Breeding Habitat Suitability Modeling to Inform Management Practices for the European Turtle Dove (Streptopelia turtur) in NE Greece

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

A brief summary

The manuscript titled "Breeding Habitat Suitability Modeling to Inform Management Practices for the European Turtle Dove (Streptopelia turtur) in NE Greece" presents the results of distribution modeling for the Turtle Dove in the Evros province of northeastern Greece. The research employed the widely used Maxent approach, and data on the species' distribution were collected through a systematic two-year study across a representative number of sites. Key findings of the study include the effects of selected ecological variables on the species' distribution, a spatially explicit representation of suitable habitat distribution, a map of suitable habitats, the quantification of the impact of the mega-fire in 2023 on suitable habitats in the Evros province, and the representation of suitable habitats within the Natura 2000 network. The results hold significant scientific importance, given that the Turtle Dove is endangered at both global and European levels, and there is a lack of information regarding population trends, habitats, status, and threats along the eastern migratory flyway, which includes the population from Greece. Furthermore, the study identified and quantified the effect of mega-fires, which represent a relatively novel and poorly studied threat in the Mediterranean. The research quantified the contribution of Natura 2000 network, which is vital considering that habitats of farmland birds, including the Turtle Dove, are generally underrepresented in protected areas. The manuscript also highlights several specific habitat management measures that could contribute to the conservation of the species.

General concept comments

Article:

The research is well-designed, featuring a very straightforward methodological approach, and the manuscript presents clear results that are commented on in a logical manner. However, I would like to point out two minor weaknesses:

1. The manuscript states that 34 variables were taken into consideration (describing land cover, climate, topography, and geology), after which some were removed from the analysis due to correlation. The first issue is that I am uncertain whether some of the variables listed in the table can be classified as geology; I believe it would be more accurate to refer to these as Soil Information (according to the source cited in the References). Additionally, none of the topographical variables are mentioned in the manuscript. Therefore, I think it is necessary to a) provide a list of all variables that were initially considered; b) review the naming of variable categories; and c) explain the rationale behind the selection of potential variables. For instance, the relationship between Mean cation exchange capacity (at pH 7), Mean organic carbon density, Mean pH of water, and species distribution is indirect, and it would be beneficial to elucidate the mechanism by which these factors interact.
2. I suggest that the manuscript include an additional map that depicts a gradient of habitat suitability. The map currently presented is binary, indicating areas that are suitable (with a presence probability higher than the selected threshold). However, a map displaying varying values of presence probability would be informative, as it would highlight the most favorable areas for the Turtle Dove within the study area.

Review:

This study holds significant relevance in terms of scientific contribution and species conservation, featuring clearly defined objectives, appropriate methodology, well-presented results, and a well-reasoned discussion and conclusions. However, several points should be emphasized in the Introduction (or potentially in the Discussion) to enhance the scientific value of the manuscript, particularly regarding the lesser-studied eastern flyway of the Turtle dove; habitats for farmland birds are generally underrepresented in protected areas, especially in S and SE. I have addressed these points in the Specific Comments. Overall, the manuscript has a clear structure, the topic is well-defined, and the information is presented comprehensively.

The figures and tables presented in the paper are clear and appropriate. The methodology and statistical approach are suitable. Ethics statements and data availability statements should be included to ensure their adequacy.

In my opinion, the manuscript should be accepted after minor revisions as outlined in the Specific Comments.

Specific comments:

Line 35: I believe that a similar comparison can be made with short-distance migrants.

Line 41: It may be beneficial to cite a more contemporary reference, considering the short generational period of the Turtle Dove—three generations equate to 15.9 years (BirdLife International 2015)—and the assertion that the population is changing rapidly (which implies that the situation may have altered over the past decade). One of the indicators of this change is the results from the Pan-European Common Bird Monitoring Scheme (PECBM) (https://pecbms.info/trends-and-indicators/species-trends/), although these are not the only indicators of population changes. This comment is merely a suggestion for the authors, not obligatory.

Line 43: I believe it is important to mention that the species is listed as Vulnerable (VU) on the global Red List (BirdLife International, 2019. Species factsheet: European Turtle-dove Streptopelia turtur. Downloaded from https://datazone.birdlife.org/species/factsheet/european-turtle-dove-streptopelia-turtur on 20/02/2025).

Lines 50-61: It may be significant to note that the Greek population is part of the so-called eastern flyway, whose status is less researched compared to the western flyway, a point that I believe is highlighted in the action plan for species conservation. I would argue that this represents a significant added value of this research.

Line 65: A clarification regarding the term "protection gap" would be useful (an alternative formulation could be "protected area gap" or something similar). A gap analysis of the spatial overlap of suitable habitats with Natura 2000 is assessed, which I believe is quite important considering that the turtle dove inhabits farmland, and that farmland bird habitats in many S, E and SE countries are disproportionately under-represented in the protected area network. The gap analysis of Natura 2000 is an informative aspect of this research that should be more prominently stated in the objectives. Therefore, while the analysis has been conducted, its significance should be emphasized in the objectives.

Lines 70-80: A few additional pieces of information would be informative: 1. What is the area of Natura 2000 sites in the Evros province? This information describes the level of protection within the study area and is later used to calculate the overlap with Natura 2000. 2. What is the area (or percentage share) of the main habitat types (Agricultural land, Forest, and seminatural areas) in the Evros province? Furthermore, a few more details that are not visible on the map would be useful (e.g., the area covered by forests versus that covered by open seminatural habitats).

Lines 81-84. Comments on the map: Since I am not familiar with the geography of the region, I am uncertain what the polygons with thin gray borders in the map background represent. Are they isohypses that describe the relief, or do they delineate habitat patches? Additionally, I suggest that instead of using "sites of turtle dove presence," the phrase "locations of turtle dove presence" be utilized (as “sites” can refer to a broader, unspecified geographical area). If I understand correctly, these refer to the central coordinates of grid cells where the turtle dove has been recorded.

Lines 85-98. Although it is obvious, I believe it is important to emphasize that the presence data pertains to the breeding season, and that the distribution maps relate to suitable breeding habitats. During migration, the habitats selected by the turtle dove are different.

Lines 100-101. I assume that the variables describing the geology are Mean Cation Exchange Capacity (at pH 7), Mean Organic Carbon Density, and Mean pH of Water. I think it would be more accurate to refer to these as Soil Information (according to the source listed in the References) rather than geology. In general, it would be useful to specify how many variables from each category (climate, land cover/habitat, topography, and geology/soil information) were considered (the text only presents the total number of variables). Furthermore, a brief description of the potential effects of the "geology" (soil) variables on the turtle dove would be beneficial. For the other variables, it is quite clear why they were chosen, as habitat characteristics are explicitly stated as a key factor in the conservation of the species; however, the assumed mechanism of effects for the "geology" variables is not as obvious (i.e., the rationale for their inclusion). What specific topographic variables were considered?

Line 133: Technical clarification regarding how suitable habitats (1x1 km raster) overlapped with polygons designating protected areas (e.g., whether there was a threshold based on which a grid cell was considered protected if it partially overlapped with a protected polygon).

Line 172: It would be more precise to state that 24% of habitats were "affected" rather than "lost" due to megafires. If I understand correctly, the percentage calculated reflects the grid cells that were impacted by the fire; however, the fire likely did not completely, uniformly, and permanently destroy all fragments of suitable habitats, especially considering that fires can contribute to a reduction in tree density in forests, which may theoretically have some positive effects. (Nonetheless, I could be mistaken as I am not fully familiar with the effects of megafires in Evros.)

Line 181: Does this refer to all types of forest in Europe or all types of forest present in the study area? I am unsure whether the turtle dove nests in, for example, boreal forests.

Line 230: "Such areas" – does this refer to portions of Natura 2000 sites where Agri-Environmental Schemes (AES) are implemented? A small clarification is needed.

Author Response

Please see the attachement

Author Response File: Author Response.doc

Reviewer 2 Report

Comments and Suggestions for Authors

General comments

 

This study focuses on a single avifauna species, namely European Turtle Dove (Streptopelia turtur). It is a modelling work with emphasis on this species' breeding sites. The rationale of this study is the shrinkage in suitable habitats.

 

Several variables were identified as important from the models. It is true that the European Turtle Dove breeds in different habitats. Tree cover density and the percentage of different types of agriculture lands were identified as important. Farms are usually not covered by tree canopy. Therefore, it is wondered whether the intersection between farmland and forest would suit European Turtle Dove. 

 

This manuscript is written in good English language and it aids the comprehension of the advanced spatial analysis. The references are relevant. Excessive self citation is not detected. More specific comments are listed below.

 

Abstract

 

Line 11 to 12

A clear study objective can be provided before stating the study methods. 

 

Line 12

The word "here" can be deleted.

 

Line 14 to 17

The important variables were listed. Combining these habitat description, the authors can provide general description of the habitat types preferred by the European Turtle Dove.

 

Line 21 to 22

The impact of wildfire was quantified by the frequency of recent fire. Yet, the recovery of the habitats can be mentioned too. 

 

Introduction 

 

Line 34

Maybe the authors can cite a few quantitative studies to illustrate the seriousness of the degradation in breeding habitats. For readers outside Europe, it would be hard to imagine the degradation. 

 

Line 43

The IUCN conservation status of this bird can also be provided. 

 

Line 50 to 61

This paragraph generally describes the species in the context of ISSAP. But it may be better to limit the description to Greece. 

 

Methods

 

Line 77

More elaboration on the characteristics of farmland may be needed, as the European Turtle Dove is probably a farmland-dependent species. 

 

Line 86 to 98

Who conducted the field surveys? Were there training on the identification of the vocalisation of the European Turtle Dove?

 

Line 100 to 135

The description of the workflow of the spatial modelling is adequate. This part can be kept in its current form. 

 

Results

 

Line 137 to 140

An overview of generated models can be provided before detailing the best one. 

 

Line 141 to 145 

It is vital to investigate the correlation among the important variables. Have any models be built using the important set only? 

 

Discussion 

 

Line 178 to 191

The discussion about the relative importance and relevance of important variables is well written. I suggest that this part should be retained in the revised versions of this manuscript 

 

Conclusion 

I have no critical comment on this section.

 

 

Comments on the Quality of English Language

The manuscript was written in fairly good English language.

Author Response

Please see the attachement

Author Response File: Author Response.doc