The Black-billed Gull is found only in New Zealand. It is essentially an inland gull, a specialised feeder, and the least likely to scavenge. During the summer thousands of pairs breed in Southland on shingle islands and at the shores of lakes and rivers. They breed in large colonies in Otago and Canterbury. A few nest in the North Island. In winter many migrate to the coast, especially to the southern shores of the North Island. They feed in open country, on lakes and rivers and at city parks and playing fields. They eat insects, small freshwater fish, invertebrates, earthworms, and flies. They catch surface aquatic animals while swimming, hovering and dipping, and seldom immerse more than their heads and necks. When feeding in flocks over small fish they attract other gulls. Such concer... read moreted attacks confuse the fish, making capture easier. They breed first at two years old. Courtship displays begin in August while still at the coast. Food-begging bouts between pairs lead to regurgitation feeding and mating. They often use the same nest site as the previous year. By early October they start building their nests. Silent 'dreads' or 'panics' - when all the birds suddenly take wing, circle and noisily drop back to the ground - are common at this time of the year, and just before the gullery is deserted. The nest is a deep depression of rootlets and small sticks neatly lined with grass. Usually two pale grey, pale olive green to pale blue eggs are laid blotched with dark and light brown. Both parents incubate for 20 to 24 days, and the eggs are never left unattended. Within 24 hours of hatching the family abandons the nest, and the parents brood, feed and defend the chicks. They feed the chicks by regurgitating food onto the ground, and older chicks sometimes take food from their parents' bills. Groups of young birds congregate in creches defended by a few adults, allowing the parents to forage for the young. Birds returning with food wander through the group until they find their own chicks. If alarmed the whole group of chicks take to the water forming a tightly packed raft, the attendant adults swimming with them or hovering above. When the alarm is over the adults shepherd the young ashore. The chicks fly at 26 days, and immediately they all disperse in mixed flocks, often to the coast. Their voice is higher pitched and more pentrating than that of a red-billed gull. Another name for them is Buller's gull.
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