Birds

The adult roseate tern. Photo by E. Vernon Laux
These graceful and highly migratory birds are preparing to head to South America for the winter. The adult roseate tern at left center is seen here with common terns, both adult and immature. Photo by E. Vernon Laux

September rocks

By E. Vernon Laux - September 7, 2006

This month is magical for birding. Every day, no matter where one looks, birds are on the move. Fleeing the approaching winter and consequent lack of food, these most mobile of creatures, ranging from loons to hummingbirds, warblers to sparrows, are all heading south from where they nested. Some birds, including many shorebird species, flee to the extreme southern portions of the planet, enjoying the higher latitudes (in the Southern Hemisphere) bountiful daylight in the Austral summer, just as they did in the Arctic six months earlier. These birds see more sunlight, annually, than any other life forms.

Menemsha and Lobsterville have been awash in birds and fish. This fall has seen large numbers of black terns appear. This freshwater-loving species nests in the interior of the continent and in the fall, small numbers move down the coast. Most years on the Vineyard the sight of one of these birds is notable. This fall they are everywhere, with at least 35 individuals working the Menemsha Bight this past week. Fishermen and birders have both been impressed by these attractive small terns.

Visible signs of bird migration are all around. Flocks of tree swallows, some numbering in the many thousands of birds, are massing in many locations, particularly along the south shore. Mixed flocks of blackbirds, common grackles, red-winged blackbirds and brown-headed cowbirds can be seen moving in thick dark clouds both early and late in the day as they move to and from roosting spots.

A concentration of small fish is attracting an assemblage of larger fish and birds that are congregating in substantial numbers in Sengekontacket Pond. The double-crested cormorant numbers are staggering with well over 2,000 individuals counted on a recent morning. The shallow estuarine waters have been roiling with striped bass and cormorants feeding voraciously on small schooling fish of a number of species.

As recently as five years ago when one saw a flock of birds - either terns or at this season small gulls (laughing gulls) - hovering over the water, it was indicative of a school of large game fish driving small fish to the surface. The small fish are attempting to escape the threat from the big fish by getting "lost" in the surface clutter of waves and wind action causing the big fish to not see as well and becoming confused by all the commotion. This gave the flying birds a great opportunity to seize the fleeing small fish at the surface.

More recently and increasingly, especially in the past couple of years, it does not mean the same thing. In recent weeks large assemblages of small gulls, primarily laughing and ring-billed with a smattering of young herring gulls thrown in, have been seen feeding in a frenzied fashion over one section or another of Sengekontacket Pond. The gulls were sometimes numbering upwards of 500 individuals and indeed looked like "smoke" on or over the water on many a day.

This tidal estuary is comprised of very shallow water with a good tidal flow and abundant marine life. It is a rich marine nursery for all sorts of invertebrate and vertebrate life forms. The pond is a most important nursery for many species of small fish that in turn are food for larger fish and, increasingly, birds. It is located in both Oak Bluffs and Edgartown bordered by the Beach Road on one side and a long and varied shoreline made up of lots of shoreline in Edgartown and Oak Bluffs.

The burgeoning double-crested cormorant population has been growing in leaps and bounds. No one is really sure why this hardy and widespread species is undergoing such a population explosion and theories vary widely. However there is no disagreement that they are expanding in number at an alarming rate.

Cormorants are not the kind of bird that inspires many fans. Unlike bluebirds or chickadees, there are no clubs or state bird status for cormorants. They are not glamorous. They are not well liked by most fisherman or dock owners. They are incredibly successful at capturing a wide range of fish both large and small and in both fresh and salt water. They are extraordinarily adaptable.

The cormorants have learned that by fishing cooperatively they can herd schooling fish in shallow water and trap them along a shoreline or sandbar. Over a thousand individual cormorants have been counted gathering to form a line, a net if you will, across the pond. They then swim in formation across the expanse of water driving fish until they get them against a barrier, usually the shoreline. The fish are trapped against this and the cormorants move in, essentially slaughtering the baitfish.

The small fish attempt to break out by jumping over the submerged cormorants thus becoming vulnerable to attack from above. This is what attracts the huge flocks of gulls and terns. The cormorants are driving schools of sand eels, silverside minnows, herring, mackerel, or even creek chubs. They will eat any type of fish that they can swallow. They swallow things that seem impossibly large for them.

At any rate this is a fascinating and exciting occurrence that goes on daily in Sengekontacket Pond. Early morning has been so full of action on the pond that it really makes a nice trip to go down Beach Road, catch the sunrise, then turn and check out the ferocious feeding activity occurring under, on, and over the pond.

Until next week - keep your eyes to the sky!

To contribute news about birding activities or sightings, call The Times Birdline, 508-693-6100, extension 33, or e-mail birds@mvtimes.com.