Table 1.

Effects of helpers on annual reproductive success

Model	Variables	Good acorn crop years	Poor acorn crop years	All years
1	N helper males	0.45 ± 0.12 (<0.001)	0.10 ± 0.08 (0.2)	0.20 ± 0.07 (0.003)
1	N helper females	−0.05 ± 0.14 (0.7)	0.16 ± 0.10 (0.1)	0.09 ± 0.08 (0.3)
2	N helpers	0.24 ± 0.08 (0.002)	0.12 ± 0.05 (0.02)	0.15 ± 0.04 (<0.001)
3	Group size	0.23 ± 0.07 (0.001)	0.15 ± 0.05 (0.002)	0.16 ± 0.04 (<0.001)
	N group years	233	360	593

Listed are effect sizes (regression coefficient ± SE) with P values in parentheses of group composition on number of young fledged determined by linear mixed-effects models controlling for N breeder males, the prior year’s acorn crop, and group history (whether there had been a turnover in breeders since the prior year or not) as fixed factors and group identity as a random factor. Included only are groups with a single breeder female; good and poor acorn crop years determined by visual surveys (see text). Model 1 includes n helper males and n helper females as separate fixed factors; model 2 includes total N helpers as a fixed factor; model 3 combines helpers and breeders into a single variable of group size. Statistically significant values are in bold