File name: Brood_Sex_Ratio_Data.csv File contains a list of young, the nest where they hatched, and their sex; ratios calculated as total males / total young in the nest Variable Description Hatchname Name of nest where individual hatched USFWS U.S. Fish and Wildlife Service band number Sex Sex as determined using genetic procedures described Year Year of study Treatment Sex-biased treatment Plot 1 = female plot; 0 = male plot PlotCode W = western plot (A in Fig. 1); E = eastern plot DomF USFWS number for dominant female Hpresent 0 = no helper present; 1 = helper present Yearscal Rescaled year variabale for year of study Plotasr The adult sex ratio documented for the plot Terrdens The density of territories documented for the plot Totyng Total number of young sampled for the nest File name: Large_CB_Groups.csv File contains a list of the territories that had large, cooperative breeding groups (i.e., > 1 helper); used to assess the prevalence of large cooperative groups Year Year of study Treatment M = male bias; C = no bias; F = female bias Plot Plot where territory occurred; E = east (Plot B in Fig. 1); W = western plot (Plot A in Fig. 1); C = outside treatment areas SimpCode Unique number for each territory Twoplus Whether territory contained ? 2 helpers (1) or only a single helper (0) Dens Territory density recorded in plot that year ScalCode Rescale of Simpcode because of convergence issues ScalYear Year code rescaled because of convergence issues MTreat Male-biased treatment (1)' 0 = no treatment File name: ASR_Analyses.csv File containing data used to assess adult sex ratios and the post-breeding sex ratios in relation to treatments and historical values. Historical ASR values were based on observations made prior to the implementation of the experiment (2005-2012) PBASR Post breeding sex ratio (total males/total individuals) TDens Density of territories in the plots that year Treat Treatment applied to the plots that year Year Year of study ASR Adult sex ratio quantified for the plot Plot Physical location of plot (A = west plot; B = east plot; C = areas outside plots HistYear Study year prior to experimental implementation ASR_pre_experiment ASR calculated for the population prior to experimental work File name: CB_Groups.csv Year Year of observation Treatment Sex-biased treatment (A = none; M = male bias; F = female bias) TreatN Numerical value for treatments Plot Physical location of plot (A = west plot; B = east plot; C = areas outside plots Helpers Number of helpers Hpresent Helpers present (1) or absent (0) SimpCode Simple code for each unique nests Dens Territory density recorded that year ScalCode Unique nest numbers rescaled because of convergence issues YearScal Year rescaled to address convergence issues Denscale Density rescaled to address convergence issues. File name: SY_Helpers.csv NestID Unique code for each nest Treatment M = male bias; N = no bias Plot Plot where territory occurred; E = east (Plot B in Fig. 1); W = western plot (Plot A in Fig. 1); C = outside treatment areas USFWS U.S. Fish and Wildlife Service band number Foster Whether male was fostered (Y = fostered; N = not fostered) ASY After second-year males; those that were serving as helpers a second year Stage Stage of experiment: 1 = 2014 and 2 = 2017 File name: Male_Dispersal.csv USFWS U.S. Fish and Wildlife Service band number Bndyr Year individual was a banded nestling Final_Disp Final dispersal; 0 = did not disperse and 1 = dispersed Bias Treatment bias where nest occurred (M = male biased; C = no bias) Constraint Binary factor for above (1 = male bias) Plot Plot where nest occurred (E = plot B in Fig. 1; W = plot A in Fig. 1; C = outside treatment plots) Fostered 0 = young not fostered; 1 = young cross=fostered Manpnest 0 = nest was not part of manipulations; 1 = nest received cross-fostered yng Nestid Unique number for each nest Nestscal Scaled unique number for nests to overcome convergence issues Yearscal Scaled unique number for each year to overcome convergence issues PFSR Post-fledge sex ratio in the plot Hpresent Presence of helper at nest (1) or no helper present (0) Terrasr Adult sex ratio for the territory (total males/ total adults) File name: Female_helper.csv Year Year of study FHelper Female helpers present (1) or not (0) Treatment Sex-biased treatment: F = female, C = none; M = Male Plot Physical plot where territory occurred (W = Plot A in Fig.1, E = Plot B; C = outside experimental plot Dens Territory density for the plot in that year ScalDens Scaled territory density to overcome convergence issues