments.
Sincerely,
Marius Jasiulionis
Author Response File: Author Response.docx
