Innovation does not indicate behavioral flexibility in great-tailed grackles

Many cross-species studies attest that innovation frequency (novel food types eaten and foraging techniques used) is a measure of behavioral flexibility and show that it positively correlates with relative brain size (corrected for body size). However, mixed results from the three studies that directly test the relationship between innovation frequency and behavioral flexibility and behavioral flexibility and brain size question both assumptions. I investigated behavioral flexibility in non-innovative great-tailed grackles that have an average sized brain, and compared their test performance with innovative, large-brained New Caledonian crows. Contrary to the prediction, grackles perform similarly to crows in experiments using clear tubes partially filled with water and containing a floating food reward, where objects must be dropped into the tube to raise the water level, bringing the food within reach. Similarly to crows, 4 out of 6 grackles preferred to drop the more functional heavy (rather than light) objects, and 2 changed their preference in a follow up experiment where the heavy objects were no longer functional, thus exhibiting behavioral flexibility. These results challenge the assumption that innovation frequency indicates behavioral flexibility since a non-innovative bird demonstrated behavioral flexibility at a level similar to that in innovative crows, and they challenge the assumption that only large brains are capable of behavioral flexibility because a bird with an average brain size solved problems similarly to large-brained crows.