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Spring Sunlight

Dave Anderson

Daylight floods a rural NH valley. A rooster crows in the village. The morning songbird chorus features mourning doves, red-wing blackbirds, a cardinal. The symphony will soon swell with grouse drumming, wood thrush flutes and a crescendo of warbler songs.

Strong sunlight of lengthening days is the catalyst that controls circadian rhythms influencing production of hormones - in birds, wild mammals and people.

Spring sunlight - not temperature - influences production of melatonin that works to synchronize ALL biological clocks. Melatonin production is inhibited by light and permitted by darkness.

The more sunlight / less melatonin connection drives biological functions of reproductive behavior, coat growth and seasonal camouflage coloring. .

Breeders with short gestation periods mate during longer daylight hours of late winter and early spring. Increasing melatonin during longer nights of late summer represses breeding. April features a rodent baby boom - prey species like mice and squirrels which fuel a corresponding boom of forest predators: weasels, canines, felines.

Breeding in animals with long gestation periods - moose and deer - is stimulated in autumn by increased melatonin production

It's fascinating to note effects of hormone chemistry and vestigial instinct in humans - particularly this spring after protracted months of bitter cold and snow! People respond positively to shorter nights. We're friendlier; more upbeat and energetic with sudden impulses to exercise or start spring cleaning. We make mental lists of chores inconceivable in January or visit garden centers and home improvement aisles. Winter lethargy is cast-off. We break dormancy. 

The return of sun to northern latitudes is the underlying agent of spring transformations.

Go outside and get some!

Naturalist Dave Anderson is Senior Director of Education for The Society for the Protection of New Hampshire Forests, where he has worked for over 30 years. He is responsible for the design and delivery of conservation-related outreach education programs including field trips, tours and presentations to Forest Society members, conservation partners, and the general public.

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