Figure 4.

Maternal effects on offspring aggressive behaviour, territory acquisition and in response to resource abundance. (a) The expression of aggression in adulthood is correlated with offspring position in the brood as measured by nestling size ranks. Earlier hatched males (filled circles) are more aggressive than later hatched males, whereas earlier hatched females (open circles) are less aggressive than later hatched females. (b) Offspring hatch order influenced territory settlement such that later hatched males were more likely to acquire a territory next to a relative compared with earlier hatched males. Shown are means and standard errors. In both (c) experimental and (d) naturally varying populations, females produced more males earlier when resources were low and more males later when resources were high. Shown are means and standard errors.