Prescribed Fire Effects on Hummingbird Taxonomic and Functional Diversity in Pine–Oak Forests in West-Central Mexico

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper explores hummingbird taxonomic and functional diversity in 3 sites with different fire regimes. It is an interesting study that can make an important contribution to our knowledge on hummingbird ecology, and therefore the results deserve to be published. However, the writing needs major restructuring. The design of the study is poorly explained which makes it difficult to interpret the results in the context of the research questions. It appears that the 3 sites are under different management regimes and have therefore experienced different fire management techniques, but this is not clearly explained. In some parts the authors speak of an experiment, in others of fire history. It is also unclear whether the sites are comparable or not apart from the fire history, and if there are therefore other habitat variables that could explain potential differences in hummingbird diversity between sites. The other problem is that the reasoning is circular in the sense that from the beginning it is said that low intensity fire will not affect hummingbirds and then that is what is found. But it is not clear then why a low intensity fire was used or how this study would then be able to help answer the research question. It seems as if the hypothesis was formulated after the results were already known. I provide some additional line-by-line comments below, I hope you will find these helpful.

Abstract lines 38-43: You state that you conducted an experimentally induced low severity fire to create habitat for hummingbirds, but then you hypothesized that this would not affect hummingbird diversity because the forest is fire prone. Then why did you use a low severity fire? If you wanted to create habitat and you already expected that your treatment wasn’t going to do this, it would make more sense that you’d use more severe burns. Alternatively, this sounds as if you formulated your hypothesis after knowing the results, which should not be done. If you expected a result but didn’t find it that’s ok, but you should state this honestly.

Line 94-98: reword this sentence

Line 98: Change to “changes in hummingbird diversity…”

Line 117: Delete “On the other hand”

Lines 117-141: Final paragraph of the introduction: rewrite this paragraph. Some of this should be in the methods (descriptions of the study site). Other parts are confusing. Clearly state what the objectives were and what you expected to find.

Lines 155-177. Why were these sites selected? What were the selection criteria? How large was each of the selected sites? You need to give more details here. Also, you mention fires with high-severity and low-severity effects; how do you define these, and were these the experimental fires? Were they really experimental? To be able to understand the results the description of the sites needs to be transparent because it is essential for the conclusion on the effects of fire on hummingbirds. Were the sites comparable? Can we really conclude on the effects of fire on hummingbirds or are there other differences between the sites that could explain the results?

Line 169-170 “and a low severity fire was in 2020”. This is a fragment not a sentence, and it is not clear what you mean.

Line 186: This is unclear: “and the peak flowering occurs in this area”.  

Line 186-187: Reword to “we established ten 25-m radius plots…” and we need a lot more information here on the design and methodology. Explain how the location of the plots was selected. Did you survey the plots always in the same order or did you vary and how?

Line 187: You didn’t explain this before, what is the suppressed fire site and the burned site? Are those the fires in 2020 you mention before? Those were experimental fires? Or were they management fires and you took advantage of this for the purpose of your study? How large was the burned area? You need to clearly explain the treatments and be transparent about the objectives of the fire (here and in the abstract/introduction: were they experimental or not?).

Lines 190-191: Did you take distance measurements?

Lines 193-200: Give more detail. How did you estimate vegetation cover? Explain the methodology. How were the other variables measured?

Line 206-207: Explain what you mean by “the diversity analysis was performed spatially”.

Line 241: 95% confidence intervals?

Line 250: R was used for all analysis? It’s not clear for all analyses.

Line 283: How many individuals of each of the species and what were their relative abundances?

Fig. 2: I suggest changing the colors to something more friendly to color blindness. It seems a lot of rare species went undetected in SC. Are we looking at fire vs. non-fire sites here? A more detailed site and treatment description in the methods and more descriptive naming of the sites will help to better interpret this figure.

Lines 316-319 and Table 2: How to interpret these values? What do they say about the functional diversity in the different sites?

Line 330: Here you refer to fire treatments. In other places you compare sites. It is unclear how these are related and this is limiting the understanding of the results and their implications.

Figure 3A: Give full species names in the legend or in the figure itself. Figs. 3B and C and 4: if sites were fire/non-fire I suggest giving more descriptive names so the reader can easily compare.

Line 373: If it is visually indistinguishable how do you know which one you observed?

Line 379: One of the sites or both?

Line 380-383: They might be unresponsive because they’re adapted to frequent low fires, but that doesn’t mean that they would be the same species or that diversity would then be the same as in sites with no fire. You need to explain this argument further.

Line 403-411: This is important information but here the paragraph come out of nowhere and is not connected to the previous one. It’s also not linked to the implications of this finding in light of your research question. I suggest rewriting this whole section.

Line 412: Delete “However”

Line 414: “this fire management strategy..” What strategy? It’s not clear what you’re referring to.

Lines 433-434: I though the fires were in 2020? The timing of these fires is really important information because it’s crucial to your hypothesis. You should make this much clearer from the beginning on.

Lines 462-472: Your management recommendations should follow from your results. You do not provide evidence for the recommendations you make here, this is out of the scope of your research.  

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Line 21 - Simple summary. I found it too similar to the abstract, and I recommend rephrasing it to

make it more reachable to a broader audience.

Line 68. In this paragraph I suggest mentioning that prescribed fires are not all destined for forest

habitats. They are also intended for grasslands, e.g., https://www.jstor.org/stable/40157552,

https://doi.org/10.1002/eap.2091

Line 131. From this line on, several ideas are repeated. I suggest rephrasing these ideais to make

this paragraph shorter.

Line 139. I suppose the authors should present a null hypothesis, in which case there would be no

differences in prescribed and suppressed forests with fire.

Lines 144-145. Are Jalisco and Colima municipalities? Please, include more details for the readers

which are not accustomed to the Mexican geopolitics.

Lines 146-147. Are Eje Neovolcânico Transversal and Sierra Madre Occidental paved roads?

Please, explain.

Line 163. I suggest incorporating in more details about the regime. Intensity, duration,

approximate months, etc.

Lines 165-167. “dominant" appears twice.

Lines 168-170. Is it possible to include the duration of each fire episode?

Line 177. I suggest, if possible, including the duration os the fire episodes and the extension they

burnt in each site. Also, it would be important to include the area (ha) of each forest so a

percentage of the burnt areas could be calculated.

Line 180 - Figure1. Perhaps more important than topographic lines, the range of the pine forests

could be included in the map. Also, if possible, the extension of the burnt areas.

Line 185. I suggest including the overall number of hummingbird species recorded within the

three study areas.

Line 187. Please, explain why there are less counting stations at SC.

Line 188. Why do the authors state the points were 25 m distant in radius, but 300 m apart from

each other. I cannot understand how the point counts were delimited.

Line 201. I could not find any supplementary material. It must be sent to the reviewers, because I

would recommend including how the covariates were obtained. It is not possible to know this

without access to the supplementary material and tables.

Lines 2019-220. No supplementary materials are available.

Lines 252; 259; 265. Please, clearly state whether all analysis were conducted within the R

environment.

Line 282. I think it would be easier for the reader to follow if the authors included a table (or

supplementary table) indicating the species and their biology, regarding their relationships with fire

in a qualitative manner. For example, which is the most associated with recent fire events. This

would help to interpret figure 4.

Line 287. As no supplementary material are available to me I do not know if the near threatened

status is global.

Line 312 - Figure 2. The extrapolated lines should reach the maximum number of individuals for all

three sites.

Line 325. 3 three

Line 373. If S. sasin is indistinguishable from S. rufus, how can the authors be sure the first

species was not recorded?

Lines 431-440. I believe this is the most important result and should be highlighted. The other

discussions seem to be irrespective of the authors’ own findings.

Line 462 - Management implications. I suggest highlighting the relevance of the extension and

last fire episode in determining hummingbird taxonomic and functional diversity. Also, as the first

paragraph of the introduction mentions the influence of anthropogenic actions, I suggest including

what would happen to the hummingbird communities at the surveyed sites in the face of

accelerated fire events caused by climate change.

Author Response

Dear Reviewer 2,

We sincerely appreciate the time and effort you put into reviewing and providing feedback to improve this manuscript. Thanks to your expertise, we were able to conduct more detailed analyses, and we believe we have significantly improved the clarity and quality of the manuscript.

Thank you for your valuable comments.

_________________________________________________________________________

Line 21 - Simple summary. I found it too similar to the abstract, and I recommend rephrasing it to make it more reachable to a broader audience.

The reviewer is correct. We reviewed the Simple Summary and compared it with the Abstract; both sections have been revised and modified accordingly.

Line 68. In this paragraph I suggest mentioning that prescribed fires are not all destined for forest

habitats. They are also intended for grasslands, e.g., https://www.jstor.org/stable/40157552,

https://doi.org/10.1002/eap.2091

Prescribed fires can create diverse landscapes with various patches and configurations, which promote avian diversity and conserve ecological functions (Docherty et al. 2020).

Line 131. From this line on, several ideas are repeated. I suggest rephrasing this idea is to make this paragraph shorter.

The reviewer is right; we re-write this last paragraph.

Still, there will be an increase in herbaceous cover and the availability of plants with flowers used by hummingbirds. We hypothesized that low-severity prescribed fire will increase the taxonomic and functional diversity of hummingbirds because it will change the vegetation structure at the understory level, providing higher resource availability. This study will provide management recommendations to aid in the conservation of hummingbirds.

Line 139. I suppose the authors should present a null hypothesis, in which case there would be no differences in prescribed and suppressed forests with fire.

We considered the 3 reviewers' suggestions regarding the hypothesis; the following hypothesis was clarified:

We hypothesized that low-severity prescribed fire will increase the taxonomic and functional diversity of hummingbirds because it will change the vegetation structure at the understory level, providing higher resource availability.

 

Lines 144-145. Are Jalisco and Colima municipalities? Please, include more details for the readers which are not accustomed to the Mexican geopolitics.

The reviewer is right, we clarified the paragraph as follows:

The SMBR is located in west-central Mexico, with 90% of its area in Jalisco state and the remaining 10% in Colima state.

Lines 146-147. Are Eje Neovolcânico Transversal and Sierra Madre Occidental paved roads?

We clarified the paragraph as follows:

It lies in the northern portion of the Sierra Madre del Sur, a mountain range in southern Mexico. RBSM borders the Trans-Mexican Volcanic Belt—a volcanic physiographic province—to the east and the Sierra Madre Occidental—a vast mountain range—to the north.

Line 163. I suggest incorporating in more details about the regime. Intensity, duration,

approximate months, etc.

The reviewer is right we incorporated detailed information about the regime in the introduction section, as follows:

Pine-oak forests in Mexico, experience frequent surface fires that occur every 5 to 35 years (1,2). Occasionally, high-severity fires create openings by burning all biomass in a torch-like manner. However, most fires in these forests are of low to moderate severity, with plant mortality primarily affecting the understory (2,3). Rodríguez-Trejo 2008; Quintero-Gradilla, et al., 2019). Canopy reduction is generally less than 25%, though small gaps can form due to the death of clusters of contiguous trees (4. The vegetation's response to fire is predominantly positive, as these forests are fire-resistant and have a strong capacity for regeneration (3). Fire incidence is higher in convex landforms and at elevated topographic positions 4.

We added the following information to the site's description:

The last recorded wildfire was in 1983, with a high-severity effect that burned the treetops. Since then, the area has been under a fire suppression regime (Figure 1D).

 

Lines 165-167. “dominant" appears twice.

Thank you. It was corrected

Lines 168-170. Is it possible to include the duration of each fire episode?

The duration of each fire depends on its severity, the fires are combated between 2 days to 7 days.

 

Line 177. I suggest, if possible, including the duration of the fire episodes and the extension they burnt in each site. Also, it would be important to include the area (ha) of each forest so a percentage of the burnt areas could be calculated.

These observations were incorporated into Figure 1 and a paragraph from lines 151 to 179.

Line 180 - Figure1. Perhaps more important than topographic lines, the range of the pine forests could be included in the map. Also, if possible, the extension of the burnt areas.

We completely modified Figure 1, addressing the observations regarding the representation of the pine-oak forest distribution and including polygons to indicate the burned areas.

Line 185. I suggest including the overall number of hummingbird species recorded within the three study areas.

We included this information in Table S3. Species list, residency, endemism category by NORMA-059-SEMARNAT-2010, category of risk by IUCN and relative abundances.

Line 187. Please, explain why there are less counting stations at SC.

Eight counting points were established because they covered the study area without edge effects. Although the total area is similar, the polygon is more elongated than the other polygons.

"Line 188. Why do the authors state the points were 25 m distant in radius but 300 m apart from each other. I cannot understand how the point counts were delimited.

In general, our point count studies follow the methodology established by Hutto et al. (1986), which is recommended for these environments. Over the past 35 years, we have used this standardized technique to compare regional and international studies. We have also confirmed that these methods are the most effective for studying hummingbirds through censuses, following Contreras-Martínez (2015). The minimum recommended distance between points is 200 meters; however, we determined that greater independence between samples (points) exists due to the hummingbirds' traplining behavior. Before sampling, the sites were established with the assistance of a rangefinder."

Line 201. I could not find any supplementary material. It must be sent to the reviewers, because I would recommend including how the covariates were obtained. It is not possible to know this without access to the supplementary material and tables.

We have provided supplementary material in this past round of revisions. We uploaded the supplement to the journal site. We will ensure that you have the supplementary material

Lines 2019-220. No supplementary materials are available.

We provided supplementary material in this past round of revisions. We uploaded this information to the journal site. We do not know why the reviewer can not see it and download it.

Lines 252; 259; 265. Please, clearly state whether all analysis were conducted within the R

environment.

We have clarified this through the following sentence: “We estimated the functional indices using species composition, abundances, and functional traits using the FD package ^58,60] and null models using Picante ⁶¹] in R-project, version 4.2.2. (lines: 279 - 283).

Line 282. I think it would be easier for the reader to follow if the authors included a table (or supplementary table) indicating the species and their biology, regarding their relationships with firein a qualitative manner. For example, which is the most associated with recent fire events. This would help to interpret figure 4.

We included this information in Supplementary material Table 3. Additionally, we reorganized Figures 3 and 4 to maintain the quantitative aspect of the results, following the same order when naming or describing the sites.

Line 287. As no supplementary material are available to me I do not know if the near threatened status is global.

We will upload the supplementary material like the last time and request the editor to provide you this information.

Line 312 - Figure 2. The extrapolated lines should reach the maximum number of individuals for all three sites.

The reviewer is correct. Based on the feedback from the other reviewers, we decided to create a new Figure 2 to better explain the taxonomic and functional diversity based on rarefaction and extrapolation values of taxonomic diversity (q0, q1, and q2), with maximum standardized coverage Cmax = 98.6%.

Line 325. 3 three

Thank you. It was corrected.

Line 373. If S. sasin is indistinguishable from S. rufus, how can the authors be sure the first

species was not recorded?

The reviewer is right. We clarified this as follows:

We found eight of the ten hummingbird species reporte in pine-oak at RBSM, 18]. Two species were absent from our survey. Allen's Hummingbird (Selasphorus sasin) is an extremely rare species that has not been recorded in our long-term hummingbird monitoring project with mist nets over the past ten years (data unpublished). Mexican Violetear (Colibri thalassinus), which has only been recorded in SMBR at locations affected by high-severity wildfires 18].

 

Lines 431-440. I believe this is the most important result and should be highlighted. The other discussions seem to be irrespective of the authors’ own findings.

The reviewer is correct. We kept this finding and modified the following parts of the discussion.

Line 462 - Management implications. I suggest highlighting the relevance of the extension and last fire episode in determining hummingbird taxonomic and functional diversity. Also, as the first paragraph of the introduction mentions the influence of anthropogenic actions, I suggest including what would happen to the hummingbird communities at the surveyed sites in the face of accelerated fire events caused by climate change.

The reviewer is correct. We clarified the recommendations based on the fire regime and the possible influence of climate change. You may review this section, and we hope it meets the requested requirements.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

General Comments

This is an interesting study on hummingbird taxonomic and functional diversity after prescribed burning in mountain forests at the boundary between Neotropical and Neartic biogeographic realms. My main suggestions about the manuscript are:

• The information on field methods and definition of variables in section 2.2. is insufficient to assess the methodology, as well as for transparency and repeatability reasons. Please, expand as suggested below.
• The information on taxonomic diversity of section 2.3.1., especially the description of q, is unclear and should be clarified.
• The Discussion should consider the time elapsed between the last fire and the counts, fire effects on vegetation and flower numbers. You could make use of this information to improve the interpretation of results and the management recommendations.

Detailed Comments

Abstract L38-43 There seem to be a contradiction between ‘we conducted an experimental low-severity prescribed fire to create a habitat for hummingbirds’ and ‘low-severity burn would not significantly impact hummingbird diversity.’ If the aim of the experiment was to create habitat for hummingbirds, then the hypothesis should be that low-severity would benefit hummingbird diversity/populations. Please, clarify.

L104. ‘local species’ something is missing here: guilds? communities?

L105 unclear what are ‘differentiation patterns’

L123 the sentence ‘do not affect the number of vegetation layers’ is unclear. Please, describe what type of fires commonly take place (Surface fire I imagine) and how they affect each layer

L135 again, the information should be about how litter, grass cover, understorey, crown are affected, not on the ‘number of layers’ that is a confusing term.

L137-141 These ideas are fine to me but contradict L38-43 of the abstract. Therefore, change the Abstract accordingly.

L150 Delete ‘temperature’

L170 ‘carried out’ is missing after ‘was’

L170 and L177 knowing the month in 2020 in which the burn ok place would be informative because the study started in October 2020.

L184 How many sampling occasions per plot?

L186-188 Are these ‘plots’ fixed or permanent (marked) plots or they are just (virtual) point counts? Are they circular, as suggested by the term ‘radius’? I think the standard ‘point count’ method applies here. Please, clarify.

L192-201 Information on the methods used to measure all these variables is lacking and is necessary.

Section 2.3 The way the repeated counts were integrated in the bird abundance variable is not mentioned (or I missed it). This is very important. Besides, is the month’s (from October to April) influence on species composition worth being explored?

L210-215 I am not familiar with this method but, after reading this paragraph, I do not understand what is q and how it is used. Please, clarify.

L241-245 This long sentence has a grammatical problem and is difficult to understand.

L312-313 Correct ‘lanes’ to ‘lines’. Add the meaning of q=0, q=1, q=2

L317 Change the dot ‘.’ With a slash ‘,’ Currently the second sentence is grammatically incorrect

Figure 3. Increase font size and line width of the PCO plots.

L346 Replace ‘shows’ by ‘showing’

L380-382 This idea does not make sense to me. If there are only small differences in bird communities between low severity fires and long unburned sites is not because fire is frequent, it is probably because the changes produced by these fires do not significantly affect the resources needed by birds. You should elaborate more on the reasons behind your findings at the taxonomical level.

L402 Replace ‘technique’ by ‘strategy’ or a similar word

L412 Delete ‘However’

Section 2.3. Try to split this very long paragraph into a few paragraphs that help readers understand the main ideas being discussed.

L416-423 This idea is interesting but can only be assessed if the reader knows how long after fire did your counts start. Include this information in methods and here try to be more explicit about the time frame of the processes mentioned in these lines. Also, you should also refer here (in general in section 4.3.) to the number of flowers you recorded among sites and across time.

Section 4.1. This section is interesting, but it is unclear how the ideas expressed derive from the specific results of this study. Try to reformulate this paragraph using your specific results on hummingbird taxonomic and functional diversity.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for attending to my revisions. I find the paper much improved and only have some minor corrections.

Simple summary: functional diversity is a technical term, explain this for a general public or use simpler wording

Line 129: low-severity prescribed fire

Line 132-137: Change to: The vegetation structure in terms of vegetation strata is expected to remain the same after a low severity fire because the ecosystem is fire resistant, but we expected an increase in herbaceous cover and the availability of flowering plants used by hummingbirds

Line 137: change “will” to “would”, and do the same for those that follow in the hypothesi

Line 453: change “will” to “would”

Line 455: We expected this because…

Line 560: correct “report”

Line 598-614: I suggest deleting this paragraph as it is out of the scope of this research

Author Response

We attached a file

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Dear editor,

the authors tackled my suggestions successfully and now I could see the supplementary material.

Comments on the Quality of English Language

I am not a native speaker, but I suggest a final English revision be conducted prior to publication.

Author Response

We attached the first round of answers to your review in the corresponding section, and here we attached the second round of answers to your questions.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

Congratulations for this improved version of the manuscript. I'm happy with all the changes made, with one exception. This concerns my previous comment: "Section 2.3 The way the repeated counts were integrated in the bird abundance variable is not mentioned (or I missed it). This is very important." I cannot find that this has been addressed.

I understand that there were 5 or 6 counts per point (monthly, from October to March). Did you use each count as a replicate and, in this case, how do you deal with temporal pseudoreplication? Or do you combine the 5 or 6 count using the maximum number of individuals counted per species? Or any other approach? This should be clearly specified beacuse it affects one of the main variables in this study.

Author Response

We attached a file.

Author Response File: Author Response.docx