The first experience most people have with roadrunners is a blur of grey as it runs across the road in front of their car, or alongside the road they are driving on. Roadrunners are pretty much the Frank Sinatra of the bird world, essentially doing things their way on their own terms. From what little is known, they are somewhat unique in their behavior. They are a predatory bird that mate for life, actively defends their territory, and are not active flyers as their name suggests. But beyond these generalities, the bird is something of an enigma. Everyone enjoys watching roadrunners, and most have an anecdotal story to tell about roadrunners, but there is very little known about the greater roadrunner’s ecology...its relationship to its environment. In 2006, wildlife researchers at the Texas AgriLife Research Center in Vernon began an in-depth study of greater roadrunners to address the gaps in our knowledge of roadrunner biology. Using radio-telemetry to track roadrunners from a distance without disturbing them, the research team began to collect data on dispersal, survival, habitat use, and nest site selection and nest success.
The roadrunner is an icon of the open rangelands of Texas and the southwest, but this is something of a misnomer. This research has shown that roadrunners seem to prefer woodland habitats–dense stands of moderate to old mesquite. This finding was not surprising in one sense given that the bird nests in trees, but at a larger scale many roadrunner home ranges contained large percentages of mesquite cover. A finer point to this was the observation of a roadrunner abandoning its home range following mechanical brush removal inside the birds’ home range.
The size of roadrunner home ranges- or the area in which a roadrunner spends the majority of its time-were surprisingly large for a bird that weighs just less than a pound. Spring-summer home ranges averaged 250 acres and were similar for males and females. During the fall and winter, home ranges averaged 50% smaller. More surprising were the dispersal abilities of young roadrunners leaving their parents territory to establish home ranges of their own; several young roadrunners have dispersed upwards of 3 miles, and the longest dispersal recorded was just over 6 miles.
In spite of the Saturday morning cartoon depicting the continual struggle with Wile E. Coyote, the Roadrunner has few natural enemies, and mortality seems to be highest during extreme drought periods when alternative prey is not available. The Vernon researchers documented the highest mortality of roadrunners in the fall and winter of 2006-07. Roadrunners were preyed upon by hawks -probably Cooper’s Hawks, and Bobcats. The only other source of mortality roadrunners face seems to be Grannies’ speeding Buick, an artifact of the birds’ tendency to hunt and travel along roadside right-of-ways.
The roadrunner research at the Vernon research center is entering its fourth year, with plans to continue for at least another 3 years. Future research will involve additional study sites to investigate spatial differences in roadrunner behavior.
Infomation for this post was provided by Dr. Dean Ransom, Assistant Professor, Texas Agriculture Research and Extension Center, Vernon, Texas.