Slow Down When There’s Snow on the Ground

It’s just common sense to take it easy and drive carefully when snow covers streets and highways.  Everyone knows that.  But did you know that slowing down when the landscape is blanketed in white can save lives even after the roadways have been cleared?

Following significant snowfalls such as the one earlier this week, birds and other wildlife are attracted to bare ground along the edges of plowed pavement.  They are often so preoccupied with the search for food that they ignore approaching cars and trucks until it is too late.

Take a look at the species found today along a one mile stretch of plowed rural roadway in the lower Susquehanna valley.

Following snow storms, birds that normally feed among leaf litter on the forest floor or in thickets and fields are attracted to plowed roads.  During their urgent search for food, many are struck and killed by motor vehicles.
White-throated Sparrows commonly congregate along roads passing through woodlands and thickets.
A juvenile White-crowned Sparrow looks for food among leaves along the edge of snow-free pavement.
Adult White-crowned Sparrows take cover in roadside shrubs until traffic passes.  Within moments they’ll return to a patch of bare ground along the road’s narrow shoulder.
Dark-eyed Juncos are commonly encountered along roads through snow-covered weedy fields and suburbia.
Song Sparrows gather along roads traversing brushy areas.
Juvenile White-crowned Sparrows and, to the upper right, an American Tree Sparrow (Spizella arborea) take refuge in a small roadside sapling after fleeing a passing automobile.
This Yellow-rumped Warbler was attracted to berry-laden shrubs and vines in a road cut with a southern exposure and patches of bare ground.
Following a snowfall, Eastern Bluebirds are regularly seen feeding along the edges of rural roads.
Horned Larks gather along the snow-free margins of roads through tundra-like farmland.

For many species of wildlife in the Lower Susquehanna River Watershed, the fragmented and impaired state of habitat already challenges their chances of surviving the winter.  Snow cover can isolate them from their limited food supplies and force them to roadsides and other dangerous locations to forage.  Mauling them with motor vehicles just adds to the escalating tragedy, so do wildlife and yourself a favor—please slow down.

Even in areas with  ideal habitat, snow cover will cause birds and other wildlife to explore bare ground along highways while seeking food.
Ring-necked Pheasants frequently become traffic casualties.  These birds feeding at roadside due to the snow cover are in increased peril.

Anthropoavians

Temperatures plummeted to well below freezing during the past two nights, but there was little sign of it in Conewago Falls this morning.  The fast current in the rapids and swirling waters in flooded Pothole Rocks did not freeze.  Ice coated the standing water in potholes only in those rocks lacking a favorable orientation to the sun for collecting solar heat during the day to conduct into the water during the cold nights.

On the shoreline, the cold snap has left its mark.  Ice covers the still waters of the wetlands.  Frost on exposed vegetation lasted until nearly noontime in shady areas.  Insect activity is now grounded and out of sight.  The leaves of the trees tumble and fall to cover the evidence of a lively summer.

The nocturnal bird flight is narrowing down to just a few species.  White-throated Sparrows, a Swamp Sparrow (Melospiza georgiana), and Song Sparrows are still on the move.  Though their numbers are not included in the migration count, hundreds of the latter are along the shoreline and in edge habitat around the falls right now.  Song Sparrows are present year-round, migrate at night, and are not seen far from cover in daylight, so migratory movements are difficult to detect.  It is certain that many, if not all of the Song Sparrows here today have migrated and arrived here recently.  The breeding population from spring and summer has probably moved further south.  And many of the birds here now may remain for the winter.  Defining the moment of this dynamic, yet discrete, population change and logging it in a count would certainly require different methods.

Song Sparrows are now abundant in the brushy edges of fields and woodlands.  They may even break into song on sunny days.

Diurnal migration was foiled today by winds from southerly directions and moderating temperatures.  The only highlight was an American Robin flight that extended into the morning for a couple of hours after daybreak and totaled over 800 birds.  This flight was peppered with an occasional flock of blackbirds.  Then too, there were the villains.

CLICK ON THE LOGO FOR TODAY’S MIGRATION COUNT TOTALS

They’re dastardly, devious, selfish, opportunistic, and abundant.  Today, they were the most numerous diurnal migrant.  Their numbers made this one of the biggest migration days of the season, but they are not recorded on the count sheet.  It’s no landmark day.  They excite no one.  For the most part, they are not recognized as migrants because of their nearly complete occupation of North America south of the taiga.  If people build on it or alter it, these birds will be there.  They’re everywhere people are.  If the rotten attributes of man were wrapped up into one bird, an “anthropoavian”, this would be it.

Meet the European Starling (Sturnus vulgaris).  Introduced into North America in 1890, the species has spread across the entire continent.  It nests in cavities in buildings and in trees.  Starlings are aggressive, particularly when nesting, and have had detrimental impacts on the populations of native cavity nesting birds, particularly Red-headed Woodpeckers, Purple Martins (Progne subis), and Eastern Bluebirds.  They commonly terrorize these and other native species to evict them from their nest sites.  European Starlings are one of the earlier of the scores of introduced plants and animals we have come to call invasive species.

Noisy flocks of European Starlings are right at home on man-made structures in city and country.

Today, thousands of European Starlings were on the move, working their way down the river shoreline and raiding berries from the vines and trees of the Riparian Woodlands.  My estimate is between three and five thousand migrated through during the morning.  But don’t worry, thousands more will be around for the winter.

European Starlings mob a Sharp-shinned Hawk from above, a common behavior.
An Eastern Bluebird feeds on the few berries left untouched by passing European Starlings.

The Dungeon

There’s something frightening going on down there.  In the sand, beneath the plants on the shoreline, there’s a pile of soil next to a hole it’s been digging.  Now, it’s dragging something toward the tunnel it made.  What does it have?  Is that alive?

We know how the system works, the food chain that is.  The small stuff is eaten by the progressively bigger things, and there are fewer of the latter than there are of the former, thus the whole network keeps operating long-term.  Some things chew plants, others devour animals whole or in part, and then there are those, like us, that do both.  In the natural ecosystem, predators keep the numerous little critters from getting out of control and decimating certain other plant or animal populations and wrecking the whole business.  When man brings an invasive and potentially destructive species to a new area, occasionally we’re fortunate enough to have a native species adapt and begin to keep the invader under control by eating it.  It maintains the balance.  It’s easy enough to understand.

Japanese Beetles (Popillia japonica) seen here on Halberd-leaved Rose Mallow.  Without predation, exploding numbers of this invasive non-indigenous insect can defoliate and kill numerous species of plants in a given area.
The Song Sparrow (Melospiza melodia) is a generalist feeder, eating seeds and invertebrates including Japanese Beetles.  This species is the omnipresent year-round occupant of shoreline vegetation along the lower Susquehanna River.

Late summer days are marked by a change in the sounds coming from the forests surrounding the falls.  For birds, breeding season is ending, so the males cease their chorus of songs and insects take over the musical duties.  The buzzing of the male “Annual Cicada” (Tibicen) is the most familiar.  The female cicada lays its eggs in the twigs of trees.  After hatching, the nymphs drop to the ground and burrow to live and feed along tree roots for the next two to five years.  A dry exoskeleton clinging to a tree trunk is evidence that a nymph has emerged from the soil and flown away as an adult.  There are adult Annual Cicadas present every year.

An “Annual Cicada”, probably a Silver-bellied Cicada (Tibicen pruinosa), clings to a stem on a Halberd-leaved Rose Mallow at Conewago Falls.

For the adult cicada, there is danger.  It looks like an enormous bee.  It’s a Cicada Killer (Specius speciosus) wasp, and it will latch onto a cicada and begin stinging while both are in flight.  The stings soon paralyze the screeching panicked cicada.  The Cicada Killer then begins the task of airlifting and/or dragging its victim to the lair it has prepared.  The cicada is placed in one of more than a dozen cells in the tunnel complex where it will serve as food for the wasp’s larvae.  The wasp lays an egg on the cicada, then leaves and pushes the hole closed.  The egg hatches in a several days and the larval grub is on its own to feast upon the hapless cicada.

A Cicada Killer (Sphecius speciosus) along the river shoreline. Despite their intimidating appearance, they do not sting humans and can be quite docile when approached.

Other species in the Solitary Wasp family (Sphecidae) have similar life cycles using specific prey which they incapacitate to serve as sustenance for their larvae.

A Solitary Wasp, probably of the genus Ammophila, drags a paralyzed moth caterpillar to its breeding dungeon in the sandy soil at Conewago Falls.  For the victim, there is no escape from the crypt.

The Solitary Wasps are an important control on the populations of their respective prey.  Additionally, the wasp’s bizarre life cycle ensures a greater survival rate for its own offspring by providing sufficient food for each of its progeny before the egg beginning its life is ever put in place.  It’s complete family planning.

The cicadas reproduce quickly and, as a species, seem to endure the assault by Cicada Killers, birds, and other predators.  The Periodical Cicadas (Magicicada), with adult flights occurring as a massive swarm of an entire population every thirteen or seventeen years, survive as species by providing predators with so ample a supply of food that most of the adults go unmolested to complete reproduction.  Stay tuned, 2021 is due to be the next Periodical Cicada year in the vicinity of Conewago Falls.

SOURCES

Eaton, Eric R., and Kenn Kaufman.  2007.  Kaufman Field Guide to Insects of North America.  Houghton Mifflin Company.  New York.