KEPOKT OX THE .MIGKATIOX OF BIRDS. 387 



III the iiieaiitinie, tlie obscrvjitioiis collected liad reached such a 

 quantity that it did not seem Judicious to expect the Union alone to 

 elaborate the material. At its instance, a special DiAision of Eco- 

 nomic Ornitholoji^y was i'stablished by the Con.uress ot the United 

 States ill the Department ot Aiiricultur«>, at hrst under the Division 

 of J*]ntomology, and Avith an annual subsidy of •fr),00(). Since the 

 year 1886 it has operated as a separate Division of Economic Orni- 

 tholoii'v and Mammalogy, with an annual a])])ropriation of $10,000. 

 Economically supi)orted in this nnumer, and under direction of Dr. 

 C. H. ]Merriam. the prosjterity of the institution is assured. 



In the year 1SS8 the Division issued a most excellent i)ublication 

 on the mijiTation of birds: lleport <ni IJird Migration in the ^lissis- 

 sii»i)i Aalley in the years 1884 and 1885, by W. W. C<K)ke. Fn this 

 work are subnutted the data which 170 observers collected respecting 

 .■)()() species of birds. The author also shows his method of investi- 

 gating the relations of the phenomenon of migration to the prevailing 

 meteorological phenomena, by which method he has extensively 

 utilized the syno})tically grouped observations of the meteorological 

 stations existing in the territory 



The old experience that weather exerts an impoitant intluence on 

 migration was now definitely confirmed. Prof. ( -ooke proved that the 

 atmospliericcentersof depression, moving from Avest to east inthespring, 

 accordingtothelawsof mc^teorology, and which are characterized by cor- 

 respomling phenomena of wind and tem))eraturc. produce in every re- 

 gion changing relations <»f temperature, nanudy, alteinate warm and 

 cold periods, whiidi changes are accompanied by dehnite nugrati(m 

 phenomena. A ''warm wave"' in the atmosphere of the region in 

 ([uestion is also a necessary condition for the beginidng of a ''bird 

 Avave," '•migration waxc.'" whose further progress is clu'cked by the 

 occurrence of a cold ])erio<l until a new warm wa\<' again jtushes it 

 forward and gi\es i-ise to otheis. 



Prof. C<»oke s]»ecilies the time of thes<' waves for Hie period cliosen 

 (1884) and for the territory in (juestion. He e\i)ressly states tiiat his 

 investigation, on account of certain circumstances, is not a complete 

 one, and that smdi a series of observations must be well prepared, and 

 carried out besides under favorable condit i(»ns. •' Pnder such adverse 

 conditions no attempt would hav'(^ been made to study the bird waves 

 were it not for the extreme importance of the subject. It is (hiring the 

 nights of bird waves that tln^ bulk of migration takes place. To study 

 migration successfully it nnist be studied when most active. More- 

 over, it is on bird waves that the action of the weather is most appar- 

 ent; hence thesis waves furnish the readiest nu'ans of studying the ic- 

 lation between meteorology and migration. The greatest drawback is 

 met with in the difficulty of ac(!urat( iy observing and re])orting bird 

 Avaves. It is by far tlie haidest i)art of the iield \\(m1< in the study of 

 migration, and re(|uires more time and more constant iiresence in the 

 held than most observers can give,'' 



