2 28 Anthony on the Black-vented Shearwater. \uu 



A complete molt of all the feathers occurs in July and August in 

 this species (P. opisthomelas) , — and a more or less complete molt 

 of the feathers of the head and body takes place in January and 

 February. P. griseus and P. creatopus also, I think, undergo a 

 complete molt in July and August, but whether they share with 

 opisthomelas a partial molt in early spring, I am unable to say from 

 lack of material taken in proper season. 



At times when I have found a pronounced flight of Shearwaters 

 near shore I have usually if not always found a flight in the oppo- 

 site direction farther at sea. This habit of flying in circles or 

 advancing in a series of loops, is very noticeable when the birds 

 are quartering the sea for small fish. Their circles are then often 

 small enough to enable one to see the entire circuit. I recently 

 made mention of this habit in a letter to Mr. Chase Littlejohn and 

 his reply, which lies before me, will bear quoting from. He says : 

 " During the summer there are untold thousands of them in 

 Alaska and they are not rare in winter. Your remarks about 

 the direction the Shearwaters flew interested me very much, 

 and bring to mind facts that I had not thought of for some 

 time. I think had it been possible for you to have followed a 

 flight for a few hours you would have found yourself back where 

 you started, for my belief is that flocks almost always, if not invaria- 

 bly, fly in circles, moving for hours, and even days in the same 

 vicinity; and then again, travelling in a given direction, but still 

 in circles. I have many times been at or near the center of a ring 

 when it was just possible to see the birds in any direction, and 

 from that down to circles only a few hundred yards in diameter. 

 When we know that they fly in circles as far as the eye can see, 

 is it not reasonable to think that they might extend it for a much 

 greater distance and move south in-shore while, as you say, they 

 were going north off-shore." 



Mr. Littlejohn's notes on the Alaskan birds refer to the Slen- 

 der-billed Shearwater, but are pertinent as I have found the flight 

 very similar in all of our species. 



