Daylight hours are on the increase. Since the winter solstice on December 21, each day the sun has climbed higher in the sky.
The additional daylight may seem imperceptible, as Dr. Emile DeVito, New Jersey Conservation Foundation’s staff biologist, points out: “Right after the solstice, it’s less than one minute each day. On February 1st, the sun is above the horizon 49 minutes longer than on New Year’s Day. Between February 1st and March 1st, another 70 minutes will be added.”
Things change more quickly in March, as we can see the sun for 83 more minutes by the time March “goes out like a lamb.”
Did you ever wonder why March “comes in like a lion?” According to Emile, it’s because around the vernal equinox on March 20, the sun is moving faster toward the northern hemisphere than at any other time.
“Picture the sun as a ball on a pendulum - the winter solstice is at the end of the swing, when the sun stops its journey south and reverses course,” he says. “The equinox is when the pendulum is speeding through the middle of its journey at the low point of the swing.”
The rapid change in solar radiation often speeds up the high altitude wind patterns, and weather systems move rapidly. You may have noticed that it stays windy through mid-April, but the days are much warmer and most folks don’t mind those windy April showers!
But how does the wildlife of this state we’re in know that spring is on the way? Our 150 bald eagle pairs have been carrying new sticks to strengthen their nests since the solstice, and some have already laid their eggs.
Most female great horned owls are already incubating their eggs! On about February 8 in central New Jersey, male cardinals will burst into territorial and courtship songs, “we-MEET-you, we-MEET-you, CHEER-so, CHEER-so.” This may occur earlier in Cape May, and later in High Point. On rainy nights in January, endangered Tiger salamanders venture into frigid breeding ponds, often beneath the ice, to mate and lay their egg masses.
On the Raritan River in Donaldson Park, below red shale cliffs in New Brunswick, male hooded mergansers have been strutting their showy headdresses and courting females for weeks, all in the hopes that one female will be suitably impressed and allow the male to follow her to her secretive nesting territory in New Jersey’s Great Swamp or Wallkill National Wildlife Refuge.
From public walkways along the Shark River in Belmar, you can spy the courtship rituals of perhaps a dozen species of ducks. In most species, female ducks select their mates on their wintering grounds, and the males follow female partners back to the place where she hatched – possibly as far away as prairie pothole ponds in Saskatchewan!
How is everything timed so well? How do these creatures “know” that spring is on the way? As far as we know, their ancestors didn’t build astronomical observatories like Stonehenge or Chichen-Itza, or take physics in high school!
“It is all controlled by hormones that are released in proportion to day length,” explains Emile. “In birds, it is the pineal gland that is regulated in part by the amount of light striking the retina. As day length increases, glandular hormonal secretions trigger the onset of physiological changes associated with breeding.”
For backyard cardinals and virtually all migratory birds, carrying extra weight hurts, since survival is linked to rapid flight. Bird ovaries and testes shrink to almost nothing after breeding finishes in summer. Without their sex hormones, birds nearly stop singing during the winter.
After the winter solstice, light strikes their retinas a little longer each day, and their pineal glands respond. The birds’ ovaries and testes regrow. When the male cardinal once again produces a threshold level of testosterone, he flies to the top of your oak tree and bursts into song in mid-February. It doesn’t matter if a blizzard has just ended, because he must proclaim his territory as soon as the wind dies down!
Meanwhile, the females grow their ovaries and pay attention once again, to the brilliant red birds singing incessantly from cold, breezy, snowy perches.
Even though it’s still winter, keep your eyes and ears open for the early signs of spring!
POSTSGo for a walk and feel better!