Duck die-off mostly a mystery

It's become the semi-annual duck die-off, with scads of common eiders (Somateria mollissima) washing ashore on Cape Cod Bay, especially in Wellfleet, and on Nantucket and Martha's Vineyard twice a year.

"Last Wednesday I walked out and did the whole Great Island walk (in Wellfleet), I started at 10:30 a.m. and got off around 3:30 p.m.," reported Cape Cod National Seashore volunteer Jackie Howard. "I'd say there were between 500 and 800 ducks. A few were gasping out their last breaths and vultures were flying around and picking at them. They were scattered over the beach. After the first cutover they really, really piled up. They smelled terrible and that nauseated me. I didn't think I'd be able to finish the walk."

Parasites seem to be involved, at least in the spring, but many questions remain unanswered. For instance, the numbers of dead birds have been much higher the past couple of years.