Behavioral flexibility, as expressed through foraging behaviors, habitat use, and social behaviors, is thought to play an important role in a species' ability to adapt to human-modified environments. However, it is rare to find evidence that links flexibility to the foraging, habitat use, and social behaviors in species that are successful in human-modified environments. Researchers gathered this evidence in two populations of great-tailed grackles, a bird species that primarily lives in human-modified environments.
The researchers found that grackles who were trained to be more flexible used a wider variety of foods and foraging techniques, but had similar habitat use patterns and social behavior as non-trained grackles. Given that this species is rapidly expanding its geographic range and shifting more toward urban and arid environments in recent years, our finding could suggest that foraging breadth, the number of different food types an individual eats, is a factor in adapting to human-modified environments.
"We may laugh at the birds in parking lots eating the leftover french fries, but actually not all birds are able to change their behavior to take advantage of these human-provided resources. So, it's interesting to find that this ability to eat many different foods is also related to the cognitive trait, behavioral flexibility," says Dr Kelsey McCune who was at the University of California Santa Barbara when she helped run the grackle research (currently at Auburn University).
Discovered a new measure of flexibility
The research team determined how flexible each grackle was using an behavioral choice test in the aviaries called reversal learning. This is a widely used test of flexibility where an individual learns to prefer a color because the food is always in that colored tube, and then their color preference is reversed to a different colored tube, which now always has the food.
After the grackles did the aviary test, they were released back to the wild and their foraging and social behavior in the wild was observed from a distance. The researchers discovered that the grackles that were more flexible in the reversal learning test also switched between eating different food types more often in the wild.
"This is such a great discovery because it is really difficult to bring birds into aviaries to measure their flexibility. Now we have the ability to measure their flexibility just by watching them in the wild," says Dr. Corina Logan at the Max Planck Institute for Evolutionary Anthropology and lead researcher. This new way of measuring flexibility will make it much more accessible to a wide range of researchers because, apart from needing to be able to tell the individuals apart, all that is needed is a pair of binoculars.
Boat-tailed grackles are not rapidly expanding, but are as flexible
Behavioral flexibility is thought to be a primary facilitator for expanding into new areas. Researchers tested this by examining flexibility in two closely related species: the great-tailed grackle, which is rapidly expanding its geographic range, and the boat-tailed grackle, which is not. The idea was that if the great-tailed grackles needed flexibility to expand their range, then the boat-tailed grackles should be less flexible.
The researchers found that both species are highly flexible, which indicates that flexibility is not the primary facilitator of a rapid range expansion. "These species are similar in many ways: they eat the same kinds of foods, live in the same kinds of places, and they even look the same. That they are also similar in their levels of flexibility was surprising given their differences in how fast they are expanding, or not, their ranges" says Dr. Logan.
These results placed in the context of the group's previous findings on these species lend further support to the idea that persistence and variability in flexibility are involved in expanding the range of the great-tailed grackle. It is likely that, historically, both species needed flexibility to adapt to human-modified environments that encroached on their habitat. Perhaps they continue to rely on flexibility to interact in these human-modified environments, which is now their primary habitat.
These findings provide an insight into what needs to be measured to predict how successful a species might be in a new environment, which could be a useful tool for conservation managers.
