Phenomenon of migration never ceases to amaze

By Chris Corio, Special to the News
Posted Sept. 03, 2010, at 7 p.m.

As I was driving over the bridge into Falmouth, a small flock of birds suddenly flashed into view. During the two-second look I had of them I was able to determine they were shorebirds. Then, in a glitter of white underbodies, they wheeled as one, crossing over the bridge before heading out onto the mudflats exposed by the falling tide.

Although I am not near a good enough birder to have been able to identify those birds in flight and with limited viewing time, I at least knew enough to guess they belonged in the family of small- to medium-size shorebirds commonly known as sandpipers.

Some of these birds actually breed in Maine — for example the spotted sandpiper — but many of them do not; the birds I saw were most likely migrants from points north, stopping to rest and refuel before continuing their journeys. This is peak migration time for these birds; their breeding season in the far north is short. While some will winter in the southern U.S., many make an arduous journey from as far north as Arctic Canada to as far south as South America.

At this time of year birders haunt the mudflats and sand flats for glimpses of these marathon fliers. As the tide goes out, the birds descend on the exposed bottom, probing the soft sand for invertebrates to fatten themselves up. Although coastal areas are the best place to see large numbers of migratory shorebirds — sometimes numbering in the thousands — one can find them in smaller numbers inland as well. These birds take advantage of muddy margins of lakes, ponds and other bodies of water. In fact, in years of low rainfall — and thus low water levels with much exposed mud — it can be a boon to migrating shorebirds.

This certainly seems to be the case this year. Bill Sheehan of Aroostook is an avid birder who meticulously documents his bird sightings in northern Maine and maintains an online birding blog. He recently wrote that his shorebird counts for points inland were higher than normal; as well, he is seeing a much greater diversity of shorebirds than is usual for his area.

In years past, I’ve seen a few sandpipers foraging along the edge of the humble drainage pond behind my place of work. It apparently is quite a productive pond; I’ve seen great blue herons, great egrets, mallard duck and a cormorant all plying its waters for food. It will be interesting to see, in the coming week or two, whether it continues to play host to migrating shorebirds.

The most memorable shorebird sighting for me was a trio of least sandpipers that were actually foraging on the tops of floating seaweed — something I had never seen before. I was especially intrigued to read about this bird’s unique feeding behavior in “The Birds of North America” species account. It is known as “surface tension transport.” Simply put, the surface tension of the water surrounding the bird’s very small prey has the power to draw the prey to the tip of its bill and into its mouth.

This sparrow-sized sandpiper is part of a group of sandpipers called “peeps,” — as they all have a similar peeplike call. They breed in the Arctic tundra and boreal forest of Alaska and northern Canada; according to the BNA, eastern populations of this bird make incredible transoceanic flights of more than 2,000 miles, from the Gulf of St. Lawrence and New England to South America.

This phenomenon of migration never ceases to amaze and humble me. Scott Weidensaul, writing in his “Living on the Wind: Across the Hemisphere with Migratory Birds,” put it succinctly:

“Migrations like this leave us staggered; we are such stodgy, rooted creatures. To think of crossing thousands of miles under our own power is as incomprehensible as jumping to the moon. Yet even the tiniest of birds perform such miracles.”

http://bangordailynews.com/2010/09/03/outdoors/phenomenon-of-migration-never-ceases-to-amaze/ printed on August 21, 2014