"i, )lf ' I Phillips, Migration and Periodic Accuracy. I'd!) 



ing 15 years of \\<>rk summed up, \\ ii li actual numbers of individuals 

 included in five daj intervals. A rough idea of dates of greatest 

 abundance is thus obtained. These 15 year bulls arrivals are 

 compared directly with the results of the previous year L910. 

 On the whole this table shows a pretty orderly invasion and de- 

 pan urc I'm- each species, although of course the country covered 

 is a large one with much mountainous territory, naturally tending 

 to lengthen ou1 the passage of migrants a great deal aboA e u ha1 it 



would lie if a small area had Iteen used for tabular work. 



Another way of getting some light on the orderliness of the 

 species in migral ion is by comparing in a long series of years, ad ual 

 first arrivals with average first arrivals. In Cooke's various papers 

 in 'Bird Lore' on the migration of X. A. Sparrows there is u large 

 number df 3uch records. We will take only a few of the most 

 striking eases where observations extend over a long period, so as 

 to gel the greatesl possible chance Tor departures from the normal. 



Rose-breasted Grosbeak at Wasington, I). C, L8 years; earliest, 

 .May I ; average May .">. For the same species observed at Engle- 

 wood, X. .)., 1 1' years; earliest, May 1; average May 6. Ballston 

 Spa, X. V., II years; earliest, May 4; average May 10. St. 

 Johnsbury, Vt., L2 years; earliest, May (i; average May 10. 

 Chicago, III., -I years; earliest, April 25; averageMay3. Warter- 

 loo, Ind., I I years; earliest, April 28, average May 2. Aweme, 

 Manitoba, L6 years; earliest, May L2, average, May l(i. 



For the White-crowned Sparrow at Ottawa, Ontario, 24 years; 

 earliest, April 30; average, May 7. For the White-throated Spar- 

 row at Ottawa, Ontario, 27 years; earliest, April 15; average, 



April 26. 



For the Blue Grossbeak at Raleigh, X. C, i'I years; earliest, 

 April 25; average May _'. St. Onaga, Kan., 15 years; earliest, 

 May 1 ; average May 5. 



[ndigo Bunting at Raleigh, X. C, 23 years; earliest, April 23; 

 average, May I. Renovo, Pa., Hi years; earliest, May 2, average 



May !). 



In thus considering a biologic problem such as migration, it is as 



well to remark here that we are laying ourselves open to the jusl 



criticism which biometricians incur when they rely solely on figures. 



This we realize fully. Perhaps data from individual birds, which 



