Bulletin A T o. zj. 53 



rose and formed the rear-guard. In this way the whole flock secured a 

 short breathing time, part by part. Occasionally the flock became more 

 broken up and extended from the van to the rear than represented in 

 either of the figures. Rarely two flocks were formed during the flight. 



We have seen that the advancing season brought certain changes in 

 the habits of the birds resorting to the roost at night. These changes 

 had several causes, chief among which was the food supply. All young 

 birds subsisted upon insects for some days after occupying the roost for 

 the first time. As they grew older the diet of both young and old was 

 changed to blackberries, upon which the birds seemed to subsist while 

 they were to be found in sufficient abundance. A green corn diet followed 

 the blackberry diet, and corn formed the staple of grackle food as 

 long as the birds inhabited the trees. Grasshoppers were everywhere 

 abundant during the entire summer, inviting the grackles to a hearty and 

 easily obtained meal where ever they might go ; but I was unable to find 

 any grasshopper or other insect remains in the droppings after the birds 

 began eating blackberries. The damage inflicted upon the green corn crop 

 must have been considerable, much of which, I suspect, was laid at the 

 door of the crow, since flocks of two or three hundred crows were seen 

 every day in the south-western part of the county. No doubt the crows 

 ate their full share of green corn, but the grackles were many times more 

 numerous and literally covered some corn fields. Twice I surprised them 

 at a hasty evening lunch while they were resting on their way to the 

 roost. None of the corn fields in the vicinity of Oberlin were molested 

 during the latter part of July, and all of August and September. They 

 showed their cunning by passing the night miles from the scene of their 

 daylight depredations. I assume that the flock does not disperse during 

 the day but forages as a flock, because the farmers and others who ought 

 to know tell me of huge flocks of "blackbirds" seen at all times of the 

 day, and because such flocks were every day occurrences during the 

 summer at my old home in central Iowa, where the conditions are the 

 same as here in Ohio, Earlier in the season, while they were foraging 

 for the young, they were found singly or in small troops. 



Another cause for the change in habits as the season advanced, one 

 whose influence was very marked, was the summer molt. I say "sum- 

 mer molt" because the first feathers were shed on June 14, and the last 

 feathers were fully renewed early in October. Feathers were collected 

 every day during the summer in order to determine, if possible, the exact 

 order in which the flight feathers were renewed, and also to determine 

 the length of time occupied in molting. The birds were also carefully 

 watched from day to day to further determine the progress of the molt. 



