Methods:
We surveyed published academic and grey literature via keyword searches (e.g. “Somateria mollissima” “clutch size”) through Google Scholar, ‘citation snowballing’ (pursuing reference trails; see e.g. Greenhalgh & Peacock, 2005), and cross-referencing authors’ personal databases. Additionally, a call for data was posted on the IUCN Species Survival Commission’s Duck Specialist Group website (www.ducksg.org/2018/10/seaducks/the-not-so-common-eider-can-you-help/), circulated through the corresponding mailing list, and advertised by ANH on Twitter in January 2019 and at conferences (the British Ecological Society’s ‘Quantitative Ecology’ meeting in July 2019; the European Ornithologists’ Union Conference in August 2019; and the Ecological Society of America’s annual meeting in August 2020) thereafter. 
The call for data elicited three previously inaccessible datasets, of which one was recorded in Icelandic and another in Russian, broadening language coverage since non-English language reports were otherwise only covered by citations in English-language publications. 

Accessible vital rate estimates, and associated metadata, were collated in a relational database in Microsoft Excel, linked by a unique ID number associated with each study (or unique unpublished combinations thereof). A list of data sources used in the study are provided in the Data sources section of the associated publication. We focussed on the vital rates required to parameterise matrix population models (MPMs), which are used widely by population ecologists and conservation biologists to project population dynamics over time. We therefore included the following vital rates: 1st year survival (measured either from hatching, or from fledging, to 1 year old), 2nd year survival, adult survival, breeding propensities for 2- to 5-year-olds (both probability of having recruited at a given age, and breeding propensity at a given age), adult female breeding propensity, clutch size, hatching success and fledging success (alternatively included in 1st year survival where measured from hatching). 
We define: (i) hatching success as the proportion of all laid eggs that hatch (if probability of successful nesting – i.e. of at least one egg hatching – was provided, we used it to calculate hatching success where feasible), and (ii) fledging success as the proportion of hatchlings that fledge.

Where provided by the authors, we recorded the following metadata at the study level: location (country and geographic coordinates); subspecies; and population trend (classified as increasing, decreasing, stable, or variable). Further, for each estimate we recorded: sample size; variance measures (as provided and/or calculable from reported information); start and end years; and any covariates (freeform).

We did not formally screen studies, preferring instead to provide as complete a reference database as possible. We facilitate filtering with the following assignations: verification status (whether the source was seen in the original or cited by another verified source); precision (some estimates were simply the midpoints of observed ranges); and independence (which is not met when multiple estimates are provided by the same study, or when separate studies are based on the same datasets).



Greenhalgh, T., & Peacock, R. (2005). Effectiveness and efficiency of search methods in systematic reviews of complex evidence: Audit of primary sources. British Medical Journal, 331(7524), 1064–1065. https://doi.org/10.1136/bmj.38636.593461.68


Usage notes:
The database is available in full as an xlsx spreadsheet (including header comments providing further information), or as a series of csv files for each sheet (comments not included, although they are provided in the dataset README .txt file). 

The ‘master’ sheet provides study-level information, with each study being assigned a unique identifier: numeric 1-127 for published studies, upper case A-B for unpublished contributed datasets (ID 127/Ragnarsdóttir et al., 2021 was contributed through the call for data but is published online, as an Icelandic-language publication not accessible through English-language searches), and lower case aa-ee for combinations of datasets reported in published studies (such as the combination: “Nyegaard, 2004 [thesis]; H.G. Gilchrist unpubl. data” reported in Gilliland et al., 2009, Table 1). Estimates and associated metadata for each vital rate are then recorded in separate sheets, with the ID column relating back to the studies in the ‘master’ sheet. Vital rate sheets include columns to replace imprecise overall study-level population growth rate, geographical coordinates, and subspecies entries where appropriate; for example, if the study provided vital rate data for each of several locations. 
Further information specific to each column can be found in comment boxes associated with the headers (.xlsx file only, but copied below), and both studies and estimates are further annotated in ‘Comments’ columns where relevant. A text file with an English translation by AP of the summary from ID 127/Ragnarsdóttir et al., 2021 is also provided (see Nicol-Harper_202110_VitalRates_RagnarsdottirTranslation.txt).

The two forms of breeding propensities for 2- to 5-year-olds correspond to two of the recruitment quantities discussed in Pradel & Lebreton (1999): the probability of having recruited at a given age, which sums to 1 across all possible ages of recruitment, is equivalent to their αi (specifically, the second version described on p. S80); breeding propensities at age i (2 ≤ i ≤ 5) correspond to their ai. Vital rates referring to subadults are assumed to refer to both sexes, whereas adult survival may refer to either sex or both (specified in the database), while adult breeding propensity has thus far only been estimated for females.



Pradel, R., & Lebreton, J.-D. (1999). Comparison of different approaches to the study of local recruitment of breeders. Bird Study, 46(sup1), S74–S81. https://doi.org/10.1080/00063659909477234

Ragnarsdóttir, S. B., Thorstensen, S., & Metúsalemsson, S. (2021). Fuglalíf í óshólmum Eyjafjarðarár: könnun 2020 með samanburði við fyrri ár. [The birdlife of the delta area of river Eyjafjaðará, N-Iceland: The results of a survey in year 2020 in comparison to former years.] Náttúrufræðistofnun Íslands NÍ21001. 62 pp. (In Icelandic). Available at: https://utgafa.ni.is/skyrslur/2021/NI-21001.pdf accessed 5th October 2021.

Gilliland, S. G., Grant Gilchrist, H., Rockwell, R. F., Robertson, G. J., Savard, J.-P. L., Merkel, F., & Mosbech, A. (2009). Evaluating the Sustainability of Harvest Among Northern Common Eiders Somateria mollissima borealis in Greenland and Canada. Wildlife Biology, 15(1), 24–36. https://doi.org/10.2981/07-005



Header comments:

<MASTER sheet:>

ID: unique identifier for data source:
> regular studies, numbered from 1
> contributed data, capital letters from A
> combos of cited studies, double lower-case letters from aa

Authors: authors of:
> regular studies, as stated
> contributed data - contact Alex Nicol-Harper (a.nicol-harper@soton.ac.uk)
> combos of cited studies, see Verified.source column

Pub.year: year study published

Further.ID: additional information to help with study identification (e.g. when there are papers by the same author/s published in the same year)

Country: country in which study takes place; Svalbard has separate ISO2 (see next column) to rest of Norway, so listed separately here

ISO2: ISO alpha-2 country code from www.wikipedia.org/wiki/ISO_3166-1_alpha-2 A/O January 2020 - N/A's where: no country given, or multiple countries given; Svalbard and Greenland listed separately to Norway and Denmark, respectively, as makes ecological sense; USSR (SU) listed separately to Russia (RU); UK nations all under GB

Lat.prov: latitude as provided in paper; all latitudes refer to North

Long.prov: longitude as provided in paper; E = east, W = West

Lat.dec: latitude as decimal (either as provided, or calculated from min/sec provided or implied - via Google Maps search and 'what's here' on red pin or similar, and https://www.fcc.gov/media/radio/dms-decimal)

Long.dec: longitude as decimal (either as provided, or calculated from min/sec provided or implied - via Google Maps search and 'what's here' on red pin or similar, and https://www.fcc.gov/media/radio/dms-decimal)

Subspecies.prov: subspecies as provided, or evident from location (where unequivocal)

Lambda.trend: where provided, estimate of population growth rate (λ):
> = increasing (>1)
< = decreasing (<1)
*=* = approx. stable (~1)
Variable = 2+ of above states across study period

Verified.YN: was the source seen in the original (i.e. verified, Y), or only as a citation in a verified source (ID given in next column, N)


<all sub-sheets:>

Var.prov: variance as provided in the study

Var.calc: variance calculated from other information in the study

[as above, for SD = standard deviation, and SE = standard error]

n: sample size: number of individuals monitored (e.g. number of individuals tagged as part of capture-mark-recapture programme)

rm_MfR: 'remove means based on range' e.g. where clutch size is given as "4-5" and reported in the Estimate column as 4.5

rm_ind: 'remove to retain independence' - for more conservative analyses, remove estimates which are unlikely to be independent*:
> Y = yes, remove 
> N = no, keep
> M = meta-analyse (e.g. find weighted mean across 5 estimates in same study for 5 different years) 
*may not be independent due to: multiple estimates from same data, using different methods (select one, e.g. lowest variance); estimates contributing to estimates given by a subsequent study e.g. meta-analysis (keep meta-analysis, remove contributing estimates)

ow_Lambda.trend: 'overwrite provided lambda trend' where multiple subpopulations and/or timepoints are included in one publication (with different estimates)

ow_Subspecies.prov: 'overwrite provided subspecies' - where multiple estimates within the same study (identical ID) refer to different subspecies

ow_Lat.dec: 'overwrite latitude (decimal)' - where multiple estimates within the same study (identical ID) refer to different locations

ow_Long.dec: 'overwrite longitude (decimal)' - where multiple estimates within the same study (identical ID) refer to different locations


<additionally, for SUBsa only>

Sex: of individuals contributing to the estimate:
> F = female
> M = male
> B = both (combined)




