Here in NE, Spring has come, and along with it, the wild songbirds. They are a welcome relief from the silence of winter, but how do they know when to start their racket?
Here, they seem to start calling about 1 hour before sunrise-and call it quits just about at sunrise.
How do they sense the time?
When it starts getting light, and when it starts going dark. Mystery solved.
Yeah, if for some reason there’s a false dawn, or a lot of human-generated light that they’re not used to, they will also wake up and begin chirping.
“Twilight” mean both dawn and dusk – there is a period of lightening before sunrise as well as a period of decreasing light after sundown. Birds tend to sing at twilight.
Like most organisms, birds have endogenous circadian rhythms. That is, they have an internal “clock” that will tell them the approximate time of day regardless of any external clues.
This said, most early morning bird song tends to start at “first light,” the first perceptible light in the morning sky, which they can detect. Similarly, they know what time it is in the late afternoon by the position of the sun in the sky and declining light levels.
Well, something told the wild geese it was time to go!