<P> If a male is interested, he will stretch his neck and erect his feathers, then bend over and peck at the ground . He will circle around and sidle up to the female, swaying his body and neck from side to side, and rubbing his breast against his partner's rump . Often the female will reject his advances with aggression, but if amenable, she signals acceptance by squatting down and raising her rump . </P> <P> Females are more aggressive than males during the courtship period, often fighting for access to mates, with fights among females accounting for more than half the aggressive interactions during this period . If females court a male that already has a partner, the incumbent female will try to repel the competitor, usually by chasing and kicking . These interactions can be prolonged, lasting up to five hours, especially when the male being fought over is single and neither female has the advantage of incumbency . In these cases, the females typically intensify their calls and displays . </P> <P> The sperm from a mating is stored by the female and can suffice to fertilise about six eggs . The pair mate every day or two, and every second or third day the female lays one of a clutch of five to fifteen very large, thick - shelled, green eggs . The shell is around 1 mm (0.04 in) thick, but rather thinner in northern regions according to indigenous Australians . The eggs are on average 13 cm × 9 cm (5.1 in × 3.5 in) and weigh between 450 and 650 g (1.0 and 1.4 lb). The maternal investment in the egg is considerable, and the proportion of yolk to albumen, at about 50%, is greater than would be predicted for a precocial egg of this size . This probably relates to the long incubation period which means the developing chick must consume greater resources before hatching . The first verified occurrence of genetically identical avian twins was demonstrated in the emu . The egg surface is granulated and pale green . During the incubation period, the egg turns dark green, although if the egg never hatches, it will turn white from the bleaching effect of the sun . </P> <P> The male becomes broody after his mate starts laying, and may begin to incubate the eggs before the clutch is complete . From this time on, he does not eat, drink, or defecate, and stands only to turn the eggs, which he does about ten times a day . He develops a brood patch, a bare area of wrinkled skin which is in intimate contact with the eggs . Over the course of the eight - week incubation period, he will lose a third of his weight and will survive on stored body fat and on any morning dew that he can reach from the nest . As with many other Australian birds, such as the superb fairywren, infidelity is the norm for emus, despite the initial pair bond: once the male starts brooding, the female usually wanders off, and may mate with other males and lay in multiple nests; thus, as many as half the chicks in a brood may not be fathered by the incubating male, or even by either parent, as emus also exhibit brood parasitism . </P>

Which large australian bird lays big green eggs