Tern make up the clutch. Most species feed on fish caught by diving from flight, but the marsh terns are insect-eaters, and some large terns will supplement their diet with small land vertebrates. Many terns are long-distance migrants, and the Arctic tern may see more daylight in a year than any other animal. Terns are long-lived birds and are relatively free from natural predators and parasites; most species are declining in numbers due directly or indirectly to human activities, including habitat loss, pollution, disturbance, and predation by introduced mammals. The Chinese crested tern is in a critical situation and three other
Tern declining populations of less than 10,000 birds. The South Asian black-bellied tern is threatened by habitat loss, egg collecting for food, pollution and predation. In New Zealand, the black-fronted tern is facing a rapid fall in numbers due to predation by introduced mammals and Australian magpies. Disturbance by cattle and sheep and by human activities is also a factor. The Peruvian tern was initially damaged by the collapse of anchoveta stocks in 1972, but breeding colonies have subsequently been lost due to building, disturbance and pollution in their coastal wetlands. The Australasian fairy tern is described as "vulnerable". Disturbance by