The Strange-tailed Tyrant is a flycatcher with an unusual tail. In addition to its regular proportional tail, it has a couple of long outer tail feathers. That's where the strange tail in its name comes from. 

However, the reason this bird is called a tyrant has less to do with its behavior and more to do with its classification. The bird is a member of the genus Alectrurus, which belongs to the family Tyrannidae. The family name reflects the aggressive nature of some members, especially the Western Kingbird.