As the fall progresses and the days grow colder here in New England, Cape Cod beach walkers are greeted with what is now a familiar sight: dead Common Eiders (mostly males) littering the Bay side shores. These events are also common in Spring, and details on the last one in May were presented in an earlier blogpost. This time, the area involved is almost identical to that in the May event. Seanetters Bud Johnson, Steve Gulrich, Diana Gaumond and Mary Myers all reported dead eiders on their walks last week, and kudos to them all for marking the carcasses with our orange SEANET cable ties–for the first time we have a good shot at a definitive number of birds found by Seanetters, and we will at last be able to determine if new carcasses are showing up while others wash back out to sea, or if the same birds persist on the beach for some time. So far, the 50-100 birds reported have been variously scavenged and decomposed. If any fresh carcasses turn up, SEANET is in a position to receive them and submit them for testing.
We have also received reports from observers of live eiders who say rafts of up to 2,000 or so of the birds have been hanging out in the Bay near where the dead birds washed up. With such a concentration of live, migrating birds, it is unclear whether the current mortality is a true “die-off” or merely the normal background mortality in a large, highly concentrated population. We hope to get to the bottom of this mysterious, recurring phenomenon eventually, and we thank Seanetters and affiliated friends for all the reports and information you have sent our way. We welcome all reports on Common Eiders out on the Cape, live or dead, so keep your eyes open and your boots on the sand out there!