Hundreds of them, as stated by several observers on the island in May and early June. What are these brown puffballs diving into and tumbling under breaking surf? Baby Common Eiders, a sea duck. And, where have they all gone? They have been transformed into teenagers or sub-adults, thanks to their rich diet on fly-larvae hiding in beached seaweed, and tiny marine invertebrates. Not only has their appearance changed, but many have been lost to predators.
Adult male and female Common Eiders display strikingly different plumages. The male eider sports bold black and white plumage patterns. And there is more - during courting the male’s breast is a light pink, with a splash of light green on the side of his head.
By comparison, the females look like uniform drab-brown footballs.
But at close views the females show exquisite brown hues with intricate patterns.
Those patterns are her camouflage while on the nest. Somewhere along the shore, perhaps under bushes, she builds a nest from her down feathers. She incubates her eggs for approximately three weeks, mostly without food or water. Even her camouflage cannot protect her from the furry ground predators on this island. The female eiders are at a lesser risk on the smaller uninhabited islands nearby, such as Outer Green Island (Audubon stewards monitor breeding Common and Roseate Terns, Black Guillemots, and Common Eiders), Inner Green Island, and Ram Island. The male eider leaves the female during or after incubation. He does not aid in incubation duties; perhaps instead he provides moral support. When the males finally abandon the females, they gather in groups (bachelor pods). They seek safe locations from predators where they undergo a complete feather molt, making them flightless, and vulnerable.
As baby eiders hatch they gather in crèches with the female eiders. As a ‘team’ the Mother and ‘Aunts’ (those females without young) attempt to protect the tiny eiders from predators, and there are plenty of them.
The young respond to the adult calls – a type of grunting call. This call signals danger and all birds tighten their formation into a tight ball. You may hear a series of peeping from the young and grunting from the females. As danger fades, they return to feeding or paddling to and from feeding stations.
What are amazing about these young eiders are their ability to withstand the punishing waves, and their ability to dive (for food) with such puffy and buoyant downy feathers. Even in low surf days at Wharf Cove, they tumble, roll to shore, and dive through the waves without harm.
The greatest threat to them is a predator waiting on shore to grab one…temporarily stranded on shore, unprotected. The independent ones that venture too far from their crèche, alone and fearless, also face increased dangers
Adult Common Eider beaks are bizarre. A ‘nail’ at the end of the bill assists their foraging attempts. The ‘nail’ helps to dislodge mussels from rocks and for grabbing crabs and sea urchins. It works like a chisel. They either forage under water or on algae covered rocks. An unusual curvature, on both sides of the beak, angles upward toward the eye – another advantage for foraging? Strengthening for chiseling off mussels?
As the young eider matures its beak changes from a mostly triangular shape with a tiny knob at the end to that of its parents – a bizarre avian design.
As the baby eiders develop into teenagers their size increases quickly, and their puffy feathers become more adult-like making them hard to distinguish from the adults.
Later the young males’ plumages become a dullish black with white highlights, unlike the striking black and white plumage of the mature male. Female young are difficult to differentiate from the adult females.
Apart from those lost to predators; this year was a good year for the young eiders. We give tribute to those lost.
Written and photographs by: Patty Wainright
Reviewed by: Sam Wainright, Michael LaCombe, Marty, Michelle Brown