Spatiotemporal Patterns of Avian Species Richness Across Climatic Regions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study examines bird diversity patterns in Mediterranean countries by utilizing citizen science platforms, such as eBird. In my opinion, this study could be significantly improved. The introduction and materials and methods sections should be shortened substantially to focus on the research aims. Additionally, richness estimates and their analyses should be refined, as bird datasets are derived from non-controlled sampling methodologies. I suggest using rarefaction extrapolation curves to obtain richness estimates that are comparable in sampling effort among regions and years (L70-71). Other comments are shown below.

L70-71. Provide examples of these publications.
L71-73: Explain how this research plays a key role in developing ecologically based planning.
L78-86: This sentence is out of context. This paragraph should be summarized and linked to another text.
L87-90: Support these statements with references
L104-108: Previous studies are mentioned here, but no citations are provided.
L110-152: This historical information should be summarized in a few lines or included as supplementary material.
L170-171: This is a result; it should be presented in the Results section (move or delete).
L195: The world map in this figure could be deleted or made smaller to show this country in its regional context.
L208: The information in Table 1 could be displayed in Figure 1, so Table 1 could be removed.
L201-256: The information in this section is bibliographic, not methodological. Please summarize it and highlight the most important aspects that you used to test your research questions.
L274-280 and L290-292: Move this information to the data analysis section below. Here, you refer to data analysis rather than data acquisition.
L344: "We utilized the Köppen-Geiger climate classification..." Please indicate the purpose of using these data.
L329 and L354. Tables 2 and 3 and Figures 2 and 3 are only accessory; move them to the supplementary materials.
L361: "The differences..." Please explain whether these differences were in species richness or another variable.

Author Response

Dear Reviewer,

All suggestions have been carefully considered. Necessary editings are highlighted in red in the text file. We also uploaded word form of our revisions.

 

Comment 1: This study examines bird diversity patterns in Mediterranean countries by utilizing citizen science platforms, such as eBird. In my opinion, this study could be significantly improved. The introduction and materials and methods sections should be shortened substantially to focus on the research aims. Additionally, richness estimates and their analyses should be refined, as bird datasets are derived from non-controlled sampling methodologies. I suggest using rarefaction extrapolation curves to obtain richness estimates that are comparable in sampling effort among regions and years (L70-71).

Response 1: We thank the reviewer for the constructive feedback. The suggestions regarding the length and focus of the Introduction and the Materials and Methods sections, as well as the refinement of richness estimates and analyses, have been addressed and revised in accordance with the reviewer’s recommendations.

With respect to the use of rarefaction extrapolation curves, we fully acknowledge the validity of the reviewer’s perspective. However, rarefaction generally requires coverage, abundance, or frequency data, rather than presence–absence records, as it standardizes sampling to the lowest abundance level. While such an approach could theoretically have been applied regionally in our study, it was not feasible at the provincial scale. Considering each province as a sampling unit across seasons, the absence of abundance data made rarefaction inappropriate. Moreover, dependent rarefaction approaches are known to cause significant information loss, with standardized richness estimates potentially diverging from actual values.

On the other hand, independent rarefaction, as proposed by Sanders (Sanders, H. L., 1968. Marine benthic diversity: A comparative study. The American Naturalist, 102(925), 243–282), was designed to overcome some of these issues by using a different algorithm. However, this method also relies on individual abundance data, which were not available in our dataset. Additionally, if rarefaction had been applied in this study, it would have precluded us from using the Dunn test to analyze seasonal and regional variations simultaneously.

Nevertheless, we highly value the reviewer’s insightful suggestion and agree that this methodological consideration is important. Accordingly, we have included a note in the revised manuscript discussing the limitations and implications of applying rarefaction in studies based on presence–absence data.

 

Comment 2: L70-71. Provide examples of these publications.

Response 2: We appreciate the reviewer’s comment. We would like to note that the relevant examples have already been included in the manuscript. Specifically, the section reads:

"A Web of Science keyword search reveals that during 2010–2020, over 75,000 articles were published in academic journals with the word “bird” in the title or abstract—an increase of more than 70% since the previous decade [15–21]. Among these studies, those that determine the habitat preferences of bird species and relate them to climatic factors are of great importance. The findings from such research play a key role in developing ecological-based planning aimed at ensuring the sustainability of bird species [22–24]."

As indicated, the references [15–24] cited in this section serve as concrete examples of the studies mentioned.

 

Comment 3: L71-73: Explain how this research plays a key role in developing ecologically based planning.

Response 3: We appreciate this insightful comment. The sentence has been revised to better clarify the role of such research in ecological planning. The revised version reads:

"The findings from such research play a key role in developing ecologically based planning aimed at ensuring the sustainability of bird species, as they provide critical evidence on how habitat preferences interact with climatic factors. Such insights are essential for identifying priority areas for conservation, designing effective habitat management strategies, and ensuring that migratory routes and breeding grounds remain viable under changing environmental conditions [22–24]. A recent review of the scientific literature, largely focused on Europe and North America, shows that 24% of the 570 bird species studied globally have already been negatively affected by climate change to date, while only 13% have responseed positively. For half of those studied, the impact remains uncertain [25,26]."

 

Comment 4: L78-86: This sentence is out of context. This paragraph should be summarized and linked to another text.

Response 4: We thank the reviewer for this helpful observation. We have revised the paragraph to provide a concise summary that links directly to the surrounding text. The revised version reads:

"Birds, with their global distribution and ecological diversity, are highly sensitive to environmental change and can act as early indicators of ecological threats. Many species are already responseing to climate change by shifting their distributions or altering the timing of key life-cycle events such as migration [21,27]."

This revision removes the excessive detail while preserving the essential context and linking the content more directly to the following discussion on climate change impacts.

 

Comment 5: L87-90: Support these statements with references

Response 5: We thank the reviewer for this important comment. The section has been revised to include the requested supporting references. The updated version now reads:
"Bird migration occurs as an instinctive response to survival and the search for new habitats when the topographic and climatic factors in their living areas are altered, either naturally or artificially (Moss, 2015; Raja et al., 2024). During migration, birds often follow the same routes every year (Trierweiler et al., 2014)."

These references strengthen the statements and ensure that the claims are well-supported by recent and authoritative literature.

 

Comment 6: L104-108: Previous studies are mentioned here, but no citations are provided.

Response 6: We have revised the section to include appropriate citations supporting the statements about previous research trends. The updated version now reads:

"As evident from the information provided, environmental factors such as topography and climate, along with migratory routes, are key parameters influencing the distribution of bird species (Moudrý and Šímová, 2013; Somveille et al., 2019). A review of studies in this field reveals that early research primarily focused on fauna identification (Kumerloeve, 1961; Ergene, 1945). However, over time, factors such as shifts in ecological paradigms, advancements in statistical approaches, and technological developments have broadened the perspective of these studies (Wood and De Pietri, 2015).

These references provide the necessary scholarly support for the statements and strengthen the contextual background of the paragraph.

 

Comment 7: L110-152: This historical information should be summarized in a few lines or included as supplementary material.

Response 7: The paragraph has been substantially revised and condensed to improve focus and flow. The updated version now reads:

"In Türkiye, ornithological research has a history of more than a century. Early efforts in the 1920s by Turkish biologist Ali Wahby and subsequent work by foreign and local scholars laid the foundation for documenting the country’s avifauna [30]. From the mid-20th century onwards, systematic studies expanded with contributions from Prof. Curt Kosswig, Dr. Saadet Ergene, and later Max Kasparek, whose publications and the first national inventory of Important Bird and Biodiversity Areas (IBAs) marked significant milestones [33,40]. These pioneering efforts provided the baseline knowledge that underpins modern ornithological research and conservation planning in Türkiye, where IBAs now play a central role in safeguarding avian diversity [41,42]."

 

Comment 8: L170-171: This is a result; it should be presented in the Results section (move or delete).

Response 8: The sentence in question has been removed from the Introduction to maintain the appropriate structure and to ensure that results are only presented in the Results section.

 

Comment 9: L195: The world map in this figure could be deleted or made smaller to show this country in its regional context.

Response 9: The location map was deleted considering the number of pages in the article. Study area was expressed in the text in detail.

 

Comment 10: L208: The information in Table 1 could be displayed in Figure 1, so Table 1 could be removed.

Response 10: Table 1 has been removed. Regions are expressed in the text.

 

Comment 11: L201-256: The information in this section is bibliographic, not methodological. Please summarize it and highlight the most important aspects that you used to test your research questions.

Response 11: The section has been revised to provide a more concise summary that directly emphasizes the aspects relevant to our research questions. The updated version now reads:

"Türkiye, situated at the crossroads of Europe, Asia, and Africa, lies on two major global bird migration routes and hosts exceptional avian diversity. According to recent Trakus data, over 500 bird species have been recorded in the country, with the majority listed on the IUCN Red List [66–68]. Its location across three major phytogeographical regions (Euro-Siberian, Mediterranean, and Irano-Turanian) and its varied topography and climate provide a wide range of habitats that critically influence bird species richness and migration patterns [69–71]. Key migratory corridors such as the Bosphorus, the Dardanelles, and Iskenderun Bay support massive seasonal movements, including the largest raptor migration in the Western Palearctic [28,77]. These ecological and geographical features formed the basis for our analysis of spatial, climatic, and seasonal variations in avian species richness across Türkiye."

This revision ensures that only the information directly relevant to the study’s objectives is included, while the broader historical and descriptive details have been omitted for clarity and focus.

 

Comment 12: L274-280 and L290-292: Move this information to the data analysis section below. Here, you refer to data analysis rather than data acquisition.

Response 12: The sentences which referred to data analysis rather than data acquisition, have been removed from this section to avoid redundancy and maintain clarity.

 

Comment 13: L344: "We utilized the Köppen-Geiger climate classification..." Please indicate the purpose of using these data.

Reponse 13: The sentence has been revised to clearly indicate the purpose of using the Köppen-Geiger classification. The updated version now reads:

"We utilized the Köppen-Geiger climate classification, one of the most widely applied and globally recognized systems, due to its ability to integrate both temperature and precipitation patterns into ecologically meaningful climate categories. This approach enabled us to illustrate regional climatic differences in a standardized manner and to directly assess their influence on spatial and seasonal variations in avian species richness across Türkiye. Originally introduced by Köppen in 1900 and refined by Geiger in 1961, this classification remains a cornerstone in ecological and biogeographical research [132,133] (Table 1)."

This revision provides a clear scientific rationale for the use of the Köppen-Geiger classification in the context of our study.

 

Comment 14: L329 and L354. Tables 2 and 3 and Figures 2 and 3 are only accessory; move them to the supplementary materials.

Response 14: In accordance with the reviewer’s recommendation, Table 2, Table 3, and Figure 2 have been moved to the supplementary material. However, Figure 3 has been retained in the main text, as it is directly linked to Figure 4 and represents a key output of the applied methodology. Relocating it to the supplementary section would make it difficult for readers to follow the flow of results and the connection between figures.

 

Comment 15: L361: "The differences..." Please explain whether these differences were in species richness or another variable.

Response 15: This part has been revised to specify the variable under investigation. The updated version now reads:

"To determine the appropriate method for assessing whether the differences in bird species richness across seasons, regions, and Köppen-Geiger climate classes were statistically significant, the Kolmogorov-Smirnov normality test [85–87] was applied. Since the analysis showed that the assumption of normality was not met, a logarithmic transformation was applied to the data. However, even after this transformation, the normality assumption was still not satisfied. Hence, we used the non-parametric Kruskal-Wallis test [88] to examine the differences between groups."

This revision makes it clear that the differences assessed refer specifically to bird species richness.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The study is based on eBbird data collected by the Cornell Lab in USA. Data collected by bird watchers may contribute to good scientific anaysis, and the paper exemplifies this. The statistical analysis was proberly conducted and results are well-presented on the maps. The study provides vital information on diversity of migrants birds for a country which was not well-studied in that regard, but very important for migratory birds.

The major problem with the paper is that we actually do not know what was the sample size upon which authors based their conclusions. Even in the whole statistical analysis, it is not known about the sample size, and it is crutial to properly evaluate the whole study. In lines 269-270 they provide this sample (89 milions of checklisr, 1.2 bln. records collected by 700 000 birdwatchers), but this is for the whole world, not for Turkey. We need to know these figures for Turkey.  

The other problem with the paper is that the "Introduction'  and to a lesser degree 'Study area' and 'Methods' sections are to long. Lots of unnsecessary information. The 'Introduction' should be shortened at least by 50%. For example most of the informations in lines 65-73, 78-103, 110-140 can be deleted. On the other hand there is a lack of vital information in the 'Introduction' section: what was the aim/hypothesis of this study? In the study area, no information on the surface size of the country as well as all the provinces are provided. Also the size of area affects the number of bird species recorded in each province, although the authors have not discussed this issue. 

The maps (Figure 3 and 4) comprise the core of this paper, data are here well presented, but the maps would be much more interesting/comprehensive if the borders of the three major zones  (Mediterranean, Euro-Siberian and Irano-Turanian; line 222) are also shown on these maps.  Perhaps the regions listed in Table 1 should also include the information on the three zones (each region should be affiliated to one or two of these 3 zones).

In Table 3 English names should be also included. The lines 440-449, where statistical mathod is described, should be shifted to 'Methods' section.

There are some minor technical errors, eg. in line 401: Apus pallidus should be in italics; and  in line 586 'National' should be with small letter.

  

Author Response

Dear Reviewer,

All suggestions have been carefully considered. Necessary editings are highlighted in red in the text file. We also uploaded word form of our revisions.

 

Comment 1: The major problem with the paper is that we actually do not know what was the sample size upon which authors based their conclusions. Even in the whole statistical analysis, it is not known about the sample size, and it is crutial to properly evaluate the whole study. In lines 269-270 they provide this sample (89 milions of checklisr, 1.2 bln. records collected by 700 000 birdwatchers), but this is for the whole world, not for Turkey. We need to know these figures for Turkey. 

Response 1: The relevant section has been revised accordingly. The study is based on bird species data from the Trakuş and eBird databases. Trakuş, which has documented bird species in Türkiye since 2007, reports that by 2023 a total of 461 species had been confirmed, with 505 species potentially occurring in the country [68; Kocaman, 2023]. The number of birdwatchers contributing to these records has increased from about 200 in 2010 to over 8,700 by 2025 [Dinç & Ok, 2022; Kocaman & Arslan, 2023]. As of 2025, Türkiye ranks 33rd globally in bird observations, with more than 179,000 individual records. The provinces with the highest observation numbers include İstanbul (36,122) and Ankara (12,790), reflecting a significant increase in recent years [135].

This clarification ensures that the results are transparently linked to Türkiye-specific data rather than global datasets.

 

Comment 2: The other problem with the paper is that the "Introduction'  and to a lesser degree 'Study area' and 'Methods' sections are to long. Lots of unnsecessary information. The 'Introduction' should be shortened at least by 50%. For example most of the informations in lines 65-73, 78-103, 110-140 can be deleted. On the other hand there is a lack of vital information in the 'Introduction' section: what was the aim/hypothesis of this study? In the study area, no information on the surface size of the country as well as all the provinces are provided. Also the size of area affects the number of bird species recorded in each province, although the authors have not discussed this issue.

Response 2:We thank the reviewer for this insightful comment. In accordance with the recommendation, the Introduction, Study Area, and Methods sections have been substantially shortened by removing unnecessary details, particularly those indicated by the reviewer. To address the lack of clarity regarding the scope of the study, the aim and hypothesis have now been explicitly added to the end of the Introduction:

"The primary aim of this study was to investigate the spatial, seasonal, and climatic variations in bird species richness across Türkiye, a key region located at the intersection of major migratory flyways. We hypothesized that bird species richness would show significant variation among provinces, reflecting differences in climate, topography, and habitat diversity, and that both seasonal dynamics and climatic conditions would play critical roles in shaping these patterns."

Additionally, information on the surface size of Türkiye and its provinces has been added to the Study Area section. The potential influence of area size on species richness has also been discussed in the Discussion section to address this important point.

Added part to the discussion: “While these ecological and habitat-related factors strongly influence avian richness, the comparability of richness estimates across regions and seasons also depends on the methods used to standardize data. Rarefaction extrapolation curves are often suggested for such purposes, as they account for unequal sampling effort. However, the application of rarefaction was not feasible in this study. This is because rarefaction requires abundance, frequency, or coverage data, whereas our dataset was based on presence–absence records at the provincial level. Dependent rarefaction could have resulted in substantial infor-mation loss, and independent approaches (Sanders, 1968) also require abundance data that were not available. Moreover, applying rarefaction in this context would have limited our ability to use Dunn’s test to examine both seasonal and regional differences simul-taneously. Nevertheless, rarefaction remains a valuable tool for enhancing comparability in biodiversity studies, and we recommend its consideration in future research where appropriate abundance data are available.”

 

Comment 3: The maps (Figure 3 and 4) comprise the core of this paper, data are here well presented, but the maps would be much more interesting/comprehensive if the borders of the three major zones (Mediterranean, Euro-Siberian and Irano-Turanian; line 222) are also shown on these maps. Perhaps the regions listed in Table 1 should also include the information on the three zones (each region should be affiliated to one or two of these 3 zones).

Response 3: We thank the reviewer for this thoughtful and constructive suggestion. In line with another reviewer’s comment, Table 1 was removed and its content integrated into the main text to improve clarity and flow. However, we fully agree that associating geographical regions with phytogeographical zones provides valuable ecological context. Therefore, we revised the “Study Area” and “Avifauna and Migration Routes of Türkiye” sections to explicitly include information on the three major phytogeographical zones (Euro-Siberian, Mediterranean, and Irano-Turanian) and their spatial correspondence with Türkiye’s geographical regions.

This revision ensures that readers gain a clearer understanding of how the country’s topographical and climatic diversity aligns with major phytogeographical divisions, which in turn influence avian biodiversity. While we did not incorporate these phytogeographical borders directly into the maps due to limitations in spatial resolution and overlap, we believe the inclusion of this information in the text enhances the ecological depth of the study.

 

Comment 4: In Table 3 English names should be also included. The lines 440–449, where the statistical method is described, should be shifted to the 'Methods' section.

Response 4: We thank the reviewer for these helpful suggestions. In accordance with the recommendation, Table 3 has been moved to the supplementary material and the English names of the bird species have been added. Additionally, the lines describing the statistical method (440–449) have been revised and relocated to the Methods section to ensure methodological clarity and consistency.

 

Comment 5: There are some minor technical errors, eg. in line 401: Apus pallidus should be in italics; and  in line 586 'National' should be with small letter.

Response 5: We thank the reviewer for the careful reading of our manuscript. The first issue has been corrected, and Apus pallidus is now written in italics. Regarding the second point, we would like to clarify that “Nature Conservation and National Parks” refers to the official name of a governmental body; therefore, “National” remains capitalized as part of the proper noun.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I see that the authors have improved their manuscript following my previous comments. I think only one point needs to be discussed: how variation in the sampling effort could have impacted the results. It is known that citizen science data is heterogeneously distributed, so regions with more data should exhibit more species than less explored regions (this effect may be modified by differences in area between regions).

Author Response

Comments1: I see that the authors have improved their manuscript following my previous comments. I think only one point needs to be discussed: how variation in the sampling effort could have impacted the results. It is known that citizen science data is heterogeneously distributed, so regions with more data should exhibit more species than less explored regions (this effect may be modified by differences in area between regions).

Response1: 

We thank the reviewer for this very insightful and well‑founded comment. We agree that relying solely on species richness data, while providing a consistent and comparable measure across provinces, does not fully capture ecological dynamics that could be revealed through abundance or frequency data. As the reviewer correctly notes, incorporating such measures could improve accuracy. However, we also note that in large‑scale citizen science datasets such as those used here, abundance and frequency records often introduce additional biases due to uneven observer effort and inconsistent reporting practices.

To address this point, In our latest version, we added the necessary clarifications to the end of the Discussion section (Line 514-527). We believe this is a very important clarification that will inform future studies. We explain that although abundance data could offer valuable ecological insights, their use without standardized sampling protocols may actually amplify bias. We also highlight that dependent rarefaction approaches risk substantial information loss, while independent rarefaction methods (Sanders, 1968) require abundance data that were unavailable in this context. Consequently, directly observed species richness at the provincial scale was deemed the most reliable metric for this study. Nevertheless, we emphasize that this represents a limitation, and we recommend that future research integrate standardized abundance or frequency data, when available, to refine understanding of avian diversity across Türkiye.

Author Response File: Author Response.docx