Comparison of Bird-Species Richness Between 1987 and 2024 Reveals the Urban Forest as a Stable Biodiversity Refugium in a Dynamic Urbanized Landscape

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Maintaining avian diversity represents one of the key ecological functions of urban forests, and conducting long-term studies on bird diversity serves as a valuable approach to assessing the stability of urban forest ecosystem services.

This study compares bird species richness in urban forests between 1987 and 2024, which is a commendable effort in demonstrating the role of urban forests in conserving avian biodiversity. However, the manuscript suffers from significant methodological and analytical shortcomings, which undermine the validity of its conclusions. Crucially, the study primarily examines differences in bird species richness between two discrete time points (1987 and 2024), rather than presenting a long-term dynamic analysis spanning the 37-year period. This distinction should be clarified in the text to avoid misinterpretation. Furthermore, the study would benefit from incorporating habitat surveys to establish relationships between environmental variables and avian communities. Such data would strengthen the scientific basis for the conclusions and proposed management strategies.

 

Specific concerns are outlined below:

1. Introduction: The literature review is generally well-presented. However, the final paragraph lacks clarity regarding the specific research methodology, objectives, and novelty of the study. These elements should be explicitly stated.
2. Section 1. Study area: A clearer overview of the study area is required. This should include essential details such as urban forest area, forest shape, and prevailing climatic conditions. Furthermore, as the research focuses on birds within the urban forest, an overview of the bird species distribution within the study area should also be provided. An appropriately annotated location map depicting these features should be included to enhance clarity.
3. Section 2. Bird census: The statement “All birds detected via line transect were identified both visually and acoustically [1]” requires clarification on the specific tools or methods used for acoustic identification of bird species.
4. Section 2. Bird census: The section states that bird data from 1987 (line transect survey) and 2023-2024 (point counts) were used. Although Section 2.3 mentions that “the 2023–2024 census was compared to the 1987 census, which employed the same line-transect method [39]:” this section (2.2) itself must clearly describe the methodology and content of the 1987 survey.
5. Section 2. Bird census: The number of transects and their spatial distribution within the study area must be explicitly stated. his information should be visually represented on the location map recommended in point 2 to improve methodological transparency.
6. Section 2.2. Bird census: The formulae used for calculating “the absolute counts and relative dominance (%)” need to be explicitly provided.
7. Similarly, Section 2.3. Assessment of long-term change in bird-species richness: The computational rationale or procedure for Sörensen’s index (QS) and Jaccard’s index (Ja) must be clearly specified. Either the calculation formulae or a precise description of their derivation should be included.
8. Methodological Clarification: The fundamental nature of the study is an assessment of the difference in bird species richness between two specific points in time (1987 and 2024). The phrasing “37-year change” often implies a documented trend derived from regular surveys conducted throughout that period. The manuscript should be amended to clarify that this is a comparison of two endpoints years, not a continuous dynamic trend analysis based on interim surveys.
9. Figure 1 & Table 1: 1: The meaning of the x-axis requires clarification. While it seemingly represents bird species, entries 43-49 lack corresponding data and should be removed. Furthermore, the figure requires revision to ensure all axes are clearly labeled. A contradiction exists between the claim “A total of 42 bird species were recorded during the 2023–2024 breeding season” and Table 1 showing 49 species. Table 1 must be corrected to accurately reflect the reported findings, species listed in Table 1 should be assigned numerical identifiers corresponding to those used on the x-axis of Fig. 1.
10. Table headings should be repeated on subsequent pages if tables extend beyond a single page, to ensure results are presented clearly.
11. Section 3.2. Comparison of long-term changes in bird-species richness over a 37-year timespan: Given that the study compares only two endpoints rather than documenting change dynamics over the 37 years, the title and analysis within this section should be revised to accurately reflect the nature of the data (i.e., a comparison between two time points).
12. Discussion Sections 4.2 & 4.3: Section 4.2 Paragraph 4: The content of this paragraph appears introductory rather than discursive. The Discussion should focus on comparing the study's findings with existing literature to contextualize, support, or extend current knowledge. Section 4.3: Similar to the point above, this section currently contains elements that are not sufficiently focused on discussing the implications in light of the presented results and existing knowledge. Strengthening the link between findings, literature, and management implications is necessary.
13. Section 4.3. Implications for urban forest management: The statement “The results of this study confirm the key role of urban habitat heterogeneity: greater cover of grass, bushes, and trees is related to increased bird taxonomic diversity, while phylogenetic diversity is positively affected by the presence of grass, trees, and water bodies.” makes specific claims about vegetation-bird relationships. However, the research methodology did not include surveys of habitat vegetation composition concurrent with the bird surveys, nor does the analysis establish such relationships. Consequently, the findings presented in this study appear insufficient to substantiate these specific management implications related to vegetation structure. To support such conclusions, incorporating concurrent habitat surveys and analyses linking environmental variables to bird diversity is essential.

 

 

Author Response

Dear Reviewer 1, many thanks for your valuable comments to the submitted manuscript. I have accepted all of your recommendations and the manuscript has been corrected:

Comment of Reviewer	Response of Author
Crucially, the study primarily examines differences in bird species richness between two discrete time points (1987 and 2024), rather than presenting a long-term dynamic analysis spanning the 37-year period.	Accepted: Confusing Title and relevant text in the body of manuscript has been corrected to better form indicated that the study is based on comparison between two time points.
Furthermore, the study would benefit from incorporating habitat surveys…. Such data would strengthen the scientific basis for the conclusions and proposed management strategies.	Accepted: Habitat description with more details as well as management info have been added.
Introduction: The literature review is generally well-presented. However, the final paragraph lacks clarity regarding the specific research methodology, objectives, and novelty of the study.	Accepted – the new paragraph has been added following this recommendation of R1.
Section 1. Study area: A clearer overview of the study area is required. This should include essential details such as urban forest area, forest shape, and prevailing climatic conditions…	Accepted – two new paragraphs have been added following this recommendation of R1.
Section 2. Bird census: The statement “All birds detected via line transect were identified both visually and acoustically [1]” requires clarification…..	Accepted. The former confusing statement has been corrected.
Section 2. Bird census: The section states that bird data from 1987 (line transect survey) and 2023-2024 (point counts) were used. Although Section 2.3 mentions that “the 2023–2024 census was compared to the 1987 census, which employed the same line-transect method”.	Corrected. Info about point-census was a mistake, right is “line transect” of course.
Section 2. Bird census: The number of transects and their spatial distribution within the study area must be explicitly stated...	Accepted: Better description of line-transect location has been added.
Section 2.2. Bird census: The formulae used for calculating “the absolute counts and relative dominance (%)” need to be explicitly provided.	Accepted: Corrected.
Similarly, Section 2.3. Assessment of long-term change in bird-species richness: The computational rationale or procedure for Sörensen’s index (QS) and Jaccard’s index (Ja) must be clearly specified.	Accepted: Relevant primary references of methodological procedure for both indices has been added to the text.
Methodological Clarification: The fundamental nature of the study is an assessment of the difference in bird species richness between two specific points in time (1987 and 2024). The phrasing “37-year change” often implies a documented trend derived from regular surveys conducted throughout that period.	Accepted: Confusing text has been changed following this valuable comment of a Reviewer in order to clarify that this is a comparison of two endpoints years, not a continuous dynamic trend analysis.
Figure 1 & Table 1: 1: The meaning of the x-axis requires clarification. While it seemingly represents bird species, entries 43-49 lack corresponding data and should be removed. A contradiction exists between the claim “A total of 42 bird species were recorded during the 2023–2024 breeding season” and Table 1 showing 49 species.	Figure 1 and Table 1 have been checked and corrected following this comment. Table 1 includes 42 species per seasons 2023/24.
Table headings should be repeated on subsequent pages if tables extend beyond a single page, to ensure results are presented clearly.	Accepted: It will be corrected in the frame of editing of the text.
Section 3.2. Comparison of long-term changes in bird-species richness over a 37-year timespan: Given that the study compares only two endpoints rather than documenting change dynamics over the 37 years, the title and analysis within this section should be revised.	Accepted: Following above general comment of a Reviewer as well as this comment, the Title and relevant parts of the text have been corrected.
Discussion Sections 4.2 & 4.3: Section 4.2 Paragraph 4: The content of this paragraph appears introductory rather than discursive…. Section 4.3: Similar to the point above, this section currently contains elements that are not sufficiently focused on discussing the implications in light of the presented results.	I agree with this comment. Discussion has been corrected to the form better reflected original results of the study and implications to management is now limited only to current forest habitat in study area. Some “narrative” redundant text has been deleted.
Section 4.3. Implications for urban forest management: The statement “The results of this study confirm the key role of urban habitat heterogeneity: greater cover of grass, bushes, and trees is related to increased bird taxonomic diversity, while phylogenetic diversity is positively affected by the presence of grass, trees, and water bodies.” makes specific claims about vegetation-bird relationships…… To support such conclusions, incorporating concurrent habitat surveys ….is essential.	Accepted: Rephrased and corrected. Mentioned statement comes from reference (now corrected). Habitat description in details has been added to Methods. Discussion related to relationship between current state of habitat and bird richness species corrected including discussion about linking environmental variables to bird diversity.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The author should modify the text a little according to the suggestions in the pdf. In addition I would suggest to cite at least some seminal papers published by Blondel, as 1) Blondel, J. Synthesis: the history of forest bird avifaunas of the world. In: Biogeography and ecology of forest bird communities; Keast, A., Ed.; SPB Academic Publ., The Hague, Netherlands, 1990, pp. 371‒377. 2) Blondel, J. (1990) Biogeography and history of forest bird faunas in the Mediterranean zone. In: Biogeography and ecology of forest bird communities (ed. by Keast, A.), pp. 95‒107. SPB Academic Publ., The Hague, Netherlands. However, I suggest to search in the web other papers on the subject 'bird & forests'.

Finally, I would suggest the author to re-writing the Discussion, particularly the 'Long-term changes in urban forest bird communities', basing it only on the results obtained in the comparison 1987-2024 of breeding birds, and trying to explore the reasons of the differences noticed, that I consider significant (if used another test).

Comments for author File: Comments.pdf

Author Response

Dear Reviewer 1, many thanks for your valuable comments to the submitted manuscript. I have accepted all of your recommendations and the manuscript has been corrected:

Comment of Reviewer	Response of Author
The author should modify the text a little according to the suggestions in the pdf.	Accepted: Text has been corrected as a Reviewer suggested (using comments in PDF file).
In addition I would suggest to cite at least some seminal papers published by Blondel… However, I suggest to search in the web other papers on the subject 'bird & forests'.	Accepted: Missing suggested references have been added. Also, new reference DOI: 10.3161/00016454AO2022.57.1.002 relevant to the context of Discussion has been newly added.
Finally, I would suggest the author to re-writing the Discussion, particularly the 'Long-term changes in urban forest bird communities', basing it only on the results obtained in the comparison 1987-2024 of breeding birds…	Accepted: section Discussion has been seriously reworked in order to better reflect original findings of this study and redundant parts (beyond the exact scope of the study) have been deleted.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Review of the article titled “Long-term changes of bird-species richness revealed urban forest as a stable biodiversity refugee in dynamic urbanized land scape” (ID forests-3765637).

 

Machar presents a survey on differences in bird assemblages inhabiting urban forest in one of towns of Czech Republic. The Author compares data from two breeding periods divided by 30 years. These data are interesting and important for understanding changes in woodland bird abundance in urban forests. But this study has also some serious drabacks that decrease significance of presented results and conclusions.

First, the title and aims suggest examination of long-term trends, whereas this study does not present any trends, as data were collected just in two periods, and nothing is known about changes in bird occurrence and abundance between them. The Author is aware of this problem. Therefore at least title and aim of this study should be modified. Also many conclusions about species trends should be avoided.

It would be good to discuss observed differences on the background of trends of particular species in Czech R. or Central Europe.

Next, I have problem in accepting that total number of birds obvserved was compared. Better would be to use the highest number of individuals of a given species from five counts. Such variable is less affected by some random factors.

Moreover, I am not sure why number of individuals was used as metric, instead of number of breeding sites (territories, or the best – number of territorial males/pairs). Total number of individuals is not the best proxy of real number of breeding birds, as randomly in some sites females could be counted, as well as some vagrant individuals or even young birds.

Next, why data from two years 2023-2024 are compared to single year 1987? Data from 2023-2024 include sum, or some average from 2 years? Counting in 2 years for sure will produce more records per species (and also could increase number of species) than count in just one year.

“effect. Therefore, it is not surprising that there has been long term stability in European forest bird populations since the early 1980s [63],…” – this statement is true for overall bird assemblages, especially for common birds, but it is not true for most of rare and vulnerable species.

I do not understand this sentence “The presence of bushes in urban gardens and parks significantly mitigate the negative effects of high phylogenetic relatedness of birds in urbanized areas]. – and citation is missing here, I quess.

 

 

Fig. 1 should include data from both periods.

 

Table 2 is redundant and unnecessary.

 

Author Response

Dear Reviewer. many thanks for your valuable comments. I believe that all of your important recommendations have been accepted in corrected version of the manuscript:

Comment of Reviewer	Response of Author
First, the title and aims suggest examination of long-term trends, whereas this study does not present any trends, as data were collected just in two periods, and nothing is known about changes in bird occurrence and abundance between them. The Author is aware of this problem. Therefore at least title and aim of this study should be modified.	Accepted: I aware that Title is confusing. In fact, the study is based on comparison between two time points (1987 and 2024), not on long-term dynamic changes.
Next, I have problem in accepting that total number of birds observed was compared. Better would be to use the highest number of individuals of a given species from five counts. Such variable is less affected by some random factors.	I understand to this comment. But, I think the comparison between older results (1987) and current results (2023/24) should be based on similar approach. So, if authors of older research published data dealing with average bird numbers, current data should be also an average, not the highest number as a Reviewer suggested.
Moreover, I am not sure why number of individuals was used as metric, instead of number of breeding sites (territories, or the best – number of territorial males/pairs). Total number of individuals is not the best proxy of real number of breeding birds, as randomly in some sites females could be counted, as well as some vagrant individuals or even young birds.	I agree with a Reviewer that total number of individuals is not the best proxy. But in my opinion, another interpretation of field count should be confusing. The line-transect is fast – but in other hand - not very reliable method for interpretation of bird territories number for most of detected species. This method produced some random observations, which can be easy excluded (e.g. it is obvious that some specific bird species observed in transect have not breeding connection to the studied habitat), but some observation can be only very hardly excluded or included (it comes from the nature of the field method…).
Next, why data from two years 2023-2024 are compared to single year 1987? Data from 2023-2024 include sum, or some average from 2 years? Counting in 2 years for sure will produce more records per species (and also could increase number of species) than count in just one year.	Following above comment of R and my response, data from 23/24 research are average from repeating line-transect (similarly as data from 1987 are also average from repeating line-transect counts).
“effect. Therefore, it is not surprising that there has been long term stability in European forest bird populations since the early 1980s [63],…” – this statement is true for overall bird assemblages, especially for common birds, but it is not true for most of rare and vulnerable species.	Ok, I agree. Text has been deleted. But general statements about some species-trends can be disputable. Recently, we can see e.g. a decline of Anthus trivialis and Locustella fluviatilis (maybe also Ciconia nigra) in some areas of Central-European floodplain forests. But we know very little about it, it should be any local/regional fluctuations or … who exactly knows? These species decline from protected areas. On the other hand, some very rare Central-European forest bird species are increasing, e.g. Tetrao urogallus in Sumava mountains… In my opinion, only very long-term time ranges can indicated any real trends, e.g. extinction of Tetrao tetrix from European lowland floodplain forests during 20th century.
I do not understand this sentence “The presence of bushes in urban gardens and parks significantly mitigate the negative effects of high phylogenetic relatedness of birds in urbanized areas]. – and citation is missing here, I quess.	Accepted. Maybe it was a bad translation of the word “relatedness”. Corrected and citation added.
Table 2 is redundant and unnecessary.	Yes, this table should be considered as redundant. But I think the table is useful for clear presentation, so I suggest to apply it in the manuscript.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors' revisions have enhanced manuscript quality and improved textual clarity. However, regarding avian surveys using the line transect method, clarification of survey methodology remains critical. Several concerns from the initial review persist:

 

​​1. Page 4, Lines 141-144: While birds were surveyed through both visual observation and acoustic recording, the specific acoustic identification technology must be specified (e.g., mobile applications, birdsong recognition AI models). Additionally, methodology to avoid duplicate records between acoustic and visual observations requires clarification.

​​2. Page 4, Lines 145-147: Calculation methodology for relative dominance (%) of bird speciesremains undefined. Explicit formulae or computational procedures must be provided

3. Avian data derive from line transect surveys, yet key parameters –number of transects deployed within the study area and their spatial distribution – are still not clearly stated.

4. The manuscript’s Percent match metric (30%) appears elevated. The authors should consider lowering this threshold value.

Author Response

Dear Reviewer 1, many thanks for your valuable comments. I have replied in attached file. Regards, Ivo Machar

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In the first round I suggested some changes, but the author ignored them and did not justify the reason. I regret for this, and I report in the pdf the main changes that I consider very important before publishing this paper.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer 2, many thanks for your valuable comments. I have replied in attached file. Regards, Ivo Machar

 

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

I do not have more comments on this manuscript. The Author's responses convinced most of my previous critical comments. 

Author Response

Dear Reviewer 3, many thanks for your evaluation. Regards, Ivo Machar