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The Blatnik Bridge sets a backdrop for the flying gulls and terns nesting on Interstate Island.2 of 9
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Wooden pegs mark nest sites that terns scooped into the ground on Interstate Island between Minnesota and Wisconsin.3 of 9
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The yellow areas indicate tern summer migration in the United States and Canada.4 of 9
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Scott Pearson, with the Wisconsin Department of Natural Resources, bands a tern chick.5 of 9
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Wooden pegs mark nest sites that terns scooped into the ground on Interstate Island between Minnesota and Wisconsin.6 of 9
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Tern in flight.7 of 9
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The Blatnik Bridge sets a backdrop for the flying gulls and terns nesting on Interstate Island.8 of 9
224ternmap
The yellow areas indicate tern summer migration in the United States and Canada.9 of 9
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Tern eggs in a nest.By Fred Strand
Even in the middle of summer, white covers the small island on the south side of the Blatnik Bridge between Duluth, Minnesota, and Superior, Wisconsin.
Unlike winter snow, these flakes not only flutter to the ground, they often hover above it, diving and rising or heading for the river or the lake in a flurry of graceful wing flaps.
Many of the white birds in the air here represent our small successes in keeping common terns on the shores of Lake Superior.
There is not much common about common terns in the lake basin. Common terns nest in only two places on the lake: at the St. Louis River estuary and at Chequamegon Bay near Ashland, Wisconsin.
Fewer than 300 nesting pairs frequent Lake Superior, but two decades of nesting protection and promotion on the western lakeshore have allowed these beautifully agile flyers to hold their own here.
The title “common” stems from terns’ cosmopolitan distribution along North America’s eastern coast where they were and are abundant. Near the Great Lakes, common tern populations, never plentiful, have declined dramatically. At Lake Superior, terns arrive in early May and remain until the end of August.
Many people mistakenly refer to common terns as “sea gulls,” the name frequently used for all gulls and terns. But while terns and gulls are closely related - both in the [Laridae] family - terns are not gulls. Built for speed and maneuverability, terns are smaller, with longer wings. Superb and graceful flyers, they hover, flitter and dive headfirst into the water to capture fish. You will not see terns among the gulls free-loading at fast-food drive ups; they shun all but live-catch foods.
Common tern populations near the Great Lakes have declined since the 1960s. Loss of suitable breeding habitat is a factor. Common terns, associated with large bodies of water, need relatively vegetation-free islands or peninsulas, naturally protected from most predators, to safely scoop their cup-shaped nests into the ground.
Conditions in areas to which “our” common terns migrate - usually the Gulf of Mexico and Central America - also impact local tern populations.
More people along the lake increase the land needs for housing, industry, transportation and recreation and the safe havens that terns need to raise chicks are altered. Predators such as great horned owls, mink, skunks, herring gulls and nest-site competitors like the ring-billed gulls, all thriving in altered habitats, contribute to the loss of terns. Successful growth of natural vegetation and possible chemical contamination also may affect common terns.
In the 1970s, the Minnesota and Wisconsin departments of natural resources (DNR) identified the lack of suitable, legally secure nesting and young-rearing habitat as critical to boosting tern populations.
In the early 1970s, Lake Superior terns were nesting only at the Duluth Seaway Port Authority in the St. Louis River estuary and in the ruins of an old ore dock in Chequamegon Bay.
At the St. Louis River, the preferred nesting land was built for shipping-related industry. Predators, nest-site competitors and human disturbances caused problems for terns there. An even greater concern at the time was future stress. Industrial use would increase at this location and so it was crucial to develop tern nesting habitat elsewhere in the estuary.
Meanwhile, the ore dock ruins in Chequamegon Bay didn’t offer the best outlook for continued successful nesting. The dock ruins were heavily vegetated, making it poor tern habitat, and it was privately owned with the potential to be developed for industrial or recreational use. Still, it was the best habitat around.
Since the 1970s, the two DNRs, working with other partners, have restored or created tern nesting habitat at six western lake locations. But the adage “If you build it, they will come” doesn’t necessarily hold true for wildlife choosing breeding sites.
Of the six sites, common terns successfully nest in two, ironically both human-created sites that replaced the human-altered sites.
Two currently unused sites are maintained in hopes of yet luring terns there and two other sites - at Barker’s Island in Superior and Hearding Island off of Minnesota (Park) Point in Duluth - are no longer managed for terns.
The old dock ruins in Ashland was our first project. Initially vegetation was removed to improve nesting habitat. In the spring of 1986, the docks, now known as Ashland Tern Island, were rebuilt. This was a cooperative venture between many volunteers, the Wisconsin DNR, the city of Ashland, which is now the landowner, and the Wisconsin Coastal Management Program, which funded the restoration. New walls were built and the inside of the crib was filled with concrete rubble and rock, then capped with sand.
This project was finished none too soon. Terns immediately made nest cups in the sand and an egg was laid two days after the work was done.
Ashland Tern Island has hosted tern nests every year since it was rebuilt. Predation of chicks by great-horned owls and of eggs and chicks by mink has been a problem, but removal of one or two individual predators usually solves that for a breeding season. In recent years, about 75 pairs of terns nest at this site annually.
In Chequamegon Bay, we didn’t want all of our tern eggs in one basket (or location). If a catastrophic event occurred there, we wanted terns to nest at a second site. A wooden cribbed, sand-capped island was built on top of a small dock ruins near the Northern States Power bayfront plant in 1987. The island looks like suitable tern habitat to our human eyes, but so far the terns have ignored it.
In the St. Louis River estuary, protection of tern nesting meant luring the terns to a completely new site away from the Duluth Seaway Port Authority.
Interstate Island, created by dredge wastes, is appropriately named with part of the island in Minnesota and part in Wisconsin. In 1989 the Minnesota DNR, using Reinvest in Minnesota funding, cleared the woody vegetation to suit tern nesting needs. Terns colonized the island with 81 pairs nesting that year. They have successfully nested there every year since then.
A threat arose the year after terns began nesting on Interstate Island, however. Ring-billed gulls, which are thriving, discovered the great habitat. Because they return earlier than terns, they have become a major nesting com-petitor. About 10,500 pairs of gulls nest there.
In this competition, the two DNRs cheat on behalf of the endangered birds. While we “allow” gulls to nest on about half of the island, we destroy gull eggs and nests - with an appropriate federal permit - established on the “tern” half. This annual sweep has allowed about 215 tern pairs to nest there.
As in Chequamegon Bay, we wanted to create a second tern-egg basket in the St. Louis River estuary.
In 1984, 1987 and 1988, terns attempted to nest on a low-lying sand spit in Allouez Bay. Each year high waves and water destroyed the nests or young. In 1994, with funding from the Environmental Protection Agency’s Great Lakes National Protection Office, we elevated the height of the Allouez Bay sand spit by building wooden crib walls and filling behind the walls with sand. Even though terns have not returned here since this work was completed, we continue to maintain it as a potential tern nesting site.
Trying to keep common terns somewhat common in western Lake Superior is an on-going struggle. We wait each year to see if unused nesting sites will be occupied. Creation and management of suitable and legally secure habitat remain key.
There are encouraging signs. The annual leg banding of chicks lets us monitor nesting success and determine productivity at both colonies. By trapping banded adults and visual observations of color-marked leg bands we can track the adult terns from both Chequamegon Bay and the St. Louis River estuary.
An important question is: Do chicks fledged from one site become breeding adults at the other site?
Although we’ve learned the answer over the years, I had one of my greatest thrills in 1998 when we captured a particular adult tern on Interstate Island. Its band told us this: 14 years earlier we had banded this bird as a chick in Ashland.
It was an uncommon and welcome testimony to survival of the common tern.
Common Tern Facts
Average length/weight: 13-16 inches/3.5-4.5 ounces.
Appearance: Both sexes, virtually identical, are predominantly white. In breeding season, they sport black caps, orange bills with black tips and pale gray backs and wings. After breeding, the cap diminishes to gray and bill color fades by the end of summer.
Nest type: Simple cup-shaped depressions in the ground, frequently rimmed with small pieces of wood or dried vegetation. Colonial nesters, terns nest and rear young as a group in a relatively small area. Almost all eggs are laid, incubated and hatched and the young raised over a short period of time.
Typical food: In western Lake Superior, emerald (lake) shiners and spottail shiners are the main prey.
Breeding habitat: Areas of sparse vegetation elevated to allow for water drainage and visibility that protect against predators and nesting-site competitors and that provide an adequate food supply relatively near the colony site.
Migration: A common tern is documented as the longest migrator. A bird, banded in Finland, was captured 16,000 miles away in Australia. An arctic tern holds second place; banded in Russia it was caught 14,000 miles away, also in Australia.
Predators: On the ground - red fox, skunk, mink, raccoon, dogs; in the air - great-horned owls, ruddy turnstones, herring gulls. Some of these predators are more numerous and widespread than in the past because of human habitat alterations, especially great-horned owls, skunks and raccoons.
Estimated Lake Superior population: 300 nesting pairs.