Image via WikipediaThere is still so much we have to discover about birds. As far as I know there are no hard and fast rules defining a call from a song.
Bird Calls are usually short inborn sounds both male and female birds make throughout the year. Birds use calls in a variety of contexts, such as to announce their location, to warn if there are predators nearby, to spread the word about a food source, and as a basic form of communication.
Bird Songs have two main functions: to defend a territory and to attract a mate. Usually heard in the spring, songs tend to be longer, and more complex then calls. Most songs are sung by males that inherit a basic unstructured song that they can improve on based on what they hear from their father’s song or close male neighbors. And just as our love songs have changed over the years, scientists have shown that birds also update their songs.
But not all songbirds sing songs. Blue Jays might imitate a squeaky gate. Starlings can produce a string of songs from different birds as well as other noises. And the Cedar Waxwings seem to have lost their ability to sing any song at all.
According to Donald Kroodsma in The Backyard Birdsong Guide, Cedar Waxwings make two basic types of calls: a high, thin seee and a more buzzy bzee but no song. In fact during breeding season the waxwings tend to be noticeable more quiet which seems to be an evolutionary reversal for birds.
However, they may not need songs because Cedar Waxwings are social birds that form large flocks and often nest in loose clusters with over a dozen nests close together. So with no need to defend a territory through song, the males may use the wax on their wings to impress females as well as their wonderful courtship dances.
Still, there are a lot of unanswered questions for ornithologist, young or old, to answer in the future.