A Duck with Teeth in Raritan Bay

After a few days of mid-winter warmth and one day of 60 degree plus temperatures, the Lower New York Bay environment was back into the freezer. It was frigid at first light on Saturday, Groundhog Day. It was 18 degrees Fahrenheit. By mid-day the temperature had climbed only about twelve degrees to the lower 30s. 

Despite the freezing temperature (it is winter after all), the sky was bright blue and the sun was glowing yellow. A beautiful day to be out, not in. I ventured out along Raritan Bay for a walk at Cliffwood Beach in Aberdeen Township, located on the other side of the bay from Staten Island.  While seal sightings tend to dominate my attention this time of year, the day was marine mammal free.

Instead, I got to see several novel looking Red-breasted Mergansers drifting and periodically diving under the frigid waters. Though common winter birds in local estuarine waters, they tend to be quiet and shy; not always easy to spot. The birds are apt to fly away at the first hint of danger. 

 Yet, this small flock of mergansers seemed oblivious to the cold conditions and to me as well. They were probably too busy foraging for a fishy meal among the waves to be scared off.

Also known as Common Sawbills, Red-breasted Mergansers are excellent fishing birds and are the only duck in North America to feed almost exclusively on fish. Their bodies have evolved over time to be first rate fish-catching birds. They are streamlined-shaped ducks that can swim underwater for nearly a minute and have a distinctive long pointed scarlet-orange bill to catch small fish. 

(Male & female Red-breasted Mergansers swimming in Raritan Bay)

 Red-breasted Mergansers get the name "sawbill" due to a really unique adaptation. Mergansers are special birds. They have teeth. Okay, maybe not a set of pearly whites like you and I. Many modern-day birds have gizzards in their lower stomach to grind food, often with the aid of ingested pebbles, stones, or sand.

Yet merganser are a little different. True, they have gizzards, but they also have serrations or "sawteeth" on the edge of their bill to help grab a slippery and slimy fish underwater. No other duck around here has these tiny sharp-pointed "teeth" along the edge of their upper and lower bills, only the mergansers. This makes them distinctive among the diversity of ducks that call the Lower New York Bay estuary home during the winter. 

(A merganser with a small fish in its sharp-pointed bill)

 Long-ago naturalists realized the tiny teeth-like projections of mergansers. The scientific name for the Red-breasted Merganser is Mergus serrator, meaning a diving sawyer, a reference to their so-called sharp "teeth" that makes their bill appear like a saw While mergansers sometimes can be seen eating crabs, shrimps, aquatic insects, or even tadpoles, frogs, and worms, their bills are tailored made to catch and feed mostly on fresh fish.

Sometime around Thanksgiving, flocks of Red-breasted Mergansers arrive to coastal waters around New Jersey and New York. They fly in from their nesting grounds around lakes and rivers located among the low scrubby vegetation in the northern tundra region of Canada.

 The birds fly well over three thousand miles in the fall to pull into a busy metropolitan estuary bounded by skyscrapers on one end and suburban sprawl on the other end, with large cargo ships and smaller boats bustling for space in-between. It's a total about face for the mergansers who arrive from the relative remoteness of the tundra. Yet, the birds come here every winter for the promise of plenty of aquatic food and few predators. 

Come late March or early April , the mergansers will be off again, though some may linger in the bay until the end of May. Even ducks can be procrastinators.

Not me. After an hour and half, I got cold feet  and left to find something warm to drink. So much for trying to be a cold weather duck. Still, a few close-up pictures of Red-breasted mergansers was a nice reward for venturing out on this frosty winter's day.