COUES ON BIRDS OF DAKOTA AND MONTANA. 563 



List of specimens — Coutinued. 



MNIOTILTA YARIA, (L.) Yieill. 



Black-and-white Creeper. 



A single specimen was taken at Pembina, where it probably breeds, 

 though the fact was not ascertained. Not found further west. In the 

 Missouri region, it has not been traced beyond old Fort Pierre, where 

 Dr. Hayden some years since observed it. 



List of specimens. 



HELMINTIIOPHAGA PEKEGRIXA, {Wils.) Cah. 



Tennessee Warbler. 



Upon my arrival at Pembina, the beginning of June, I at once per- 

 ceived that the vernal migration of the present species past this point 

 was about to be concluded. This was evidenced by the great dispro- 

 portion of the sexes, for out of thirteen specimens secured and examined 

 only three proved to be males. In this case, as in many others, the 

 males lead the van during the migration, the females bringing up the 

 rear a little later. Such preponderance of females, tahen among speci- 

 mens indiscriminately secured, is a pretty sure indication that the 

 migration is in progress ; for when the birds stop, and begin breeding, 

 many more of the active and musical males than of the quiet, shy, and 

 unobtrusive females will be likely to be observed, as was strikingly 

 illustrated on the same spot by the Mourning Warblers. Another indi- 

 cation of the rapid progress of the migration was the steady current, 

 so to speak, of these birds that flowed along the waters of the river itself. 

 The general course of the river is nearly due north and south, and it 

 thus forms a convenient and attractive highway of migration, along 



