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Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
The role of social and ecological processes in structuring
animal populations: a case study from automated tracking
of wild birds
Damien R. Farine, Josh A. Firth, Lucy M. Aplin, Ross A. Crates, Antica Culina, Colin J.
Garroway, Camilla A. Hinde, Lindall R. Kidd, Nicole D. Milligan, Ioannis Psorakis, Reinder
Radersma, Brecht Verhelst, Bernhard Voelkl and Ben C. Sheldon
Article citation details
R. Soc. open sci. 2: 150057.
http://dx.doi.org/10.1098/rsos.150057
Review timeline
Original submission:
Revised submission:
Final acceptance:
2 February 2015
20 March 2015
23 March 2015
Note: Reports are unedited and appear as
submitted by the referee. The review history
appears in chronological order.
Review History
RSOS-150057.R0 (Original submission)
Review form: Reviewer 1 (Jennifer Gill)
Is the manuscript scientifically sound in its present form?
Yes
Are the interpretations and conclusions justified by the results?
Yes
Is the language acceptable?
Yes
Is it clear how to access all supporting data?
Data will be uploaded to Dryad and supplementary data are clear (but see the suggestions for
improving presentation, in response to authors).
© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons
Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use,
provided the original author and source are credited
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2
Do you have any ethical concerns with this paper?
No
Have you any concerns about statistical analyses in this paper?
No
Recommendation?
Accept with minor revision (please list in comments)
Comments to the Author(s)
This study uses data from the very high-resolution tracking of individual tits in Wytham Wood to
explore patterns of group composition over space and time. The data that this study has
generated have great potential to uncover important individual-level drivers of key ecological
and evolutionary processes. I enjoyed reading the manuscript and I think the authors should be
congratulated on extracting some very interesting and important patterns from these complex
and fascinating data. My comments below relate to slight concerns over potential systematic
biases that could result from the method of group classification, and I think there are some details
of the presentation (of the figures, in particular) that could be clearer.
Line 57: I think this might be clearer as ‘...those influenced by dominance or sex’?
Line 118: Details of methods used to determine sex should be reported here (was sex determined
for nestlings, or only on post-fledging recapture?)
Line 148: presumably tagged individuals have to be at the feeder in order to be recorded? Is there
then a risk of systematic bias of which individuals (or phenotypes) within a flock have access to
the feeder, and are therefore recorded as being flock members?
Lines 154-159: were there any attempts to verify this analytical method for inferring group size
and membership from these data? I can well imagine that defining a group in the field is just as
hard as extracting it from the data, but perhaps sensitivity analyses of the analytical outputs have
been carried out, to consider the robustness of the predicted group sizes and memberships?
Line 157: better as ‘to which they have...belonging.’
Line 180: use should be plural
Line 199: how were birds defined as being ‘born outside of the study area’? Were these birds that
had been ringed outside of Wytham or birds that were unringed on capture within Wytham, and
assumed to have been born outside? If the latter, it would help to give some estimate of the
potential for broods within Wytham to go unringed (eg those from natural cavities?).
Line 208: presumably these morphometrics are only available for birds caught/recaught when
fully grown? It might help to say in the opening section of the Methods what proportion of birds
are ringed as chicks and then recaught as adults?
Line 295: iteration should be singular
Line 312: Table S1 doesn’t appear to be in the Supplementary file.
Lines 316 & 318: is this SD? Should state that here or in Methods.
Line 318: is the 274 needed before individual?
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3
Line 320: I think it would help to reiterate what aspect of the groups is being assessed here – eg
Stability of group membership?
Line 322: I’m not quite sure what ‘in the first 10 minutes of the observed data’ means? Fig 1a
suggests that this is an analysis of the time gap between groups, in which case does this mean
when the inter-group interval was less than 10 minutes? Some rewording would help here I
think.
Line 326-327: it seems odd to describe an analysis showing stability over short time spans (<10
mins) as ‘highly fluid across short periods of time’. Might this be better phrased as something like
‘the composition of groups was therefore only stable over very short periods (<10 minutes)’?
Lines 333-343: this is a really fascinating result but it made me wonder whether this could be a
function of classifying groups on the basis of time at the feeder. For example, when the local tit
population is larger, are other species also be more likely to be present, and could their presence
at the feeders influence the time between visits by tits and thus the classification of group size?
Line 338: there should be a comma between group and respectively
Line 378: would ‘more evenly distributed’ be better than ‘more dissasortative’? The latter is not
very intuitive (same comment for the figure legend).
Line 384: but there are no observed data presented on this figure?
Line 391: the analysis to which this p>0.05 belongs should be presented (ie statistic & DF, with
details in the Methods).
Line 402: should this be ‘individuals of the same age category’?
Line 405-406: this sentence doesn’t seem to fit here – it is not really interpretation of the results
(what is meant by ‘long-term pattern’), so should probably be moved to the Discussion or
reworded.
Line 439: typo: two ‘associations’
Lines 443-444: there something wrong with the end of this sentence (a through followed by a to),
and synchrony in what?
Line 448: the meaning of ‘mixed by sex’ isn’t very clear – does this mean a more even sex ratio
than expected by chance?
Line 682: this figure is not very easy to follow because the legend doesn’t explain what is on the
y-axis
Line 686: should be ‘observed data differ’
Lines 687-688: how are age and sex represented on this figure? The legend needs to explain the yaxis on both panels.
Lines 690-692: this legend needs to explain the figure contents – what is on the y-axis? It may be
repetition but I think each legend needs to provide a complete explanation of figure contents –
having interpretation without description of contents is very confusing.
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4
Table 1: this gives very little information, and so may be better summarised in the text or moved
to supplementary material.
Figure 5: no datapoints shown (legend to Fig 3 says black lines show observed data).
Figure S4: legend doesn’t say which panel is which group.
Jenny Gill
University of East Anglia
Review form: Reviewer 2 (Alexandra Pavlova)
Is the manuscript scientifically sound in its present form?
Yes
Are the interpretations and conclusions justified by the results?
Yes
Is the language acceptable?
Yes
Is it clear how to access all supporting data?
Supplementary materials are available, data will be uploaded to Dryad upon acceptance
Do you have any ethical concerns with this paper?
No
Have you any concerns about statistical analyses in this paper?
I do not feel qualified to assess the statistics
Recommendation?
Accept as is
Comments to the Author(s)
In this paper, social and phenotypic structure of fission-fusion groups of wintering great tits were
explored using data from an automated detection system of PIT-tagged great tits. To differentiate
spatial and social effects, authors created two data-randomisation-based null models (phenotypic
null and spatiotemporally-controlled null) and compared observed data to these expectations.
Several significant results were found (e.g. large groups had more juvenile females and fewer
adult males, groups had non-random disassociation of sexes and non-random association of age
classes) which were attributed to spatial or social drivers.
I found this paper an excellent read. Introduction is well-written and nicely sets up the study,
methods appear sound, sample sizes of pit-tagged individuals are admirably large, discussion is
clear and conclusions are reasonable. Thus, I highly recommend this paper for publication.
I had just one question (how birds were sexed?) and one very minor comment:
L337 perhaps for clarity, change “relationship between population size and group size” to
“relationship between population size and mean or maximum group size”
Alexandra Pavlova, PhD
School of Biological Sciences, Monash University
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5
Decision letter (RSOS-150057)
19-Mar-2015
Dear Dr Farine
On behalf of the Editor, I am pleased to inform you that your Manuscript RSOS-150057 entitled
"The role of social and ecological processes in structuring animal populations: a case study from
automated tracking of wild birds" has been accepted for publication in Royal Society Open
Science subject to minor revision in accordance with the referee suggestions. Please find the
referees' comments at the end of this email.
The reviewers and Subject Editor have recommended publication, but also suggest some minor
revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your
manuscript.
• Ethics statement
If your study uses humans or animals please include details of the ethical approval received,
including the name of the committee that granted approval. For human studies please also detail
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• Data accessibility
It is a condition of publication that all supporting data are made available either as
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All submissions, other than those with a single author, must include an Authors’ Contributions
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All contributors who do not meet all of these criteria should be included in the
acknowledgements.
We suggest the following format:
AB carried out the molecular lab work, participated in data analysis, carried out sequence
alignments, participated in the design of the study and drafted the manuscript; CD carried out
the statistical analyses; EF collected field data; GH conceived of the study, designed the study,
coordinated the study and helped draft the manuscript. All authors gave final approval for
publication.
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6
• Acknowledgements
Please acknowledge anyone who contributed to the study but did not meet the authorship
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Because the schedule for publication is very tight, it is a condition of publication that you submit
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look
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Associate Editor Comments to Author:
Associate Editor: 1
Comments to the Author:
Two reviewers have commented on your manuscript, and their largely favourable comments are
given here. I'd like to give you the opportunity to respond to the comments made by both of them
in a revised version of the manuscript.
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7
Author's Response to Decision Letter for (RSOS-150057)
Appendix A.
Appendix
A
Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
We thank both reviewers for their supportive comments and for highlighting
areas that require more clarity. We have followed all the suggestions and
implemented all the changes proposed by the reviewers. Where further details
are required, we provide these below.
Reviewer: 1
Comments to the Author(s)
This study uses data from the very high-resolution tracking of individual tits in
Wytham Wood to explore patterns of group composition over space and time.
The data that this study has generated have great potential to uncover important
individual-level drivers of key ecological and evolutionary processes. I enjoyed
reading the manuscript and I think the authors should be congratulated on
extracting some very interesting and important patterns from these complex and
fascinating data. My comments below relate to slight concerns over potential
systematic biases that could result from the method of group classification, and I
think there are some details of the presentation (of the figures, in particular) that
could be clearer.
Line 57: I think this might be clearer as ‘...those influenced by dominance or sex’?
DONE
Line 118: Details of methods used to determine sex should be reported here
(was sex determined for nestlings, or only on post-fledging recapture?)
DONE - we have also added details on the percentage of birds sexed (93.1%).
Line 148: presumably tagged individuals have to be at the feeder in order to be
recorded? Is there then a risk of systematic bias of which individuals (or
phenotypes) within a flock have access to the feeder, and are therefore recorded
as being flock members?
We have no evidence any biases exist in visits to feeders. Great tits (the focal
species in this study) are dominant over all species other than nuthatches (which
are uncommon at our study site), and these subordinate species all regularly
visit (they are also PIT-tagged). Because birds are collecting unhusked sunflower
seeds, they only briefly perch on one of the two access holes to collect a seed
before flying off to process it. This greatly reduces scramble competition at
feeders compared to other food types. For example, we find no difference in the
number of detections between bold and shy birds (Aplin et al 2013 Ecol Lett).
Lines 154-159: were there any attempts to verify this analytical method for
inferring group size and membership from these data? I can well imagine that
defining a group in the field is just as hard as extracting it from the data, but
perhaps sensitivity analyses of the analytical outputs have been carried out, to
consider the robustness of the predicted group sizes and memberships?
We have a just had a paper accepted that does this sensitivity analysis, finding
that the Gaussian Mixture Model better captures the network from a synthetic
datastream generated by a known network. We have added the following text: "
resulting in a more accurate social network than other approaches (Psorakis et al.
accepted)."
Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
Line 157: better as ‘to which they have...belonging.’
DONE
Line 180: use should be plural
DONE
Line 199: how were birds defined as being ‘born outside of the study area’? Were
these birds that had been ringed outside of Wytham or birds that were unringed
on capture within Wytham, and assumed to have been born outside? If the latter,
it would help to give some estimate of the potential for broods within Wytham to
go unringed (eg those from natural cavities?).
The proportion of nestlings born in natural cavities is estimated to be very low.
This was surveyed in the 1970s by Greenwood, Harvey & Perrins 1979, and
more recent estimates based on mark-recapture methods support this (Kidd et
al. in revision). We have added a sentence to cover this.
Line 208: presumably these morphometrics are only available for birds
caught/recaught when fully grown? It might help to say in the opening section of
the Methods what proportion of birds are ringed as chicks and then recaught as
adults?
DONE (see comment Line 118)
Line 295: iteration should be singular
DONE
Line 312: Table S1 doesn’t appear to be in the Supplementary file.
FIXED - table S1 had been removed as the information was integrated into the
text.
Lines 316 & 318: is this SD? Should state that here or in Methods.
DONE – these are actually SE and this has been added to the text.
Line 318: is the 274 needed before individual?
FIXED - there was an issue with the format of the document - the 274 was an old
line number converted to text.
Line 320: I think it would help to reiterate what aspect of the groups is being
assessed here – eg Stability of group membership?
DONE - we have changed the heading as suggested
Line 322: I’m not quite sure what ‘in the first 10 minutes of the observed data’
means? Fig 1a suggests that this is an analysis of the time gap between groups, in
which case does this mean when the inter-group interval was less than 10
minutes? Some rewording would help here I think.
FIXED - changes 'of the observed data' to 'after being observed'.
Line 326-327: it seems odd to describe an analysis showing stability over short
time spans (<10 mins) as ‘highly fluid across short periods of time’. Might this be
Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
better phrased as something like ‘the composition of groups was therefore only
stable over very short periods (<10 minutes)’?
DONE - text changed as suggested by the reviewer.
Lines 333-343: this is a really fascinating result but it made me wonder whether
this could be a function of classifying groups on the basis of time at the feeder.
For example, when the local tit population is larger, are other species also be
more likely to be present, and could their presence at the feeders influence the
time between visits by tits and thus the classification of group size?
Because the Gaussian Mixture Model captures normally-distributed group visit
times, so long as the other species are randomly distributed within these (which
they are), they will not affect the group detections. This is a very good point
though, and we are glad that the reviewer has made it because it suggest they
understand the method clearly. When we first generated these networks, we did
consider whether we should include all species (they are all PIT-tagged) when
detecting groups. Work done by the first author on these mixed-species
assemblages involved including all individuals in the Gaussian Mixture Model
(see Farine et al 2012 for example), and a comparison of these data showed that
both datastreams were reasonably identical (the Gaussian Mixture Model is nondeterministic, and so some differences are expected) and generated identical
social networks.
Line 338: there should be a comma between group and respectively
DONE
Line 378: would ‘more evenly distributed’ be better than ‘more dissasortative’?
The latter is not very intuitive (same comment for the figure legend).
DONE for both cases
Line 384: but there are no observed data presented on this figure?
FIXED - we have clarified the text. In particular, moved the reference to the
figure to a more appropriate part of the text.
Line 391: the analysis to which this p>0.05 belongs should be presented (ie
statistic & DF, with details in the Methods).
FIXED- this P>0.05 simply referred to the observed data not falling outside of the
range of the null model. We have removed the value from here as it was not
conveying any useful additional information beyond the figure.
Line 402: should this be ‘individuals of the same age category’?
DONE
Line 405-406: this sentence doesn’t seem to fit here – it is not really
interpretation of the results (what is meant by ‘long-term pattern’), so should
probably be moved to the Discussion or reworded.
FIXED - we have removed the sentence
Line 439: typo: two ‘associations’
DONE
Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
Lines 443-444: there something wrong with the end of this sentence (a through
followed by a to), and synchrony in what?
FIXED
Line 448: the meaning of ‘mixed by sex’ isn’t very clear – does this mean a more
even sex ratio than expected by chance?
FIXED
Line 682: this figure is not very easy to follow because the legend doesn’t explain
what is on the y-axis
FIXED – we have clarified the figure caption to explain what each component of
the plot is. In this case, we state in the first sentence that the y-axis represent the
proportion of males that were juveniles in (a) and proportion of females that
were juveniles in (b).
Line 686: should be ‘observed data differ’
FIXED
Lines 687-688: how are age and sex represented on this figure? The legend
needs to explain the y-axis on both panels.
FIXED – we have clarified all 5 figure captions, which were lacking in clarity.
Lines 690-692: this legend needs to explain the figure contents – what is on the
y-axis? It may be repetition but I think each legend needs to provide a complete
explanation of figure contents – having interpretation without description of
contents is very confusing.
FIXED – we have added detail to the caption of Figure 4
Table 1: this gives very little information, and so may be better summarised in
the text or moved to supplementary material.
MOVED – we have moved this table to supplementary materials.
Figure 5: no datapoints shown (legend to Fig 3 says black lines show observed
data).
FIXED – we have specifically mentioned that the observed data is now along y=1,
and that Figure S6 shows the non-ratio data.
Figure S4: legend doesn’t say which panel is which group.
FIXED
Jenny Gill
University of East Anglia
Reviewer: 2
Comments to the Author(s)
In this paper, social and phenotypic structure of fission-fusion groups of
wintering great tits were explored using data from an automated detection
Downloaded from http://rsos.royalsocietypublishing.org/ on July 7, 2015
system of PIT-tagged great tits. To differentiate spatial and social effects, authors
created two data-randomisation-based null models (phenotypic null and
spatiotemporally-controlled null) and compared observed data to these
expectations. Several significant results were found (e.g. large groups had more
juvenile females and fewer adult males, groups had non-random disassociation
of sexes and non-random association of age classes) which were attributed to
spatial or social drivers.
I found this paper an excellent read. Introduction is well-written and nicely sets
up the study, methods appear sound, sample sizes of pit-tagged individuals are
admirably large, discussion is clear and conclusions are reasonable. Thus, I
highly recommend this paper for publication.
I had just one question (how birds were sexed?)
FIXED – birds were sexed using breast strip width, which is highly dimorphic in
great tits.
and one very minor comment:
L337 perhaps for clarity, change “relationship between population size and
group size” to “relationship between population size and mean or maximum
group size”
DONE
Alexandra Pavlova, PhD
School of Biological Sciences, Monash University