°!9i8 Phillips, Migration <m<l Periodic Accuracy. 197 



al Concordville. The Grand Total is Aj>ril 22 for first arrival, 

 while the grand computed 'bulk arrival' is April 2'.i for the 

 entire period. This shows that first arrivals are not mere strag- 

 glers, for if they were, the records of the different Philadelphia 

 stations would not give such uniform results. 



In Stone's 'The birds of Eastern Pennsylvania and New Jersey, 

 IMil ' are given lists of arrival at Germantown, Pa., for 50 species 

 from iss") io L892. Those showing greal constancy are the 

 Chimney Swift, Baltimore Oriole, Barn Swallow, Yellow Warbler, 

 Blackpoll Warbler, Oven-bird, Redstart and Catbird. These 

 records of course are not the work of so many observers as the 

 'Cassinia ' records. 



I'm- tin- period 1893 L900 there is another set of arrival records ' 

 which shows as very accurate birds, the Chimney Swift, Baltimore 



Oriole, Barn Swallow, Wood Thrush and others. We note that 



the same speeies come up with accuracy performances at. different 

 times mid in different localities. 



Mr. Brewster 2 has called attention to the probable dependence 

 of species upon each other for purposes of guidance. He shows 



how Hocks are made up of many species and how rare stragglers 



arc always found in the company of other species. He also men- 

 tions the case of lost birds, that is, rare stragglers, almost always 

 turning oul to he the young of the season. It is of course apparent 

 that many species migrate together. On the great May rush sev- 

 eral species arrive each day on an average. From the 'Cassinia' 

 table of 1911 we get 4 species on May 4, 2 May 5, 2 May 6, 1 May 7, 

 :. May 8, -' May <>, 1 May 10, 2 May 11 and 2 May 12. This 

 refers to common species only, exact dates for rare birds being much 

 harder to compute. Hut however dependent species are upon 

 each Other during their journeys, we cannot escape from the fact 

 that cadi has its characteristic time period, for if it did not, we 

 would get a very different picture of migration. The birds would 

 then come in greal scattering waves, transient migrants would be 

 longer in passing a given point, and the whole phenomenon would 

 lose much of its present orderliness. Of the II common Ilunga- 



i (iissinia, 1901, p. .i~. 

 \J. moii-s of the Nuttall Club, No. 1, issr,. 



