Sky
Why you can see the moon in the daytime sky
The moon spends almost as much time up in daylight as at night, and on the right days it sits plainly in the blue sky.
What to notice outside around Sudbury in May
Each one says when to look, how to notice it, and where the facts come from.
Sky
Sky
Sundogs and sun halos: how ice crystals bend sunlight
Ice crystals high in the atmosphere can bend sunlight into a pale ring around the sun or bright patches on either side of it.
Sky
Crepuscular rays: sunbeams fanning out near sunrise and sunset
When broken clouds and haze meet a low sun, bright and dark bands can fan across the sky near sunrise or sunset.
Sky
How the sunset point moves along the horizon through the year
Where the sun sets on your skyline slides north through spring and south through autumn, fastest near the equinoxes and nearly still at each solstice.
Sky
The Big Dipper never sets from eastern Massachusetts
From eastern Massachusetts the Big Dipper is circumpolar, circling Polaris once a day, though the tip of its handle skims the horizon at its lowest.
Sky
Your own shadow by full moonlight
A clear full moon casts a sharp shadow. Moonlight is reflected sunlight, hundreds of thousands of times fainter than direct sun.
Sky
Northern lights on a strong geomagnetic storm night
On rare strong geomagnetic storm nights the northern lights may glow low in the north, and a phone camera can show color the eye misses.
Sky
The twinkle test: how to tell a planet from a star
Stars twinkle because they are single points of light; a bright point that shines steady is often a planet, a tiny disk instead.
Sky
The moon illusion: why the rising moon looks so big
A rising full moon looks huge but measures the same width as it does higher in the sky. Test it with your fingernail.
Sky
Earthshine: the faint glow on a crescent Moon's dark side
On a thin crescent Moon the dark part of the disk can glow faintly, lit by sunlight that bounced off Earth first.
Sky
How to spot satellites crossing the sky after dusk
Satellites, including the International Space Station, glide across the sky as steady points of light after sunset and before sunrise, lit by sunlight.
Sky
Sun pillars: a column of light above the low sun
A narrow shaft of light standing up from the sun at sunrise or sunset, made by glints from millions of nearly flat ice crystals drifting level.
Sky
Earth's shadow and the Belt of Venus after sunset
On a clear evening a dark blue-gray band rises low in the east after sunset. It is the shadow of the Earth, with the pink Belt of Venus above it.
Weather
Weather
Morning dew and the dew point: why grass is soaked without rain
When surfaces cool below the dew point, water vapor condenses into droplets on grass, cars and webs by morning.
Weather
How to find low pressure with your back to the wind
Stand with your back to a steady wind and the center of low pressure lies off to your left, a little ahead.
Weather
What a jet contrail says about the air up high
A short-lived contrail means relatively dry air high up; one that lingers and spreads means the air up there holds a lot of moisture.
Birds
Birds
Crow or raven: how to tell them apart by the tail
Crows and common ravens are both big black birds, and the tail settles it at a glance: a crow's opens like a fan, a raven's like a wedge.
Birds
Pileated woodpecker holes in dead trees
Pileated woodpeckers chisel large rectangular holes into dead trees, stumps and logs to reach carpenter ants, leaving big wood chips below.
Birds
Owl pellets and whitewash: signs of an owl roost
Owls cough up the fur and bones of prey as pellets, and under a roost tree they reuse, pellets and white droppings can pile up.
Birds
Carolina wren song: the tea-kettle bird that sings all year
A small rusty-brown wren with a white eyebrow that lives in Massachusetts all year and is one of the few birds that sings in every month.
Birds
White-breasted nuthatch: the bird that climbs down trees headfirst
The white-breasted nuthatch climbs down tree trunks headfirst and hangs under branches, which woodpeckers and brown creepers cannot do.
Birds
Downy or hairy woodpecker: how to tell them apart
The two look nearly identical. Compare the bill to the head: short and stubby on the downy, nearly as long as the head on the hairy.
Birds
Belted kingfishers rattle along rivers and ponds
A belted kingfisher announces itself with a dry rattle, hovers over water, and plunges headfirst for a fish. The female is the more colorful one.
Birds
Spotted sandpipers teeter along pond and river shores
The spotted sandpiper bobs the back half of its body as it walks the water's edge. In this species the female courts the males.
Birds
Green herons hide along shaded shores
The green heron is a small heron so good at hiding in cover that it often goes unseen until it flushes with a loud skeow.
Birds
Wood duck mothers lead ducklings through shoreline cover
Wood ducklings leap from a tree-hole nest a day after hatching and follow their mother to water, then hide in the shrubby edges of ponds and rivers.
Birds
Bank swallows nest in burrows in sandy riverbanks
Bank swallows dig their own nest tunnels into steep sand or gravel banks. Mass Audubon rates them strongly declining in Massachusetts.
Birds
Dogs and nesting plovers: why beaches limit dogs from April 1
Piping plovers nest on open sand and treat dogs as predators, so many Massachusetts beaches ban dogs or require leashes through summer.
Birds
Spring warblers and songbirds on the Hellcat boardwalk
The refuge says spring migration brings hordes of songbirds and warblers from late April to early June. Its Hellcat boardwalk is wheelchair accessible.
Birds
May migrant birds at Mount Auburn Cemetery
Mount Auburn Cemetery says May is when migrant birds peak on its grounds, and its timetable lists which birds to expect each week.
Birds
The purple martin colony at Long Pasture's accessible trail
Purple martins nest in gourds and boxes people put up, and Long Pasture keeps gourd racks along its All Persons Trail.
Birds
Cornell NestWatch bird boxes along Allens Pond's accessible trail
Bird boxes beside the Allens Pond All Persons Trail are part of Cornell's NestWatch project and have been used by tree swallows and bluebirds.
Birds
Bobolinks nesting beside Wachusett Meadow's accessible trail
Bobolinks nest on the ground in tall grass from May. Wachusett Meadow's All Persons Trail passes a 10-acre meadow where they nest.
Birds
Wood ducks and beaver dams along the Nashua River Rail Trail
Mass Audubon credits the return of beavers for the spread of wood ducks, and the watershed group says a day on the rail trail may bring a sighting.
Birds
Bobolinks at the Fort River Division's accessible trail
Bobolinks arrive on Massachusetts grasslands in early May. The Fort River Division's fully accessible trail passes through grassland.
Birds
Blue Jays that mimic hawk calls
Blue Jays often copy the screams of Red-shouldered and Red-tailed Hawks, so a hawk call from a yard tree is worth a look before you name it.
Birds
The Barred Owl's who-cooks-for-you call
The Barred Owl's hoot is a run of 8 to 9 notes that people hear as 'Who cooks for you?' Barred Owls live in Massachusetts year-round.
Insects
Insects
How water striders stand on a pond's surface without sinking
Water striders stand on the surface film of eastern Massachusetts ponds on water-repellent, hairy legs, denting it into dimples without breaking through.
Insects
Moths at street lamps and lit shop fronts on warm summer nights
A light that is already burning on a warm, still night, a street lamp or a lit shop front, draws a small sample of the many moths out in the dark.
Insects
Luna moths at the porch light, most likely in June
Adult luna moths never feed and live only about a week, so one resting at a porch light is a brief, lucky sight, most likely in June.
Insects
Which way a snail shell coils
Held tip up with the opening facing you, a northeastern land-snail shell almost always opens on the right. Physa pond snails coil left.
Insects
Hemlock woolly adelgid: the white wool on hemlock twigs
Tiny white cottony tufts under hemlock twigs are an invasive sap-feeding insect. They start small in late fall and fill out by spring.
Plants
Plants
Counting a young white pine's age by its branch whorls
A young white pine grows one ring of branches, a whorl, for each year of upward growth, so counting the rings estimates its age.
Plants
How to read tree rings on a cut stump
A light spring band and a dark late band make one ring. Wide rings often mean good years; narrow ones can mean drought or crowding.
Plants
Tell pines apart by counting needles in a bundle
Eastern white pine has 5 needles to a bundle, pitch pine 3, and red pine 2 that snap when bent, though some planted pines have 2 as well.
Plants
Azaleas, rhododendrons and mountain laurel in bloom at Maudslay
Maudslay State Park holds one of the largest wild stands of mountain laurel in eastern Massachusetts. Leashed dogs are welcome.
Plants
Lilac season at the Arnold Arboretum, with leashed dogs
The Arnold Arboretum holds one of the oldest and largest lilac collections in North America. Dogs must be leashed at all times.
Mammals
Mammals
Big brown bats hunting over yards at dusk in eastern Massachusetts
The most common bat in Massachusetts suburbs, the big brown bat, leaves its roost in the evening to hunt insects over yards, ponds and field edges.
Mammals
Beaver signs: chewed stumps and pale wood chips along pond edges
Beavers work mostly at night, so pointed stumps, pale wood chips and paired tooth grooves along a pond edge are often easier to find than the animal.
Mammals
Red squirrel cone piles under the pines
Red squirrels strip pine, spruce and hemlock cones at a favorite stump or log, and the scales pile up there over years, up to two feet high.
Mammals
Porcupines cannot throw quills, but a nosy dog can get quilled
Mass Audubon says porcupines raise their quills rather than shoot them. If a dog is quilled, Cornell says see a veterinarian; do not pull them yourself.
Mammals
If a skunk sprays your dog, soap alone will not cut it
Cornell's vet college explains why skunk spray resists soap and gives a peroxide, baking soda and dish soap mix for the dog.
Mammals
Fishers: not cats, and not the night scream
The fisher is a large member of the weasel family, not a cat. It lives throughout Massachusetts except on Nantucket and Martha's Vineyard.
Fungi
Fungi
Why lichen turns bright green after rain
Rain turns a lichen's gray outer layer see-through so the green algal partner shows, while lichens with cyanobacteria go dark green, brown or black.
Fungi
Black knot on cherry trees: the black lumps are a fungus
Hard black swellings on a roadside cherry's twigs are black knot, a native fungus, not fire damage or an insect gall, and it can keep growing for decades.
Fungi
British soldier lichen and its bright red caps
A pale green lichen with tiny stalks tipped in bright red, found on old stumps, rotting logs, mossy ground and weathered fence posts.
Fungi
Old man's beard lichen and its stretchy inner cord
A pale gray-green, hair-like lichen on twigs and branches; it is sensitive to air pollution, and a stretched strand has an elastic cord inside.
Fungi
Tinder conk: the gray hoof fungus on birch and beech
A hard, gray, hoof-shaped fungus on birch and beech trunks that lives for years and can be seen in every season.
Fungi
Lichens on gravestones and old stone walls
The gray, yellow-green and orange crusts on old stone are lichens, a fungus living with an alga, slow growing and differing from one stone type to another.
Fungi
Split gill fungus, the fan that shrivels and revives
A small fuzzy gray-white fan on dead hardwood whose gills are split down the middle. It shrivels in dry spells and starts working again after rain.
Fungi
Chaga: the black, burnt-looking fungus lump on birch trunks
The black, deeply cracked lump on a living birch trunk is chaga, a fungus, not a burn scar or a woody burl. It can sit on the tree for many years.
Fungi
Blue-green stained wood from the Chlorociboria fungus
Fallen sticks and logs stained bright blue-green are colored by a cup fungus called Chlorociboria. Its tiny turquoise cups appear far less often.
Amphibians
Amphibians
Spring peepers: the tiny frogs behind the spring wetland chorus
From the first mild evenings of March into May, male spring peepers small enough to sit on a quarter chorus from wetlands across eastern Massachusetts.
Amphibians
Fairy shrimp swimming upside down in spring woodland pools
Fairy shrimp are inch-long crustaceans that swim on their backs in woodland pools that fill each spring, hatching from eggs that sat out the dry months.
Landscape
Landscape
Stone walls in New England woods and the farms they once edged
Almost every stone wall in New England woods was a field or pasture edge, built of glacial stones farmers cleared between the Revolution and the Civil War.
Landscape
Kettle holes: ponds and hollows left by melting glacial ice
Some round ponds and deep hollows in eastern Massachusetts mark where a block of ice, stranded and buried as the last glacier retreated, slowly melted.
Landscape
Glacial erratics: lone boulders the ice sheet left behind
A huge lone boulder in the woods or a field is often not local rock: the last ice sheet carried it from elsewhere and dropped it as it melted.
Landscape
Pits and mounds: how uprooted trees shape the forest floor
A mound beside a hollow marks a tree blown over long ago, its roots lifting soil and stone that stayed behind after they rotted.
Landscape
Eskers: winding ridges left by glacial meltwater rivers
An esker is a long, winding ridge of sand and gravel laid down by a meltwater river in a channel within or beneath the last ice sheet.
Landscape
Drumlins: smooth oval hills shaped by glacial ice
Drumlins are smooth, oval hills of glacial till streamlined by moving ice, and eastern Massachusetts has many of them.
Landscape
Wolf trees: old open-grown giants inside young woods
A wolf tree is a huge, wide-crowned tree with low thick limbs among straighter younger trees, a likely sign the spot was once a pasture or field edge.
Landscape
River herring climb fish ladders in spring
Each spring river herring swim up Massachusetts rivers, and at a fish ladder you can watch them dart up the steps in quick bursts.
Landscape
Shad pass underwater windows at Connecticut River fishways
American shad swim up the Connecticut River each spring, and two public fishways have underwater windows where you can watch them go by.
Landscape
Fallfish build stone-pile nests in Massachusetts streams
The fallfish, the largest minnow in Massachusetts, carries small stones in its mouth to build a mound nest that other fish also use.
Landscape
Mass Audubon sanctuaries ban dogs while many state parks welcome them
Dog rules on Massachusetts trails come from the landowner: DCR, state wildlife lands, Mass Audubon and The Trustees each have their own.
Landscape
Glacial striations on Massachusetts bedrock ledges
Fine parallel scratches and grooves on bare ledges were cut by stones in the base of an ice sheet, and they record which way the ice moved.
Landscape
Roxbury Puddingstone, the Massachusetts state rock
Roxbury Puddingstone is old gravel of rounded pebbles and cobbles cemented into hard rock. It crops out in ledges and cliffs in and around Boston.