Thursday, August 6, 2015

Shorebird Migration

Johnsons Mills Spectacle

Migrant Sandpipers
Every July and August an avian spectacle occurs on New Brunswick shores.  Migrating shorebirds rest and feed on our ocean shorelines on their way southward.  New Brunswick is an important stopover for migrating plovers and sandpipers and other shorebirds as they make their very long journey to the south. 

The eastern end of the Bay of Fundy is especially important for these birds.  There they gather in huge flocks to feed on mud shrimp.  That enables them to add much-needed body fat for their remaining journey to the Caribbean and South America.  These birds need to feed heavily and double their body weight in order to get enough energy to make the trip.

Pictured here is the Semipalmated Sandpiper which gathers in such huge flocks.  About 80% of the world's population of this species gathers in the upper Bay of Fundy during migration.  Upwards to 2 million birds gather there over the 6-week migration period.  Johnsons Mills (35 km south of Monction, near Dorchester) and Mary's Point (near Harvey) are two places where many birds gather.  Fortunately both areas have been made a nature preserve.  The Nature Conservancy of Canada protects land at Johnsons Mills and Mary's Point is part of the Shepody National Wildlife Area and is managed by Environment Canada.

Resting Sandpipers
The Semipalmated Sandpiper is a small sandpiper, about 15 cm long (6.3 inches).  It breeds on the Arctic tundra from Alaska to Labrador.  During fall migration it passes through here to winter in Mexico and South America. The birds feed on small arthropods, amphipods, mollusks, polychaetes and annelids in fresh and salt water by probing in the mud.  They nest on the ground in a hollow lined with grass. 

Johnsons Mills Showing Migrating Semipalmated Sandpipers
While visiting Johnsons Mills last week we saw a flock of 20,000 birds.  At high tide this flock is concentrated just above the tide line.  What a sight that is!  The birds are crowded in 'shoulder to shoulder' and somehow manage good group dynamics.  They vocalize often with a churk or a cheet.  In the resting flock some birds are sleeping, some are jostling for position, and many are flying out over the water only to return again and resettle in the flock.  This resting period lasts until the tide drops  exposing the mudflats so the birds can feed again.

The group dynamics is fascinating.  In flight the birds fly tightly together.  When the flock turns, they all turn at once so when you are watching the flock, at one moment you see their dark-coloured backs and the next you see their silver bellies.  So, the flock looks dark at one moment and silver the next.  It makes one wonder how they signal to flock members what the next move is.  The flocks fly in huge lines close to the ocean waves.  The long lines are many birds wide and thousands long.  These lines form spirals, ells and esses over the ocean.  To see thousands of birds performing aerial manoeuvres and then landing close to your viewing area is indeed a spectacle.

We are lucky to be able to provide an essential resting/feeding area for these birds.  It is an important legacy of which we must be responsible stewards.

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