-->-->PONE-D-26-04075-->-->Periodicity in Steller's eider (Polysticta stelleri) population size and density on the Arctic Coastal Plain, Alaska, revealed using generalized additive models) population size and density on the Arctic Coastal Plain, Alaska, revealed using generalized additive models-->-->PLOS One

Dear Dr. Osnas,

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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-->5. Review Comments to the Author

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Reviewer #1: I am not experienced in the use of spatio-temporal generalized additive models, whose presentation is perhaps the most important contribution of this paper to the general readership of PLoS ONE. I suggest that alternative reviewers with greater expertise in this area should also be consulted. However, the methods are described quite thoroughly and intuitively, and the people listed in the Acknowledgements who have already reviewed the paper are well qualified in terms of relevant statistical experience and familiarity with the study system.

My assessment is that this is a very carefully prepared paper, in which sophisticated statistical analyses are presented in a readable and understandable way. The figures are effective and comprehensive. Thorough comparison of the new and traditional methods is quite valuable, given that the traditional methods have been used in multiple venues and will probably be continued to maintain time series. The novel analyses of cyclic patterns, verified by two different analytical approaches, are important to future evaluation of trends for both the target species and the many others analyzed by the design-based estimates. These analyses also provide new insights into potential lemming cycles in this study area and future efforts to characterize and understand them. The spatial trends in eider distributions will be helpful in management planning.

The paper is well-enough written that, uncharacteristically, I have few suggestions to make. Essentially all my comments are trivial grammatical corrections.

1. L 117. Please replace “the above” by “equation (2)”

2. L 351. Replace “miss-identification” by “misidentification”

3. L 360. Delete “and” before “Medium”

4. L 462. Replace “spectorgram” by “spectrogram”

5. L 465. Replace “ocilation” bny “oscillation”

6. L 577. Replace “miss-matched” by “mismatched”

Reviewer #2: This study demonstrates that generalized additive models provide more precise and consistent estimates of Steller’s eider population size and density in Alaska than traditional design-based methods. The results also highlight significant cyclical fluctuations in population size which have strong implications for interpreting trend estimates used for population recovery. Additionally, density analyses provide further evidence of high concentrations in the northern part of the survey area and indications of northward shifts in density. These findings offer improved methods for assessing population trends and recovery of Steller’s eiders, a problem that has made decision-making challenging in the past. The author appropriately cited the relevant literature both on the species and modeling methods and provided sufficient context for non-specialist readers. The data and analyses are robust, appropriately support the claims, and are well-organized and easy to access via the linked github repository. Methods are sufficiently detailed to reproduce the analysis (especially including the detailed code). The manuscript is well-written but see minor comments below for typos and other small suggestions. I have no major issues or comments for the author to address. Note: I did not run all of the code but the files that I opened looked organized and were easy to access.

Specific Comments:

• Lines 113-119: The concerns highlighted here may warrant further explanation – it’s not made clear here exactly why the estimator is better than the ratio estimator if there are issues in estimation with a strong density gradient. Given the system and the assumptions of a ratio estimator I agree that this is likely better, but this section could use work to explain why including citations if possible. Additionally, the last sentence includes “case” twice, I would suggest the second one be changed to “specific system”.

• Line 465: typo, “ocilation” . “oscillation”

• Line 564: “When” seems to start with a bolded “W” – this occurs in a couple of other locations but it may be a rendering problem in adobe.

• Figures

o Figures 1 and 2 show the same area with the same distance but are different sizes – consider constraining the output size to be consistent.

o Figure 3 may be easier to read as a “lollipop” chart and better y axis – but not necessary.

o Figure 4 is the only two-part figure that shows up together and has A/B labels within the plot. Check all of the two-part and three-part figures for consistency before resubmission.

o Figure 9B doesn’t seem necessary for communicating any results – consider removing or emphasizing the purpose of including it.

o Figure 15 “period” is really far from the numbers of the y-axis. Might be easier to see what is happening if the x-axis had more years but turn then 45 or 90 degrees.

o The trends/abundance figures may benefit from reducing the background noise, specifically, reducing the number of gridlines, making the background white, etc. Just a style choice but it would be easier to read.

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Reviewer #1: No

Reviewer #2: No

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Periodicity in Steller's eider (Polysticta stelleri) population size and density on the Arctic Coastal Plain, Alaska, revealed using generalized additive models) population size and density on the Arctic Coastal Plain, Alaska, revealed using generalized additive models

PONE-D-26-04075R1

Dear Dr. Osnas,

Thank you for submitting a revised version of your manuscript and addressing the minor issues identified by the reviewers. I also have to credit the editorial office for asking you to address the copyright, formatting, and other technical issues associated with the manuscript. I'm pleased to let you know that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets any remaining technical requirements that the editorial office identifies.

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Section Editor

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