From the middle of October to late November, the black-footed tern can be found on its inland breeding habitat. Here, they nest in colonies of up to 50 pairs, and typically lay two eggs in a simple scrape in the shingle. Like other New Zealand terns, both parents take turns to incubate the eggs, for a period of 21 to 23 days (2) (6), during which time they can exhibit very aggressive behaviour. They will dive at any intruders, screeching harshly, and often striking the intruder’s head with their feet. Whilst this is effective on sheep and hawks, unfortunately their fearless attacks do little to deter predators such as cats and dogs (5) (6). The chicks fledge at around 30 days old (3).
Whilst breeding, they will search for food in flocks, over rivers, lakes and farmland. Their tendency to follow farmers’ ploughs, catching insects and worms from the freshly dug earth, has earned them the names ploughboys or the ploughman’s friend (3). They fly over rivers and lakes, dipping down to feed on mayflies and stoneflies from the surface, and sometimes even diving into the water to take small fish. Once summer and breeding is over, they move to the coast, and again feed on worms from coastal farmland, but also on crustaceans from the ocean (6).