The northern screech-owls are found in eastern states, such as New Jersey and New York. The screech owls are named for their piercing calls. The normal territorial call is not a hoot as with some owls, but a trill consisting of more than 4 individual calls per second given in rapid succession (although the sound does not resemble screeching or screaming). They also have a kind of “song” which is used in courtship and, as a duet, between members of a pair. Calls differ widely between species in type and pitch, and in the field are often the first indication of these birds’ presence, as well as the most reliable means to distinguish between species. The distinctness of many species of screech owls was first realized when vastly differing calls of externally similar birds from adjacent regions were noted.