ECOLOGY OF ISLE ROYALE. 109 



Thrush, Solitary Sandpiper, Magnolia Warbler, Palm' Warbler, Oven- 

 bird, Bay-breasted Warbler, Blue Headed Vireo, Blackpoll Warbler, 

 Savannah Sparrow, Black-throated Green Warbler, Grinnell's Water 

 Thrush, Marsh Hawk, Catbird, Black-throated Blue Warbler, Nash- 

 ville Warbler, Philadelphia Vireo, Eed-eyed Vireo, Lincoln's Sparrow, 

 Connecticut Warbler, Ruby-crowned Kinglet, Gray-cheeked Thrush, 

 Broad-winged Hawk and White-crowned Sparrow. 



The following were seen on September 13 : Chipping Sparrow, White- 

 throated Sparrow, Sharp-shinned Hawk, Sparrow Hawk, Flicker, Her- 

 mit Thrush, Pigeon Hawk, Robin, Palm Warbler, Blackpoll Warbler, 

 Savannah Sparrow, Marsh Hawk, Lincoln's Sparrow, Gray-cheeked 

 Thrush, White-crowned Spai-row, Horned Lark and Yellow-bellied 

 Flycatcher. 



5. Fifth Wave. On September 16 the bulk of the Rusty Crackles 

 arrived. A few had been seen the day previous, but only scattered in- 

 dividuals composing the vanguard of the large, noisy flocks to follow. 

 The area of highest pressure was oif the New England states, while 

 the low pressure centered in Kansas. The barometer stood 30.0 inches, 

 temperature 50°, and an easterly wind with a cloudy sky. While this 

 was one of the smallest of the sharply defined waves, it present's a 

 marked contrast to most of the others. Although the area of highest 

 pressure was not near Isle Royale, as during most waves, the barometer 

 stood at 30.0 inches, which was higher than for the area to the west 

 and south; the wind was from the east and the sky cloudy in con- 

 trast to the northAvest wind and clear sky of the other waves. 



6. 8ixtli Wave. On September 18 the high area was far to the 

 east (Maine) and the low centered over Kansas. The barometer steod 

 at 29.8 inches, with a clear sky, northeast wind, and a temperature of 

 .52°. Like the last this was comparatively a small wave and only in- 

 volved a single species, the American Pipit, which came in large flocks 

 numbering from perhaps 100 to 200 birds. 



V. THE RELATION OF WEATHER TO MIGRATION. 



Cooke ('88, p. 16,) makes the following statement in regard to the 

 relation of temperature and barometric pressure during migration, "The 

 area of the lowest pressure is never stationary but constantly moving, 

 and in an easterly direction. It may be moving northeast, east, siouth- 

 east, and rarely north or south; but never northwest, west, nor south- 

 west. The usual direction in the Mississippi Valley is a little south 

 of east." Warm waves, which are associated with areas of low pres: 

 sure, therefore begin, in the northwest, and move toward tlie southeast. 

 "It is a law of the movement of winds that they gO' toward areas of 

 low pressure, and from an area of high pressure." "But an ai-ea of 

 low pressure is followed by one of high pressure, producing an opposite 

 effect, and the isotherms which bent north to welcome the coming of the 

 low area turn rapidly southward before the icy breath which blows 

 from an area of high pressure. Thus the cold and warm waves both 

 come from! the same quarter, and both move in the same direction; 

 that is the direction in which the area of low pressure is advancing."' 

 It will thus be seen that the temperature and the direction of the wind 

 over any given area ai'e both associated with the barometric pressure 



