118 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



The numbers of these summer birds at Ipswich I have estimated 

 at various times with considerable care and by various methods. 

 Sometimes, I have measured the sand bar which they covered, or 

 the strip of beach or the length of the line in the water abreast of the 

 beach, and, by allowing a certain number to the square or linear 

 yard, have arrived at a fairly accurate estimate, which I believe in 

 most cases has been below rather than above the mark. The follow- 

 ing are some of the dates and the numbers: June 21, 1903, 2,000; 

 July 27, 1903, 2,500; November 20, 1904, 8,000; July 16, 1905, 28,800; 

 July 20, 1907, 5,000; July 12, 1908, 5,000. The large number given 

 for July 16, 1905, was obtained from the measurement of the area 

 occupied by a flock. This was an area of 28,800 square yards, where 

 the birds had stood nearly shoulder to shoulder. Even if there 

 was only one bird in every square yard, the numbers would almost 

 exceed belief. 



After the middle of September the ponds about Boston where 

 shooting is forbidden are frequented daily by this bird. The num- 

 bers are sometimes so great that the authorities have at times been 

 alarmed lest the waters of the reservoirs be polluted by the droppings 

 of the birds, or by typhoid baccilli, which they fear may be carried on 

 the feet or plumage from sewage on which the gulls feed. I have 

 made especial note of the gulls visiting the Back Bay Basin of Bos- 

 ton, bounded by Boston and Cambridge, and the center of a great 

 area of brick and mortar. For some years past the tides have been 

 excluded and the water is fresh. The gulls do not spend the night 

 here, but come in from the sea, flying high over the houses at sunrise 

 or from time to time during the day. At times companies of many 

 hundreds ride the water. Later in the winter the gulls collect in 

 great flocks on the ice. I have seen several acres of ice here, as well 

 as on Fresh Pond, Cambridge, covered thickly with gulls. 



The duration of the visits of the gulls to the fresh-water ponds 

 varies. Sometimes they fly back to the harbor or sea within half an 

 hour, sometimes they tarry much longer ; but, as often happens, some 

 are coming and going all day, so it is difficult to say how long the 

 majority remain. However that may be, the ponds are deserted by 

 them at sunset. On one occasion a large flock of gulls remained in 

 Charles River Basin as late as 9 o'clock on a mild December night. 

 It is possible that some food may be obtained on the surface of these 

 bodies of fresh water, but the gulls appear to spend most of their 

 time there gossiping in groups as they float in closely crowded ranks 

 on the surface of the water or stand shoulder to shoulder on the ice. 



The subject of the drinking of fresh water has already been dis- 

 cussed above. As the gulls do not spend the night in the small fresh- 

 water ponds on the coast, and as they fly toward the sea at sunset, 

 it is evident that they must spend the night on or near salt water. 



