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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.