Age Difference, Not Food Scarcity or Sibling Interactions, May Drive Brood Reduction in Wild Scarlet Macaws in Southeastern Peru
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
This manuscript presents difficult-to-obtain data on wild Scarlet Macaws to address important questions about the survival of chicks during the nestling stage. The fact that these data were collected from wild macaws, and includes behavioral observations of behavior within the nest cavity, makes the study especially valuable. Although the sample sizes are on the small side for some analyses, the authors are careful to recognize these limitations, and provide power analyses to assess the confidence with which they can make conclusions.
Overall the manuscript is well organized and well written. My comments, although numerous, are minor (mostly suggestions to improve the writing).
-Throughout the ms, I would suggest hyphenating first-hatched, second-hatched, etc.
l.97 “…we present a brief…”
l.101 “within broods. Second hatched…are targets of…” Here and in most of the subsequent hypotheses, hypothesis statements contain two semicolons (followed by a capitalized word) which does not seem grammatically correct. I would suggest replacing the second semicolon with either a period or a semicolon.
l.121 Should read “1 091 416 ha”
l.126 “during 18 consecutive”
l.128 “In 11 breeding seasons”
l.129 “we installed video cameras in…”
l.131 “at 37 wild macaw nest sites” or “in 37 wild macaw nests” (the term “nest site” is more general, referring to the physical location of a nest on the landscape)
l.133 “All nests were checked…” Were chicks banded (or otherwise marked)?
l.134 “nest monitoring was suspended for 26 days, and resumed when the first …”
l.135 “After chicks hatched, the.”
l.142 “did not gain weight”
l.146 “used a video camera system”
l.147-148 “From 2007 to 2010, we made non-continuous recordings during observations…”
l.149 “We made continuous…”
l.150 “we made two-hour…”
l.151-152 I believe you mean “From 2012 to 2018, we made 6-hour continuous recordings at three specific…”
l.153-154 “These 6-hour recordings were on the following schedule:” The wording in this sentence is confusing: do you mean “until starving chicks died or (2) every other day…”? (i.e. “or” instead of “and”?)
l.155-156 “We were not always able to follow…”
l.158 What do you mean by “We tested both observers”?
l.161 “chicks that starved to death with second chicks…”
l.172 “were included in all of the analyses.”
l.175 capitalize “Pro” Were all tests 2-tailed?
l.190 Your justification for throwing out this data point is not provided until the following paragraph; it would be best to state your justification here. Was this chick excluded from all analyses, or only certain ones?
l.198 Please explain what you mean that “chick order did not change”
l.199 “which starved”
l.200-202 see note for l.190
l.218-219 delete “and tallied”
l.241 remove period in “all data.in”
l.260-261 This explains how you identified chick feeding, but it’s not clear how feeding was quantified. The text that follows mentions both “feedings” and “feeding rates.” Did you count feeding bouts (if so, how was a “bout” defined)? Was feeding bout duration taken into account? You also need to explain how feeding rates were estimated.
l.264 “starvation” (delete the “s”)
l.275 -276 “we calculated the ratio using feeding data from when both…”
l.276 “For broods in which second chicks fledged, calculations were done for: …”
l.278-279 suggested re-wording: “We did not include data from video recordings for which chicks could not be identified for >50% of feedings.
l.280 “parents that were not given supplemental food, and…”
l.286 Did you use a binary logistic regression here and in logistic regression analyses described below?
l.310 Throughout the Results section, p-values could be reported simply as “p = #” instead of “p-value = #” Also, throughout the section, when reporting statistically significant results, you can simply say “X differed from Y” (saying “X differed significantly from Y” is redundant, because if the difference is not statistically significant, then you cannot state that there is a difference).
l.311 “death of macaw chicks at our study site was starvation.”
l.312-313 “we did not find any cases of death…”
l.314-315 The wording is a bit ambiguous here. For example, regarding the second chicks: did 60% of the second chicks died of starvation? Or do you mean that: of the second chicks that died of a known cause, 60% of the deaths were caused by starvation? I think you mean the latter, in which case you want to refer to a percentage of the deaths, rather than a percentage of chicks.
l.316 Kind of a gruesome heading :(
l.330 Change the period after “chicks” to a semicolon “;”
l.331 Add a period after “Table 1)”
l.334 Change the period after “chicks” to a semicolon “;”
l.339 “by an experienced” or “by a trained”
l.342 “age 36 d” or “age 36 days”
l.343 “Data were obtained over 18 consecutive..”
Figure 1 I had a difficult time identifying lines for a couple of reasons: The legend doesn’t clearly illustrate the different line types; the dotted line for starved 4th chicks is very similar to that of the outlier chick; also, in the legend the ALL chick orders plot symbol appears to be a solid square, but on the graph the plot symbols appear as “X”s (or tick marks?).
l.349 It would be more correct to say “Weight gain in Scarlet Macaw chicks.” …because those that fledged are also included.
l.351 “The dark solid line corresponds…”
l.372 “Mean pushes against chicks starved”?
l.373 Replace the period after “N = 7 chicks” with a semicolon “;”
l.373 “Mean pushes against chicks that did not starve”?
l.374 Replace the period after “chicks” with a semicolon “;”
l.381 “We observed only five instances in which a chick…”
l.383 “days old, when all…”
l.384 “(on average chicks opened their eyes at the age of …. days [40]).”
l.387 “the parent to feed it.” (“themselves” implies that parents fed themselves, or that chicks fed themselves, neither of which is the case)
l.389 replace the colon “:” after “14 second chicks” with a comma “,”
l.394 “that fewer second chicks…”
l.396 Since there were no significant differences, it would be more concise to say “did not differ between starved and non-starved chicks.”
l.397-398 “Given the available sample size, our analysis had…”
l.402 “Food abundance during the nestling phase…”
l.414 provide a sample size (N) for this mean
l.415 Replace period after “per hr” with a semicolon “;”
l.416 Replace comma after “starvation” with a semicolon “;”
l.428 Replace period after “N=9” with a semicolon “;”
l.435 Replace commas after “starve” and ”P=0.0058” with semicolons “;”
l.441 Replace comma after “chicks” with a semicolon “;”
l.442 Replace comma after “chicks” with a semicolon “;”
l.447 “did not starve”
l.458 Upon reading this, I wondered whether you have data on the spacing between egg-laying events and/or hatching dates? I was initially surprised that there would be a 5-day separation between first and second chicks, but I can imagine that a combination of 2-3 days between laying and a delay of a couple of days in the onset of incubation could result in a 5-day difference in hatch dates.
l.461 “Brood reduction in parrots…” (since App.B only includes parrots)
l.462 “starvation was…” “in our study species” or simply “in our study”
l.463 “chicks starved, and…” and “chicks starved.”
l.465 “control by parent of food distribution…”
l.466 “to death, and…”
l.467 “(2) a larger age difference between brood members was associated with a higher probability of starvation for the second chick.”
l.470 “Chicks that starved during our study exhibited a variety of symptoms.”
l.471 “they were: …”
l.473 delete “for the rest of the body” (that is implied when you say “disproportionally”)
l.473 correct spelling is “bony”
l.473-474 “dull eyes”
l.476-477 “These signs of malnutrition observed in our study have been…”
l.478 delete “as many of….problems”
l.487 “showed that while starved second chicks were fed less than first chicks, third chicks…”
l.493 “to death quickly because…” (only use “quicker” if you’re making a specific comparison to something else)
l.506-507 “chick starvation. This was the case for the first 36 days of the brood, for the first 15 days of the brood, and also for the 7-day…”
l.508 “second chicks in our study…”
l.510 “Parrotlet, where…”
l.515 “did not occur due to food stress, and starvation…”
l.516 “starvation was not associated with peaks in…”
l.521 “in the driest year of a study, when…”
l.523 I would suggest replacing “However” with “In contrast” or “On the other hand”
l.526 “population in which no…”
l.526 “In that study…” (otherwise it sounds like you’re referring to your own study”
l.527-528 “their nests, using area one fourth… populations in which no second…”
l.530 “… starvation in our study may…”
l.531 “issues with” is kind of vague… what exactly do you mean here?
l.532 “a true absence of a relationship between food availability and…”
l.533 “could have been too small”
l.536-537 “Quantification of food availability in an area bigger…”
l.545 “not an important factor causing chick starvation in our study species.”
l.547 “Scarlet Macaw parents directly control food distribution”
l.549 “the difference in…” is unclear; possible re-wording: “difference between first and second chick feeding rates when second chicks starved…”
l.551 “feeding ratios for broods in which second chicks fledged and those in which second chicks starved…”
l.553 “and limiting food…”
l.555 “we” should not be capitalized; “we repeatedly observed…”
l.555-556 “their crops were completely full, while second chicks were on the other side…”
l.561 “low locomotor control”
l.563 For the sake of consistency: “Budgerigars” (instead of “Budgies”)
l.564 I would delete “especially the females” here. This additional info is provided in the sentences that follow.
l.564 “Female budgerigars fed…”
l.565-566 this sentence is confusing
l.567-568 “both males and females, but when…”
l.569 All chicks lost weight? Or only last-hatched (or later-hatched) chicks?
l.569 “males switched to feeding all…”
l.570 “switched to feeding first…”
l.572 Avoid anthropomorphizing (e.g., “in the hope of”). Possible re-wording: “investment, thereby increasing the chances of fledging…”
l.579 “might not be fixed throughout…”
l.580 “growth parameters of first and second…”
l.582 “second chicks, allowing them to…”
l.585 “did not starve, but this…”
l.586 “and large standard deviations in our dataset, our analysis had very low power to… 20%, so…”
l.589 “subsequently hatched chick, and the…”
l.594 “Parrotlets, in which egg…”; remove comma after “quality)”
l.595 “laying order [64], but are supported by data from…”
l.600 “7 to 16 days, resulting in…”
l.603 “soon after the…” “of starvation; however, when they hatched…”
l.605 “done with Green-rumped Parrotlets, in which the…
l.606 “was found to be a function of…”; add a comma after “synchrony [13]”
l.607 “lower starvation probabilities” or “lower starvation rates”
l.608 “asynchrony are key drivers of starvation-mediated…”
l.610-611 “suggest that the role of age differences in driving starvation may be more nuanced.”
l.619 “monitored separately, because…”
l.621 “In contrast, a 20-day…”
l.628 “among Scarlet Macaw nestlings…”
l.630-631 I would remove the parentheses, and add a comma after “of starvation”
l.631 “Our work suggests that…”
l.634 “days), if…” Perhaps say “necessary feeding” or “age-specific feeding”
l.635 “drops greatly”
l.636 “developmental stage and parental care requirements of young…”
l.637-638 “in wild Scarlet Macaws.” Delete “in this system”
l.639 “strengthens the case”
Comments on the Quality of English Language
(see above)
Author Response
Suggestion:-Throughout the ms, I would suggest hyphenating first-hatched, second-hatched, etc.
Reply: We are ok with this suggestion, but leave this decision up to the English language editors at MDPI.
l.97 “…we present a brief…”
Done
l.101 “within broods. Second hatched…are targets of…” Here and in most of the subsequent hypotheses, hypothesis statements contain two semicolons (followed by a capitalized word) which does not seem grammatically correct. I would suggest replacing the second semicolon with either a period or a semicolon.
Done
l.121 Should read “1 091 416 ha”
Done
l.126 “during 18 consecutive”
Done
l.128 “In 11 breeding seasons”
Done
l.129 “we installed video cameras in…”
Done
l.131 “at 37 wild macaw nest sites” or “in 37 wild macaw nests” (the term “nest site” is more general, referring to the physical location of a nest on the landscape)
Done
l.133 “All nests were checked…” Were chicks banded (or otherwise marked)?
Done
l.134 “nest monitoring was suspended for 26 days, and resumed when the first …”
Done
l.135 “After chicks hatched, the.”
Done
l.142 “did not gain weight”
Done
l.146 “used a video camera system”
Done
l.147-148 “From 2007 to 2010, we made non-continuous recordings during observations…”
Done
l.149 “We made continuous…”
Done
l.150 “we made two-hour…”
Done
l.151-152 I believe you mean “From 2012 to 2018, we made 6-hour continuous recordings at three specific…”
Yes and Done
l.153-154 “These 6-hour recordings were on the following schedule:” The wording in this sentence is confusing: do you mean “until starving chicks died or (2) every other day…”? (i.e. “or” instead of “and”?)
Done
l.155-156 “We were not always able to follow…”
Done
l.158 What do you mean by “We tested both observers”?
Additional text added to clarify
l.161 “chicks that starved to death with second chicks…”
Done
l.172 “were included in all of the analyses.”
Done
l.175 capitalize “Pro” Were all tests 2-tailed?
Done
l.190 Your justification for throwing out this data point is not provided until the following paragraph; it would be best to state your justification here. Was this chick excluded from all analyses, or only certain ones?
Done
l.198 Please explain what you mean that “chick order did not change”
Done
l.199 “which starved”
Done
l.200-202 see note for l.190
Done
l.218-219 delete “and tallied”
Done
l.241 remove period in “all data.in”
Done
l.260-261 This explains how you identified chick feeding, but it’s not clear how feeding was quantified. The text that follows mentions both “feedings” and “feeding rates.” Did you count feeding bouts (if so, how was a “bout” defined)? Was feeding bout duration taken into account? You also need to explain how feeding rates were estimated.
We defined bout in the methods to address this
l.264 “starvation” (delete the “s”)
Done
l.275 -276 “we calculated the ratio using feeding data from when both…”
Done
l.276 “For broods in which second chicks fledged, calculations were done for: …”
Done
l.278-279 suggested re-wording: “We did not include data from video recordings for which chicks could not be identified for >50% of feedings.
Done
l.280 “parents that were not given supplemental food, and…”
Done
l.286 Did you use a binary logistic regression here and in logistic regression analyses described below?
Yes
l.310 Throughout the Results section, p-values could be reported simply as “p = #” instead of “p-value = #” Also, throughout the section, when reporting statistically significant results, you can simply say “X differed from Y” (saying “X differed significantly from Y” is redundant, because if the difference is not statistically significant, then you cannot state that there is a difference).
Done
l.311 “death of macaw chicks at our study site was starvation.”
Done
l.312-313 “we did not find any cases of death…”
Done
l.314-315 The wording is a bit ambiguous here. For example, regarding the second chicks: did 60% of the second chicks died of starvation? Or do you mean that: of the second chicks that died of a known cause, 60% of the deaths were caused by starvation? I think you mean the latter, in which case you want to refer to a percentage of the deaths, rather than a percentage of chicks.
Done
l.316 Kind of a gruesome heading :(
Sorry, sometimes it’s a jungle out there!
l.330 Change the period after “chicks” to a semicolon “;”
Done
l.331 Add a period after “Table 1)”
Done
l.334 Change the period after “chicks” to a semicolon “;”
Done
l.339 “by an experienced” or “by a trained”
Done
l.342 “age 36 d” or “age 36 days”
Done
l.343 “Data were obtained over 18 consecutive..”
Done
Figure 1 I had a difficult time identifying lines for a couple of reasons: The legend doesn’t clearly illustrate the different line types; the dotted line for starved 4th chicks is very similar to that of the outlier chick; also, in the legend the ALL chick orders plot symbol appears to be a solid square, but on the graph the plot symbols appear as “X”s (or tick marks?).
Graph was redone in color.
l.349 It would be more correct to say “Weight gain in Scarlet Macaw chicks.” …because those that fledged are also included.
Done
l.351 “The dark solid line corresponds…”
Done
l.372 “Mean pushes against chicks starved”?
Done
l.373 Replace the period after “N = 7 chicks” with a semicolon “;”
Done
l.373 “Mean pushes against chicks that did not starve”?
Done
l.374 Replace the period after “chicks” with a semicolon “;”
Done
l.381 “We observed only five instances in which a chick…”
Done
l.383 “days old, when all…”
Done
l.384 “(on average chicks opened their eyes at the age of …. days [40]).”
Done
l.387 “the parent to feed it.” (“themselves” implies that parents fed themselves, or that chicks fed themselves, neither of which is the case)
changed to “them” instead of “it”
l.389 replace the colon “:” after “14 second chicks” with a comma “,”
Done
l.394 “that fewer second chicks…”
Done
l.396 Since there were no significant differences, it would be more concise to say “did not differ between starved and non-starved chicks.”
We understand the request here, but given our small sample sizes, we feel it is important to make it clear that there were no interesting trends here that even suggest underlying possible significance. No change made.
l.397-398 “Given the available sample size, our analysis had…”
Done
l.402 “Food abundance during the nestling phase…”
Done
l.414 provide a sample size (N) for this mean
Sample size provided
l.415 Replace period after “per hr” with a semicolon “;”
Done
l.416 Replace comma after “starvation” with a semicolon “;”
Done
l.428 Replace period after “N=9” with a semicolon “;”
Done
l.435 Replace commas after “starve” and ”P=0.0058” with semicolons “;”
Done
l.441 Replace comma after “chicks” with a semicolon “;”
Done
l.442 Replace comma after “chicks” with a semicolon “;”
Done
l.447 “did not starve”
Done
l.458 Upon reading this, I wondered whether you have data on the spacing between egg-laying events and/or hatching dates? I was initially surprised that there would be a 5-day separation between first and second chicks, but I can imagine that a combination of 2-3 days between laying and a delay of a couple of days in the onset of incubation could result in a 5-day difference in hatch dates.
Unfortunately we do not have sufficient data on egg laying and initiation of incubation. We do realize and agree that this is the next logical line of inquiry in this system. No change made.
l.461 “Brood reduction in parrots…” (since App.B only includes parrots)
Done
l.462 “starvation was…” “in our study species” or simply “in our study”
Done
l.463 “chicks starved, and…” and “chicks starved.”
Done
l.465 “control by parent of food distribution…”
changed to direct parental control of food distribution
l.466 “to death, and…”
Done
l.467 “(2) a larger age difference between brood members was associated with a higher probability of starvation for the second chick.”
Done
l.470 “Chicks that starved during our study exhibited a variety of symptoms.”
Done
l.471 “they were: …”
Done
l.473 delete “for the rest of the body” (that is implied when you say “disproportionally”)
Done
l.473 correct spelling is “bony”
Done
l.473-474 “dull eyes”
Done
l.476-477 “These signs of malnutrition observed in our study have been…”
Done
l.478 delete “as many of….problems”
Removing this content does not improve the flow or reduce redundancy. No change made.
l.487 “showed that while starved second chicks were fed less than first chicks, third chicks…”
Done
l.493 “to death quickly because…” (only use “quicker” if you’re making a specific comparison to something else)
changed to: even quicker than third chicks
l.506-507 “chick starvation. This was the case for the first 36 days of the brood, for the first 15 days of the brood, and also for the 7-day…”
Done
l.508 “second chicks in our study…”
Done
l.510 “Parrotlet, where…”
Done
l.515 “did not occur due to food stress, and starvation…”
Done
l.516 “starvation was not associated with peaks in…”
Done
l.521 “in the driest year of a study, when…”
Done
l.523 I would suggest replacing “However” with “In contrast” or “On the other hand”
Done
l.526 “population in which no…”
Done
l.526 “In that study…” (otherwise it sounds like you’re referring to your own study”
Done
l.527-528 “their nests, using area one fourth… populations in which no second…”
Done
l.530 “… starvation in our study may…”
Done
l.531 “issues with” is kind of vague… what exactly do you mean here?
We deleted “issues with” and just left chick diet specificity, which is the topic of the entire next paragraph.
l.532 “a true absence of a relationship between food availability and…”
Done
l.533 “could have been too small”
Done
l.536-537 “Quantification of food availability in an area bigger…”
Done
l.545 “not an important factor causing chick starvation in our study species.”
Done
l.547 “Scarlet Macaw parents directly control food distribution”
Done
l.549 “the difference in…” is unclear; possible re-wording: “difference between first and second chick feeding rates when second chicks starved…”
Done
l.551 “feeding ratios for broods in which second chicks fledged and those in which second chicks starved…”
Done
l.553 “and limiting food…”
Done
l.555 “we” should not be capitalized; “we repeatedly observed…”
Done
l.555-556 “their crops were completely full, while second chicks were on the other side…”
Done
l.561 “low locomotor control”
Done
l.563 For the sake of consistency: “Budgerigars” (instead of “Budgies”)
Done
l.564 I would delete “especially the females” here. This additional info is provided in the sentences that follow.
Done
l.564 “Female budgerigars fed…”
Done
l.565-566 this sentence is confusing
Clarified
l.567-568 “both males and females, but when…”
l.569 All chicks lost weight? Or only last-hatched (or later-hatched) chicks?
Clarified in the text
l.569 “males switched to feeding all…”
Done
l.570 “switched to feeding first…”
Done
l.572 Avoid anthropomorphizing (e.g., “in the hope of”). Possible re-wording: “investment, thereby increasing the chances of fledging…”
Done
l.579 “might not be fixed throughout…”
Done
l.580 “growth parameters of first and second…”
Done
l.582 “second chicks, allowing them to…”
Done
l.585 “did not starve, but this…”
Done
l.586 “and large standard deviations in our dataset, our analysis had very low power to… 20%, so…”
Done
l.589 “subsequently hatched chick, and the…”
Done
l.594 “Parrotlets, in which egg…”; remove comma after “quality)”
Done
l.595 “laying order [64], but are supported by data from…”
Word suggested no comma, so no change made.
l.600 “7 to 16 days, resulting in…”
Done
l.603 “soon after the…” “of starvation; however, when they hatched…”
Done
l.605 “done with Green-rumped Parrotlets, in which the…
Done
l.606 “was found to be a function of…”; add a comma after “synchrony [13]”
Done
l.607 “lower starvation probabilities” or “lower starvation rates”
Done
l.608 “asynchrony are key drivers of starvation-mediated…”
Done
l.610-611 “suggest that the role of age differences in driving starvation may be more nuanced.”
Done
l.619 “monitored separately, because…”
Done
l.621 “In contrast, a 20-day…”
Done
l.628 “among Scarlet Macaw nestlings…”
Done
l.630-631 I would remove the parentheses, and add a comma after “of starvation”
Done
l.631 “Our work suggests that…”
Done
l.634 “days), if…” Perhaps say “necessary feeding” or “age-specific feeding”
Done
l.635 “drops greatly”
Done
l.636 “developmental stage and parental care requirements of young…”
Done
l.637-638 “in wild Scarlet Macaws.” Delete “in this system”
Done
l.639 “strengthens the case”
Done . . . wow that was a whole lot of specific comments!!
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript reports a fascinating study of the causes of brood reduction in a Macaw species. It uses an impressive long-term data set to examine alternative hypotheses of brood reduction either through siblicide or filial infanticide. Unfortunately, subsets of the data are required due to methodological changes across the 18-year study period. This is understandable where data has been collected with CCTV given the rapid miniaturization and improvement in capability of this technology across the study period. The authors compensate for potential data deficiencies through power analysis and find insufficient statistical power in only one instance. However, what is missing from the methodology is recognition of probable pseudo-replication in the parental sample. One assumes multiple broods from the same parents are included in the dataset. Pseudo-replication constrains the generality of results, and the authors are not guilty of over-generalisation. They are clear that their conclusions reference only their study population of Macaws. Even so they have made a valuable contribution to our understanding of the cause(s) of brood reduction in parrots and the larger avifauna. My only qualification is that the focus on the chicks leaves insufficient discussion on the costs/benefits of brood reduction through filial infanticide to the parents’ reproductive success.
The manuscript is well-written and the methods and results well-presented. There is informative imagery of chicks in Appendix A. The methods might include an image of a representative nest and brood from the observer’s perspective to better engage the reader. The discussion canvasses a comprehensive literature and brings clarity to the authors’ conclusions. However, there are a few grammatical errors and inconsistencies in the text, as highlighted in the following, that should be addressed before publication.
Line 75: from the nest
Line 77: carcasses
Line 97: we present
Line 101: that are the target
Line 112: ‘less at hatching’ than what comparator?
Line 163: did not
Line 212: an adult’s beak
Line 232: an adult’s beak
Line 339: experienced
Line 384: average chick
Line 338: Pushing the adult’s beak
Line 447: and the significant
Line 478: have been used
Line 530: of a relationship
Line 537” 2.5 km radius
Line 550: second chicks
Line 563 and 564: Budgerigars
Line 569: and females
Line 635: drops greatly
Comments on the Quality of English LanguageSee above
Author Response
Comment: Missing from the methodology is recognition of probable pseudo-replication in the parental sample. One assumes multiple broods from the same parents are included in the dataset.
Reply: Information on the number of broods from the same nest structures was included to clarify this.
Comment: Pseudo-replication constrains the generality of results, and the authors are not guilty of over-generalisation. They are clear that their conclusions reference only their study population of Macaws. Even so they have made a valuable contribution to our understanding of the cause(s) of brood reduction in parrots and the larger avifauna.
Reply: We included information on the number of chicks per nest site in the Methods to give an idea of the level of repetition in the data set.
Comment: My only qualification is that the focus on the chicks leaves insufficient discussion on the costs/benefits of brood reduction through filial infanticide to the parents’ reproductive success.
Reply: Unfortunately, we don’t have the correct type of data to address this issue so any discussion would be highly speculative. Also, the paper is already quite long so trying to add this topic would make the paper quite unwieldly.
Comment: The methods might include an image of a representative nest and brood from the observer’s perspective to better engage the reader.
Reply: Included as per request.
Line 75: from the nest
Done
Line 77: carcasses
Done
Line 97: we present
Done
Line 101: that are the target
Correction from Reviewer one used here
Line 112: ‘less at hatching’ than what comparator?
Clarified “Hatch weight of second chicks is likely to be negatively related to probability of starvation, with heavier chicks having lower starvation rates.”
Line 163: did not
Done
Line 212: an adult’s beak
Done
Line 232: an adult’s beak
Done
Line 339: experienced
Done
Line 384: average chick
Reviewer 1 suggestion used.
Line 338: Pushing the adult’s beak
Done
Line 447: and the significant
Done
Line 478: have been used
Reviewer one suggestion used for rewrite here
Line 530: of a relationship
Done
Line 537” 2.5 km radius
Done
Line 550: second chicks
Done
Line 563 and 564: Budgerigars
Done
Line 569: and females
Done
Line 635: drops greatly
Done
