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
California least tern considered conspecific with the little tern. "Sternula albifrons", which has an extensive Old World distribution. The little tern differs from the least tern mainly in that its rump and tail are white, not grey, and it has a different call. California least tern The California least tern, "Sternula antillarum browni", is a subspecies of least tern that breeds primarily in bays of the Pacific Ocean within a very limited range of Southern California, in San Francisco Bay and in northern regions of Mexico. This migratory bird is a U.S. federally listed endangered subspecies. The total population of the subspecies amounted