The “after you” gesture in a bird

Description

Japanese tits build their nests in tree cavities with a small entrance, and males and females enter the nest one at a time. We observed that Japanese tits carrying a food item often fluttered their wings in front of their mates when perched nearby their nestbox with a food item. We proposed the hypothesis that wing-fluttering in Japanese tits functions as a gesture that prompts their mate to enter the nest first, and we tested this hypothesis in our study. Analyzing the effects of social contexts and sex on the occurrence of wing-fluttering behavior, we found that parents flutter their wings only in the presence of their mate, with females performing this visual display more frequently than males. Next, we examined the effects of females' wing-fluttering and parental arrival order (which sex visited the nest first) on the nest entry order and the latency of males to enter the nestbox. Our results indicate that wing-fluttering prompts the mate to enter the nest first, suggesting that this behavior functions as a gesture conveying a request message (“after you”).

Steps to reproduce

We collected data from a population of Japanese tits breeding using nestboxes in Nagano, Japan, from May 27 to June 6, 2023. At each nest, we (two observers) recorded the behavior of both males and females ca. 15 m from the nestbox. We started observations after confirming that both parents made at least one feeding visit in order to ensure that they were not responding to us. We made observations of at least 40 feeding events per nest and noted the social context (presence or absence of mates within 5-m of the nestbox), parents’ sex, and the occurrence of wing-fluttering behavior. In cases where both parents were present outside the nest, we recorded the order in which they arrived at the nest site and entered the nestbox. During the observations, we set up two video cameras at the observation location: one focused on the nest entrance and the other captured parental behavior. We used the video recordings to measure the latency of birds (males) to enter the nest (i.e., the delay between the time when males encountered females and the time when males entered the nestbox).

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