Why There Are Spikes All Over This Island Straddling The Minnesota-Wisconsin Border

Whether boating by or catching a glimpse from shore, you might wonder why there are what looks like a bunch of spikes or posts all over Interstate Island in the Duluth Harbor, right on the border between Minnesota and Wisconsin.

I was recently out on a boat ride when I saw what looked like a whole bunch of posts or spikes all over the island. It looked almost like a bunch of young dead trees all over the place, but closer examination showed all of whatever was covering the island to be metal.

I know that they've been doing some rehabilitation to this island, but the porcupine spike-like covering on the island left me confused, so I investigated.

What's going on with Interstate Island?

This seemingly nondescript island in the Duluth Harbor is actually pretty important. Interstate Island, not far from the Blatnik Bridge in the St. Louis River right on the Minnesota-Wisconsin border between Duluth and Superior is home to one of only two remaining common tern colonies on Lake Superior.

While they're called the "common tern", this threatened species is not super common on the Great Lakes, with only two home locations on Lake Superior. With one of them being Interstate Island, that makes it a pretty important spot!

In addition, the island is also home to the endangered Piping Plover, so the island is very valuable territory for two bird species with dwindling populations and diminishing home territory.

These brids' home island in the Twin Ports area has been facing a few threats, with one of them being erosion and changing water levels on the St. Louis River.

One of the efforts to restore the island has been to raise the elevation of the island to be more resilient during times of high water and to restore the size of the island from erosion.

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The effort, which got underway about a decade ago, raised the elevation of the island by about 10 feet and added about 5.5 acres of surface area to the island using sand and gravel, including some dredged materials form the harbor.

What about the spikes on the island? Why are they there?

I mentioned that there had been a few threats to the tern population, with one of them being erosion and water levels. The other threat is that of another bird population.

Anyone who has spent any time in Canal Park or near the harbor knows that there is a pretty robust gull population in the area. This gull population had been wreaking havoc with the nesting colony as well, occupying the island en masse.

To prevent this, an elaborate system of wires and fencing was put up on the island to keep the gulls out while allowing the terns to continue to make the island home.

The spikes seen sticking out of the island are supporting the fencing on the island that's been there to protect the terns.

Terns and Piping Plover are both smaller bird species than gulls, so the fencing and wires allow the smaller birds to go about their lives normally while the larger gulls are kept out.