Skip to content

ICYMI: A Popular Local Invader

June 22, 2016

In Case You Missed It: From the New York Times


Photo Credit Tony Hisgett


There’s an aura of power around invasive species. How is it that they can sweep in and take over from the locals? Are they more adaptable, tougher? What are their secrets?

The great-tailed grackle is a case in point. North America has its own similar species — the common and boat-tailed grackle. But the great-tailed bird, Quiscalus mexicanus, native to Central America, is one of the most invasive species in the United States.

The black birds with iridescent feathers were prized by the Aztec emperor Auitzotl, who, by some accounts, relocated some of them from Veracruz to near Mexico City about 500 years ago.

Over the past century or so the bird has spread north and its range is still expanding, particularly in the West, where it haunts cattle feed lots and big dairy farms. The birds are also quite happy in urban areas, like Santa Barbara, Calif., where Corina J. Logan captured and later released some grackle for recent experiments.

Great-tailed grackles first caught the attention of Dr. Logan, now at Cambridge University, in 2004 when she was doing undergraduate research in Costa Rica.

“They’ll actually walk right up and look you in the eye,” she said. “They look like they’re so smart.”

Years later, having earned her Ph.D. at Cambridge, she decided to look more closely at them because she was interested in behavioral flexibility. Grackles, for example, might look under rocks at the beach for something to eat, or switch to discarded sandwich wrappers in a city park.

There is another kind of behavioral change — innovation. That’s solving new problems either by adapting an existing kind of behavior or coming up with a new one. For instance, some crows and other birds have dropped stones in water to make the level rise so they can get a floating treat. Dr. Logan said that scientists have thought about flexibility and innovation as two sides of the same coin, and both are very characteristic of invasive species. But recently some researchers have wondered if they may be separate abilities.

Sign Up for the Science Times Newsletter
Every week, we’ll bring you stories that capture the wonders of the human body, nature and the cosmos.
Dr. Logan, then working at the SAGE Center for the Study of the Mind at U.C. Santa Barbara, wanted to see if the grackles were as innovative as they were flexible. They seemed like good candidates for the experiments because, although they are very adaptable, they have relatively small brains compared with birds like crows, which are part of the very smart and inventive corvid family.

So she challenged the birds she had trapped with some problems that required new behaviors to solve, using unfamiliar kinds of actions.

In one situation, she presented them with a stick that could be used to get food. The grackles don’t use tools in the wild, and they couldn’t figure out how to use one in an experiment, even after an experimenter showed them how.

In a second experiment, she offered them the chance to get a treat by pulling a string, either horizontally or vertically. None of the birds got the treat.

The great-tailed grackles did not show a capacity for innovation, despite their flexibility. So, Dr. Logan concluded in a report in Royal Society Open Science, innovation may not be so important for colonizing new environments. The grackles are doing pretty well without it. Perhaps, she said, scientists might reconsider how they think about what makes for a successful invasive species.

The birds in the test, all let go after the experiment, are listed by name in the scientific report: Tequila, Margarita, Cerveza and Michelada in one group, and Refresh, Horchata, Batido and Jugo in another.

“I was chatting with a restaurant owner where I was trapping the birds,” Dr. Logan said. He told her the grackles were bold in snatching items from tables that patrons had just vacated. He said, “They even drink the tequila”, Dr. Logan added.

Since it was a Mexican restaurant and Dr. Logan had already decided the birds ought to have Spanish names, she decided to name the birds after menu items — alcoholic drinks for the first group, nonalcoholic drinks for the second. She hopes to return to Santa Barbara for more research on grackles and already has plans for naming the next group.

“Appetizers,” she said.


One Comment
  1. Chukar permalink*
    June 22, 2016 11:26 am

    In my experience, GT Grackles appeared first appeared in California in Imperial Valley. By 1982 they’d spread out to various desert oases harboring both water & reeds; I saw several at Death Valley’s Furnace Creek Golf Course in May’82. Next location was California City (Kern Co.) Central Park in May’87. My first L.A. County sighting was Harbor Lake, Sept.’91. Our first Malibu Lagoon sighting was 4 birds on 8/26/01. In 2015 they were at the lagoon 10 out of 11 count dates. They now seem to be breeding not at the lagoon, but at Legacy Park north of the shopping center. They appear to drive Yellow-headed Blackbirds out of any location they invade. Chuck Almdale


Comments are closed.

%d bloggers like this: