Did anyone notice a large gathering of Common Eiders on Woodlanding Cove (end of Great Pond Rd) on April 6 and 7? Valerie did – so off we went to investigate what was causing the commotion.
The Common Eiders, a Common Loon, a few Herring and Black-backed Gulls were searching for something on the shallow bottom of the cove.
The eiders and the loon were ‘spotting’ – swimming along with their heads submerged. Once their prey was spotted, they dove. But they surfaced with nothing to show for their efforts. Their bills did not hold a crab or mussel that is a typical bounty for an eider, and the loon did not appear to be catching fish.
Eider pair 'spotting'
Female eider 'spotting'
Female eider plunging
Male eider 'spotting
Male eider swimming underwater
Puzzled, we watched a Herring Gull at the shoreline, poking around the rocks, swallowing something, at first indistinguishable to us. Finally, the gull pulled a large dark worm from the rocky shore. A yummy bonanza of slimy worms. Evidently the eiders and the one loon were ‘slurping down’ their worms while under water. Gulls routinely steal invertebrate prey from sea ducks, especially eiders. The eiders took advantage of easily swallowing the worms before any gull could take their prize.
Herring Gull and unidentified worm
So what kind of worms are they and why are they in such abundance. We consulted with Sam, a marine biologist, who wrote the previous blog on sand worms (Crazy About Worms: May 13, 2021, a type of worm with segmented bodies (polychaetes). Generally when polychaete worms spawn they leave their protected burrows on the ocean floor, to release their gametes. The adult worms will die naturally, unless consumed by predators - birds, fish, or other invertebrates such as crabs. A sad ending for the worms but a bounty for any predator clever enough to find them. How did the eiders know they were spawning in that particular cove? Sam noted similar Common Eider behavior at Spar Cove.
Speaking of worm-loving birds. What about the American Robin that we so identify with the earthworm? Michael is curious why so few robins are seen on Peaks Island as compared to the mainland. Not enough topsoil on this rocky-ledgy island?
Photo © PILP photo library
Photos © and written by: Patty Wainright
Reviewed by: Sam Wainright, Valerie Kelly, Marty, Michael LaCombe, Michelle Brown