Mortality on the Beach

The tip of the Leelanau peninsula is a low-lying, rocky spit of land that pushes into the northern reaches of Lake Michigan north of Sleeping Bear Dunes. My good friend Karin lives about a half hour from the point, and I decided I was going to take a few hours and drive up to see it.

Leelanau State Park encompasses most of the tip, and consists of two areas--a campground and lighthouse on the point and a trail network a bit to the west, separated by private land. I drove up to the campground as my main objective was not to hike but to see the "beach" and look for waterfowl.

The water level is low, and there was a wide expanse of rocky shore past the campground. A tall stand of vegetation blocked my view of the water, but I moved through it carefully in case any birds were on the other side. Sure enough, as I emerged, I saw a raft of waterfowl moving quickly away through the water--I'd been spotted. Rats.

I was walking carefully across the bumpy beach when I saw, directly in my path, a dead long-tailed duck. My heart sank. I'd seen my first long-tailed duck last year in East Tawas, and it was such an exciting moment. Now to see one dead on the beach, headless, was very sad. I examined his beautiful tail feathers and webbed feet.

Dead long-tailed duck on the beach at Leelanau State Park. (Taken with my iPhone 4s, which takes amazingly good photos.)

When I looked around the beach I saw another carcass to my left, so I went to have a look. Again I felt that wave of sadness when I found an immature common loon, belly up on the rocks. Some critter had claimed it, defecating on its right wing.

Dead immature common loon.

I examined this bird closely too. It's not often one gets to be this close to these birds. I just wish it were under different circumstances.

I wandered around a bit more, and on my way back across the beach I found another dead loon, this one an eclipse phase adult.

I have heard about the mortality of waterfowl due to botulism in the Great Lakes, but hadn't seen it up close and personal. This really brought it home for me. Not because the birds were dead--death is a part of life, I accept that without qualm. What bothers me is that the death of these birds is a result of our carelessness and ignorance.

What I've read is this (and it isn't pretty):  Clostridium botulinum bacterium is naturally occurring. It becomes concentrated under certain conditions, and scientists think that invasive species to the Great Lakes are playing a big part. Invasive zebra and quagga muscles (which arrived in the ballast water of foreign ships) filter the water to a much clearer, "cleaner" condition than is normally present in the Great Lakes. This allows sunlight to penetrate the water to a much great depth. This, combined with elevated air temperatures, causes the water to heat up. As the water warms and sunlight reaches farther down, algae grows. Too much algae and the water becomes oxygen depleted. This creates an environment where botulism thrives.

How the toxin enters the food chain is another mystery, but scientists speculate that it is eaten by invertebrates on the bottom of the lakes. The invertebrates then are eaten by fish, primarily the invasive round gobie, a bottom feeder. The toxin affects the fish's nervous system and they swim erratically or float near the surface. The are easy pickings for larger fish and fish-eating birds, like loons. Botulism also affects the loons' nervous system, ultimately making it impossible for them to hold their heads up, and they drown. Once they wash ashore, they may be consumed by other animals, and maggots growing on the decomposing body are eaten by other birds, and the mortality spreads.

So, basically, our introduction of invasive species and the warming of our climate are almost certainly to blame for the tens of thousands of waterfowl and loons that have died in the past decade. It's a clear example of how our carelessness has effects that go far beyond what we can imagine.

You can watch a short video about the die-off this year at Sleeping Bear Dunes here.
 
(Lori later informed me that one of the birds that eats maggots from dead fish and birds is the critically endangered piping plover.)