23 
seeming volume was due in part to the greater number of observers, 
for in each district the number of records of this wave was about pro- 
portionate to the number and excellence of the observers. It seems 
probable that to the northeastward the limit of the wave was at Madi- 
son, Wis., and thence up the Mississippi to Saint Paul. There is a 
striking similarity in the species which were reported from the sta- 
tions between Saint Paul and Saint Louis, but while the northern 
stations reported the first males, Saint Louis reported the first females 
and bulk. Nearly one-half of the record is made up of notes on the 
Baltimore Oriole, Orchard Oriole, Rose-breasted Grosbeak, Indigo Bunt- 
ing, Bobolink, Catbird, and Redheaded Woodpecker. No less than 
twelve records of the Baltimore Oriole were sent from six different 
States. These species would now be looked for in vain in the notes 
from Manitoba. <A great bird wave was felt there, it is true, but the 
species composing it were totally different, being those, like the Yellow- 
rumped Warbler and White-crowned Sparrow, which passed through 
the central district some weeks before. As in the great wave studied in 
March, about half as many notes were reported the day after the wave 
had passed (in this case May 6), but these notes came from the same 
places as the day before, and were in ones and twos, indicating that 
they treated of species which arrived the day before but escaped notice. 
The only exception to this was in northeastern Wisconsin, where the 
notes indicated a large local wave; but, even here, it seems more likely 
that the observer was unable to be in the field May 5, and consequently 
did not see the arrivals until the next day. 
The period described above was followed by a north wind. The low 
area had passed east of the Mississippi Valley, and was followed by 
colder and at the same time cloudier weather. During May 7 and 8 
there was not a record of the whole eighty with a S., SE., or SW. wind. 
But the birds did not stop. There seems to have been a regular though 
not rapid advance, for on the night of May 6 there were thirty-six ree- 
ords, every one with N. or NW. wind and cloudy sky. Had this state 
of things lasted but a single night, one might be inclined to regard the 
records as mistakes on the part of the observers, but the whole eighty 
records for the two nights can not be wrong, and the inference is that 
during the latter part of migration there is no night so unfavorable but 
that some migration takes place. 
The least movement of the seven nights under consideration took 
place on the night previous to May 9. A low area had developed two 
days before in Manitoba and had passed across Lake Superior, becom- 
ing central at Port Huron May 8, at 11 p.m. It had produced a great 
rise of temperature (5° to 11°) in the Upper Mississippi Valley —so much 
so as to make this section actually warmer than the middle portion. At 
La Crosse the thermometer registered 70°; at Saint Louis, 65°; Omaha, 
69°; Little Rock, 669; Bismarck, 55°; Fort Elliott, 53°; but the area 
extended'so far north that the south wind it caused was of too short 
