The Prothoxotary Warbler 115 



to its value. This Okoboji record, however, Avould tend to 

 make the Heron Lake record probable.* 



An interesting pro])leni which naturally arises is as to the 

 route by which these birds reached the lake region (refer- 

 ring solely to the Okoboji record). It is not a great distance 

 along tlie Des Moines river from Webster county, where the 

 species has ))een recorded, to the lake region. But the Des 

 Moines valley lies on the ea.st of the divide, while the lakes 

 are on the west; and there are no streams or valleys connect- 

 ing. The actual distance across from the Des Moines valley 

 to the lakes at this point ^\•ould only be about eighteen miles. 



However, if the V)irds follow the river valleys strictly in 

 their migration (and, conse((uently, in extending their range) 

 we must look to the JMissouri river drainage basin for the 

 route of the Okolioji l)irds. From the investigations of Loucks, 

 Roberts, Adams, and others, it seems to be pretty well estab- 

 lished that the species in question is very closely restricted 

 to the river valleys in its movements, as well as its breeding. 



The outlet of Lake Okoboji is through a chain of several 

 smaller lakes (including the Upper and Lower Gar lakes, and 

 Lake ]\Iinnewashta) into a shallow and swampy creek which 

 empties into the Little Sioux river about a mile below the 

 town of Milford. This river, after traversing the north- 

 western portion of Iowa, finally empties into the JMissouri 

 river a1)0ut midway between Sioux City and Council Bluffs. 



Taking into account the ]Missouri river records above re- 

 ferred to, it seems very probable that the Prothonotary 

 Warbler has pushed up the Little Sioux valley to the lake 

 region of Iowa. We may, therefore, await with some interest 

 reports from points in the Little Sioux valle}' with reference 

 to this species. 



The authors cited are as follows : 



1. Loucks, AV. E. The Life History and Distribution of the 

 Prothonotary Warbler in Illinois. Bull. 111. State Lab. Nat. 

 Hist., IV, 1895, pp. 10-35. 



* In response to an inquiry Dr. Thos. S. Roberts writes me under date of 

 August 21. 1914, in wliicli he states tliat the Heron Lake Record has never 

 been published otherwise tlian by tlie negative reference in his article above 

 cited. He also assures nie that his reference to the bird in this locality must 

 not be considered a "record." for he placed no reliance on the information 

 as it reached him. 



