ONE GOOD TERN... (6/12/03)

Not a year goes by that we don’t learn of another endangered species of bird. While we’ve been able to see ospreys, bald eagles and peregrine falcons recover significantly because of both scientific help and the banning of DDT, other birds, such as terns, have not fared as well. Once numbering in Massachusetts in the hundreds of thousands, today their total population in the Commonwealth has diminished to a mere 25,000 birds as a result of a variety of factors.

Terns are in a family struggling to retain their place on Earth. Although four species of terns (least,.common, roseate and arctic) are evident around Cape waters, I believe they are all consistently overlooked by most people. They do not scavenge for their food as gulls often do, but rather they subsist on live fish which they catch by making a headlong dive into the ocean, usually for sand eels or sand lance. You won’t see a lineup of terns sitting on a cottage roof, and you won’t find a tern hanging around a dumpster, shopping mall parking lot or out at the landfill.

I am very fond of terns and admire their way of life. They make incredibly long migrations between their summer and winter homes, some going as far as 10,000 to 12,000 miles one way — and they do this twice a year! Although terns are closely related to seagulls, sharing a general black-and-grey pattern of plumage with their cousins, they have slim silvery bodies and deeply forked tails. Terns nest in dense colonies, emit earnest cries that form the background for any day at a Massachusetts beach and are the symbol for the Massachusetts Audubon Society.

Perhaps the best way to tell the four major species of terns that nest on our coasts is by the colors of their bills, although in the case of the least tern, size is a decidedly distinguishing feature. Least terns are an inch or two smaller than a robin, and have a yellow bill. Common terns are 14 1/2 inches in length and have a black-tipped, red-orange bill. Arctic terns which reach their southernmost breeding in our area are an inch larger than commons and have a blood-red bill.

The fourth, the rarest and with the sad distinction of being declared Federally endangered, is the roseate tern, with an almost entirely black bill and noticeably graceful flight. Of the 3,000 North American pairs, more than half nest in Massachusetts. Ian Nesbet, writing for Mass. Audubon Society bulletin said, “The roseate tern is more characteristic of Massachusetts than any other bird species. Ever since the colonies on the islands around Cape Cod were first described in the 1870’s, more than half the roseate tern population of North America has nested within the state.”

Four major factors have been primarily responsible for tern population declines in this century: The first was the shooting of terns for their feathers to decorate women’s hats; the second has been the increase in the North Atlantic populations of herring and great black-backed gulls, which were scarce until the 1930s. After that, the increase in both open dumping of garbage and the fishing industry encouraged these birds to proliferate. To illustrate this, from 1960-1980, gulls increased from one nesting pair to 15,300!

Gulls start nesting in April, so by the time the terns return in May, gulls have already chosen the choicest, most secure nesting sites, forcing the terns to nest where predators and human disturbance cause nesting failure. Not only is habitat lost, pesticides affect the birds, their eggs and their young. The third cause in terns’ decline is the increase of coastal development and pollution, highlighted most recently by the oil spill in Buzzards Bay.

A serious increase in predation from skunks, raccoons and other mammals, as well as great horned owls and black-crowned night-herons on terns’ colonies is the fourth reason that their numbers have dropped so much. The numbers of these predators has increased unnaturally because of man’s activities. Therefore, since man has played a major role in causing the decline of our tern populations, we must work to improve their odds for survival.

I hope the next time you are at the shore, especially where there are islands nearby offshore, such as Monomoy off Chatham, Penikese Island in Buzzards Bay and Muskeget Island off Nantucket, you will watch for these interesting avian aristocrats. I think you will come to appreciate them as I do and will want to do what you can to protect them.