^6j. Brewster on Rob ; n /?oos/s. robber 



cases as not to aflect the comparison, although doubtless they 

 would swell both totals materially. The figures as they stand, 

 however, are sufficiently impressive. 



I made no counts at the Maple Swamp roost, but as I remember 

 it, it never contained more than about 2000 birds. Its successor at 

 Little River was not only very much larger, but if my notes and 

 memory can be trusted, was by far the largest gathering that has 

 ever fallen under my observation. Thus I find that on the evening 

 of Aug. 4, 1S75, I estimated the Robins which came in on two 

 sides only at 25,000. This estimate was not mere guess work 

 but was based on a count of the birds which passed during an 

 average minute, multiplied by the number of minutes occupied 

 by the passage of the bulk of the flight. Such a method, of course, 

 is far from exact, and it very probably gave exaggerated results, 

 but a deduction of fifty per cent would surely eliminate all possi- 

 ble exaggeration. As the birds were coming in quite as numer- 

 ously on the two sides opposite to those where my estimate was 

 made, it follows that the total, after making the above deduction, 

 was still 25,000, and this I feel sure was far below the actual 

 number. 



The Norton roost is comparatively small, although, according 

 to some careful counts made this season by Mr. Batchelder, it 

 occasionally reaches an aggregate of about 1500 birds. The 

 Longwood roost at the time of my last visit contained certainly 

 1000 and probably 1500 Robins. 



During the past season Mr. Faxon saw a few Robins going to 

 the Beaver Brook roost as early as June 11, but I have never ob- 

 served any well-marked flights at Cambridge before the 20th of 

 that month. The time probably depends somewhat on the date 

 at which the first broods of young are strong enough to make 

 the necessary eflbrt, for the earlier gatherings are composed 

 chiefly of young birds still in spotted plumage. Perhaps not all 

 of those able to undertake the journey actually perform it at this 

 period, for the movement, at its inception, is slight, and it gains 

 momentum slowly. After July i it increases more rapidly, and 

 by the middle of July becomes widespread and general, although 

 it does not usually reach its height until the latter part of that 

 month or early in August. By this time the old birds have 

 brought out their second broods, and old and young of both sexes 

 and all ages and conditions join the general throng. In fact it is 



