South-migrating Shorebirds pass through this area of the upper Bay of Fundy

Dorchester Cape and Johnson's Mills, near Sackville, New Brunswick

Fireweed blooms peak in mid-August

Chamerion Angustifolium, Johnsons Mills, New Brunswick, August 13, 2015

Roosting Semipalmated Sandpipers (far left) on tidal flats

Bay of Fundy, Johnsons Mills, August 13, 2015. The Semipalmated Sandpipers blend in perfectly with the rocks and debris along the wrackline.

Roosting Adult Semipalmated Sandpiper

This is an adult Semipalmated Sandpiper, with worn molting feathers. The worn breeding feathers (darkeer) are being replaced by gray winter feathers.

Roosting Adult Semipalmated Sandpipers

Johnsons Mills, Bay of Fundy, New Brunswick, August 13, 2015

Large mass of roosting Semipalmated Sandpipers

Johnson's Mills, Bay of Fundy, New Brunswick, August 13, 2015.

On the wing, through the fog

The fog was thick as pea soup when we arrived at the shore midmorning August 13. When the Semipalmated Sandpipers lifted off and wheeled in a large mass, it was difficult to see them at first, but they then flew toward us. It was an amazing spectacle.

Ventral view of birds in flight

These adult semipalmated Sandpipers have a white chest and underparts with a light gray striped necklace.

Dorsal view of Semipalmated Sandpipers in flight

The two-toned (darker and lighter) primary and secondary feathers and scapulars show up very clearly in flight.

A dense cloud of sandpipers on approach, feet deployed for landing

Over 20,000 Semipalmated Sandpipers on the wing

Johnson's Mills, Bay of Fundy, New Brunswick

A large cloud of birds in flight pass over roosting birds on the shore

Johnson's Mills, Bay of Fundy, New Brunswick, August 13, 2015

Thousands of birds alighting into a group of roosting birds

Somehow these birds have figured out air traffic control, and each bird lands on its own spot. Another of nature's impenetrable miracles.

Another photograph of a very dense cloud of Semipalmated Sandpipers in flight

Each bird is landing with a trajectory and final resting spot that is figured out within two or three seconds.

A flock of about 10,000 Semipalmated Sandpipers on the wing, dorsal view

Johnson's Mills, Bay of Fundy, New Brunswick, August 13, 2015

As the tide recedes, the birds begin to feed on the exposed mudflats

These birds are feeding primarily on mudshrimp, fat-rich crustaceans that live just below the tidal surface.

As the tide recedes further, the sandpipers fan out to feed on the exposed mudflats

When the Semipalmated Sandpipers arrive at the upper Bay of Fundy in late July and early August, their average weight is about one ounce. After two or three weeks of feeding on fat-rich mudshrimp, their weight increases to about two ounces, sufficient to power their three-day journey to South America.

Exposed mudflats on falling tide, about an hour after high tide.

Tens of thousands of Semipalmated Sandpipers can be seen feeding in the brighter blue-gray patch of exposed mudflats.

A field of tansies with mid-afternoon cumulus clouds, Johnsons Mills, New Brunswick