Possibly, you don’t believe it. Possibly, you are still huddled next to your ott lamp, praying for July.
It is officially spring.
This designation means something, yes, but the cut and dry nature of a date to start a season is for our benefit. Seasons don’t really come on one day and stop on another, of course. They are a continuum that may fluctuate from year to year. The birds certainly know this.
Go ahead, stick your head outside, more birds are singing now than two months ago. When I get up around dawn, there’s at least five species of birds signing loudly on my city block: American robin, dark-eyed junco, Bewick’s wren, song sparrow, and black-capped chickadee. What are they being so noisy about and why now?
Sound is a major part of the bird world, second only to vision. Theses songs and other noises are made for a sole purpose, to communicate. The birds in our neighborhood vocalize year-round. You hear American crows cawing, house sparrows chirping, and other various twittering even in the dead of winter. However these are usually simple, unimpressive single note calls, not complex, variable songs. These calls are communicating all sorts of things like “I’m over here,” where a predator is, or where good food is. However, something happens as spring’s hold on the temperate world increases, birds start to make different noises. They sing.
For a person who has been trapped under gray skies, hearing bird song on a decent day might seem to echo your joy. You think “even the birds are happy for the sun.” While it’s true birds might be more active on a warmer day, their singing isn’t likely celebratory. They are advertising.
A lot of the birds we see flocking in winter, separate into territories and pairs during spring and summer. Suddenly those robins aren’t in flocks on the lawn at Cal Anderson, but are distributed throughout usable habitat, typically with better space going to the fitter birds. How do they distinguish those territories? One way is with song.
Many species react quite strongly to another of their species singing nearby. A series of videos released by researchers on UW campus showed song sparrows (Melospiza melodia) singing back at a recorded song as a warning to a presumed interloper, a stuffed song sparrow, before attacking it when it didn’t leave. A fight isn’t a bird’s first choice, which is why they sing, but it seems a little intense to defend your territory simply for say, food, especially when availability increases with spring. The thing is, these birds singing (almost always) are male.
That should tell you something else. These guys aren’t just sectioning off areas for bachelorhood, they are trying to get some action. Rather, they are attempting to reproduce, which from a biologist’s point of view is the final goal of all sexually reproducing species; to pass on their genes. So these songsters are not only telling other dudes, to get off their lawn, they may also be telling the ladies they are virile, genetically superior specimens.
How do these birds know when it’s time to start singing? If you are a song sparrow, you are like most songbirds and take cues from the environment. After all, if you are trying to attract a mate, there’s little point in putting much energy toward singing in the depths of winter when you can’t raise young. So as the days lengthen, the birds rev their engines, their hormones ramp up, and singing increases. Average air temperatures may make a difference as well and with wide spread species, like the song sparrow, individuals living in Capitol Hill probably start singing sooner than birds in the Cascade foothills.
Birds song is not so simple and many a book has covered the wonderful complexities of these vocalizations. Not all birds sing either, our smaller perching birds are known for it, but typically any bird has means of displaying for the opposite sex or to advertise territory boundaries. However, there are species where pairs duet. Birds who don’t vocalize but use their bodies to create the same messages, which effectively becomes their song (many woodpeckers drum on wood, or anything else that resonates well). Our dainty Pacific wren belts out a song that’s an amazing 10 times the volume of a rooster, when measured per unit weight. Yet ultimately, most birds around here take springtime cues to start displaying and with some thoughtfulness, we’re likely to notice the pigeons strutting on the sidewalk and song sparrows singing in our backyards.
Previously on Pikes/Pines