48 Bulletin No. 13. 



all noise had stopped, when it became too dark to see the birds more 

 than five rods away. 



About 350 cowbirds and a few robins entered the roost after the great- 

 est flight of grackles. At 5:30 the cowbirds were gathered in the trees 

 north of the campus awaiting an opportunity to steal into the northern- 

 most trees of the roost. They were seen on the roof of Council Hall 

 and the First Congregational Church some minutes before the first 

 grackles put in an appearance. On succeeding days the cowbirds came 

 first to the roof of Council Hall, where they remained for half an hour 

 before perching in the trees south of the building preparatory to their 

 plunge into the grackle roost. 



The first large flock of grackles was sighted a little west of south com- 

 ing over a considerable woods a mile and a half away. Their habit of 

 flying so low made it impossible to see them farther away because they 

 were hidden by the woods. From here they came in almost a direct line 

 to the south end of Professor street, then turned directly up that street 

 to the intersection of Elm street, then passed east of the Second Congre- 

 gational Church and the Chapel to the campus. Many of the birds 

 stopped in the trees north of the Chapel and in those south of Spear 

 Library, while more flew directly to the roost or to the trees west of it. 

 During the summer the direction of the flight varied somewhat, although 

 it was southerly at all times. The birds invariably turned eastward to 

 pass east of the church and Chapel building at night, and never neglected 

 to pass east of them in the morning, even though their final direction 

 was decidedly westerly. It is difficult to resist the conclusion that the 

 tall steeple of the Second Church served the grackles as a landmark on 

 their evening return, but why they should always pass on the east side of 

 it is not clear. It may be that the large buildings on the . west side of 

 Professor street caused the eastward movement. During the previous 

 years the birds had not followed this route, nor had they during the early 

 part of 1896, so it could not have been a fixed habit. It was only after 

 the birds had begun to form into large flocks that they followed any 

 definite line of flight at all. 



As we have seen, during May, June and the early part of July the 

 birds had not gathered into any considerable flocks, either at their morn- 

 ing departure or evening arrival ; but the gregarious instinct asserted 

 itself more and more as the season advanced and the necessity for a 

 wider range of feeding ground increased. Early in the season the birds 

 were not yet free from the care of the young, and so were naturally 

 busied in different places by different things. The numerous small flocks 



