The use of Sliding Window Technique is relatively novel in ornithological research. Reports of trends in the breeding biology of the three specie involved are interesting per se.
The following comments refer to statements or information reported in the ms by line number:
Line 212 and following: In the graphs shown in figure 4 the window periods do not seem to be similar, as stated in the ms, actually they seem to differ. In the Methods section the authors state that "If the median start and end dates did not overlap between the two data subsets, we considered this support for a shift in the time period of environmental variation that best predicts chick growth." However, in this case the graph in Fig. 4 shows different time periods for the windows between historical and recent study periods but the authors state that they are similar. There needs to be a better explanation in the Methods, and Results section and illustrating Figures and figure legends.
Also, three study periods are shown in the Figures (historical, recent, and entire study), but they are not mentioned, nor properly explained in the Figure legends. Therefore, the texts in these sections are confusing and do not seem to be adequately reflecting the results.
The description of what is visible in the figure is confusing, since the opposite of what is stated in the text seems to be illustrated in the figure. The figure shows that windows shifted from the incubation and growth periods to the pre-laying after 1995. The text states the opposite.
Line 225: These descriptions do not seem to coincide with what is shown in the figures.
Line 267-268: How can authors explain this perplexing result? Is there another environmental factor that may be explaining this phenomenon?
Line 279-280: This statement is too vague. Authors do not explain what is the relationship. What conditions would be associated with higher temperatures and, simultaneously, viceversa? Or there may be a problem with the narrative, so it is confusing.
Line 299: In recent years, environmental conditions have tended to change abruptly during times corresponding to the mid and late stages of the nesting season of seabirds, and might be interfering with the interpretation of the data in the sense that in historical times the environmental conditions tended to remain stable, e.i. good all season if they were good in the early nesting season. At present these conditions may be good during the early nesting period, but change abruptly to poor in the middle or late nesting period. This could be the cause why the authors are finding these results, and should be taken into consideration in their discussion. There are plenty of publications describing this recent phenomenon considering local vs. regional anomalies and heat-waves, which could be checked and included in the discussion.
Lines 337-342: Too many suppositions, without enough supporting references.
Line 347: Skeletal size and body mass are not the same. Body condition needs to be taken into consideration: a smaller individual could have a smaller skeleton but higher fat tissue content, which could help survival, or viceversa, a larger individual could have a larger skeleton but less fat content which might reduce survival.

In Conclusions authors recognize the limitations of their analysis and stress new factors occurring in the present times that may render predictions hard to achieve. This is an important result of their work and something that must probably be stressed in this section as a factor to consider for management purposes.