Numerical discrimination by wild mockingbirds

We are interested in testing the abilities of wild Notrthern Mockingbirds (Mimus polyglottos) to discriminate on the basis of number. My students and I designed and built special feeders that dispense mealworms (larvae of Tenebrio beetles). The mealworms are suspended within the feeder on a platform that is held in place by bamboo sticks on two sides. If all of the sticks are removed on either side, the platform will tip and release the mealworms. Each side of the feeder can have 1 to 6 sticks. A discriminating mockingbird should recognize which side of the feeder has fewer sticks and pull these, releasing the mealworms with the least amount of effort. Here is an illustrated example:

The approach

In this example mockingbird number 3 (White & Yellow bands) approaches a feeder with two sticks on one side and four sticks on the other. For each of these trials, we randomly assigned which side would have two sticks and which would have four. We also used a randomization procedure to determine which of the six hole positions on each side to use for the sticks.

Stick 1 Good choice!

Stick 2 Excellent work!

Success. A well deserved reward!

Video:

Student collaborators:

Jen Smolinski
Mike Gaydos
Hank Kerschen
Sirisha Manyam
Mike Horejs