EASTERN ROBIN 31 



Our Massachusetts Robin roosts are invariably in low-lying woods which are 

 usually swampy and are composed of such deciduous trees as maples, oaks, chest- 

 nuts, and birches, sometimes mixed with white pines. I have never known 

 Robins actually to spend the night, however, in the latter, or indeed in any 

 species of evergreen, except at Falmouth, Mass., where there has been a small 

 gathering, these past two seasons, in a white cedar swamp. The trees in the roost 

 may be tall and old with spreading tops, or crowded saplings only twenty to 

 thirty feet in height, but it is essential that they furnish a dense canopy of foliage 

 of sufficient extent to accommodate the birds which assemble there. As a rule, the 

 woods are remote from buildings, and surrounded by open fields or meadows, but 

 the latter may be hemmed in closely by houses, as is the case with a roost which 

 at present exists in the very heart of Cambridge. A roost once established is 

 resorted to nightly, not only during an entire season, but for many successive 

 seasons. Nevertheless it is sometimes abandoned either with or without obvious 

 cause, as the following account of the movements of the Cambridge Robins 

 during the past twenty odd years will show. 



We can form some idea of the multitude of birds that may compose 

 these gatherings from the following quotation from Mr. Brewster's 

 article: 



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, 1875, 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 possible exag- 

 geration. As the birds were coming in quite as numerously 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. 



Of the dates when the roosts are resorted to, he says: 



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

 roost as early as June 11, but I have never observed 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 effort, 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 1 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 

 nearly certain that during August practically all our Robins visit some roost 

 nightly. * * * 



After the middle of September the roosting flights diminish rapidly, and by the 

 end of the first week in October the roosts are practically deserted. The latest 



