198 Tyler, Simultaneous Action. \a^\ 



LApril 



SIMULTANEOUS ACTION OF BIRDS: A SUGGESTION. 



BY WINSOR M. TYLER, M. D. 



The House Sparrow (Passer domesticus) affords a good example 

 of a habit common among Fringilline birds when gathered in flocks, 

 the habit of all starting up as one bird from their feeding ground 

 and returning almost immediately from perches near by, singly or a 

 few birds at a time. On any day between November and March, 

 in town centres where House Sparrows congregate, large numbers 

 of these birds may be watched going through this interesting 

 manoeuvre. 



At sunrise on the morning of December 29, 1912, more than a 

 hundred Sparrows were feeding in the snow-covered street which 

 passes through the centre of Lexington, Mass. Over the space of 

 an acre or two, the birds were collected in half a dozen flocks at 

 points in the street where food was plenty. Although busy filling 

 their crops after a fifteen-hour fast, they remained on the ground 

 scarcely a full minute at a time; without apparent reason, and 

 with no warning note that I could detect, a flock whirred away into 

 the elm branches overhead and within a few seconds the birds began 

 gradually to re-assemble at the place they had just left. Other 

 flocks did precisely the same thing. The instant departure of a 

 large flock is impressive; there is no frightened start of one bird, the 

 others trailing on behind; the birds rise with the suddenness of a 

 rifle's crack. 



The birds fly back and forth between the street and some near 

 cover so frequently that they spend perhaps no more than two- 

 thirds of the time in feeding. When they rise in a body it happens 

 rarely that one or two birds do not leave with the others, but feed 

 on, undisturbed by the precipitous flight of the majority. Indi- 

 vidual action is occasionally shown also by a single bird, who flies 

 off to join another flock. This flying off of one of their number has 

 apparently no effect on the remainder. Individual action, although 

 occurring in members of a flock of feeding Sparrows, is the excep- 

 tion; as a rule the flock moves as a unit. 



As one watches the Sparrows leave their feeding ground time 



