Population Trend of Colonially Nesting Heron Species in Greece
and Christos Astaras 1Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsI found your long-term and wide ranging research on population trend of colonial herons very well conducted and interesting. Such studies are rare and badly needed to advance one of the core issues of ecology, the interpretation of fluctuations in population and distribution, and in order to provide basic data for nature conservation.
Your results suggest intriguing comparison with the patters recorded in other Mediterranean countries. E. g. the increase in number of colonies and the expansion to new wetlands recorded in Greece is not what could be expected during population decline. Yet the same pattern, range expansion during population decrease, occurred for several heron species in Italy as well. I believe that an additional factor for the establishment of new and smaller colonies even during population decline could be the increased tolerance of human presence. This may allow herons to start colonies on sites such suburban parks or dry woods where they did not bred before. A diminished flight distance is evident in herons at the foraging sites as well. Unfortunately it is hard to test this hypothesis, we would need quantative data of the changes in flight distance over the past decades.
Comments for author File: 
Comments.pdf
I feel that your ms. could benefit by some adjustments in layout and in language. Please consider my suggestions as Comments in the attached pdf copy of the ms., as well as the following major points.
Extremely regular trend is shown for some species (Fig. 4 and 12) especially from 1988 to 2008. Such regularity is suspect, because nest numbers usually fluctuate somehow from year to year. You may need to discuss this anomaly. Were these trend based on very few data during the period without fluctuations ?
In the Figures showing population trends, the numbers on the y-axis (where “count” likely means “number of nests”) often do not coincide with the number of nest in the species’ description. E.g. in Fig. 2 the 1990 count reads about 3500 nests, but on row 229 the species description says “The highest number of nests was recorded in 2009 (n=2506)”. Same and even higher discrepancy occurs for Fig. 4 , 6, 8, 10, 12. Maybe this is because the Counts are not yearly numbers of nests, but some statistics calculated by TRIM ? Then the captions would be erroneous when stating that “the dots the number of nests every year”
The Results claim that a trend exists in the size and in the number of colonies of each species, and these trends are depicted by a regression line in Fig. 3, 5, 7, 9, 11, 13. I am convinced it is so, but you need to support the significance of each trends using appropriate statistics, or discuss why the trend does not reach significance (few data points ?)
The Chapter “3.8 New colonies” focuses again on the issue of change in number of colonies, that was already treated in the species description (page 7-15) and in Fig. 3, 5, 7, 9, 11, 13. Moreover, Table 4 is somewhat confusing. It would be better to unify these two treatments of change in colony number and size, with a description in the Results, and then with the interpretation in the Discussion.
Chapter “3.9 Threats” does not belong to the Results, as it does not report any new findings. It discusses only published information and hypotheses, therefore it is to be moved to the Discussion
The Discussion would benefit from the adoption of a more concise style. Some example of how to eliminate redundant words while keeping meaning intact, can be seen as barred words in the attached pdf.
Usually, journal prefer the use of past tense, not present, when describing results. Check throughout the ms.
Author Response
Response to Reviewer 1Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsReview comments on birds-2942105
In this study, Kazantzidis et al. tried to examine the available data on colonially nesting heron species in Greece for over three decades (1988 – 2018) in order to estimate the population trend of individual species. The topic of this study is interesting and the results may be important for the conservation of heron species in Greece. Overall, the manuscript is easy to follow and the data statistics seem to be appropriate. Therefore, I have no major concerns on the manuscript.
However, the following issues need to be clarified before it can be considered for publication (L=line).
1. L61-64. “Three species are threatened according to the Red Data Book of the threatened Animals of Greece (Purple Heron – Endangered, Great White Egret – Vulnerable, Black-crowned Night Heron – Near Threatened)”. It should be noted that only species classified as “Critical Endangered, Endangered and Vulnerable” are considered to be threatened, while Near Threatened species are not threatened!
2. L71 and other related numbers throughout the manuscript: Replace “1.400” with “1,400” or “1.400”.
3. L385-411. The section of “3.9 Threats” should be moved to or combined into the discussion section as there are no figure or table to show these “results”.
4. L413-488. It is better to add certain subtitle such as “4.1. Population trend of heron species”.
5. L421-467. There is no need to use the boldfaces for the heron species.
6. L489-567. It is better to add certain subtitle such as “4.2. Drivers of heron nesting population trends”.
7. L637. Please add “of heron species in” after “Annex. Conservation status”.
8. Appendix A. There were large differences in extinction risk between the Greek Red Data Book and the IUCN Red List. Mismatches between the two Red Lists are most likely to be caused by scale-dependent changes in listing and access to different data (Milner-Gulland et al. 2006). One explanation for your results is that the smaller the area of assessment, the higher the threat status, because a smaller area often implies a smaller population size and a higher chance of meeting red listing criteria (Milner-Gulland et al. 2006).
Reference
Milner-Gulland, E. J. et al. 2006. Application of IUCN red listing criteria at the regional and national levels: a case study from Central Asia. Biodivers. Conserv. 15: 1873–1886.
Author Response
Response to Reviewer 2Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript entitled “Population Trend of Colonially Nesting Heron Species in Greece” monitor the seven colonial breeding heron species at 65 colonies across 37 wetlands in Greece during 1988-2018, which studied the population trend of the seven species. This long time series is useful for the management. The manuscript is well prepared. However, there are some points should be improved. The comments are as below:
Main comments
(1) How to deal with the influence of different survey frequency on the results.
(2) The study aims to research the population trend and the drivers of the trend of these species based on the long time series data. The structure should be organized focusing on these two points in results and discussion commonly. The results of 3.1-3.7, which were organized by species, were disorder and not related with the scientific question close. The reader is glad to see the results closed with the questions. The result should be clear and the Figure 2-13 could be merged.
(3) The result of 3.9 showed the descriptions of the threats. However, it is better to quantify them. The key point of the study is to explore the behind driver of the population changes.
(4) The reader wants to know the relationships between heron population trends and potential factors. Such as, climate factor, landscape factor, human activity.
(5) Commonly, every paragraph should have its conclusion at beginning or end of the paragraph. And there are some relatives between paragraphs. Many paragraphs in the manuscript are short and independent, which could be merged.
Minor comments
Line 31, what monitoring?
Line 53, which European countries?
Line 55, please use the punctuation correctly.
Line 57-60, the frond of the brackets is missing.
Line 104-105, please add the reference.
Line 166, Lack the punctuation, and “In” should be changed as “in”.
Line 197-217, Please short and combine these four paragraphs. The results should be clear and concise.
Comments on the Quality of English LanguageThe English language of manuscript could be improved.
Author Response
Response to Reviewer 3Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript entitled “Population Trend of Colonially Nesting Heron Species in Greece” studied the population trends of the colonially nesting heron species in Greece from 1988 to 2018, which is benefit to the waterbird conservation and wetland management. The long time series data is worth publishing. However, several key points occurred in the manuscript.
(1) The was one scientific question in the manuscript from current structure. From the result section, the driver of population trends is not the scientific question, because it just be discussed in the discussion section. If the potential factors are not able for current study, the scientific question should be edited, such as the Simple Summary, Abstract, and introduction section.
(2) The figure 1 should be improved because it lacked the compass and plotting scale.
(3) It is Ok to display the potential factor influencing the population trends at the beginning of “4.2 Drivers of heron nesting population trends” section. However, the following paragraph should discuss each /key factor.
(4) The conclusion section should be edited. This section should display the conclusion from the current study clearly and succinctly.
(5) The style of references should be consistent, such as with/without DOI (N0, 47?48?)?
Comments on the Quality of English LanguageThe english language is ok.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
