20 PROCEEDINGS OF THE 



Pennsylvania which I frequented most — Delaware and Chester 

 counties, nor in any other part of Philadelphia county than the 

 one already mentioned near Frankford. Wo must conclude 

 therefore that a very marked diminution in the number of the 

 Dickcissels had been going on for at least ten or fifteen years 

 previously to 1870. The history of their final decadence in the 

 Delaware Valley is given in the records appended to this paper. 

 But what has caused this remarkable local decadence and dis- 

 appearance ? This is the paramount query of every one inter- 

 ested in this unique case. I say unique. So far as I can 

 recollect there is no parallel to it in this country where a species 

 of migratory bird inhabiting in summer, two stretches of low- 

 land country separated by a mountain chain but wintering in 

 common territory, should be extirpated from the eastern branch 

 of that breeding area, and at the same time increase in the 

 western one. The persistency of migratory individuals in re- 

 turning to their natal homes is one of the recognized instincts of 

 birds. On this account we would be slow to believe that the 

 Dickcissel history here recorded indicates merely a deflection of 

 the migrating host and not a case of extinction or extirpation. 

 On the other hand, we know of no local causes of decrease. 

 Our native birds of similar range and habits in the Middle 

 States have shown no serious diminution. The English Sparrow 

 and the pot-hunter do not figure especially in the life economy 

 of the Dickcissel. It has been suggested by some that the mow- 

 ing machine at nesting time did the business. It is true that the 

 great increase in use of mowing machines covers the later period 

 of their disappearance; but it appears they were diminishing 

 before the day of mowing machines. Then again in the west, 

 where they are as numerous as ever in the most highly cultivated 

 regions, the mowing machine is quite as fatal as with us. Why 

 should a mowing machine be more fatal than the old mowing 

 scythe ? Both of them cut at or below the level of the average 

 nest of this species, which is generally a few inches above the 

 ground, and often much higher. If it can be proved that the 

 eastern birds always nested on or very near the ground in mow- 

 ing fields and the western contingent generally in bushes and 

 such places as were not mowed or were avoided, there would 



