Table 1.

Results for all models: fixed effects

Model no.	Fixed effects	Results	N species	N study	N observations
1	Siblings present y/n	F1,71.8 = 6.69, P = 0.0097	60	108	336
2	Brood size	F1,31.0 = 4.57, P = 0.033
3	Siblings present y/n	F1,67.0 = 8.45, P = 0.0050	51	98	317
	No. of future broods possible	F1,87.9 = 3.13, P = 0.080
4	Brood size	F1,82.2 = 11.87, P = 0.0009
	No. of future broods possible	F1,83.5 = 7.22, P = 0.0087
5	Siblings present y/n	F1,84.2 = 0.42, P = 0.42	49	96	314
	No. of future broods possible	F1,95.4 = 9.39, P = 0.0028
	Full vs. half siblings likelihood	F1,112.5 = 6.94, P = 0.0096
6	Brood size	F1,87.1 = 3.07, P = 0.083
	No. of future broods possible	F1,86.4 = 13.09, P = 0.0005
	Full vs. half siblings likelihood	F1,89.6 = 5.98, P = 0.016
7	Siblings present y/n	F1,60.5 = 0, P = 1	31	68	230
	No. of future broods possible	F1,58.4 = 3.10, P = 0.083
	Full vs. half siblings likelihood	F1,76.0 = 3.77, P = 0.056
	Extrapair paternity	F1,58.5 = 0.04, P = 0.84
8	Brood size	F1,66.2 = 3.87, P = 0.053
	No. of future broods possible	F1,58.3 = 4.94, P = 0.038
	Full vs. half siblings likelihood	F1,67.1 = 1.00, P = 0.32
	Extrapair paternity	F1,58.5 = 0.27, P = 0.61

Mean results (conditional Wald statistics) of 500 ASReml linear mixed models. Models controlled for phylogeny, repeated measures on studies, and species, and were weighted by study sample size (the number of broods used to calculate the original test statistic). Fixed effects in bold are significant at the P < 0.05 level and in italics at the P < 0.10 level. Models are grouped by the dataset used for analysis, as sample size decreased in later analyses due to unavailable life history data.