GREATER BLACK-BACKED GULL. 
503 
bited grassy isles. In the motionless and expansive flight 
of these fine birds, together with their loud laughing 
bark, which is at times very much like the cry of that 
bird, they bear considerable resemblance to the eagle. 
I have many times watched a number of them with great 
interest, when almost beyond my sight, whirling round 
and round in intersecting circles, and for a length of time 
without apparently moving a feather of their wings, 
much in the manner in which, according to Audubon, 
a tribe of vultures survey the surrounding country in 
search of food. 
