Some species of terns (including the Royal terns pictured here) exhibit a mysterious behavior called the “dread” and we don’t know exactly why they do it.
Tern colonies are almost always a cacophony of noise with the sounds of squawks and chatter from breeding adults and groups of juveniles. Even at night the noise is constant. Sometimes though, the entire colony will fall utterly quiet together in a sustained period of silence that we call the dread. Often the birds will leave their nests as a group while they fly together in perfect silence.
After the dread the birds quickly return to their normal chatter. We don’t yet know what this behavior means but it has been theorized to be a form of social bonding, a threat response, or even just plain fun.
If you’re interested in what the dread sounds like, have a listen from a researcher who observed tern populations firsthand.
