No joy in California towhee's song
Birdsong brings great joy to many. A robin song on an early March day as winter is loosening its grip reminds us that warmer days filled with flowers and more birdsong are soon approaching. I smile as I zip my coat just a little bit higher.
Ask any number of people why a bird sings, and many will answer that birds are happy and they sing for joy.
Well, it is late May, and the California towhee in my yard is singing. It is not bringing me joy nor is the towhee likely joyful. The song of this large brown sparrow is not elaborate. It is a short, accelerating trill that has a metallic tone to it. The male has been singing for two weeks now, pretty much nonstop.
California towhees tend to mate for life. There is divorce in the bird world. Someone studied adelie penguins and discovered a divorce rate of about 14 percent annually, but I am not aware of divorce among California towhees.
California towhees are relatively long-lived birds, and pairs tend to be long-lasting.
All winter at my feeding station, if I see a California towhee, I can be assured the mate is nearby. They do almost everything together.
Now as far as the reason birds sing, there are a great many. The two most important are to attract a mate and to defend a territory. In the case of California towhees, they apparently sing little if at all to defend a territory. This is unusual for a songbird, but different birds use songs in different ways. They are also nonmigratory, and apparently territory boundaries are relatively stable and infrequently tested by others.
California towhees sing to attract a mate. Having found a mate, the male returns to a discrete silence as the pair searches the leaf litter for insects and seeds and raises a family. Males of a great many other birds continue to sing after finding a mate. Besides defending the territory, this encourages faithfulness in a mate or unfaithfulness in the mates of others. There are other reasons to continue singing after finding a mate, but not for the California towhee.
The initiation of singing by the California towhee almost certainly signals the loss of its mate. The timing suggests that the female was taken as she was incubating. Ground-nesting birds such as the towhee are vulnerable to a wide range of predators, mostly mammals, ranging from rats to opossums and raccoons to cats. I do not know where this pair had its nest, but the full battery of predators is certainly present in my yard.
The extended period of singing is particularly sad, as it speaks to the inability of the male to find a new mate. I suspect there are few other California towhees in our neighborhood. California towhees rely on woody vegetation close to the ground both for foraging and nesting. As my neighbors fireproof the area around their homes by removing brush, there is less and less habitat for them. When I first moved to my property, I knew of several pairs of California towhees in the neighborhood. Now, it appears the lone male is the last remaining bird.
As strange as it sounds, each morning as I retrieve the newspaper, I am hoping that I do not hear the song of the towhee. This might signal the arrival of a new mate.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.