by Diane Constable

We are quickly approaching March 20, the date of this year’s vernal equinox, also known as the first day of spring. It is the date upon which the amount of daylight equals the amount of darkness across the world. The sun rises true east, parallel to the equator, and sets true west. Due to the orbit and the tilt of the earth, the amount of daylight and warmer temperatures will increase in the Northern Hemisphere, while these same will decrease in the Southern Hemisphere. The word “vernal” comes from the Latin word for spring (“ver”), and “equinox” means equal night. 

Historically many nationalities and religions celebrate this change of season as the beginning of a new year, complete with celebrations and festivals to acknowledge the return of the sun, the beginning of the growing season, and a time of renewal. The Druid structure of Stonehenge in England is an example of an ancient structure built to celebrate the vernal equinox, as is the Mayan pyramid found in Yucatan, Mexico. The Chinese believed that if you were to balance a raw egg on its end on the day of the spring equinox, it would be a sign that all of nature was in harmony.

But there is more to this annual astrological occurrence. As the minutes of daylight increase, ecological changes are triggered. Softly blowing south winds bring the early smells associated with spring, and with them, you can watch for coming changes. The landscape is in transition, from white snow to brown mud, then to green grasses and flowering plants. Water levels change with the melting snow; soil begins to defrost and release its nutrients. Vernal ponds form, which support many early plants, migrating waterfowl, and amphibians. Later, as summer approaches, the ponds will dry up awaiting the next vernal equinox.

The increasing sunlight following the vernal equinox triggers proteins in plants—called phytochromes—that activate plants to begin growing. We see this in swelling buds on trees and shrubs and some plant starting to send out shoots and leaves, which will feed the awakening birds, insects, and mammals.

Dormant insects react to the increasing sun and warmth due to photoreceptors in their brains. They become more active and search for food and mates. Monarch butterflies wintering in Mexico are triggered to revive from a semi-stupor to begin their journey north to Michigan and other northern states.

Birds, too, are chemically affected by the increased daylight that results in hormonal changes. Migrant birds begin their pilgrimage north to their breeding grounds. The male feathering begins to change to its breeding plumage, and it’s singing becomes more frequent and more complicated as it tries to attract mates. Females choose mates and start nesting behavior, all triggered by the vernal equinox.

Mammals also sense the increase of sunlight through retinal light-sensitive cells in the eyes, called ganglion cells, which are not involved in vision. Seasonal changes in mammals also include coat density and color changes; hibernating animals begin to awaken and search out food and mates, while moving toward spring feeding grounds.

In today’s modern world, the vernal equinox is also a time for us human mammals to celebrate and enjoy spring by increasing our outdoor activities, planting crops and gardens, and of course playing baseball!