Silver gulls Larus novaehollandiae in south-western Australia lay eggs over an eight-month period with peaks in April, July and September. Clutch-sizes, egg-sizes and laying-intervals did not differ between these three peaks, hut second eggs were smaller than first-laid eggs on each occasion.
Rapid yolk deposition took 7–14 days. Daily increments of yolk growth were neither constant nor maternally influenced. The yolks of first-laid eggs were laid down faster than the yolks of subsequent eggs. Egg size, weight and composition, as well as the period of rapid yolk deposition, may be proximately linked to the age, breeding experience, and body condition of laying females.