143 



at Keokuk and St. Louis May 17, and by the next night it had ex- 

 tended to Cairo and Memphis. The maximum heat did not reach 

 Vicksburg until the night of May 19. Thus this warm wave was four 

 days in passing from the Rocky Mountains to Vicksburg. Before it 

 had reached the Gulf States another cold wave had already started in 

 the northwest. May 17, at Ouster, Mont., the temperature was re- 

 duced to 53°. This cold wave, also passing south and east, reached 

 Vicksburg May 20, the next night after the warm wave. In this way 

 waves are constantly passing, and their influence on the migration of 

 birds is very marked. 



The Signal Service reports show that a warm wave culminated in the 

 Lower Mississippi region on the night of March 30. The next day the 

 first Kingbird noted in the spring of 1884 was seen at Rodney, 

 Miss., (latitude 31° 52'). (It was reported that a few remained all 

 winter at latitude 29° 57' in Louisiana, as indeed they do throughout 

 most of the Gulf States.) For the next ten days there was no general 

 or widespread atmospheric wave. The northern half of the Mississippi 

 Valley was visited by short snow-storms followed by still shorter 

 periods of sunshine, while the weather in the southern part was of an 

 indeterminate character. During this period, and after a night when 

 the temperature was scarcely above freezing, the first Kingbird was 

 noted from latitude 37° 08' in Missouri. There is no reason for challeng- 

 ing the record, for in so well-known a bird there is little chance of 

 erroneous identification. But the probability^ is that the bird really 

 arrived the night before, when the temperature was nearly fifteen 

 degrees warmer, and escaped detection. However that may be, it is 

 evident that very little movement took place until the advent of the 

 warm wave which started in the Rocky Mountains on the 12th of 

 April and was very pronounced in the Lower Mississippi Valley during 

 the nights of the 13th and the 15th, the temperature being 29 degrees 

 warmer than a few nights before. This renewed the advance and 

 brought the first Kingbirds to latitude 33° 34/ in Mississippi on the 15th, 

 and to latitude 33° 36' in Texas on the 16th. After a decided but 

 short cold wave another warm wave passed over most of the Missis- 

 sippi Valley on the night of April 17. It brought three males to Saint 

 Louis, and the next day the bulk was reported from latitude 37° 08' in 

 Missouri. A few days later two notes were received from Illinois, just 

 opposite Saint Louis. It may be that the birds came during the slight 

 rise of temperature during the night of April 21, but it is more proba- 

 ble that they came on the night of the 17th and were not noticed until 

 later. The next note in order of latitude is that from latitude 36° 56' in 

 Missouri, where the first was not recorded till April 25; but since a 

 station in latitude 37° 08 / in Missouri, only a few miles distant, had 

 previously reported both the first and bulk, it may be considered that 

 the species was accidentally overlooked until long after it had arrived. 



On April 25 a warm wave was at its height at Yankton and Omaha, 



