Fourth of July marks the turning point of the natural year

Happy Fourth! As we celebrate our nation’s 250th birthday, it will be a jubilant red, white and blue day of fireworks, barbecues, parades and a big road race.

For nature lovers, Fourth of July also has another special significance: It’s used as a rule-of-thumb date to mark the turning point — the high noon — of the natural year.

Since summer’s first day on June 21, the days have been growing shorter as the Northern Hemisphere slowly starts tilting toward autumn. Sky observers say the Fourth of July is when the shortening of days becomes noticeably more rapid.

We still have a lot more of summer left, though. Notably, the “dog days of summer“ are upon us — said to be the hottest, muggiest part of the year. The dog days are the 40-day period spanning from July 3 to Aug. 11, placing the Fourth of July right at the start of this notorious stretch of summer.

While some folks believe dog days refers to dogs panting in the heat, the term’s true origins trace back to ancient Greeks and Romans, who linked dog days to the shiny Dog Star Sirius. Around July 3 every year, Sirius begins its daily rising and setting with the sun. The ancients believed that the bright star and the sun moving in concert across the daytime generated the sweltering heat, drought, sudden thunderstorms, lethargy and mad dogs during July and August.

There’s no scientific proof of that. Southerners, however, have their own dog day beliefs. Many folks believe, for instance, that snakes — even nonvenomous ones — are more aggressive in the dog day heat and will aggressively attack humans. There’s no truth to that, either — although the dog days period is prime egg-laying time for several Georgia snake species, including corn, rat, Eastern hognose and rainbow snakes.

With the commencement of dog days, the iconic sounds of summer are starting — the ceaseless droning and buzzing of dog day cicadas by day and katydids by night. Unlike periodical cicadas, dog day cicadas appear every year around this time. Males are famous for their loud, high-pitched, buzzing calls in the treetops to attract mates.

For us bird lovers, July 4th holds another cue — a rule-of-thumb date for when higher numbers of ruby-throated hummingbirds start returning to feeders. After a heavy showing in early spring at backyard feeders, the tiny birds seemed to disappear as they began nesting and developing a strong appetite for tiny insects and natural nectar instead of the sweet liquid from feeders. Now, they are coming back to feeders as the decreasing daylight triggers their powerful instinct to rapidly fatten up and gain energy for their arduous migration to winter grounds in Mexico and Central America.