Last weekend, we launched Daylight Saving Time, when we turned our clocks one hour forward to take advantage of more light during our waking hours.

But clocks don’t make the days shorter or longer – the tilt of the Earth in relationship to the sun does that. As the Earth revolves around the sun throughout the year, the relationship between the Earth’s tilt and the sun shifts, giving us seasons. During winter, the northern latitudes are tilted away from the sun, creating shorter days. However, since the winter solstice in December, our region has gained an additional one to four minutes of light each day. The increase in light is incremental, but it makes a noticeable and important difference.

The change of light is extremely important to plants and animals. Many aspects of their life cycles are triggered by changing light or photoperiod. The relationship between the photoperiod and the emergence of leaves and flowers, migration, mating, and molting of fur and feathers has evolved over time because the changing light is a more reliable indicator of seasons than varying temperatures. For example, in the past 10 years, temperatures recorded at the Concord Municipal Airport on March 8 have varied greatly. The lows ranged from -0.9°F to 32°F and the highs for that day ranged between 34°F to 60°F. In contrast during that same time period, the daylight on March 10 is consistently 11 hours and 38 to 40 minutes.

If plants responded only to temperature, a few 60° days in March could fool them into opening their buds. If those warm days were followed by below-freezing temperatures, the buds would be killed. This happens occasionally. However, bud and flower growth are primarily activated by a photoreceptor protein in the plant which detects the length of the night. As nights get shorter, these proteins prompt growth of the leaf and flower tissues in the buds.

Once the growth has begun, temperature may impact the rate at which buds open. That is why some years there may be a slightly earlier or later flush of apple blossoms or lilac flowers, but the variation from year to year is usually only by a few days rather than weeks, due to the photoperiod.

Warming temperatures rather than photoperiod is a more significant trigger for change in some insects. Emerging from winter dormancy based on temperature puts them out of synch with plants that are blossoming based on day length. This shift is one of many impacts of a changing climate.

The shifting length of night and day initiates the color change of snowshoe hare and weasel fur. At this time of year, when the ground may still be white with snow, brown fur will begin to replace the white pelt which has helped these animals blend in with their surroundings and keep warm in the winter. The molt of the hare takes about three months to complete, so starting in March when the days are getting longer keeps them on schedule to be completely brown in May.

These physical adaptations are not the only changes that we can observe as days lengthen. Step outside and listen. You may hear the sweet clear whistle of the black-capped chickadee which started singing its spring song in February as the days became noticeably longer. “Spring’s here” is one paraphrase of its tune. Some people confuse the call with an eastern phoebe because they hear the song as “fee-bee.” We won’t hear the phoebe’s raspier and emphatic “FEE-BEE” for several more weeks when it returns from its southern winter home.

The behavior of woodpeckers has also changed. Their spring sound is a percussive drumming, made by rapidly tapping their beak against a hollow tree or other resonating structure. All these sounds function as territorial indicators and/or mate attraction because with spring also comes the season of reproduction.

Light stimulates the pituitary gland in animals to release hormones that affect reproduction. Seasonal migration, mating calls, feather color change such as the yellowing of goldfinches, gathering of nesting materials, are the physical and behavioral responses to shorter nights and longer days and are preparations for creating offspring.

So, while you enjoy the increased light and the promise of spring, pay attention to ways that our wild neighbors are also responding to longer days. There is a lot going on even if it still feels like winter!