The fall migration is well under way. Where did the summer go?

Migrations are tremendously expensive undertakings for birds. They must pack on fat to fuel each leg of their long journey. To see fall migratory birds, finding an abundant food source is a good strategy. Putting on fat quickly is an imperative for migrating birds, so they know the best places to eat.

My wife and I spend a lot of time in Lubec on Cobscook Bay. The area is a wonderful birding destination with lots of accessible conserved land. During the fall migration my wife and I use the strategy of going to the food to find the birds.

The South Lubec Sand Bar can be hopping with shorebirds and other water birds from August into October. This bar is about a mile long and is adjacent to an expansive sandflat along the South Lubec Road. This sandflat is the best restaurant in the area for sandpipers and plovers.

Sandpipers forage by rapidly probing into the sediment, capturing invertebrates by feel. Their bills are well equipped with touch receptors. The sandpipers prey on small shrimp-like crustaceans called Corophium and polychaete worms, marine relatives of earthworms. These invertebrates are found in the lower to middle part of the intertidal zone.

Plovers use a different feeding technique, relying more on their vision than their touch. A plover stands and looks for movement in the sediment, then runs to the unsuspecting ragworm, bloodworm or other invertebrate. This form of feeding is called ambush predation or run-and-peck predation.

The plovers and sandpipers are dispersed broadly across the flat at low tide. Birding at this stage of the tide is fruitless.

The trick is to let the rising tide bring the birds to you. As the tide starts to cover the productive part of the flat, the birds seem to redouble their feeding efforts as they are forced higher and higher in the intertidal zone. They congregate along the rising tide line, seemingly oblivious of the humans staring at them.

For an hour or so, a large number of shorebirds will be congregated in a narrow swath, affording great views. Eventually the tide will force the birds to higher ground. The birds fly off to local fields or other open habitats, and the show is over.

I have found that arriving at the sandbar four hours before predicted high tide is optimal. The birds start congregating within the next hour. By two hours before high tide the birds will have gone to roost.

Of course it’s possible to arrive at high tide and wait for the birds to return. I have had less success with this method, as the birds seem to be more aware of human presence.

We walked the sandbar recently with a group of friends. Diversity and numbers of birds vary from day to day. We had a corker of a day but not high bird diversity. We enjoyed stunning close-up views of many least and semipalmated sandpipers. The leasts, with their reddish-brown upper parts and yellow-green legs, are lovely birds.

We had fun picking out the occasional white-rumped sandpiper. These birds are easy to identify in flight by their namesake white rump. On the ground, they are similar in color to the gray semipalmated sandpipers but a bit larger. The tail of a white-rump extends well beyond the folded wings, unlike the shorter tail of semipalmated sandpipers.

A few semipalmated plovers and greater yellowlegs rounded out our list. We often see a merlin, peregrine falcon and even a parasitic jaeger hunting the shorebirds, but not that day.

Of course this technique of letting the tide bring the shorebirds to you works on any intertidal mudflat. Give it a try.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at:

whwilson@colby.edu