The effect of parental condition on egg-size and reproductive success in short-tailed shearwaters Puffinus tenuirostris.

Eggs were exchanged between 50 pairs of shorttailed shearwaters Puffinus tenuirostris on Great Dog Island, Bass Strait, Australia, in an attempt to distinguish the intrinsic effects of egg-size from any effects stemming from differential quality of parental care. At 64 "experimental" nests, large and small eggs were exchanged whereas at 36 "control" nests, eggs of equivalent, medium, size were exchanged. Egg-size appeared independent of maternal effects. In both groups, hatching and fledging success were independent both of eggsize and of the body condition of the attending parents. This suggests that breeding success in these birds may be more closely related to the behavioural traits of parents than to physiological factors.