12 is the magic number

Most daytime-active animals respond to daylengths of 12 hours or more by getting ready to reproduce:  singing, courtship displays, nesting, territorial disputes, etc.  There are hundreds of studies showing this works in a huge variety of species from bacteria to bugs to birds, etc. (Actually, some plants, too.)

"I just feel like singing"

“I just feel like singing”

But actually, it’s not only the absolute length of the day that is important, but the increasing or decreasing nature of the day length.  Right now, we are gaining an additional 3 minutes of daylight each day, as the sun rises higher on its arc through the sky, a welcome change from the dreary days of December.

"I can't tell you how happy that makes me!"

“I can’t tell you how happy that makes me!”

We won’t hit the magic number of 12 hours of light from sunrise to sunset until March 18 in Minnesota, but you know birds will be singing their heads off by then.  So, is 12 really the magic number?

"What?  I have to wait until March 18 to start singing?"

“What? I have to wait until March 18 to start singing?  That just makes me grumpy!”

Factor in that beautiful light that we receive at dawn (morning civil twilight when the sun is 6 degrees below the horizon until sunrise) and at dusk (sunset through evening civil twilight when the sun is again 6 degrees below the horizon), and we will reach the 12 hours of daylight on February 26 in Minnesota.

So I propose an experiment.  Look up the dates for 12 hours of light from sunrise to sunset vs 12 hours of light from dawn (morning civil twilight) to dusk (evening civil twilight) in your area and monitor how much singing you hear before or between or after those dates.   What cues are birds really using to get them started on their “spring fling?”

I’ll check back with you in April.

10 thoughts on “12 is the magic number

  1. Good inquiry-based science post going on here today, Sue! 😉 Love your cardinal pics, by the way. They really do ‘fire up’ the winter landscape, as Mary Oliver says, as nothing else can do!

  2. 12 hours from sunrise to sunset occurs in Chicago on March 18th, and 12 hours from dawn to dusk is on February 25th. My cardinals start singing every year just before Valentine’s Day so I would say dawn to dusk is probably the right measurement. I’ll let you know when one sings this year. 🙂

    I have a family of cardinals in my yard this winter, the only bright spot in the desolate view out my back door. Yesterday I noticed one of the males perched at top of the apple tree instead of low in the shrubs.

  3. 12 is definitely the magic number here today in Seattle what with the Seahawks parade and all the 12th Man hoopla 🙂 so I am amused by the timing of your post! Not that I am at the parade…far away from it, in fact, and just refilled the suet feeder for the birds, to help tide them over the next few days and continue fueling their first early spring tentative songs!

    • Quite unintended — but apropos I guess, with the crushing victory the Seahawks enjoyed the other day. I am not a football fan, but I do love Seattle (the city and surrounds).

Please Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s