• Horned Screamers, known as the unicorns of the bird world, live around lakes, ponds, rivers and marshes in tropical areas. They can be found from Colombia and Ecuador all the way to south-central Brazil.
• They are called horned screamers because of a piece of firm tissue shaped like a horn that grows in the middle of their foreheads. Some birds have horns that are 0.1 m (or six inches) long!
• However, unlike other animals with horns, such as rhinos or rams, the horned screamer’s horn might not be a weapon because it is loosely attached to the skull and can snap off if it grows too long. But don’t worry, because the broken horn grows back over time.
• These birds also have sharp bony extensions on their wings. They use these to fight each other and defend their territory.
• Horned screamers also have tiny air sacs in their skin and bones that reduce the weight of this large bird and help them fly long distances easily. Sometimes, when these birds take off, their air sacs collapse all at the same time, causing a crackling sound.
• Horned screamers have three main sounds: “mo-coo-ca”, “yoik-yok”, and the trumpet. It’s because of their “mo-coo-ca” call that locals call these birds ‘mahooka’.
• Listen to what the horned screamer sounds like here.

Source:
National Geographic