Sunday, July 23, 2017  

Migration: Moving with the Seasons


In nature seasonal changes are occurring all the time. These can be observed by watching the way the wind moves through trees, the waving grasses of a meadow and by observing the migration of animals and birds.
Migration is defined as “the seasonal movement often north and south along a flyway, between breeding and wintering grounds.” Migration is a magical mystery. It is learned and passed down through the generations. Elaborate migration maps attest to the complexity.

The timing of migration is controlled primarily by changes in the length of day as well as response to warmer or cooler weather. Celestial cues from the sun and stars and earth’s magnetic field as well as mental maps all play a role. Different species of birds and other animals develop independently oriented instincts. In Virginia with our vast expanse of shoreline, the migration of our birds becomes a twice yearly ritual viewed by many. The distance covered during bird migrations can be amazing with the Artic Tern holding the record with flights slightly more than 3000 miles from the Antarctica to the Artic each year.

Most birds in flocks fly at varying altitudes. Suddenly, the skies of a winter day come alive as the birds arrive for a feast of the berries from black gum trees, persimmons and many varieties of shrubs.

Seabirds fly low over water but gain altitude over land. Penguins, unable to fly, migrate by swimming. Humpback and fin whales can be observed in their yearly migration in late December to mid-March off the coast of Virginia Beach where the rich waters of the bay open to the ocean. The Virginia Aquarium and Marine Science Center offers whale-watching excursions.

Migrations have been reported in the Bible and by ancient Greeks and Aristotle. Yearly celebrations are planned around the timing of migrations such as swallows when they return to Capistrano and monarch butterflies migrating to the hills of Mexico.

The migratory process is an extremely arduous one. Flocks fly incredible distances and need sustenance and resting places along the way. Threats to migration include habitat destruction, windmills and power lines. The migration of birds is dependent upon healthy habitat and vegetation to support their nutritional needs as they fly. Conservation groups such as Ducks Unlimited and the National Wildlife Federation of Reston, Virginia serve to preserve the much needed wetlands. Ducks Unlimited started in 1937 during a severe drought. The drought caused a massive loss of plant material which not only developed the infamous “Dust Bowl” in the middle of our country, but plagued the waterfowl populations, plunging populations to unprecedented lows. A small group of sportsmen joined together to establish this conservation organization to preserve wetlands throughout the country.

VIMS (Virginia Institute of Marine Science), the Department of Environmental Quality and Audubon are involved in monitoring not only the migration process but the habitats so vastly needed for it to occur.

Eelgrass so vital for providing food and habitat for waterfowl, fish, shellfish and invertebrates is being monitored and restored to promote healthy migrations. Eelgrass has the added benefit of removing excess nutrients of nitrogen and phosphorus. It therefore controls unwanted algae growth as well as producing oxygen (see The House and Home Magazine-December 2014/January 2015 and “The Color of Our Water”). A healthy eelgrass wetland has the added benefit of eliminating sediment thus reducing shoreline erosion by absorbing wave energy.

Audubon chapters are a wealth of knowledge. They conduct yearly bird counts to help monitor the bird populations. Look for the local chapters to offer walks along with informative programs. Skilled birders are an unending source of ornithological wealth.

It Begins

As if to illustrate their own particular migration patterns, we are able to observe the arrivals and departure of individual species each year at varying times. At the end of the summer, as the days shorten and the nights cool, the mass exodus begins. Hummingbirds are suddenly gone from our gardens. Interestingly enough, bluebirds often thought to migrate, actually overwinter in this area. They will nest 5 or 6 to a bluebird box in an attempt to keep warm.

Osprey and seabirds begin to migrate to South America. Warblers and other songbirds with their charming calls are suddenly missing in our woods. Large flocks of birds can be seen lined up on the electric and telephone wires and rising in gentle waves while feeding on the stubble of cornfields.

With the exodus of some species, others appear. Some are traveling and others are overwintering on the waters of our rivers, inland ponds and coves of the Chesapeake Bay. In October, duck hunting season begins in response to the arrival of early migratory ducks. “V” formations of Canada geese honk to announce their arrival as their presence tells us of the changing season.

The early wintertime of November and early December is heralded by the arrival of some of the migrating waterfowl. Look for flocks of scaup, wigeon, teal, mallard, black ducks, pintail, and the beautiful wood duck at this time.

In January, during walks through the woods, we are able to view and hear vast flocks of robins that have migrated from the north and treat us to their spring-like calls. In northern states, they are thought of as the herald of spring. The good news is these birds often overwinter in Virginia. In early January, snow geese migrate from Alaska to Maryland and Delaware and can be seen in the air, fields and the waters of the northern tip of the Chesapeake Bay.This time of the year is a great time to put out bird feeders because with the change in weather, freezing temperatures, and the ice and snow native seeds become more difficult to obtain.

Raptors, birds of prey, which include: hawks, eagles, kites, harriers, falcons, owls and osprey vary in their migratory process. Some join in the annual migration and others overwinter in one place.As the winter tightens its grasp, different flocks and species of ducks appear in a somewhat orderly manor on the water. This progression changes year to year dependent upon the weather.
Winter Viewing of 
Waterfowl on our Waters

Viewing birds varies in proximal areas according to place, weather and time. What may be seen in one location may vary greatly a few miles away. During the severe winter of 2013-14, snowy owls, normally wintering further north, migrated from the severe cold to the shores of Virginia to the delight of those birders who viewed them.

Many other varieties of duck continue to appear and inhabit our winter waters. They include: mergansers, buffleheads, goldeneyes, oldsquaw and the comical grebe with its perky little head atop a curving neck. Large flocks of canvasbacks follow, congregating in flocks of hundreds. Swans can be spotted near the bay and the surrounding waterways.

The Heralding of Spring

Long before spring has officially arrived by the calendar, signs can be seen in our woods. Songbirds, having wintered in South America and Mexico, begin their return waking up the woods with the sound of their calls announcing their arrival. Most songbirds migrate at nighttime to attempt to avoid predators. On a moonlit night they can be seen flying across the moon.

The arrival of songbirds coincides with the continuing migration of the ducks. Overnight the waters are clear of the varying flocks which have taken flight for places north. The dance has begun again. The magic of spring is upon us. The woods come alive with the sound of birds, all kinds of green sprouts are poking up and the buds on branches swell with new life. Spring is on its way. 

Special thanks to: Paul Servis and Tom Saunders of the Northern Neck Audubon Society for their excellent and patient assistance in the writing of this article.