143 
at Keokuk and St. Louis May 17, and by the next night it had ex- 
tended to Cairo and Memphis. Tbe 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 Custer, Mont., the temperature was re- 
duced to 58°. 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 northernhalf 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 tbis 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 noreason 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 15th 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 notein order of latitude is thatfrom latitude 36° 56/ in 
Missouri, where the first was not recorded till April 25; but since a 
station in latitude 37° 0S’ 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, 
