Analysis of the Distribution Pattern and Trait Determinants of Avian Diversity at Mid-Altitude in the Gyirong Valley

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General
This paper seeks to relate bird species traits to bird distributions and they then proposal to give conservation suggestions for birds in the Gyirong valley.   I found the study area to be interesting, particularly given the altitudinal gradient covered. 
However, the paper seemed a bit thin in places. Although the aims are outlined, it wasn’t clear to me what the hypotheses were/ specific questions that were going to be addressed.  I felt the introduction lacked a section on specifically why the authors expected the findings of their study to be useful for the “targeted conservation strategies” that they mention in the abstract. Please can the introduction have a few lines on that.  Later, the final conclusions are that habitat heterogeneity should be conserved, but that is a general conclusion that just about every study should conclude, and would not require these interesting analyses to arrive at.  
I include some specific suggestions below.
Specific
Line 23 – insert year after May-June
Lines 24 – 25 - We analyzed the influence of bird species composition, habitat distribution, and ecological characteristics on bird distribution patterns using R 4.4. – how does bird species composition affect bird distribution patterns, do you look at species interactions? 

Line 27 – change order of sentence, as written, it makes it look as if Phylloscopidae are in a different order to Muscicapidae
Line 29 ff – “birds of different ecological types” –please expand on what that means? Do you mean generalists vs specialists, or do you refer to feeding or perhaps nesting niches? 
Line 30 – entire sentence, is this a finding of your study, or is this a general finding you are reporting from the literature? Did you assess conservation threat status of your species?  Remember that an abstract needs to be able to be read as a “Stand alone” piece, and the reader must have a good idea of your main aims, results and conclusions after reading it.
Line 62ff – the line “The environment acts as a filter for birds at different elevations, with harsh natural conditions often filtering out species with strong adaptability[10, 13].” “Filtering out” makes it sound as if species with strong adaptability are excluded, whereas the opposite is true. So I think perhaps say something like “often leaving only strongly adaptable species within assemblages”?
Lines 65ff – this entire paragraph lacks references to support it. Please remedy this.
line 120 perhaps here you should say what the morphological characters are that you measure, or put them in a table and refer to that, here.
Line 130 – to what distance from the observer did you include birds? Or was it unlimited distance? How did you ensure you didn’t double count birds, i.e. count the same bird twice?
Line 144 – I have no idea what varnivorous means, and I can’t seem to find out from google. What does this mean? I also don’t see that you have granivorous birds included, which I find strange?
Line 147 – suggest giving these trait data in a table in the online supplementary information, and referring to that, here – it will be a useful resource for other researchers, who will also then cite your paper.
Line 153 – preface this with a “In order to..” statement, to explain WHY you are doing certain things in your methods.  So, e.g. “to account for phylogenetic relatedness, we…”
Line 168- 169 – correlation analysis – is that one trait per analysis? What about if a trait is affected by other traits, and you have to account for that, first?
Line 196 – are there really no granivorous birds in this system?
Line 225- You discuss a relationship with human created habitats, but you say you were trying to avoid human affected habitats, in your intro/methods?
Line 228 – why do these two robins have the same scientific name?
Figure 5 – plural of families is misspelt
Line 274 – “morphological traits such as bill length, body length, tail length, tarsus length, weight, and wing length significantly promote the construction of bird population size.” Please reword, I am not sure what is being said, here. Same applies to the following sentence.
Line 291 – rather start your discussion with a short paragraph containing your real “Whiz-bang” findings.
Line 302 – Pheasants are not Passeriformes 
Line 366- you use flower eating and nectarivorous interchangeably. Perhaps choose one and stick with it. Nectarivorous is more traditional, if I understand the way you’re using it.

 

Author Response

Comments and Suggestions for Authors

General

This paper seeks to relate bird species traits to bird distributions and they then proposal to give conservation suggestions for birds in the Gyirong valley.   I found the study area to be interesting, particularly given the altitudinal gradient covered. 

Response: We sincerely appreciate your insightful comments and constructive suggestions

Comments 1: [However, the paper seemed a bit thin in places. Although the aims are outlined, it wasn’t clear to me what the hypotheses were/ specific questions that were going to be addressed.  I felt the introduction lacked a section on specifically why the authors expected the findings of their study to be useful for the “targeted conservation strategies” that they mention in the abstract. Please can the introduction have a few lines on that. ] 

Response 1:[Based on field observations,we think that the diet and morphological characteristics of birds influence the distribution patterns of birds in mountainous areas.]

Comments 2:Later, the final conclusions are that habitat heterogeneity should be conserved, but that is a general conclusion that just about every study should conclude, and would not require these interesting analyses to arrive at.  

Response 2:[Thank you for your suggestions.We have made adjustments in the discussion sections,so we focused on the impact of diet and morphological characteristics on bird community structure in the discussion section.]

Comments 3: [Line 23 – insert year after May-June]

Response 3: [We have inserted year after May-June

(L 23) (May-June 2024)]

Comments 4: [Lines 24 – 25 - We analyzed the influence of bird species composition, habitat distribution, and ecological characteristics on bird distribution patterns using R 4.4. – how does bird species composition affect bird distribution patterns, do you look at species interactions? ]

Response 4： [The previous expression was not accurate，so we revised it as follows:

(L 25-26) We analyzed the bird species composition, habitat distribution, and the influence of ecological characteristics on bird distribution patterns using R 4.4.]

Comments 5: [Line 27 – change order of sentence, as written, it makes it look as if Phylloscopidae are in a different order to Muscicapidae]

Response 5：[We Reorganized the content of the sentence as follows:

(L 28-30) Among them, birds from the families Muscicapidae and Phylloscopidae within the order Passeriformes constitute the dominant groups.]

Comments 6: [Line 29 ff – “birds of different ecological types” –please expand on what that means? Do you mean generalists vs specialists, or do you refer to feeding or perhaps nesting niches? ]

Response 6：[We Reorganized the content of the sentence as follows:

(L 31-32) Birds with different diets and morphological traits show distinct differentiation in habitat selection.]

Comments 7: [Line 30 – entire sentence, is this a finding of your study, or is this a general finding you are reporting from the literature? Did you assess conservation threat status of your species?  Remember that an abstract needs to be able to be read as a “Stand alone” piece, and the reader must have a good idea of your main aims, results and conclusions after reading it.]

Response 7：[This is a finding of our study ,the finding is explained by Figure 3 b and Figure 5 a.

(L 32-34) The higher the specialization rate of ecological characteristics, the smaller the population size of the birds, and the more likely they are to become endangered species.]

Comments 8: [Line 62ff – the line “The environment acts as a filter for birds at different elevations, with harsh natural conditions often filtering out species with strong adaptability[10, 13].” “Filtering out” makes it sound as if species with strong adaptability are excluded, whereas the opposite is true. So I think perhaps say something like “often leaving only strongly adaptable species within assemblages”?]

Response 8：[The sentence has been revised according to your suggestions as follows:

(L 63-65) The environment acts as a filter for birds at different elevations, with harsh natural conditions often  leaving only strongly adaptable species within assemblages[10, 13].]

Comments 9: [Lines 65ff – this entire paragraph lacks references to support it. Please remedy this.]

Response 9：[(L 66-78) The references have been added in the corresponding locations.

The research on the impact of ecological traits on bird communities mainly focuses on diet, body size, and the influence of ecological traits on community stability and seasonal migration patterns. Insectivorous birds prefer to choose seasons with abundant insects (breeding season) and areas with rich vegetation (such as forests), while frugivorous birds are more active in habitats where fruits are ripe[17]. Large-bodied birds are more inclined to forage in open habitats, whereas small-bodied birds mainly inhabit areas with dense vegetation[18]. The "fast-slow" functional traits of species have a greater impact on the stability of bird communities. Birds with "fast" functional traits (such as high reproductive rates and high metabolic rates) play a more critical role in maintaining community stability[19]. Montane breeding birds exhibit vertical migration, which generally follows three patterns: downslope shift, upslope shift, or no shift. Species that breeding at high and mid-elevations, nesting in shrubs, and having an omnivorous diet tend to downslope shift during the non-breeding season[5].]

Comments 10: [line 120 perhaps here you should say what the morphological characters are that you measure, or put them in a table and refer to that, here.]

Response 10: [(L 158-160) A total of 46 bird species were captured, and their morphological traits, including weight, body length, bill length, wing length, tail length, and tarsus length, were measured (Appendix Table S1).]

Comments 11: [Line 130 – to what distance from the observer did you include birds? Or was it unlimited distance? How did you ensure you didn’t double count birds, i.e. count the same bird twice?]

Response 11：[(L 136-139) In grassland habitats, bird species and their numbers seen or heard within 50 m on either side of the transect were recorded. In forest habitats, bird species and their numbers seen or heard within 25 m on either side of the transect were recorded [25], birds flying from the direction that had already been surveyed were not recorded to avoid double-counting.]

Comments 12: [Line 144 – I have no idea what varnivorous means, and I can’t seem to find out from google. What does this mean? I also don’t see that you have granivorous birds included, which I find strange?]

Response 12：[(L 157) The spelling of ”varnivorous” is incorrect; the correct word is “carnivorous”， we have revised it in the manuscript.]

Comments 13: [Line 147 – suggest giving these trait data in a table in the online supplementary information, and referring to that, here – it will be a useful resource for other researchers, who will also then cite your paper.]

Response 13：[We have tabulated these traits and placed them in Supplementary Table S1.]

Comments 14: [Line 153 – preface this with a “In order to..” statement, to explain WHY you are doing certain things in your methods.  So, e.g. “to account for phylogenetic relatedness, we…”]

Response 14：[(L 167-168) In order to understand the distribution pattern of bird diversity in the Gyirong Valley and the impact of traits on bird distribution, we conducted the following analyses.]

Comments 15: [Line 168- 169 – correlation analysis – is that one trait per analysis? What about if a trait is affected by other traits, and you have to account for that, first?]

Response 15：[(L 186-188) In this analysis, we employed a Structural Equation Modeling (SEM) approach, taking into account the interrelationships among traits.]

Comments 16: [Line 196 – are there really no granivorous birds in this system?]

Response 16: [I’m so sorry for the writing mistake. (L 218) There is no “granivorous birds” in this system; the correct word is “carnivorous.”]

Comments 17: [Line 225- You discuss a relationship with human created habitats, but you say you were trying to avoid human affected habitats, in your intro/methods?]

Response 17：[The intention was to express the effort to avoid disturbances from road traffic as much as possible.

(L 109-110) The road to the mountain has not been paved, resulting in relatively low levels of traffic disturbance.]

Comments 18: [Line 228 – why do these two robins have the same scientific name?]

Response 18：[Previous translation was incorrect. (L 280-282) We have rechecked the English and Latin names of the birds mentioned in the text. Such as the Plumbeous Water Redstart (Phoenicurus fuliginosus), Blue Whistling (Myophonus caeruleus), and White-capped Redstart (Phoenicurus leucocephalus)]

Comments 19: [Figure 5 – plural of families is misspelt]

Response 19：[Thank you for your reminding ,we have corrected the wrong word in the Figure 5.]

Comments 20: [Line 274 – “morphological traits such as bill length, body length, tail length, tarsus length, weight, and wing length significantly promote the construction of bird population size.” Please reword, I am not sure what is being said, here. Same applies to the following sentence.]

Response 20：[We have reinterpreted the content of that section as follows:

(L 347-350) At the elevation band of 2800-3400 m, morphological traits of birds such as bill length, body length, tail length, tarsus length, weight, and wing length are positively correlated with bird population size. That is, the larger the morphological traits of birds in this elevation band, the larger their population size.]

Comments 21: [Line 291 – rather start your discussion with a short paragraph containing your real “Whiz-bang” findings.]

Response 21：[We have added this content to the text as follows:

(L 366-375) This study explored the species composition, ecological traits, and the relationship between ecological traits and distribution patterns of breeding birds at mid-elevations in the Gyirong Valley. It provides a new perspective for mountain bird research and highlights the importance of habitat heterogeneity in shaping bird community structure. We recommend that habitat heterogeneity be emphasized in the conservation of mountain ecosystems to meet the habitat needs of birds with different ecological traits. Future research should be conducted in a broader range of typical mountain ecosystems and over longer time periods to more deeply reveal the long-term impacts of ecological traits on bird distribution patterns and to further improve the scientific system for the conservation and management of mountain birds.]

Comments 22: [Line 302 – Pheasants are not Passeriformes ]

Response 22：[Thank you for your reminding. We checked that pheasants are Galliformes, We did not find any pheasants on line 302. ]

Comments 23: [Line 366- you use flower eating and nectarivorous interchangeably. Perhaps choose one and stick with it. Nectarivorous is more traditional, if I understand the way you’re using it.]

Response 23：[Thank you for your suggestion. (L 408) We have changed "flower eating" to "nectarivorous" and unified the terminology throughout the text.]

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

An interesting manuscript that studies the effect of altitude on the composition of bird communities. There are many interesting observations and information in the manuscript, but in some cases it lacks coherence. I summarize my comments below and recommend that the manuscript be further worked on and the weaker parts be fine-tuned. The manuscript declares an overlap with nature conservation, which would suit it very well, but especially from this perspective, a number of things still need to be added to and interpreted in the text.

Methods

L121 – 123 It would be necessary to describe how individual habitats are influenced by humans and to what extent they occur at individual altitudes. For agricultural land, I assume that extensive farming will be involved, but are forests economically influenced in any way? Do grasslands serve as pastures? What animals, etc. These things deserve a deeper description for further interpretation of the results.

L128 Surveys were conducted during the peak bird activity periods, 4 hours after sunrise and 3 hours before sunset - In my experience, evening activity is much lower than morning activity, and it also lasts for a shorter period of time. 3 hours before sunset seems quite a long time to me. Did you take this fact into your methodology? This problem can be solved, for example, by alternating the times of surveys on individual transects.

In the methodology does not also state how many surveys was made on each transect and how the surveys were distributed over the monitored period. Likewise, there is no information on how the final abundance for each transect was obtained - average, maximum or sum of the surveys carried out?

L130 It is not even stated at what distance from the transect you recorded the birds, which is a very important piece of information from a methodological point of view – “near the transects” is not enough. Even if this distance was not precisely determined, it should be stated. Another problem may be that the monitored habitats are of different clarity and the difference between them may bias the results.

L132 How many meters of nets were used at each site and how many days were birds captured?

L140 It would probably be more appropriate to unify the terminology within the article - guilds x traits.

Results

Results do not seem very clear, I recommend breaking them down by individual traits - Feeding traits and Morphological traits (instead of sub-chapters 3.2 and 3.3). always describe the composition of the trait and then its distribution pattern on the gradient of altitude and habitats.

The distribution pattern on the elevation gradient is described very inadequately, first in Figure 3a the total representation of individual food traits is shown and then in Figure 4a the range where they occur. But that does not tell us much, quantification of their representation in each elevation band would show much more. I recommend keeping Figure 4a, where the occurrence/absence is shown, but adding an even more detailed scheme of the distribution of individual traits in individual elevation bands. Similarly for size groups.

The results suddenly show the representation of individual traits in different types of habitats - but the methodology does not describe anywhere that the occurrence in individual habitats was recorded. The habitats themselves are only mentioned as a list of where they occur (L121 - 123), but their representation at individual altitudes is not quantified in any way, nor to which habitat types the records were assigned. This needs to be properly described in the methodology.

In the results, different units are used for different outputs - biomass (the methodology does not define how it was calculated), individuals, number of species, even though in one figure different traits are evaluated in different ways (Fig 4) - unifying the views would greatly contribute to the clarity of the outputs and enable a clear interpretation of the results. Both the view through bird richness and abundance are interesting - I would easily choose the procedure that both outputs will be listed in the results for each evaluation.

Even though one of the main aims is: „propose corresponding conservation suggestions for birds in the Gyirong Valley“ The article does not describe conservation traits (in the sense Zasadil et al. 2020) in any detail, only chapter 3.1 states which of the identified species are protected at the national level and which are included in the IUCN red lists. However, there is no quantification of the occurrence of these species in terms of altitudes and habitats. If the study is to have any conservation implications, I recommend focusing more on these conservation traits and evaluating them. From a conservation perspective, the occurrence of endemic species, etc., is also interesting.

How does total abundance and bird richness change with altitude? Some studies show a decreasing trend (e.g. Kebrle et al. 2022). Has this been confirmed here?

L189 Figure 2a I think it would rather belong in the appendices.

L189 Figure 2b The units in which biomass is expressed are not listed.

L196 foraging guilds – elsewhere in the text is used the term “feeding guilds” - the terminology needs to be unified within the article.

L210 Fig 3b In my opinion, it doesn't say much, either explain how this image is useful for the work or leave it out. Much more interesting is, for example, the distribution of individual clusters by altitude or habitats (Fig 4 c,d)

L246 wouldn't a "bird assemblage composition" be better?

Discussion and Conclusions

If the article is to have a conservation impact, it would be good to include not only the overall heterogeneity of the environment, but also to emphasize key habitats for the protection of bird biodiversity and the assessment of the impact of humans, natural processes and disturbances.

Author Response

Comments and Suggestions for Authors

An interesting manuscript that studies the effect of altitude on the composition of bird communities. There are many interesting observations and information in the manuscript, but in some cases it lacks coherence. I summarize my comments below and recommend that the manuscript be further worked on and the weaker parts be fine-tuned. The manuscript declares an overlap with nature conservation, which would suit it very well, but especially from this perspective, a number of things still need to be added to and interpreted in the text.

Response: We sincerely appreciate your insightful comments and constructive suggestions

Methods

Comments 1: [L121 – 123 It would be necessary to describe how individual habitats are influenced by humans and to what extent they occur at individual altitudes. For agricultural land, I assume that extensive farming will be involved, but are forests economically influenced in any way? Do grasslands serve as pastures? What animals, etc. These things deserve a deeper description for further interpretation of the results.]

Response 1：[The content of the section has been supplemented according to your suggestions.

(L 108-125) Dola Mountain is located to the southeast of Gyirong Town, with a summit elevation of approximately 4000 m. The road to the mountain has not been paved, resulting in relatively low levels of traffic disturbance. Between 2800 and 3100 m, the dominant vegetation consists of coniferous forests and shrublands, interspersed with small patches of farmland. Gyirong Town and Langjiu Village are situated within this elevation band. The urban area covers about 0.73 square kilometers, and traffic is the primary source of disturbance in this band, but the impact is relatively small.From 3100 to 3400 m, coniferous forests and farmland are predominant. Zha Village is located within this elevation band, where agricultural activities are the main source of disturbance. Between 3400 and 3700 m, mixed coniferous and broadleaf forests are the dominant vegetation type. Human activities are minimal, and there is no significant human disturbance in this band.The elevation band from 3700 to 4000 m is characterized by alpine meadows and shrublands, which serve as summer pastures for Zha Village and Kabang Village. Grazing is the primary disturbance in this band, but the scale of grazing is relatively small.The Dola Mountain area is not only home to a large number of rare birds but also provides ideal habitats for birds due to its diverse ecological environments. Different species of birds inhabit forests, shrublands, meadows, and agricultural landscapes.

 

No systematic surveys of other organisms have been conducted along this route,therefore, So we didn’t describe the animals in detail in the text. However, during the survey, we find several mammal species, including the Golden jackal(Canis aureus), Eurasian Wild Pig(Sus scrofa), yellow-throated marten(Martes flavigula), Mainland Leopard Cat(Prionailurus bengalensis), and Northem Red Muntjac(Muntiacus vaginalis).]

Comments 2: [L128 Surveys were conducted during the peak bird activity periods, 4 hours after sunrise and 3 hours before sunset - In my experience, evening activity is much lower than morning activity, and it also lasts for a shorter period of time. 3 hours before sunset seems quite a long time to me. Did you take this fact into your methodology? This problem can be solved, for example, by alternating the times of surveys on individual transects.]

Response 2：[(L 133-136) Thank you for your suggestions. We also noticed this phenomenon that evening activity is much lower than morning activity during the investigation. Surveys were conducted during peak bird activity periods, specifically 4 hours after sunrise and 3 hours before sunset. In each elevation band, two transects were surveyed in the morning and one in the afternoon.]

Comments 3: [In the methodology does not also state how many surveys was made on each transect and how the surveys were distributed over the monitored period. Likewise, there is no information on how the final abundance for each transect was obtained - average, maximum or sum of the surveys carried out?]

Response 3：[(L 139-142) During the survey, detailed records were kept of the habitats where bird activities were observed. A complete set of bird surveys was conducted for each elevation band, and the final abundance for each transect was obtained by summing the results of all surveys.]

Comments 4: [L130 It is not even stated at what distance from the transect you recorded the birds, which is a very important piece of information from a methodological point of view – “near the transects” is not enough. Even if this distance was not precisely determined, it should be stated. Another problem may be that the monitored habitats are of different clarity and the difference between them may bias the results.]

Response 4：[(L 136-139) In grassland habitats, bird species and their numbers seen or heard within 50 m on either side of the transect were recorded. In forest habitats, bird species and their numbers seen or heard within 25 m on either side of the transect were recorded.

Thank you for your suggestions. We also find that the thoroughness of the habitat survey in areas with high vegetation density is lower than that in habitats with an open view. S0 we slow down the survey speed in forest habitats to enhance the thoroughness of the survey.]

Comments 5: [L132 How many meters of nets were used at each site and how many days were birds captured?]

Response 5：[(L 144-146 ) A total of 13 mist netting sites were established, with each site equipped with 2–3 mist nets measuring 10 m in length and 6 m in width. Bird capture operations at each site lasted for two days. ]

Comments 6: [L140 It would probably be more appropriate to unify the terminology within the article - guilds x traits.]

Response 6：[Thank you for reminding ,we have unified guilds and traits,including the information in the picture and text.]

Results

Comments 7: [Results do not seem very clear, I recommend breaking them down by individual traits - Feeding traits and Morphological traits (instead of sub-chapters 3.2 and 3.3). always describe the composition of the trait and then its distribution pattern on the gradient of altitude and habitats.]

Response 7：[We have reorganized the discussion section according to your suggestions.

(L 392-492) 4.2. Diet and its impact on the distribution pattern of birds in the Gyirong Valley

In the Gyirong Valley, insectivorous and omnivorous birds account for 44.74% and 46.05% of the total bird species, respectively (Figure 3a), holding an absolute dominance. This indicates that the habitats of the Gyirong Valley can provide abundant food resources for insectivorous and omnivorous birds. This is likely related to the rich vegetation, high habitat heterogeneity, and strong habitat connectivity at mid-elevations in the Gyirong Valley [40]. Additionally, omnivorous birds possess strong food adaptation strategies [41].The availability of food affects the utilization of habitats by birds, which in turn influences the community structure of birds [42]. Analysis of the relationship between bird diet and the environment reveals that, carnivorous and scavenging birds, such as the Himalayan Buzzard and Himalayan Vulture, are large raptors that primarily inhabit the grassland habitats at high elevations (Figure 4a, b). The high-elevation areas are relatively open with strong winds, which are conducive to the soaring, gliding, and circling flight patterns of large raptors [43, 44]. Additionally, the grassland habitats support a variety of small and medium-sized mammals that serve as the main food source for carnivorous birds [45-47]. Large raptors prefer to reside in mountainous and plateau regions, which provide relatively safe nesting environments and extensive territories [48-50]. Nectarivorous birds are active in the shrub forests at mid to low elevations in the study area (Figure 4a, b). The breeding season for birds in the Gyirong Valley is from May to June, during which the shrub forests between 2800 and 3400 m are in full bloom, providing abundant nectar for nectarivorous birds. The distribution of nectarivorous birds, such as sunbirds, shows distinct seasonal changes following the flowering periods of vegetation [5]. Insectivorous and omnivorous birds are distributed across all elevation bands and habitats, with a primary focus on arbor forests and shrub forests (Figure 4a, b). The distribution characteristics of these birds are closely related to food resources and habitat diversity. Both forest and agricultural ecosystems provide rich food resources for insectivorous and omnivorous birds [40, 51]. Insectivorous-carnivorous birds are mainly active in farmlands, wetlands, and shrub forests between 2800 and 4000 m. The primary species in this group are the Grey-backed Shrike (Lanius tephronotus ) and Blue Whistling Thrush(Myophonus caeruleus). Farmlands, wetlands, and shrub forests provide these birds with a variety of food sources, including insects, rodents, and amphibians (Figure 4a, b).Diet has a significant impact on bird population sizes. Birds with broader diets tend to have larger population sizes, while those with specialized diets are more dependent on specific food sources and are more vulnerable to threats [17, 52]. During the breeding season in the Gyirong Valley, insectivorous and omnivorous birds are the dominant groups, and both groups include species with relatively large population sizes. Other dietary groups, such as nectarivorous, carnivorous, scavenging, and insectivorous-carnivorous birds, have fewer species and smaller population sizes. These groups are more specialized and are more prone to endangerment, containing a higher proportion of species that require conservation attention [53] (Figure 3b, Figure 5a).

4.3. Morphological traits and their impact on the distribution pattern of birds in the Gyirong Valley

A K-means clustering analysis was conducted on birds at mid-elevations in the Gyirong Valley, revealing that smaller-bodied birds have a greater number of species. Small birds have stronger adaptability to habitats and more diverse food sources. They also typically possess higher mobility and flexibility, which allows them to better evade predators [54]. These survival strategies increase the species diversity of small birds. In contrast, large birds have poor heat dissipation capabilities and face greater survival pressures in high-temperature environments. They are also more dependent on specific food sources and are more susceptible to changes in food availability. These birds often have higher ecological trait specificity and are more likely to become endangered species [53, 55] (Figure 3b).The analysis of the relationship between bird body size and environment reveals that giant and larges birds are primarily active in the grassland and shrubland habitats at mid- to high elevations (Figure 4c, d). During the breeding season in the Gyirong Valley, the giant bird species includes the Himalayan Vulture, while large birds mainly consist of the Common Raven (Corvus corax ), Red-billed Chough (Pyrrhocorax pyrrhocorax ), and Himalayan Buzzard. Birds in high-altitude areas tend to have larger body sizes and longer wings, which are adaptations to the high energy demands of flying at high elevations. Additionally, larger birds have slower surface heat dissipation and stronger cold tolerance [56, 57].Mediums and miniatures birds are mainly active in the complex vegetation habitats at mid- to low elevations (Figure 4c, d). Mediums birds include laughingthrushes and thrushes, which are closely associated with agricultural landscapes. Field surveys have found that these birds often forage in cow dung around farmlands and villages. Miniature birds include warblers, finches, and tits. Smaller birds are adapted to complex, high-density vegetation habitats [56], which not only provide abundant food resources but also offer good cover and safe nesting sites for these birds [58].The results of the Structural Equation Modeling (SEM) show that jumping ability is the primary factor influencing the number of bird families in the Gyirong Valley and is positively correlated with bird diversity (Figure 5b). The study area is mainly a forest ecosystem with high vegetation density. Jumping ability can help birds more effectively obtain food, thereby better utilizing different ecological niches. Jumping ability may also influence the flight patterns of birds. The jumping and short-distance flights of birds help them to quickly disperse within local areas, thereby expanding their population size and distribution range [59-61].The population size of birds in the Gyirong Valley is influenced by tail length, weight, body length, and tarsus length. Birds with higher ratios of tail length to weight, tail length to body length, and tarsus length to body length tend to have larger population sizes (Figure 5c). These higher ratios indicate relatively greater movement flexibility, which allows birds to more efficiently utilize environmental resources and better adapt to environmental changes, thereby resulting in larger population sizes [62, 63].Bird body size affects habitat selection by birds [64, 65], while vegetation cover and land-use types also influence bird distribution [66, 67]. In the 2800-3400 m elevation band of the Gyirong Valley, which is dominated by coniferous forests, shrublands, and farmlands, bill length, body length, tail length, tarsus length, weight, and wing length are positively correlated with bird population size. Mediums birds, which are larger and more combative than miniatures birds, have a competitive advantage in terms of food and habitat in this type of environment. As a result, species such as the Variegated Laughingthrush, Rufous Sibia, and Oriental Turtle Dove have larger population sizes in this elevation band.In contrast, bill length, body length, tail length, weight, and wing length are negatively correlated with bird population size in the 3400–3700 m elevation band, which is characterized by mixed coniferous and broadleaf forests. Smaller birds generally have higher flight efficiency and maneuverability, allowing them to navigate complex environments more easily. This elevation band hosts large populations of small birds, such as warblers, which thrive in the narrow spaces of the mixed forests.Tarsus length, weight, and wing length contribute significantly to bird population size in the 3700–4000 m elevation band, which is dominated by alpine meadows and shrublands. Birds in the grasslands are mostly ground-dwelling species [68]. Species such as the Red-billed Chough, Himalayan Vulture, and Horned Lark, which are adept at running and soaring, contribute significantly to the grassland bird community structure. The Blyth's Leaf Warbler and Buff-barred Warbler contribute more to the shrubland bird community structure in this elevation band (Figure 6a, b).]

Comments 8: [The distribution pattern on the elevation gradient is described very inadequately, first in Figure 3a the total representation of individual food traits is shown and then in Figure 4a the range where they occur. But that does not tell us much, quantification of their representation in each elevation band would show much more. I recommend keeping Figure 4a, where the occurrence/absence is shown, but adding an even more detailed scheme of the distribution of individual traits in individual elevation bands. Similarly for size groups.]

Response 8：[(L241-312)The distribution of different bird groups has been described in detail according to your suggestions.Figures 4 a ,b have been redrawn.Figure 4a shows the elevational distribution ranges of birds with different diets as well as the species distribution of these dietary groups across various elevation bands.Figure 4b illustrates the species distribution of birds with different diets across various habitats. And we detailed the elevational and habitat distributions of birds with different diets and body sizes. 

The distribution of birds across different foraging guilds along the elevation gradient was analyzed. In the 2800-3100 m elevation band, a total of 35 bird species were recorded, including insectivorous (17 species, 48.57%), insectivorous-carnivorous (2 species, 5.71%), nectarivorous (2 species, 5.71%), and omnivorous (14 species, 40.00%) birds.In the 3100-3400 m elevation band, 37 bird species were recorded, including insectivorous (14 species, 37.84%), insectivorous-carnivorous (2 species, 5.41%), nectarivorous (1 species, 2.70%), and omnivorous (20 species, 54.05%) birds.In the 3400-3700 m elevation band, 33 bird species were recorded, including carnivorous (1 species, 3.03%), insectivorous (14 species, 42.42%), insectivorous-carnivorous (1 species, 3.03%), omnivorous (16 species, 48.49%), and scavenging (1 species, 3.03%) birds.In the 3700-4000 m elevation band, 25 bird species were recorded, including carnivorous (1 species, 4.00%), insectivorous (11 species, 44.00%), insectivorous-carnivorous (1 species, 4.00%), omnivorous (11 species, 44.00%), and scavenging (1 species, 4.00%) birds.Carnivorous and scavenging birds, which are large raptors, prefer the high-altitude areas between 3400 and 4000 m in the study area. Nectarivorous birds, mainly sunbirds, are active in the 2800-3400 m elevation band. Insectivorous and omnivorous birds are the most diverse and widely distributed across all elevation bands in the study area. Insectivorous-carnivorous birds are active across the entire elevation range from 2800 to 4000 m (Figure 4a).An analysis of the habitat environments of different foraging guilds of birds revealed the following: In the arbor forest habitat, 24 bird species were recorded, including insectivorous (16 species, 66.67%) and omnivorous (8 species, 33.33%) birds. In the farmland habitat, 3 bird species were recorded, all of which were omnivorous. In the grassland habitat, 8 bird species were recorded, including carnivorous (1 species, 12.50%), insectivorous (1 species, 12.50%), insectivorous-carnivorous (1 species, 12.50%), omnivorous (4 species, 50.00%), and scavenging (1 species, 12.50%) birds. In residential areas, 1 bird species was recorded, which was omnivorous. In the shrubland habitat, 10 bird species were recorded, including insectivorous (6 species, 60.00%) and omnivorous (4 species, 40.00%) birds. In the shrub forest habitat, 50 bird species were recorded, including insectivorous (20 species, 40.00%), insectivorous-carnivorous (2 species, 4.00%), nectarivorous (3 species, 6.00%), and omnivorous (25 species, 50.00%) birds. In the wetland habitat, 4 bird species were recorded, including insectivorous (2 species, 50.00%), insectivorous-carnivorous (1 species, 25.00%), and omnivorous (1 species, 25.00%) birds.Insectivorous and omnivorous birds are mainly active in arbor forests and shrub forests and are distributed across various habitats. Large raptors that are carnivorous and scavenging primarily inhabit grassland environments. Nectarivorous birds are mainly found in shrub forests. Insectivorous-carnivorous birds are distributed across all elevation bands but are primarily active in farmlands, wetlands, and shrub forests between 2800 and 3400 m. Habitats closely associated with human activities are predominantly occupied by omnivorous and insectivorous birds that are less wary about humans. Specialized bird species, such as the Plumbeous Water Redstart (Phoenicurus fuliginosus), Blue Whistling (Myophonus caeruleus), and White-capped Redstart (Phoenicurus leucocephalus), are found in wetland habitats (Figure 4b). The distribution of different bird groups across elevations was analyzed. In the 2800-3100 m elevation band, 35 bird species were recorded, including mediums (10 species, 28.57%), larges (3 species, 8.57%), and miniatures (22 species, 62.86%).In the 3100-3400 m elevation band, 37 bird species were recorded, including mediums (11 species, 29.73%), larges (3 species, 8.11%), and miniatures (23 species, 62.16%).In the 3400-3700 m elevation band, 31 bird species were recorded, including mediums (9 species, 29.03%), larges (2 species, 6.45%), giant (1 species, 3.23%), and miniatures (19 species, 61.29%).In the 3700-4000 m elevation band, 25 bird species were recorded, including mediums (4 species, 16.00%), larges (5 species, 20.00%), giant (1 species, 4.00%), and miniatures (15 species, 60.00%).Miniatures, mediums, and larges are distributed across all elevation bands, while giant birds are mainly active in the 3400-4000 m elevation band (Figure 4c).An analysis of the habitat environments of different bird groups revealed the following: In the arbor forest habitat, 24 bird species were recorded, including mediums (5 species, 20.83%), larges (1 species, 4.17%), and miniatures (18 species, 75.00%). In the farmland habitat, 3 bird species were recorded, including mediums (1 species, 33.33%), larges (1 species, 33.33%), and miniatures (1 species, 33.33%). In the grassland habitat, 8 bird species were recorded, including mediums (2 species, 25.00%), larges (3 species, 37.50%), giant (1 species, 12.50%), and miniatures (2 species, 25.00%). In residential areas, 1 bird species was recorded, which was mediums. In the shrubland habitat, 10 bird species were recorded, including mediums (2 species, 20.00%), larges (1 species, 10.00%), and miniatures (7 species, 70.00%). In the shrub forest habitat, 50 bird species were recorded, including mediums (12 species, 24.00%), larges (3 species, 6.00%), and miniatures (35 species, 70.00%). In the wetland habitat, 4 bird species were recorded, including mediums (1 species, 25.00%), larges (1 species, 25.00%), and miniatures (2 species, 50.00%).The grassland habitat had the most diverse bird groups, with four groups recorded. The arbor forest, shrub forest, and shrubland habitats hosted the largest number of bird species. Habitats with frequent human activity (farmlands and residential areas) had fewer bird groups, mainly consisting of species from the Fringillidae, Garrulacidae, and Corvidae families. Specialized bird species from the other three groups, except giant, were also found in the wetland habitat (Figure 4d).]

Comments 9: [The results suddenly show the representation of individual traits in different types of habitats - but the methodology does not describe anywhere that the occurrence in individual habitats was recorded. The habitats themselves are only mentioned as a list of where they occur (L121 - 123), but their representation at individual altitudes is not quantified in any way, nor to which habitat types the records were assigned. This needs to be properly described in the methodology.]

Response 9：[(L139-141)During the investigation, the altitude of bird activities, habitats, and the number of individuals of different bird species were recorded in detail.]

Comments 10: [In the results, different units are used for different outputs - biomass (the methodology does not define how it was calculated), individuals, number of species, even though in one figure different traits are evaluated in different ways (Fig 4) - unifying the views would greatly contribute to the clarity of the outputs and enable a clear interpretation of the results. Both the view through bird richness and abundance are interesting - I would easily choose the procedure that both outputs will be listed in the results for each evaluation.]

Response 10：[Thank you for your suggestions. The previous expression was not accurate.Bird body weight (g) was used in the calculation.The calculation result is IRI.

(L 215) Figure 2 is bird species dominant groups in the breeding season in Gyirong Valley.

(L 170-176) IRI = (N + W) × F × 10000 [29], where N is the ratio of the number of individuals of a species to the total number of individuals; W is the ratio of the biomass of a species to the total biomass; and F is the ratio of the number of transects where the species was recorded to the total number of transects. Generally, species with IRI ≥ 1000 are considered dominant species, those with 100 ≤ IRI < 1000 are common species, those with 10 ≤ IRI < 100 are general species, and those with IRI < 10 are rare species.

The study site was selected in the mid-elevation section of the Gyirong Valley. Since bird richness did not show any significant changes along the elevation gradient, the content was not analyzed in detail in the text. We have redrawn Figures 4a and 4b, with the y-axis unified to represent the number of species.]

Comments 11: [Even though one of the main aims is: „propose corresponding conservation suggestions for birds in the Gyirong Valley“ The article does not describe conservation traits (in the sense Zasadil et al. 2020) in any detail, only chapter 3.1 states which of the identified species are protected at the national level and which are included in the IUCN red lists. However, there is no quantification of the occurrence of these species in terms of altitudes and habitats. If the study is to have any conservation implications, I recommend focusing more on these conservation traits and evaluating them. From a conservation perspective, the occurrence of endemic species, etc., is also interesting.]

Response 11：[We have added basic information about the protection bird in the article,and quantified the occurrence of these species across different altitudes and habitats(Figure 4).

(L210-211)Table 1. Protected bird species in the Gyirong Valley, NT = Near Threatened.]

Species	Individuals	Diets	Preference	Clusters	Red-List	Conservation Status
Garrulax maximus Gyps himalayensis Lophura leucomelanos Buteo refectus Garrulax ocellatus	3 7 6 1 11	omnivorous scavenging omnivorous carnivorous omnivorous	Shrub forest Grassland Shrub forest Grassland Shrub forest	mediums gaint larges larges mediums	NT	Ⅱ Ⅱ Ⅱ Ⅱ Ⅱ

 

Comments 12: [How does total abundance and bird richness change with altitude? Some studies show a decreasing trend (e.g. Kebrle et al. 2022). Has this been confirmed here?]

Response12：[The number of species shows no obvious change along the altitude gradient,the possible reason is that the study area we selected is in the middle altitude zone.However,our survey results from the pass of the Gyirong County to Gyirong Port in 2023 confirmed Kebrle et al’s finding.]

Comments 13: [L189 Figure 2a I think it would rather belong in the appendices.]

Response 13：[We have placed Figure 2a in the appendices.]

Comments 14: [L189 Figure 2b The units in which biomass is expressed are not listed.]

Response 14：[Figure 2b has been reorganized,it is dominant groups in the breeding season in Gyirong Valley.

(L171-177) IRI = (N + W) × F × 10000 [28], where N is the ratio of the number of individuals of a species to the total number of individuals; W is the ratio of the biomass of a species to the total biomass; and F is the ratio of the number of transects where the species was recorded to the total number of transects. Generally, species with IRI ≥ 1000 are considered dominant species, those with 100 ≤ IRI < 1000 are common species, those with 10 ≤ IRI < 100 are general species, and those with IRI < 10 are rare species.]

Comments 15: [L196 foraging guilds – elsewhere in the text is used the term “feeding guilds” - the terminology needs to be unified within the article.]

Response 15：[The “feeding guilds” in the article has been replaced with "foraging guilds".]

Comments 16: [L210 Fig 3b In my opinion, it doesn't say much, either explain how this image is useful for the work or leave it out. Much more interesting is, for example, the distribution of individual clusters by altitude or habitats (Fig 4 c,d)]

Response 16：[The clustering results show that the more unique the morphological traits of birds are, the fewer the number of bird species. (Figure 3b).

Figure 3b is the basis for the classification of body type groups.

(L 282-312) The (Fig 4 c,d) has been described in detail in the text.

The distribution of different bird groups across elevations was analyzed. In the 2800-3100 m elevation band, 35 bird species were recorded, including mediums (10 species, 28.57%), larges (3 species, 8.57%), and miniatures (22 species, 62.86%).In the 3100-3400 m elevation band, 37 bird species were recorded, including mediums (11 species, 29.73%), larges (3 species, 8.11%), and miniatures (23 species, 62.16%).In the 3400-3700 m elevation band, 31 bird species were recorded, including mediums (9 species, 29.03%), larges (2 species, 6.45%), giant (1 species, 3.23%), and miniatures (19 species, 61.29%).In the 3700-4000 m elevation band, 25 bird species were recorded, including mediums (4 species, 16.00%), larges (5 species, 20.00%), giant (1 species, 4.00%), and miniatures (15 species, 60.00%).Miniatures, mediums, and larges are distributed across all elevation bands, while giant birds are mainly active in the 3400-4000 m elevation band (Figure 4c).An analysis of the habitat environments of different bird groups revealed the following: In the arbor forest habitat, 24 bird species were recorded, including mediums (5 species, 20.83%), larges (1 species, 4.17%), and miniatures (18 species, 75.00%). In the farmland habitat, 3 bird species were recorded, including mediums (1 species, 33.33%), larges (1 species, 33.33%), and miniatures (1 species, 33.33%). In the grassland habitat, 8 bird species were recorded, including mediums (2 species, 25.00%), larges (3 species, 37.50%), giant (1 species, 12.50%), and miniatures (2 species, 25.00%). In residential areas, 1 bird species was recorded, which was mediums. In the shrubland habitat, 10 bird species were recorded, including mediums (2 species, 20.00%), larges (1 species, 10.00%), and miniatures (7 species, 70.00%). In the shrub forest habitat, 50 bird species were recorded, including mediums (12 species, 24.00%), larges (3 species, 6.00%), and miniatures (35 species, 70.00%). In the wetland habitat, 4 bird species were recorded, including mediums (1 species, 25.00%), larges (1 species, 25.00%), and miniatures (2 species, 50.00%).The grassland habitat had the most diverse bird groups, with four groups recorded. The arbor forest, shrub forest, and shrubland habitats hosted the largest number of bird species. Habitats with frequent human activity (farmlands and residential areas) had fewer bird groups, mainly consisting of species from the Fringillidae, Garrulacidae, and Corvidae families. Specialized bird species from the other three groups, except giant, were also found in the wetland habitat (Figure 4d).]

Comments 17:  [L246 wouldn't a "bird assemblage composition" be better?]

Response 17：[(L318)The content has been changed to"bird assemblage composition".]

Discussion and Conclusions

Comments 18: [If the article is to have a conservation impact, it would be good to include not only the overall heterogeneity of the environment, but also to emphasize key habitats for the protection of bird biodiversity and the assessment of the impact of humans, natural processes and disturbances.]

Response 18：[The importance of habitat protection was emphasized in the results section.

(494-503) This study explored the composition, distribution patterns, and ecological traits of birds during the breeding season in the mid-elevation of the Gyirong Valley. It revealed the significant role of ecological traits in shaping the distribution patterns of birds in this region, providing new insights for mountain bird research. We recommend that habitat heterogeneity be emphasized in the conservation of mountain ecosystems to meet the habitat needs of birds with diverse ecological traits. Future research should be conducted in a broader range of typical mountain ecosystems over extended periods to more deeply uncover the long-term impacts of ecological traits on bird distribution patterns and to further refine the scientific framework for the conservation and management of mountain birds.

During the survey,the types and intensity of disturbances were not quantified;therefore,the impact of disturbances on birds was not specifically discussed in the text.We will pay attention to the disturbances in future studies .]

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for incorporating the comments from the review and the resulting revisions to the manuscript. In my opinion, the manuscript can be published in this form.

Author Response

Dear reviewers,

 

I would like to express my sincere gratitude to you for your meticulous review of the manuscript and for the valuable comments provided.

I am truly honored and excited to learn that my manuscript can be published in its current form.

I appreciate the suggestions you have offered, which have enhanced the clarity of our research. Thank you once again for your recognition and support of the manuscript.

I am looking forward to the official publication of the manuscript and hope that this research will contribute to our field of study.

 

Best regards,

Huaiming Jin

19 March 2025

Author Response File: Author Response.docx