On the Caribbean island of Barbados, Carib Grackles are known for brazenly darting into restaurants and stealing scraps of food. Thanks in part to this unnatural foraging behavior, the birds have managed to thrive on the urbanized island with little remaining forest habitat. It was this resilience that first drew biologist Simon Ducatez to the island to study how the tropical blackbird removes obstacles in search of food. As a result of this research, Ducatez began to wonder: Could a bird’s innovative nature predict its risk of extinction?
Inspired, Ducatez embarked on an 8-year mission to find out. But first, he needed a dataset to study. Ducatez turned to Louis Lefebvre, a biologist at McGill University who has spent 20 years searching for and compiling evidence of foraging innovations in the wild. Together the two formed an international team that analyzed more than 3,800 individual observations by birdwatchers and researchers worldwide to see whether adaptive foragers had a higher chance of survival.
What they found supported Ducatez’s thesis: When facing habitat loss, creative foragers are more likely to resist extinction than those stuck in their ways. In addition, the more creative the behaviors observed for a given species, the less it was found to be at risk. The findings were published this week in Nature Ecology and Evolution.
While many of the observations analyzed in the study are more commonly known—fry-stealing gulls or dumpster-diving ravens, for instance—some were much more unusual: Meat-deprived Himalayan Griffons turning to pine needles, Great Cormorants timing their fishing with currents created by commercial ferries in New Zealand, Yellow-rumped warblers eating flies from heated milk at a dairy farm during a freeze, and American Crows opening nuts by dropping them on the freeway. “They seem to be using cars as hammers,” Ducatez, the lead author on the paper, says.
To conduct their analysis, the authors used these innovations, small and big, as a measure of “behavioral plasticity,” which they define as the ability of some animals to change their behavior to adapt to environmental stress like food shortages and extreme climate events. The number of observed innovations of each species was then cross-referenced with their level of extinction risk according to the Red List of the International Union for Conservation of Nature (IUCN). The new findings, the researchers argue, position behavioral plasticity among a trifecta of strategies birds use to adapt to environmental changes, along with ecological generalism (the tendency of some animals to utilize a variety of resources in different environments), and life history.
“This (study) is exciting because it highlights the possibility of an important role of behavior and perhaps cognition in species persistence,” says Emily DuVal, an associate professor at Florida State University who was not involved in the study. For DuVal, though, whether the more unusual behaviors can be used as a metric for behavioral plasticity warrants more critical study. “Expressing a behavior that is a rare component of an animal’s foraging repertoire is different than plastic expression of different behaviors given different environmental circumstances,” she says. “Identifying the latter is a much higher bar to reach, as it requires in-depth observation of different populations or environmental circumstances.”
DuVal also points out that the oddest observations are more likely to be reported while not necessarily being as vital to the survival of an entire species. Smaller, subtler foraging shifts are probably more indicative of long-term success, she says. The study authors did try to address this by repeating the analysis separately for minor food innovations, such as the addition of a new seed to a bird’s diet, and for more unusual innovations like a new foraging technique. They found that both types of innovations decreased the risk of extinction.
Additionally, not all of the more than 8,000 species involved in the analysis are considered well-studied birds. While the researchers found consistent results for both well-studied birds and lesser-known birds, DuVal says it would also be interesting to repeat the analysis specifically on a subset of species from Lefebvre’s database for which foraging behavior has been explicitly studied in detail. Testing only species with well-studied foraging habits may predict population dynamics even more clearly, she says.
As an indirect measure, the study authors used the number of published studies on a given species to determine if it is well-studied. Because foraging is one of the most studied aspects of birds’ ecology, Ducatez said, generally, the foraging behavior and diets of well-known birds are understood. But ultimately, “it is tricky to directly calculate how well a species foraging behavior is known,” he says.
Ducatez is also careful to clarify that while the study found flexible foraging to give species a survival advantage, innovative behavior does not mean that the species as a whole will survive. “It’s more an indicator that the species is able to invent something new to confront some challenges in its environment,” he says.
These challenges are vast. North America alone has already lost an estimated 3 billion birds since 1970, according to one study, as humans destroy their habitats, build glass towers in the sky, and alter the climate at an unprecedented speed. And while behavioral plasticity may help buffer against some of these perils, no matter how clever or innovative birds are, they are no match for direct threats like hunting and poaching or competition from invasive species, the study says. Parrots, for example, are highly innovative, but because they reproduce at a slow pace, they cannot always produce offspring fast enough to recover from human activities like the pet trade.
For its part, the new study and its findings could prove to be a valuable conservation tool, helping to prioritize which species will need the most help in the Anthropocene, Ducatez says. “What we see here is species that are not that innovative are probably not going to have it easy when their habitats change.”