THE OOLOGIST 



131 



Two Sparrows of Sherburne County, 

 Minnesota. 



During the spring of 1915 I added to 

 my list of Sherburne County birds two 

 sparrows; the Field Sparrow and the 

 Nelson Sparrow. 



I find both are common birds and 

 interesting from a musical standpoint. 

 Though not a great musician, the Field 

 Sparrow sings commonly in the mid- 

 dle of the dryest, hottest days when 

 other birds are silent, while the Nel- 

 son Sparrow does the same thing in 

 the night, being especially musical on 

 rainy or foggy nights. Both of these 

 birds I believe to be new records for 

 Sherburne County, not because they 

 are rare or extending their range but 

 for lack of collecting which would 

 identify them. 



Bernard Bailey. 



A Systematic Study of the Diving Pro- 

 cess of Erismatura jamaicensis. 



For three years the writer has ob- 

 served the Ruddy Duck (Erismatura 

 jamaicensis) at "Nigger Sloughs," 

 seventeen miles south of Los Angeles 

 in Los Angeles County, Southern Cal- 

 ifornia. 



The little "wire-tail" is a common 

 resident of Southern California 

 throughout the year. It breeds in tule 

 marshes from the middle of April to 

 the middle of June. 



On April 9, 1913, the writer's atten- 

 tion was drawn to the peculiar diving 

 process which is characteristic of the 

 species. It was at East Marsh, a 

 small slough adjoining the main lakes. 

 We were fortunate to have been able 

 to approach within seventeen feet of 

 an adult male bird. He was resting 

 quietly on the surface of the water 

 among swamp willow trees; in a mo- 

 ment he was aware of our presence. 

 He raised his head erect, his sinister 

 eye was observant, curious and ques- 

 tioning. Then slowly he began to 



paddle forward — we judge a distance 

 of three feet and then, like a flash he 

 disappeared beneath the surface of the 

 water. Fortunately, the water was 

 clear so that we could see him dive 

 to the bottom and reappear again 

 about twenty feet distant from the 

 place from which he first appeared. 

 We observed that the bird immediate- 

 ly rose out of the water and flew away. 



Our study of the diving process of 

 the Erismatura jamaicensis is quite 

 technical and would take several pages 

 of explanation to satisfy the readers. 

 We have studied twenty-nine cases of 

 the peculiar diving process of this spe- 

 cies. The angle taken by the bird in 

 its downward movement beneath the 

 water and its reappearance to the sur- 

 face again has computed together with 

 the distance traveled under water in 

 all cases. We have authentic data 

 concerning its arrival and departure 

 and the various factors governing its 

 distribution in Southern California. 

 This study is to be a contribution from 

 the department of Experimental Biol- 

 ogy in the University of Southern Cali- 

 fornia. There will appear in our pub- 

 lication several photographs of the 

 Ruddy Duck in various positions, to- 

 gether with maps and charts illustra- 

 tive of every movement taken by the 

 birds from the time they are discov- 

 ered resting on the surface of the 

 water until they reappear from their 

 dive and fly away across the lakes or 

 among the willow trees. We have com- 

 pleted observations of nine female and 

 twenty male ducks of the genue Eris- 

 matura. We have to complete thirty- 

 seven before the season closes. 



We will submit for publication in 

 THE OOLOGIST, at a later date a 

 brief resume of our study of the div- 

 ing process of this very interesting 

 little species believing that it will be 

 of general interest to those interested 

 in Ornithological technique. 



Alfred Cookman, A.B. 



