Birds are great communicators, and they “talk” using song, body language, and even musical instruments. But now, one species of pigeon is whistling a new tune—with its feathers. Crested pigeons, large birds indigenous to Australia, make a warbling noise when they flap their wings to take off. The upstroke of each wing beat produces a 1.3-kilohertz low note, and the downstroke produces a 2.9-kilohertz high note. To find out whether this distinctive sound is used to communicate, a group first examined the feathers themselves. They found that the noise was coming from the eighth feather on the pigeon's wing; when this feather was removed, the high note disappeared. However, when the feather was placed in a wind tunnel, the high-frequency sound returned. To see how other birds reacted to the noise, the researchers played audio recordings of slow and fast wing beats to pigeons in their natural habitat. During the slow beats, the birds stayed where they were. But the faster wing beats set the birds fleeing. That means these wing whistles are likely serving as a type of warning signal, the researchers report today in Current Biology. Because the notes cycle back and forth between high and low, the speed of the cycle informs the pigeons whether there is danger, or whether it’s just another bird taking off.