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Wednesday, February 26, 2014

A Bird That Prefers to Run


Greater Roadrunner, Geococcyx californianus

Spend any amount of time in Texas or the southwestern United States and you’ll undoubtedly spot the Greater Roadrunner, a long-legged, ground-dwelling member of the cuckoo family.  It is regionally called ‘paisano’, meaning constant friend or compatriot.  This large chicken-like bird, with its long tail and shaggy crest, is fully capable of flying, but usually runs instead, at speeds up to 18 miles per hour.  True to its name, a group of these birds is known as a ‘marathon’ or a ‘race’ of roadrunners.   

From a behavioral point of view, the roadrunner is a fascinating subject.  This signature bird of the southwest slows its bodily functions at night, and conserves body heat by lowering its temperature and becoming lethargic.  In the early morning, it can warm itself up without expending a lot of energy.  Turning its back to the sun, it erects its feathers to expose an underlying patch of black skin between its wings that helps it quickly absorb more solar energy.  When running at top speed, it holds its head and tail flat and parallel to the ground.   

Roadrunner warming up in the sun by exposing dark skin

The roadrunner is an opportunistic forager, and while it can catch small birds at feeders and nest boxes, more often it eats a variety of fruits, seeds, as well as venomous prey items, including large insects, spiders, scorpions, and even rattlesnakes.  Surprisingly agile, two birds will frequently cooperate to kill a large snake, taking turns to distract it, pin its head with their heavy bill, and beat it against a rock or the ground.  When alarmed or curious, the roadrunner raises its crest and white-edged tail, and utters a series of coos or rapidly clatters its beak.

Living in dry, open habitats, the roadrunner has adapted by developing salt glands in front of its eyes to excrete excess salt from its blood.  While these glands are more common in ocean-going birds that drink seawater, the roadrunner is able to go without drinking water as long as it eats food with high moisture content, but will drink water if it is available.  When courting, many male roadrunners attract a female with cooing calls and then offer her food, usually in the form of a dead lizard.  If the female accepts, copulation occurs, during which the food is often exchanged.

Roadrunners in love

In a small tree, scrubby bush, or a stand of cactus, both parents build a shallow platform of thorny sticks, line it with leaves, grass, feathers, and occasionally shed snake skins.  Clutch size can vary from two to six eggs, depending on the food supply.  If all the eggs do not hatch at roughly the same time (called asynchronous hatching), and the food supply declines during the breeding season, the parents may eat the younger chicks or feed them to their older siblings.  In times of abundant food, roadrunners will double-brood, or raise a second family just as soon as the first is out of the nest.

Greater Roadrunner populations appear stable across their range, and are seen in central Texas year-round.  However, like most species, they tend to disappear when their habitat is fragmented by development.    

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!