Noise Pollution and Urban Birds Breeding in the Center of the Iberian Peninsula: Effects on Diversity and Abundance

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is dealing with the distribution of bird species along three noise level gradients, viz., high, medium and low levels present in different cities of central Spain. Authors have identified 81 species belonging to 37 families. Authors have explored the bird population density and distribution from 2019 to 2021. The content or theme of the manuscript is not novel and a number of studies have already been published with similar themes from different regions of the world. However, ss such the manuscript is interesting and have merit to be published in the journal. 33 species were found following all the study criterias have explored further for different statistical analysis. However, there are a few areas where the manuscript is lacking impetus to recommend for publication in its present form. The similarity index of the manuscript is very high, which might be due to already availability of the manuscript as Pre-print version. The authors need to include some information related to habitat characteristics. Results can be better presented. Multivariate analysis or Ordination related analysis can be included for clear presentation and understanding of the data with respect to different noise levels. Authors can also highlight the invasive and native species with respect to different noise levels. A few additional and specific comments / suggestions are given in the attached pdf file. The manuscript can be reconsidered for publication after incorporating these suggestions.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Some of the sentences are not clearly presented which can be rephrased for better clarity and understanding. A few sentences are marked in the attached pdf file.

Author Response

Thank you for all recommendations and corrections. In the next document we respond to all corrections and suggestions

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript concerns an interesting ornithological study conducted in urbanized areas. Once published, these results are bound to attract interest, as there are still fewer studies on the avifauna of cities than those conducted outside urban areas. However, this manuscript requires some pre-publication corrections, which I have listed below.

1. The main topic of this manuscript is the impact of noise pollution on avifauna in Spanish cities. Although the Introduction is well-written, but in my opinion it would have been worthwhile to develop some of the themes in the first paragraph in order to familiarise readers with the very important issues raised here. Some more details with citations can be provided, e.g. on the effects of urbanisation on bird behaviour and collisions with glass surfaces. Cat predation has been underestimated, and there are many papers from the USA and Europe showing the enormous scale of this phenomenon. There are also bird species that have mostly moved to cities like swifts and magpies (at least in my country). Urban populations of some species have stopped migrating. I also miss the use of the term synurbization, which fits perfectly here.
2. Lines 74-76. There is a lack of citation here.
3. In several places in the text, a mark appears to move a word to the next line when the word is far from the edge of the page.
4.  Lines 88-89. Noise measurements were taken throughout the morning at various times. However, there are huge differences in noise levels between early and late morning, when many people travel to workplaces and schools. This description is therefore inaccurate. We also expect significant differences in noise level between Sundays and weekdays. Are these measurements only taken on weekdays?
5. Were noise measurements repeated during the visit? How many times? Or were noise measurements taken only once during the visit? Repetition and averaging of their results would be advisable. 
6. Categories of noise level (page 3). Line 93 - it is written that 'noise pollution levels were high and continuous throughout the day' - but earlier it was written that noise measurements were taken in the morning only. This should be clarified or corrected.
7.  Categories of noise level (page 3). In line 90 it is written that these categories were validated by statistical analysis. but I cannot see result of this analysis. 
8. Mean values are different, but ranges overlap in great extent. How was the decision made to classify a site into a particular noise level category? 
9. Figure 1. City names and the kilometre scale should be larger. 
10. Figure 1. If any administrative boundaries are shown on the map, the names of these provinces should be given.
11. Lines 119-120. It is not clear on what basis the authors decided that 10 minutes of observation is optimal. Are there any publications using a similar, or the same, methodology?
12. Sampling was conducted during the breeding season, between March 2019 and August 2021. The breeding season of a species varies in different parts of Europe. Therefore, more precise date is needed here. After all, I suppose the research was not conducted in December, and the broadly indicated timing of the research may indicate this. Moreover, we can expect that the number of discovered birds decrease in later part of the breeding season. Late in the season, the birds' vocal activity declines and visual detection in dense vegetation is difficult. Since each area was inspected several times, were the dates of these inspections different? The solution would be to use a generalised linear model:

number of species ~ noise level + day numer in a yearn + habitat

In this way you will see in a comprehensive way which factor had significant influence (positive or negative) on number of species recorded (or number of individuals). Including habitat type is optional, but the habitat (or amount of green areas) may be important. The current approach to data analysis assesses each factor separately, which is not advisable with this type of data.

13. There are only 34 items in the list of references. While 81 are cited in the text.

14. Line 139. What does the term “most frequent species” mean? Were they designated on the basis of percentage, or perhaps abundance, or in some other way. This should be clarified in the Methods chapter.

15. Line 143. What is 10000 here? Is this a multiplier? If so, the multiplication sign is missing.

16. Lines 146-150. This is true, but I suggest using a generalised linear model for a comprehensive analysis of all factors.

17. Lines 154-155. In the Methods there is a lack of description of this method.

18. Table 1 is quite extensive and is perhaps better placed in the Appendix.

19. Line 208. Scientific names should be in italics.

20. Tables 2 and 3. It is not clear whether these tables only show species whose densities vary with noise levels.

21. Line 241. similar - but to what?

22. Lines 243-245. This sentence is not entirely clear. Please reword it.

23. Lines 276-277. This claim needs to be developed. Why are the results of other authors sometimes so different?

24. Line 317. What does 'population quality' mean in this context? This can refer to many population characteristics. 

Author Response

Thank you for all recommendations and corrections. In the next document we respond to all corrections and suggestions

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been revised substantially in light of the suggestions given earlier. There are a few minor concerns which need to be addressed before proceeding further.

1. The no. of unique species must not be common in all the three noise levels. Therefore, authors are advised to present the no. of common and unique species for all the noise level categories separately to avoid any further confusion.
2. Also, 17 species were absent from any of the noise level, then when and where they were observed in this study? And how they are related with the aim of this study should be clearly stated.
3. There are spacing issue between text and citations. Authors need to work on it thoroughly throughout the manuscript, particularly Introduction section.
4. A few sentences can be better presented for more clarity.
5. In the Appendix table, elaborate all the abbreviations used below the table as footnotes for more clarity.
6. Cross-check all the references cited in text are listed and vice versa.

After incorporating these suggestions, the manuscript can be reconsidered for proceeding further.

Author Response

Thank you for all comments and suggestion. We answer all comments in next document and in changes in manuscript in red. 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

After all these correction, in my opinion, the manuscript may be published.

Author Response

Thank you very much for your contributions and your approval.