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 Eedheaded 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, whicn 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 5 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. Duriug May 7 and 8 

 there was not a record of the whole eighty with a S., SE., or S W. 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 rec- 

 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° 5 Omaha, 

 09o • Little Rock, C6°; Bismarck, 55° ; Fort Elliott, 53° ; but the area 

 extended so far north that the south wind it caused was of too short 



