Every year, we mark the beginning and end of colder weather by looking for Hooded Mergansers overwintering on our Hilton Head lagoon.
The first few ducks arrived early last November. In a few weeks, most will have left for breeding grounds inland and farther North.
We’ll miss watching them cruise back and forth, sometimes in flotillas of several dozen. Newcomers to a group may fly in at
high speed, making impressive crash landings as they skid across the surface and brake with their feet.
Mergansers start pairing up during their winter here.
Courting males make a spectacle of themselves – bobbing their black, crested heads, flaring the white patches on their “hoods,” stretching, flapping, and emitting frog-like croaks.
The brown, crested females are more serene.
Along with several other Species, Hooded Mergansers are called diving ducks, since they feed by diving below the
water surface. Most dives are brief, but mergansers reportedly can stay underwater for as long as two minutes. Once one
duck pops below the surface, others often follow.
They rely heavily on vision to locate and pursue a variety of freshwater prey -- mostly fish, but also tadpoles, frogs, crayfish,
and insects. Their webbed feet propel them through the water, and their slim, serrated beaks secure wriggling prey.
Their eyesight is enhanced by an extra, transparent eyelid that acts like goggles while they’re swimming and protects their eyes from debris.
Mergansers are clumsy on land, however, because their legs are attached far back on their bodies, a position that makes it easier for them to tip forward into the water.
In spring on their breeding grounds, Hooded Mergansers nest in tree cavities in wetlands, often Appropriating Wood Duck
nest boxes. Sometimes merganser females drop eggs in already occupied merganser nests or even in Wood Duck nests, an
example of what biologists call “brood parasitism.”
Typically the adoptive parent incubates the foreign eggs along with her own.
As in other species of ducks, merganser chicks are self-sufficient soon after hatching. When only a day old, they tumble out of the nest box to the ground, follow their mother to the water, and start swimming and feeding on their own.
Their dives are shallow at first, but within a week or so they’re diving like pros.
Vicky McMillan, a retired biologist formerly at Colgate University,lives on Hilton Head Island. She can be reached at firstname.lastname@example.org.