Field Almanac: A Month-by-Month Nature Calendar

Nature keeps a loose schedule, and once you learn it the year gets more interesting. Wood frogs start quacking from flooded woods on the first mild, rainy nights of late winter. Brook trout color up and spawn as the water cools in fall. Warblers stream north just as the oaks leaf out and the caterpillars they feed on hatch. This almanac is our month-by-month calendar of what to look and listen for, written mostly for the eastern and central United States, with nods to the Pacific Northwest, the Rockies, the Plains and the Southwest where the timing or the cast of characters is different.

Read every entry as a window, not an appointment. Spring travels north and uphill, and fall comes back down, so the same event can arrive weeks apart in a valley town and on the ridge above it, or in Georgia and in Maine. A warm spell, a late frost or a dry summer can push things earlier or later in any given year. Keep a simple notebook of first sightings and before long you'll have a calendar for your own patch that's better than ours.

For river levels, air quality and other live conditions, see our guide to public maps and data tools.

January

Great horned owls on the nest

Great horned owls are among the earliest nesting birds in North America. Pairs hoot back and forth at dusk through early winter, the female's voice noticeably higher than the male's, and many are already sitting on eggs by late January or February, often in an old hawk or crow nest. Listen on calm, cold evenings at the edge of the woods. If snow piles up on a sitting owl, she simply stays put.

Eagles and ducks at open water

When lakes and slow rivers freeze, birds crowd onto whatever water stays open: below dams, at warm-water outflows, at springs and on fast riffles. Bald eagles gather where fish are easy to catch, sometimes by the dozen along one stretch of a big river like the Mississippi. Look too for diving ducks such as common goldeneyes, buffleheads and mergansers, bobbing up and vanishing in the current. A pair of binoculars and a sheltered spot on shore are all you need.

Reading tracks in fresh snow

A morning after light snow is the best field guide of the year. A red fox leaves a nearly straight line of prints, each hind foot landing neatly in the front track. Cottontails bound, leaving two large hind prints ahead of two small front ones. Deer leave split hearts. Tiny tunnels and breathing holes mark voles living under the snow, where the ground stays close to freezing even on bitter nights. Follow a trail backward to see where an animal has been.

Winter stoneflies on the snow

On mild winter afternoons, look closely at the snow along a clean, rocky stream and you may see small dark insects crawling across it. These are winter stoneflies, which leave the stream as adults in the coldest months, perhaps because fewer predators are about, and walk or flutter along the banks to find mates. Their nymphs need cold, well-oxygenated water, so finding them is a quiet sign that the stream is in decent shape.

February

Skunk cabbage melts its way up

In wet woods and seeps from the Great Lakes to New England and down the Appalachians, skunk cabbage is often the first plant to flower. Its mottled purple hood pushes up through frozen mud and even snow, helped by the plant's ability to generate its own heat and stay noticeably warmer than the air around it. A faint carrion smell draws early flies and beetles to pollinate it. The big cabbage-like leaves come later, once the flowers are done.

Sap runs in the sugarbush

Maple sap flows best when nights drop below freezing and days climb above it, and that seesaw is common in late winter across New England, the Great Lakes states and the higher parts of Appalachia. Sugar maples carry the sweetest sap, though red maples, birches and even black walnut can be tapped. It takes around forty gallons of sugar maple sap to boil down to a gallon of syrup, which is why sugarhouses steam for days on end.

Red-winged blackbirds stake their claims

Before the marsh thaws, male red-winged blackbirds return and start claiming territories, flaring their red-and-yellow shoulder patches from the tops of last year's cattails. Their gurgling "conk-la-ree" is one of the surest early signs of spring across much of the country. The streaky brown females arrive a few weeks later. Common grackles and killdeer often turn up around the same time, along with loose flocks of robins working the first thawed lawns.

Birdsong picks up with the light

Lengthening days, more than warmth, are what set many resident birds singing again. Northern cardinals start whistling from treetops on bright February mornings, tufted titmice repeat "peter-peter-peter", and black-capped chickadees sing their clear two-note "fee-bee" more often. Carolina wrens, startlingly loud for their size, sing nearly year-round in the South and the Ohio Valley. Learn these few songs now, before migrants arrive and the morning chorus gets crowded.

March

Big Night at the vernal pools

On the first rainy nights when the air stays mild, spotted salamanders and wood frogs leave the forest floor and walk, sometimes in large numbers, to temporary woodland pools, often the same ones where they hatched. Wood frogs sound like distant ducks; spring peepers add a chorus of high, sleigh-bell peeps. Because the pools dry up by summer, they hold no fish to eat the eggs. Drive slowly on wet nights near wetlands, or pull over and listen.

Woodcock dance at dusk

In overgrown fields beside young woods, the American woodcock puts on one of the odder spectacles of early spring. At dusk the male gives a nasal "peent" from the ground, then spirals high into the sky with his wings twittering and tumbles back down with liquid chirps, landing close to where he started. The display begins in late winter in the South and spreads north into April. Stand still at the field edge as the light fades.

Cranes on the Platte

Each March, hundreds of thousands of sandhill cranes gather on the shallow, braided channels of the Platte River in central Nebraska, resting on sandbars at night and feeding in nearby fields by day before continuing north. At dawn and dusk the sky fills with their rolling, rattling calls, a sound you hear long before you see the birds. Smaller staging areas dot the Midwest. For those of us farther east, it's worth the trip at least once.

Cold water, high water

Snowmelt and spring rain push many rivers to their highest levels of the year, and the water stays cold even when a sunny afternoon feels like May. That combination catches paddlers off guard: a sudden plunge into cold water can cause gasping and a loss of muscle control within minutes. Dress for the water temperature, not the air, check the stream gauge before you go, and scout rapids that may have changed since last season.

April

Spring ephemerals on the forest floor

Before the trees leaf out, a burst of wildflowers makes use of the sunlight reaching the forest floor: bloodroot, hepatica, spring beauty, trout lily, Dutchman's breeches, trilliums and, in river floodplains, sheets of Virginia bluebells. Most bloom and set seed within a few weeks, then die back to roots and bulbs until next year. Ants carry off the seeds of trilliums and bloodroot for the fatty tips attached to them, planting new colonies in the process.

The first warblers return to streams

The Louisiana waterthrush, a brown, streaky warbler that bobs its tail like a sandpiper, is one of the first warblers back each spring. It nests in the banks of clear, forested streams and feeds on the aquatic insects living there, so its ringing song over a rushing creek usually means the water is in good shape. Listen in April along rocky streams in the East. Black-and-white warblers and blue-gray gnatcatchers aren't far behind.

Morels, carefully

Morel mushrooms push up as the soil warms in spring, often around dying elms and ash, in old apple orchards and near tulip trees. Hunters guard their spots closely. If you go, be certain of your identification: a true morel is hollow from tip to base when sliced lengthwise, while toxic false morels look wrinkled or brain-like and are stuffed with cottony tissue inside. Cook morels well, and when in doubt, leave the mushroom in the ground.

Early mayfly hatches

On trout streams in the Northeast and the Appalachians, April brings the first good mayfly hatches of the year, with names like quill gordon and Hendrickson that anglers have used for generations. On warm afternoons you may see small, sailboat-winged insects drifting on the surface and trout rising to take them. Mayflies, stoneflies and caddisflies together are a classic sign of clean water, which is why volunteer stream monitors count them.

May

Peak songbird migration

Warblers, vireos, orioles, tanagers and thrushes move through in waves in May, timed to the flush of caterpillars on newly opened oak leaves. Mornings after a night of south winds can be spectacular. Along the Gulf Coast the main push comes earlier, in April, and birds exhausted from crossing the Gulf sometimes drop into coastal woods in large numbers when they meet storms. In the Great Lakes region, shoreline parks and points concentrate migrants before they cross open water.

Turtles on the move

Late spring is nesting season for many turtles, and females travel overland, sometimes far from water, to dig nests in sandy or gravelly soil. Painted turtles, snapping turtles and box turtles all end up crossing roads. If you can stop safely, move a turtle across in the direction it was heading, or it will simply try again. Never lift a snapping turtle by the tail; slide it onto a car floor mat and drag it across.

Fawns left alone on purpose

White-tailed deer give birth from late spring into early summer, and a doe leaves her spotted fawn hidden in tall grass or brush for hours at a time while she feeds elsewhere, coming back to nurse. The fawn's spots and stillness are its protection. A fawn lying quietly by itself almost always has a mother nearby, waiting for you to leave. Look, take a photo from a distance, and walk on without touching it.

Snowmelt peaks in the Rockies

In the Rockies and other western mountains, rivers fed by melting snow often run highest in late spring and early summer rather than in March or April. The water is bitterly cold, fast and full of debris. Many snowmelt streams also rise through the afternoon and evening as the day's melt reaches them, so a ford that was easy at dawn can be dangerous by late afternoon. Plan stream crossings for the morning.

June

Fireflies light up the fields

On warm, still June evenings, fireflies rise from lawns and meadows, each species flashing its own pattern. The common eastern firefly draws a short upward J of light as it climbs. In parts of the Great Smoky Mountains, one species flashes in near-unison for a couple of weeks around early June. Firefly larvae spend a year or more in damp soil and leaf litter eating snails and slugs, so leaf piles and darker yards help.

Laurel and rhododendron in bloom

Mountain laurel opens its crimped pink-and-white cups in late spring along dry ridges and rocky slopes in the East. In June the purple Catawba rhododendron blooms on the high balds of the southern Appalachians, and the larger, paler great rhododendron follows into early summer in shaded ravines. Look closely at a laurel flower: its stamens are bent back under tension and spring forward to dust visiting bees with pollen.

Monarchs on the milkweed

Common milkweed blooms in early summer, with heavy, sweet-smelling clusters of dusty-pink flowers. Turn over a few leaves and you may find a single tiny white monarch egg or a caterpillar striped in yellow, black and white. Monarch caterpillars eat only milkweeds, which is why milkweed patches in roadsides, pastures and gardens matter. Plenty of other insects use the plant too, including red milkweed beetles and orange-and-black milkweed bugs.

Bats at dusk

Early summer is when many bats have their pups, often in maternity colonies tucked into barns, attics, bridges or loose tree bark. Watch over a pond or near a streetlight at dusk to see them hunting insects in sharp, erratic swoops. Several cave-hibernating species in the East have declined badly from white-nose syndrome, a fungal disease, so a healthy colony in an outbuilding is worth leaving alone until the young can fly.

July

Afternoon storms and flash floods

Summer thunderstorms build over hot afternoons and can drop heavy rain on one small watershed while the next valley stays dry. In steep terrain, small streams can rise by feet in a matter of minutes. In the desert Southwest, the summer monsoon brings the same danger to dry washes and slot canyons, often from storms miles away. Watch the sky, know your route to higher ground, and read up on why steep terrain floods so fast.

Ozone afternoons

On hot, sunny, stagnant days, ground-level ozone forms as sunlight acts on pollution from tailpipes, power plants and other sources. Levels usually climb through late morning, peak in the afternoon and fall after sunset. That daily pattern means early morning is often the better time for a run or yard work on a bad ozone day. The forecasts on AirNow show which days to watch, and what each color means.

Dog-day cicadas

Every summer, annual cicadas spend the hottest weeks droning from the treetops. Unlike periodical cicadas, which emerge in vast broods years apart, these green-and-black insects show up every year in modest numbers. Males make the rising, buzzing whine with drum-like plates on their bodies; females lay eggs in twigs. Look for their empty, split nymph skins clinging to tree bark and fence posts. At night, katydids and crickets take over the chorus.

Algae blooms in warm water

Warm, still, nutrient-rich water can grow blooms of cyanobacteria, often called blue-green algae, in lakes, ponds and slow rivers. A harmful bloom can look like pea soup, spilled paint or green scum along the shore, and some produce toxins that can sicken people and are especially dangerous to dogs. If the water looks or smells off, stay out and keep pets out, and check for posted advisories before swimming.

August

Low water, cool refuges

By late summer many streams are at their lowest, fed only by groundwater seeping in from springs and soil. The water warms in the sun, and cold-water fish such as trout crowd into spring-fed pools, shaded runs and the mouths of cool tributaries. Many anglers leave trout alone during heat waves, since a fish played in warm water may not recover. Low water is also a good time to turn small rocks and see stream insects, as long as you put the rocks back.

Hummingbirds fuel up

Ruby-throated hummingbirds get busy in late summer as they fatten up for migration, some of them crossing the Gulf of Mexico in a single flight. Look for them working patches of orange jewelweed along creeks and the scarlet spikes of cardinal flower in wet ground. Adult males leave first, so the birds at feeders from mid-August onward are mostly females and young. Keep feeders clean and filled into fall for the late travelers.

Blame the ragweed, not the goldenrod

Late summer is hay fever season, and goldenrod, blooming bright yellow in every field, often takes the blame. The usual culprit is ragweed, a plain green plant that releases huge amounts of light, wind-borne pollen at the same time. Goldenrod pollen is heavy and sticky, carried by bees, wasps and beetles rather than the wind. It's also one of the most valuable late-season foods for pollinators, so leave it standing.

Shorebirds heading south

Fall migration starts in midsummer for shorebirds. Adult sandpipers and plovers that nested in the Arctic begin moving south in July, and August brings steady traffic across mudflats, sandbars, flooded fields and the exposed edges of reservoirs drawn down by dry weather. Juveniles follow later, making the trip on their own. Bring binoculars and patience: least sandpipers, semipalmated plovers and yellowlegs are good first birds to learn.

September

Monarchs drift south

Eastern monarchs born in late summer don't breed right away; instead they fly toward the mountain forests of central Mexico to spend the winter, while most western monarchs head for the California coast. Along the way they feed heavily on goldenrod, asters and other late flowers, and they gather in overnight roosts that can turn branches orange, especially on peninsulas along the Great Lakes. Let late-blooming flowers stand to help them along.

Migrants on the weather radar

Most songbirds migrate at night, and on clear fall evenings with north winds you can watch them leave on weather radar. Shortly after sunset, rings of returns bloom outward from radar sites across the map, made not by rain but by great numbers of birds taking off at once. Pull up a National Weather Service radar loop that evening, then step outside and listen for the thin call notes of thrushes and warblers passing overhead.

Hellbenders guard their nests

In late summer and early fall, eastern hellbenders, the giant salamanders of clear, rocky streams, breed under large flat rocks. The male excavates a chamber, the female lays strings of eggs, and the male guards them, often into winter. Hellbenders breathe largely through their wrinkled skin and need cold, clean, well-oxygenated water. If you wade in a hellbender stream, leave the big rocks where they are; lifting one can wreck a nest.

First color in the high country

Fall color starts at the top. Aspen groves in the Rockies turn gold through September, often in sweeping patches, since a whole stand can be a single interconnected clone. In the East, the first reds show on high ridges and in cold northern bogs, where red maple, blackgum, sumac and Virginia creeper usually lead. Cool nights and sunny days bring out the brightest reds. Lower valleys may stay fully green for weeks.

October

Brook trout spawn in the headwaters

As the water cools in fall, brook trout move into small, cold headwater streams to spawn. Males turn vivid, with orange bellies and white-edged fins, and females fan out shallow nests called redds in clean gravel, often where groundwater wells up through the streambed. The eggs incubate through winter and hatch in late winter or early spring. If you're wading a mountain stream now, step around patches of bright, freshly cleaned gravel.

Color moves downslope

Peak color slides down the mountains through October, from bare upper ridges to blazing middle slopes to still-green valleys. Shortening days trigger the change, but weather decides the show: a run of sunny days and cool, frost-free nights brings out the deepest reds, while drought or an early hard freeze can dull it. For the best of it, find the elevation where color is peaking that week, then follow it down.

Hawks ride the ridges

Fall winds deflect upward when they hit long ridges, and migrating hawks use that lift to glide for miles with barely a wingbeat. Sharp-shinned and Cooper's hawks, red-tailed hawks, harriers and falcons all pass through in October, with golden eagles showing up along eastern ridges toward the end of the month and into November. Hawk watch sites on ridgetops and Great Lakes shorelines are good places to learn them, and experienced counters are often happy to help.

Woolly bears on the road

The fuzzy black-and-rust woolly bear caterpillars crossing roads and trails in October are looking for a sheltered spot under leaves or logs to spend the winter. Folklore says a wide rusty band predicts a mild winter, but the bands reflect the caterpillar's age and the conditions it grew up in, not the weather to come. Woolly bears can survive being frozen, then thaw in spring to spin a cocoon and become Isabella tiger moths.

November

Deer on the move

November is the peak of the white-tailed deer breeding season, the rut, across much of the country. Bucks chase does and travel widely, paying far less attention to roads than usual, and deer are most active around dawn and dusk, the same hours as the commute. Slow down on wooded roads, and when one deer crosses, expect others to follow. If one steps out in front of you, brake firmly rather than swerving.

Salmon return to Northwest streams

In the Pacific Northwest, autumn rains bring coho and chum salmon up coastal rivers and into small streams to spawn. After years at sea they fight upstream, dig redds in the gravel, spawn and die. Their bodies feed bears, eagles and gulls, and nutrients carried from the ocean end up in streamside trees. Watch quietly from bridges or banks, and keep dogs away from the carcasses: raw salmon can carry a disease that is often fatal to dogs.

Leave the leaves

Fallen leaves are winter quarters for a surprising amount of wildlife. Firefly larvae, many moth and butterfly caterpillars and cocoons, beetles and spiders all ride out the cold in leaf litter, and they in turn feed the wrens, towhees and thrushes that scratch through it. Rather than bagging leaves, rake them off the lawn into garden beds and under shrubs, or mow over them to chop them fine where they fall. More ideas are in our green tips.

Wear orange in hunting season

Fall is hunting season in much of the country, and many public forests and wildlife lands stay open to hikers at the same time. Wear a blaze-orange hat or vest when you head into the woods, put an orange collar or vest on your dog, and stay on marked trails. Look up season dates for wherever you're going before you leave home; they vary by state, by species and sometimes by type of weapon.

December

Chickadees against the cold

A black-capped chickadee weighs about as much as two quarters, yet it gets through northern winters. Chickadees spend fall hiding a great many seeds in bark crevices and remember where many of them are. On cold nights they fluff their feathers, shiver to make heat and let their body temperature drop by several degrees to save energy, a controlled kind of torpor. By dawn they're back at the feeder, calling their own name.

Winter bird counts

Around the winter holidays, birding groups across the country take part in a counting tradition that goes back more than a century: volunteers spread out across a set circle and tally every bird they see or hear in a single day. Beginners are usually welcome and paired with experienced counters, and people with feeders can often contribute from home. It's a good excuse to spend a cold day outside with people who know their birds.

Winter finch irruptions

In some winters, northern finches pour south into the lower 48: pine siskins, common redpolls, evening grosbeaks, purple finches, red and white-winged crossbills, often with red-breasted nuthatches in tow. These irruptions follow poor cone, seed and berry crops in the boreal forest, so they come irregularly, sometimes several years apart. Watch feeders stocked with black-oil sunflower and nyjer seed, and check spruce and hemlock stands for crossbills working the cones.

Ice that grows from the bottom

On frigid nights, fast streams too turbulent to freeze over can still make ice. Tiny needle-like crystals called frazil form in the chilled water and stick to rocks on the bed as spongy anchor ice, which sometimes lifts free on a sunny morning and floats away with pebbles still attached. Shelf ice builds out from the banks. All of it is unpredictable, so never walk on ice over moving water.