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Wednesday, February 5, 2014

Dabblers and Divers

Wintertime is the perfect time to look for ducks in Central Texas.  Several species that breed far north of our state’s border return to Texas in the colder months to feed in our unfrozen freshwater lakes and rivers.  From the Old English ‘duce’, the word duck is a derivative of the verb meaning to duck or dive, or bend down low as if to get under something.  It best describes the way many ducks feed, by upending or diving under the water in search of a wide variety of food sources, such as small aquatic plants, grasses,  fish, insects, amphibians, worms and mollusks.  Most ducks fall into either the dabbler or diver category.  Dabblers feed on the surface of the water, and sometimes on land, while divers disappear completely beaneath the surface and forage deep underwater.  In general, divers are heavier than dabblers, which gives them the ability to submerge more easily, but they often pay the price by having more difficulty when taking off to fly. 

Northern Shoveler, Anas clypeata

The most distinctive dabbling duck is the Northern Shoveler (Anas clypeada).  True to its name, it possesses a two and a half inch long bill, which is spoon-shaped and has a comb-like structure called a pecten at the edge of its beak.  The pecten is used to filter food from the water and to aid in preening its feathers.  A medium-sized duck, the adult male (or drake) has an iridescent green head, rusty sides, and a white chest.  When flushed from her nest, the adult female (or hen) will often defecate on the eggs, presumably to deter predators from eating them.  This species of duck is monogamous, and stays together longer than any other known pairs of dabbling duck species.  

American Wigeon, Anas americana

Another common dabbler is the American wigeon (Anas americana), whose population is increasing throughout its range.  The male has a white crown, green face patch, large white patches in its wings, and a black rear end bordered by white.  At one time this duck was known as ‘baldpate’ due to the white crown resembling a man’s bald head.   Its feeding behavior is distinctive among the dabbling ducks, as its short bill allows it to be much more efficient at plucking vegetation from both the water and sometimes even agricultural fields.  The diet of this duck has been shown to include a much higher proportion of plant matter than any other dabbler species.

Lesser Scaup, Aythya affinis

Among the most abundant and widespread freshwater diving ducks is the Lesser scaup (Aythya affinis).  The male has a slight bump or peak on the back of the head, a bluish bill with a small black tip, grey sides (black on the ends with white in the middle), and a black head, chest, and rear end.   When grasped by a predator like a grey fox, an adult Lesser scaup may play dead, rendering itself immobile with its head extended, eyes open, and wings floded close to its body.  They are capable of diving underwater the day they are hatched, but are too buoyant to stay under for long, until maturity gives them the body composition and strength they need to stay underwater for longer periods of time.

Usually found on smaller, calmer bodies of water like ponds, Ring-necked ducks (Aythya collaris) are more readily identified by the bold white ring around their bill that the subtle purplish band around their necks for which they are named.  A medium-sized diving duck, they also have a small bump or peak on the back of their black heads, with the male having a black chest, back, and rear end, with grey sides and a white stripe up the shoulder.

Gadwall, Anas strepera, is another common duck of Central Texas

The next time you visit a lake, river, or pond this winter, venture out to the quiet corners to see if you can spot one of our best known dabblers or divers!