DOI: 10.5061/dryad.k0p2ngfk3
title: Data from: Cooperative breeding in birds increases the within-year fecundity mean without increasing the variance: A potential mechanism to buffer environmental uncertainty

description: Cooperative breeding is a common strategy of vertebrates under harsh,
 unpredictable environments. Yet we do not fully understand the demographic
 mechanisms by which these species buffer environmental challenges, because
 while cooperation typically increases the fitness mean, whether it alters
 the variance to further reduce the population risk of stochastic
 extinction is unclear. We addressed this issue using a meta-analysis among
 avian cooperative breeders. Compared with their non-cooperative
 counterparts in the same populations, cooperative pairs on average fledged
 more offspring, without increasing the fecundity variance accordingly.
 This pattern held when failed nests were excluded from analysis to filter
 the effect of nest predation on the estimation of brood size at fledging,
 retaining the effect of brood reduction (the partial loss of nestlings in
 a brood). Cooperative pairs did not differ in the mean and variance of
 clutch size from non-cooperative pairs; the former had a lower level of
 brood reduction than the latter. These results suggest that mitigating
 brood reduction by cooperation is a pathway that may explain the observed
 pattern in the fecundity mean and variance. Our work highlights the
 importance of formulating the mean-variance relationship for fecundity to
 understand the evolutionary success of cooperative breeding.
description: # Data from: Cooperative breeding in birds increases the within-year
 fecundity mean without increasing the variance: A potential mechanism to
 buffer environmental uncertainty [Access this dataset on
 Dryad](https://doi.org/10.5061/dryad.k0p2ngfk3) This dataset supports a
 meta-analysis on the effects of cooperative breeding on fecundity mean and
 variance in birds. It includes pooled and year-specific reproductive data,
 a phylogenetic tree file, and analysis scripts. ## Description of the data
 and file structure We conducted a literature search on ISI Web of Science
 up to October 1, 2023, for studies on cooperative breeding in birds.
 Search terms included the names of 821 cooperatively breeding altricial
 species and related keywords. Citation Searching was also employed.
 Studies were included if they provided means and SD or SE for clutch size
 and brood size at fledging for both cooperative and non-cooperative nests,
 with at least four nests per phenotype. For detailed methods, see the main
 text. The dataset derived from **Table S1**, combined with the
 accompanying R code, allows for the reproduction of the meta-analysis
 results in this study. Additionally, **Table S2** shows that the pooled
 variance of brood size over years can serve as a reliable proxy for
 demographic stochasticity. In addition, we provided the phylogenetic tree
 file (**44species1000times.nex**) and the R scripts (**File S1 The R
 scripts used in this study.txt**) used in the analysis. ### Files and
 variables #### Files: * **Table S1** – Raw data pooled over years,
 including fecundity mean, variance, coefficient of variation (CV), and
 brood reduction level for cooperative and non-cooperative nests. * **Table
 S2** – Year-specific raw data from 8 populations, including brood size
 mean, variance, and coefficient of variation (CV). * **Phylogenetic tree
 file** – *44species1000times.nex*, used for comparative analysis. * **R
 scripts** – *File S1 The R scripts used in this study.txt*, containing all
 analysis code. #### Variables * **Table S1** **Order** – Taxonomic order
 of the species **Family** – Taxonomic family of the species **Scientific
 name of species** – Currently accepted binomial name of each species,
 consistent with the species names used in the phylogenetic tree. **Common
 name of species** – English name of the species, provided to assist with
 broader and more accurate literature searches. **Population ID** – A
 unique identifier for each study population, used to distinguish between
 different populations in the dataset. **Study ID** – A unique identifier
 for each source publication included in the meta-analysis.
 **longitude(E)** – Longitude in decimal degrees (WGS84); positive values
 indicate east. **latitude(N)** – Latitude in decimal degrees (WGS84);
 positive values indicate north. **Mean brood size within cooperative
 nests** – Average number of offspring per nest in cooperative breeding
 groups(unit: offspring/nest). **SD of brood size within cooperative
 nests** – Standard deviation of brood size in cooperative nests. **Sample
 size of cooperative nests** – Number of cooperative nests included in the
 calculation. **Mean brood size within non-cooperative nests** – Average
 number of offspring per nest in non-cooperative (pair-only) breeding
 groups(unit: offspring/nest). **SD of brood size within non-cooperative
 nests** – Standard deviation of brood size in non-cooperative nests.
 **Sample size of non-cooperative nests** – Number of non-cooperative nests
 included in the calculation. **Mean clutch size within cooperative nests**
 – Average number of eggs per nest in cooperative breeding groups(unit:
 eggs/nest). **SD of clutch size within cooperative nests** – Standard
 deviation of clutch size in cooperative nests. **Sample size for
 cooperative clutch** – Number of cooperative nests included in the clutch
 size calculation. **Mean clutch size within non-cooperative nests** –
 Average number of eggs per nest in non-cooperative (pair-only) breeding
 groups(unit: eggs/nest). **SD of clutch size within non-cooperative
 nests** – Standard deviation of clutch size in non-cooperative nests.
 **Sample size for non-cooperative clutch** – Number of non-cooperative
 nests included in the clutch size calculation. **Brood reduction level
 within cooperative nests** – Proportion of offspring loss within
 cooperative nests, with values representing the percentage of brood
 reduction (unit: %; e.g.,  10 means 10%). **Brood reduction level within
 non-cooperative nests** – Proportion of offspring loss within
 non-cooperative nests, with values representing the percentage of brood
 reduction (unit: %; e.g., 10 means 10%). **Complete nest failure** – 1
 indicates that the brood size data includes nests that failed completely,
 while 0 indicates that the data excludes such nests. **Dataset1 (n = 58)**
 – "1" indicates that the data for brood size with failed nests
 included is used from this dataset, consisting of 58 populations from 44
 species. **Dataset2 (n = 27)** – "1" indicates that the data for
 brood size with failed nests excluded is used from this dataset,
 consisting of 27 populations from 23 species. **Dataset3 (n = 17)** –
 "1" indicates that the data for clutch size is used from this
 dataset, consisting of 17 populations from 16 species. **References** –
 Lists the authors and publication years of the referenced studies.
 **Sources** – Indicates the publication where the related data can be
 found. **Reference from** – Indicates the source from which the reference
 was obtained. **Data years** – Indicates the number of years of data used
 to construct the brood size data(unit: years). * **Table S2**          
 **Species** – Scientific name of the species, consistent with Table S1.  
         **Latitude** – Latitude in decimal degrees (WGS84); positive
 values indicate north.           **Longitude** – Longitude in decimal
 degrees (WGS84); positive values indicate east.           **Research
 years** – The specific years during which the data were collected.        
   **BSCooMean** – Mean brood size within cooperative nests in a single
 year(unit: offspring/nest).           **BSCooSD** – Standard deviation of
 brood size within cooperative nests in a single year.          
 **CooCombinedSD** – Standard deviation of cooperative breeding brood size
 pooled across years.           **BSCoon** – Sample size of cooperative
 nests.           **BSNonCooMean** – Mean brood size within non-cooperative
 nests in a single year(unit: offspring/nest).           **BSNonCooSD** –
 Standard deviation of non-cooperative breeding brood size within a single
 year.           **NonCooCombinedSD** – Standard deviation of
 non-cooperative breeding brood size pooled across years.          
 **BSNonCoon** – Sample size of non-cooperative nests.          
 **Data_Validity** – Indicates whether the study was used to evaluate the
 difference between pooled and annual values (1 = included; only studies
 with sample size &gt; 5 were included).           **References** –
 Reference information, consistent with citations listed in Table S1. ##
 Sharing/Access information **Links to other publicly accessible locations
 of the data:** *
 [https://doi.org/10.1093/beheco/araf031](https://doi.org/10.1093/beheco/araf031) ## Code/software **Scripts and Code:** File S1. The R scripts used in this study. This script provides the code for the meta-analysis used in this study, as well as the code for phylogenetic paired t-tests and the calculation of interannual precipitation variability. **Software and Versions:** R: Version 4.1.2 R Packages: meta (version 7.0.0) dmetar (version 0.1.0) metafor (version 4.4.0) ape (version 5.7.1) MCMCglmm (version 2.35) phytools (version 2.0.3) ggpubr (version 0.6.0) ggplot2 (version 3.5.0) progress (version 1.2.3) ncdf4 (version 1.22) abind (version 1.4.5) raster (version 3.6.26)