Nature Notes: Transitions
By Anna Foster
It may not feel like it outside this week, but last Sunday marked the Vernal Equinox, or the first official day of spring! Of course, spring has many faces in Door County. From snowstorms, like the dump of wet slush we had last week, to sunny, 45-degree days, watching the calendar isn’t exactly a reliable source for determining when to switch out your winter jacket for your spring fleece. If you’re anything like me, you get too eager during the first “false spring” that occurs, and you spend three weeks shivering while you wait for the next warm spell.
Whatever the weather may be, the Vernal (Spring) Equinox marks a significant shift for the entire planet. On the Vernal Equinox, the sun is directly above the earth’s equator. This marks the change from shorter days and longer nights to longer days and shorter nights. Why? Because the earth is at the point in its orbit where the northern hemisphere tilts towards the sun. The days will continue to grow longer until the Summer Solstice in late June. Although it might not seem like it here in northeast Wisconsin, we’re on our way to warmer weather, and there are signs of spring all around us.
In the sanctuary, the first signs of spring appear in the swales. If you live by water, you’ve likely heard the chirps of Red-winged blackbirds coming from nearby trees or the tops of cattails. Their unmistakable “conk-la-ree” call is one of the first bird songs to return to the boreal forest. Another early arrival is the sandhill crane, whose strange trumpet-like calls can be heard starting in mid-March. Among other early spring migrators, Red-winged blackbirds and Sandhill cranes return to Door County to breed. In the sanctuary, Red-winged blackbirds nestle their nests between cattails and other sedges of the swales, while Sandhill cranes build their nests on the ground, using aquatic vegetation to make a mound for their nest.
Another sign of spring appears in the swales in late March, and if you’re walking the trails towards dusk, you won’t be able to miss it. Earlier this month, I was sitting quietly in a grove of trees with a sixth-grade class I was leading at Gibraltar. As we listened to the snow melt, we were startled by a croaking noise coming from the swamp next to us. I gathered all the students a few moments later and had them listen to a recording on my phone of a Wood frog. We all agreed that the sound we observed must have been two wood frogs calling in the nearby swamp. The first week in March is very early for a Wood frog, and unfortunately, the frogs we heard were unlikely to survive the following freezes. However, a few weeks of weather can transform a landscape.
At the end of March when the snow melts and the forests begin to thaw, Wood frogs start to emerge from their frozen state in forest leaf litter. As soon as it’s warm enough for their bodies to thaw, they make their way to vernal pools to feed and mate. The distinct duck-like croaks of a pond full of male wood frogs, who croak to attract their mate, can be deafening. Wood frogs are the first frogs to emerge from winter hibernation. Following the wood frog, Spring peepers, then Leopard frogs, and American toads. Tree frogs and Green frogs don’t come along until later in the spring.
Salamanders aren’t far behind Wood frogs, either. On the first rainy day above 40 degrees, some species of salamanders, like the Blue-spotted salamander, will emerge from hibernation and migrate to vernal pools, like Wood frogs. They’ll congregate in these temporary pools, mate, and then return to their solitary life in the forest. Unlike frogs, however, salamanders are mostly silent. If you’re driving home this spring after dark on a warm, wet evening, look out for salamanders crossing the road!
My favorite sign of spring usually returns right around the end of March, when Green Bay finally melts, and we start to get some 40–50-degree days. I’ve been scanning the sky for the last two weeks, wondering if I’ll catch a glimpse of a flock of White Pelicans gliding above me. Pelicans usually return at the end of March or early April, when there’s enough open water for them to populate small islands around the Door County Peninsula.
Pelicans started appearing on the peninsula in the 1970s. There are some records of them in Wisconsin before the mid-1800s, but they were not considered a species of breeding birds in the state until they established breeding grounds here about 20 years ago. There are currently around 4,000 breeding pairs in the Green Bay area.
White pelicans are unmistakable once you learn to spot them in the sky. They often flock together and ride heat thermals, or columns of rising hot air in the sky. The effect is like a dance; the flock will glide for minutes, back and forth, before drifting out of sight. White pelicans are mostly white, but they have a black strip on each wing that is only visible when they’re in flight. They’re very large in size, boasting an 8-foot wingspan and a large yellow bill. Look for them flying in flocks near the shoreline or out in the bay on a warm spring day.
Whether it’s sunny and 60 degrees, snowing, or raining, there are changes happening all around us this month. It may not feel like it, but we’re turning the corner to spring!