In a dimly lit forest, a sneaky marten silently stalks a group of Japanese Tits fluttering in the treetops. Then, suddenly, one of the little birds spots the invader and belts out a series of buzzy chirps. In response, the tits assemble and prepare for a preemptive attack on the predator. It's a scene that regularly plays out in the woodlands of Japan and eastern Russia, where the birds call home, and the rapid mobilization is the result of their impeccable communication skills. When danger like the marten is spotted, a flock member voices a "mobbing call"—a combination of chirps called an “alert-recruitment” sequence—to rally the troops, explains Toshitaka Suzuki, a postdoctoral expert on animal communication at Kyoto University’s Center for Ecological Research. While observing these sociable birds in the wild, Suzuki noticed that they also understand the meaning of calls from their close cousin, the Willow Tit. So, he ventured that Japanese Tits may rely on...