Feathers of Grace: The “After You” Gesture in Japanese Tits

A recent study found evidence of symbolic gesture use in Japanese tits (<i>Parus minor</i>). The study reveals how these birds use wing-fluttering movements to transmit an "after you" directive to their partners, implying a degree of cognitive skill previously thought to be unique to humans and great apes. If confirmed, this research contradicts long-held notions about animal communication by proving that Japanese tits not only participate in intricate vocal communications, which can comprise phrases with specific grammatical rules, but also use body language as a form of engagement. Here, we evaluate this claim by inspecting the data and utilizing bootstrapping to expand the sample size. We find a large variation in how frequently the "after you" gesture is employed in different bootstrap samples, suggesting that while the gesture is a consistent behavior, its frequency can vary significantly. Moreover, the timing of the male's response to the female's gesture can fluctuate, though the response itself appears to be a stable phenomenon. Beyond evaluating the bootstrapping technique, we employ causal inference to examine whether wing fluttering by female Japanese tits leads to a quicker response by males, entering the nest more swiftly. The analysis supports this hypothesis, suggesting that wing fluttering functions as an effective communicative gesture in this species, influencing male nesting behavior. However, because the frequency of the "after you" gesture varied greatly, especially in light of potential cognitive and other biases influencing the study, this bold claim should be taken with caution.