48 BIRDS OF SOUTH DAKOTA 



mon Crow. It has a black cap, white neck and belly, and gray 

 wings and back. The dull orange bill changes to red during the 

 mating season. No doubt this bird is rather rare and migratory 

 in South Dakota, yet since most Terns and Gulls are similar in 

 color and size one may sometimes be mistaken for the other. 

 They may be distinguished in flight by the fact that the Tern 

 usually carries its bill pointed downward while the Gull carries 

 its bill pointed ahead in line with the body. Another distinguish- 

 ing mark is that the Terns usually seen in our State have forked 

 tails. 



Terns are not scavengers like the Gulls. Their food con- 

 sists almost wholly of aquatic forms taken alive, part being larvae 

 of insects injurious to the farmer, and the bulk of the rest small 

 fish not useful to man. 



69. Forster's Tern (Sterna forsteri.) 



This graceful bird is smaller than the Caspian Tern 

 though similar in color, the tail feathers being darker. The tip of 

 the orange bill is also dark. 



It comes to us in migration, when it may be seen sailing 

 over lakes and rivers and darting into the water after small fish 

 or insects. 



70. Common Tern (Sterna hirundo.) 



This bird is rare even in migration in South Dakota. It 

 is about the size of the last, except that the tail is shorter. Under 

 parts dusky; back gray; crown black; bill orange tipped with 

 black. 



74. Least Tern (Sterna antillarum.) 



As the name implies, this is the smallest of our Terns. 

 It is reported as breeding in South Dakota. Forehead white 

 with black crown; gray back, and white below. 



77. Black Tern (Hydrochelidon nigra surinamensis.) 



This is preeminently our Tern. A common summer resi- 

 dent, nesting in marshy places in the eastern part of the State, 

 where it may be seen sailing gracefully over water and reeds, 

 feeding on land and water insects, or frequently resting on wire 

 fences that run through ponds and marshes. 



