The Smell of Bacteria Warfare
Even before the flowers bloom, the scent of spring fills the air.
Beneath our feet, countless microbes called Streptomyces release chemicals as they awaken and warm up this season. “One of these chemicals is geosmin, which is responsible for the earthy smell of the soil in the spring,” said Susan Perkins, a microbiologist at the American Museum of Natural History.
Streptomyces bacteria spew geosmin as a weapon against other bacteria in the soil where they live. But to us, that chemical produces a distinct smell known as petrichor, which we recognize as the earthy scent following a rainstorm.
“If you had a colony of Streptomyces in a petri dish and you opened the lid, you’d swear you had your nose in a flower pot,” Dr. Perkins said.
The Return of the Gray Whales
Gray whales undertake a mammoth adventure in the spring: the return part of their 10,000-mile, round-trip migration.
Their journey from the Arctic to Baja California, Mexico, and back is the longest of any mammal on the planet, said Ken Peterson of the Monterey Bay Aquarium in California. This time of year the whales leave the warm waters of Mexico with their newborn calves and swim up the West Coast until they reach feeding grounds in the Bering Sea.
“Seeing the gray whales heading north is a great indicator that we are heading into spring,” Mr. Peterson said.
The mothers fast throughout the trip, but the babies consume what is estimated at more than 50 gallons of milk a day. To keep their calves safe from hungry orcas, the mothers hug the shoreline near kelp forests, which offer marine researchers and people along the beach the opportunity to see the leviathans lunging through the water.
Inchworms in the Trees
“It’s definitely spring when I go out to sample insects from the trees and these caterpillars fall on my head,” said Emily Meineke, an entomologist at North Carolina State University. She’s referring to cankerworms, or inchworms, which hatch in early spring and dangle from nearly invisible webs attached to trees.
The tiny inchworm can cause big problems when it greets the East Coast in the spring. When the hungry caterpillars are not controlled, they can damage an area’s trees. Charlotte, N.C., has struggled with such outbreaks for at least two decades, Ms. Meineke said.
“They are targeting those young, delicious leaves,” she said. “The tree needs those to photosynthesize in the springtime.”
After the inchworms have eaten all of the leaves on a tree, they use their webs to swing to the next one like tiny Tarzans. And when they’ve had their fill, the inchworms drop to the ground from their threads and spin their cocoons.
Playtime for Fox Pups
Baby foxes frolic outside their dens when spring arrives.
For Roland Kays, a wildlife biologist at North Carolina State University, watching the pups emerge from their holes is a sign that the season has changed. Last year he set a camera above a den in a forest near a suburban neighborhood in Raleigh, N.C., in hopes of catching the red foxes’ first steps.
“When the parents start bringing the prey to the hole,” he said, “and then the puppies eventually come out and play and suckle at the entrance, then I know it’s spring.”
At first the pups stay in their den nestled next to their warm mother. The narrow hole where they live provides protection from hungry coyotes.
“Eventually the pups get big enough to venture out to see the real world,” Dr. Kays said. “It’s exciting to capture that on camera.”
The Season’s Bluest Color
We don’t see much of American robins until springtime, when they’re making babies in our yards or nesting in branches, bushes, awnings, gutters and eaves.
The American robin nests early in the year and typically lays a clutch of four eggs, two to four times each breeding season, which ranges from spring to early summer. After an incubation period of 12 to 14 days, the little birdies hatch, naked, blind and helpless. In five days, their bulging eyes will open, and down feathers will fluff up the little nestlings.
Within two weeks, the baby birds will leave the nest, unable to fly for another 10 days or so. If you ever see a baby robin hopping around its nest, leave it – its parents are watching it learn. In fact, the parents will continue to incubate, feed and protect their young for up to four weeks as they learn to fly and take care of themselves. After that, the young robins are on their own.
The animated GIF above comes from a video originally shot in March 2012 in the backyard of Rebecca Petty, now a state representative, in Rogers, Ark..
“The mother was pretty mad at me during the eight minutes of filming, but all the babies survived and flew away four weeks later,” Ms. Petty wrote on her YouTube page. You can watch this robin and its siblings develop day by day on Ms. Petty’s Facebook page.
– JoAnna Klein
The Changing View From Space
For Woody Turner, a program scientist at NASA, it’s the scenes from above that most vividly show the changing seasons.
“Satellite imagers that see the same point on Earth every day are ideal for tracking the spring ‘green-up’ and fall ‘brown-down’ as they move like waves across the country,” he said.
Starting a second into this video, you see the green plants begin to engulf the land and the teal phytoplankton bloom in the ocean across the Northern Hemisphere, only to recede about four seconds in when fall begins.
A Song-Filled Greeting
A song and a show welcome bird-watchers to spring.
The clear whistle of a white-throated sparrow and the raspy trill of a red-winged blackbird form a spring greeting in New York City, as do the yellow plumage of the pine warbler and the dark feathers of the rusty blackbird.
“We have a succession of bird species that slowly show up in the air,” said Paul Sweet, an ornithologist with the American Museum of Natural History.
Mr. Sweet leads nature walks in Central Park. “Rusty blackbird, Eastern phoebe and red-winged blackbirds are some of the first migrants,” he said.
The white-throated sparrow spends its winters in New York City, but only starts singing in late February or early March. “When they start singing, it’s a good sign that things are starting to change,” Mr. Sweet said.
Blossoming on Cue
Gardens that were gray and brown a few weeks ago are sprouting splotches of pink, yellow and purple. Gardeners who start to see blossoms may know that spring is here. But how do the flowers figure out that it is time to bloom?
Barbara Ambrose, a plant scientist at the New York Botanical Garden, said plants rely partially on environmental cues like temperature and light quality. Another signal, the length of the day, is also very important.
Plants, she said, can sense day length because they have circadian clocks, as people do. In the spring, plants can tell the days are growing longer by measuring how long night lasts, she said. They do this with their leaves, which are photoreceptors that react to sunshine.
“All of those environmental and internal signals feed into the same pathway, and that’s where you get this fine-tuning of flowering time,” Dr. Ambrose said.