Timing is Everything

red maple flowers
A red maple flowers at Missisquoi National Wildlife Refuge in Vermont. (Photo: Ken Sturm/USFWS)

Seen or heard any of these signs of spring yet where you live?

  • A chorus of little frogs called spring peepers.
  • The flowering of red maples.
  • A bee or butterfly.

The timing of these and other much-anticipated natural events varies by region. It also changes from year to year with temperature and precipitation.

Scientists track that timing to detect long-term trends and impacts: which plants may thrive and which may struggle, which birds may miss their rendezvous with a food source, which species will be most susceptible to wildfire, and what land managers need to do — and when — in response. The study of that timing is called phenology.

“Keeping track of phenology — nature’s calendar — helps us be better stewards of your lands today and into the future,” says Lindsay Brady, with the U.S. Fish and Wildlife Service’s Inventory and Monitoring program.

Some national wildlife refuges are turbo-charging their data collection – and inviting citizens to help – on the USFWS Phenology Network, a joint project of the Service and the USA National Phenology Network.



polar bear vs Kodiak bears
Cottongrass covers a high-elevation wetland in white blooms at Canaan Valley National Wildlife Refuge in West Virginia. (Photo: Copyright Kent Mason)

Each of the participating refuges has its own reasons for taking part.

Valle de Oro National Wildlife Refuge in New Mexico wants to track restoration impacts and engage the community. Midway Atoll National Wildlife Refuge in the Pacific wants to find out the best time to treat a pest plant, verbesina, which inhibits bird nesting.

Canaan Valley National Wildlife Refuge, which supports plant life more common to Maine and Canada than the Allegheny Mountains where it’s located, wants to know: Are its cold-climate species, like cottongrass, doomed?

If temperatures are rising, as some data suggest, says wildlife biologist Dawn Washington, “we’re like sitting ducks out here.” The refuge needs to know, she says: “Is our restoration [of native red spruce, quaking aspen, speckled alder] all for nothing? Are we going to warm up and these species aren’t going to make it?”

Three years into the refuge’s participation in the USFWS Phenology Project, Washington says, “I hope we can see some long-term trends that would help us decide: Are we going to continue to plant these northern species? Or are we going to let nature take its course?”



river otters v beaver
A bee visits a flowering butterfly milkweed plant at Minnesota Valley National Wildlife Refuge. (Photo: Courtney Celley/USFWS)

Neal Smith National Wildlife Refuge in Iowa, a newcomer to the project, wants to help stop a pollinator’s worrisome decline.

“Some of the species we are looking at are monarchs and butterfly milkweed — the monarchs, because they’re in decline and we want to know if the timing of their migration is changing,” says wildlife biologist Karen Viste Sparkman. “The butterfly milkweed is one of their food sources as caterpillars, so we want to know what’s going on with their growth and seed production, and if they will continue to be available to monarchs.

“We’re also looking at burr oak trees. Besides being an irreplaceable part of oak savannas, burr oaks are important for a lot of migrating songbirds. They host a huge number of insects that provide food for songbirds.”



coyote v panther
There’s no missing the sticky monkeyflower in blossom at Don Edwards San Francisco Bay National Wildlife Refuge.  (Photo: Robyn Boothby)

Don Edwards San Francisco Bay National Wildlife Refuge, which saw its first signs of spring in February, picked its focus species — all natives to the area — for their ease of identification, distinct growth phases, and their visual interest.

These include the coast live oak, sticky monkeyflower (which usually blooms in March) and California buckeye.

“The California poppies are blooming now,” says the refuge's outdoor recreation planner Carmen Minch, “and the American avocets are pretty much in their full breeding plumage. Western redbud is still blooming.”



ferrets vs manatee

This chart compares the reported bloom of orange bush monkeyflower at Don Edwards San Francisco Bay Refuge from 2014 to 2017. (Image: USA National Phenology Network)

The more data points you have, the more easily you can plot and visually compare yearly trends.

Above, for example, a chart shows how the flowering dates for orange bush monkeyflower compare from 2014 to 2017 at Don Edwards San Francisco Bay Refuge.

Each line on the graph shows a time when an observer recorded if the plants were in flower. A gray line indicates that there was no flowering seen on any plants. An orange line indicates that at least one plant was in flower. 

This graph shows that for the years studied, 2017 had the earliest reported flowering, while 2014 had the latest. 2017 also had the longest duration in flowering. Over time, the frequency of observations has become more consistent, with more evenly spaced lines representing observations made throughout the year. 



fruit bat in top of photo vs bighorn sheep in bottom portion of photo
Catkins, or female flowers, adorn a quaking aspen in spring in Alaska. (Photo: Linda Kershaw/NatureWatch)

The thawing of permafrost and shrinking of sea ice has put Alaska on the front lines of climate concerns. Arctic National Wildlife Refuge – which conserves habitat for to polar bears, caribou and other distinctive wildlife – has a particular stake in tracking change.

Collecting phenological data in person is tough, though, in so large and remote a place with such inhospitable weather.

For now, refuge botanist Janet Jorgenson has found a work-around by collecting data in Fairbanks, Coldfoot and other sites around Alaska.

Jorgenson is monitoring species that are important forage for caribou, elk, beavers and birds including the diamondleaf willow (Salix planifolia) and quaking aspen (Populus tremuloides), pictured above.



fruit bat in top of photo vs bighorn sheep in bottom portion of photo
An animated map shows the spread of spring leaf-out across the country this year, as measured by the first-leaf index — the appearance of the first leaves on early-season shrubs. Blue areas indicate a relatively late spring; red indicates spring is early. (Image: USA-National Phenology Network)

What pattern did spring set this year in the nation as a whole?

Back in late January, the data showed: “The west is early, the east is late,” according to Erin Posthumus, USA National Phenology Network outreach coordinator and liaison to the Service. “In the Southwest and up to Seattle, spring leaf-out of early-season plants arrived between one and six weeks earlier than the 30-year average.”

Since then, spring leaf out has moved up the East Coast, arriving earlier than usual in the Ohio Valley, Virginia and parts of Mid-Atlantic states (late-season storms notwithstanding).    

At Patuxent Research Refuge in Maryland, volunteer Ken Lavish took advantage of record 75-degree temperatures on February 20 to enjoy a walk. “The spring peepers were out and they were loud!” he says. “I am sure you could hear them from your office.” 

The Status of Spring webpage shows spring’s arrival on refuges across the country.

A forecast page shows when to treat your trees for insect pests.

Here’s how you can help track nature’s life cycle by recording natural events where you live. Here’s how refuges can take part.




Compiled by Susan_Morse@fws.gov, March 28, 2018