What to notice outside around Sudbury in April
21 things from the field guide you can notice around Sudbury in April.
Sky
- Why you can see the moon in the daytime skyThe moon spends almost as much time up in daylight as at night, and on the right days it sits plainly in the blue sky.
- Sundogs and sun halos: how ice crystals bend sunlightIce crystals high in the atmosphere can bend sunlight into a pale ring around the sun or bright patches on either side of it.
- Crepuscular rays: sunbeams fanning out near sunrise and sunsetWhen broken clouds and haze meet a low sun, bright and dark bands can fan across the sky near sunrise or sunset.
- How the sunset point moves along the horizon through the yearWhere the sun sets on your skyline slides north through spring and south through autumn, fastest near the equinoxes and nearly still at each solstice.
- The Big Dipper never sets from eastern MassachusettsFrom eastern Massachusetts the Big Dipper is circumpolar, circling Polaris once a day, though the tip of its handle skims the horizon at its lowest.
Weather
- Morning dew and the dew point: why grass is soaked without rainWhen surfaces cool below the dew point, water vapor condenses into droplets on grass, cars and webs by morning.
- Why there is frost when the air never dropped below freezingOn a clear, still night a surface facing the sky loses heat faster than the air, dropping below freezing while the air a few feet up does not.
Birds
- Dark-eyed juncos: the gray winter bird under the feederThe dark-eyed junco, a slate-grey sparrow with a white belly, is in eastern Massachusetts yards from October to April, feeding on the ground under feeders.
- Crow or raven: how to tell them apart by the tailCrows 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.
Plants
- Skunk cabbage: the early spring flower that warms itselfSkunk cabbage flowers in wet Massachusetts ground can run 15 to 35 degrees warmer than the air around them, sometimes melting the snow and ice nearby.
- Why some beech and oak trees keep their dead leaves all winterAmerican beech and several oaks carry some dead leaves into winter, a habit called marcescence, mostly on young trees and the low branches of tall ones.
Mammals
Fungi
- Why lichen turns bright green after rainRain 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.
- How fallen leaves turn back into soil over the winterUnder damp leaf piles in eastern Massachusetts yards and woodlots, microbes, millipedes and earthworms turn dead leaves back into soil nutrients.
- Black knot on cherry trees: the black lumps are a fungusHard 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.
Amphibians
- Big night: spotted salamanders crossing roads in the spring rainOn an early rainy spring night above 40 degrees, spotted salamanders and wood frogs surge across eastern Massachusetts roads toward vernal pools.
- Spring peepers: the tiny frogs behind the spring wetland chorusFrom the first mild evenings of March into May, male spring peepers small enough to sit on a quarter chorus from wetlands across eastern Massachusetts.
- Fairy shrimp swimming upside down in spring woodland poolsFairy 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
- Stone walls in the Sudbury woods and the farms they once edgedAlmost every stone wall in a Sudbury woodlot was a field or pasture edge, built of glacial stones farmers cleared between the Revolution and the Civil War.
- Kettle holes: ponds and hollows left by melting glacial iceSome round ponds and deep hollows in eastern Massachusetts mark where a block of ice, stranded and buried as the last glacier retreated, slowly melted.
- Mud season in Massachusetts: why spring ground turns to mudFor a few weeks each spring the ground holds water on top instead of taking it in, because Massachusetts groundwater peaks in March and April.