Dr. Jiani Chen, Yuqi Zou and Prof. Yue-Hua Sun from Institute of Zoology, Chinese Academy of Sciences, published a research paper "Problem-solving males become more attractive to female budgerigars" on Science, which was online on January 11, 2019. This is a story of male budgerigars gaining favor by learning feeding techniques.

In the process of sexual selection, women hope to find a smart and able partner, so cognitive ability is an important criterion for mate choice. Therefore, the evolution related to cognitive ability is not only the result of natural selection, but also the result of sexual selection. As early as in 1871 Darwin proposed such hypothesis on his famous book "The Descent of Man, and Selection in Relation to Sex", however, it was difficult to obtain conclusive evidence from other animals to explain the problem. In order to explore this problem, scientists from the Research Group of Avian Ecology in the Institute of Zoology of the Chinese Academy of Sciences used the budgerigars as the research object, with four-year of hard work in a poor lab, for the first time confirmed that the cognitive ability of birds can also be used as a criterion for sexual selection. It provides important enlightenment for people to better understand the evolution of cognition.

In the study, female budgerigars were given a chance to choose one of the two males she preferred. During a 4-day period, females spent more time with her preferred males. Next, the researchers helped the unfavoured males to learn two feeding techniques, opening the petri dishes and a small box with three steps (Figure A). After about one week of study, the unfavoured males returned to the females. The researchers asked the female to see how the returning males could easily open the boxes for food (Picture B), and how the male they had previously preferred was bewildered in front of the boxes (Picture C). After several days of observation, the researchers gave the female a chance to select again. In the second time, the choice of the females changed significantly, and they changed their minds and were willing to spend more time with former unfavoured males. Did the power of "wisdom" really help the males to regain the favor of the females? To verify this, the researchers also conducted two sets of comparative experiments. In one group, the females were allowed to view the open boxes of the males that were not preferred, while the preferred males were given only the empty boxes. As a result, the females did not change their original choice, or insisted on favoring the original ones. This suggests that food itself was not the reason for the change. In the second group, females were asked to select two females. The experiment was consistent with the initial procedure, with only two selected males being replaced with females. The results showed that the female did not change her preference for "best friend" after observing her feeding skills referring that the selection is related to sex.

Our study shows that direct observation of cognitive skills can affect animal mate selection, which supports the hypothesis started from Darwin that mate choice may affect the evolution of animal cognitive characteristics.

A: roblem-solving devices: the petri dish and the three-step box. B: he female observing a trained male opening the petri dish. C: focal female observing an untrained male trying unsuccessfully to open the dish.

The budgerigars in our lab.