The black tern is another annual migrant that we are pleased to host.  Half the size of a common gull, it is, as its name suggests, black in colour, fading to grey towards the tail.  A white leading edge on its wings, and white under tail feathers make the black tern easy to distinguish during flight and when at rest.

 

Black terns are very particular about their nesting habitat! They favour large cattail marshes, and are an “area sensitive” species, requiring large areas of habitat to successfully reproduce.  Their nests are built on floating mats of vegetation, making them vulnerable to wind and wave action, so they prefer marshes containing protected pools of water.

Watching the colonies hover over their nests and dive bomb intruders, and hearing their piercing alarm cries, it is hard to believe that the black tern is listed provincially as a “species of special concern”.  However, practices such as the banned use of powerboats in this marsh, and the manipulation of water levels to create suitable nesting habitat provide a safe haven for the black tern.

 

The black tern has disappeared from many marshes, and scientists speculate this may be attributed to urban expansion, the increased use of marshes as recreational areas where boat wakes can easily wash out nests, and the continued use of pollutants like DDT on Latin American wintering grounds.