84 Tur WiILson BuLLeTIN—NOo: 75. 
small birds, many of them no doubt warblers, as he said 
they were brightly colored, and it was in May. He said that 
the birds never struck the light unless it was misty or foggy 
and very dark. Dixon™* says, “It has been universally re- 
marked by light-keepers that birds strike most frequently on 
dark cloudy nights, with fog, haze or rain. Instances of birds 
striking on clear nights are excessively rare.” Writing of 
the large number of migrants taken on Heligoland, Gatke + 
says, “ A necessary condition for this capture is a dark uni- 
formly overcast sky, especially if there be at the same time a 
very fine precipitation of moisture.” This almost exactly de- 
scribes the conditions that occurred at the time the birds 
struck the Charity Island Light. Captain McDonald also 
told me that as a rule many more birds were killed during the 
spring migration, when the birds seemed to migrate more 
during cloudy and showery weather. Cooke % says “ Fully 60 
per cent of the spring migration of 1884 took place in cloudy 
weather. It is probable, though I am not aware that it has 
yet been proved, that in the fall migration the reverse is the 
case, and the larger movement takes place in clear weather.” 
This was certainly the condition of the fall migration of 1910 
on Charity Island, only three of the twelve distinct bird waves 
occurring on dark or cloudy nights. It is to this fact that is 
due the lesser mortality of birds about this light in the fall. 
The following localities are mentioned in the list of species: 
Charity Island —the easternmost and largest island in the 
group. 
Light-House Point—the northernmost point on Charity 
Island, on which the Light-house is situated. 
East Point —the most eastern point. 
Rattlesnake Point —the point lying between Light-House 
Point and South Point, on the west side of the island. 
*The Migration of Birds, p. 269. 
y+“ Heligoland as an Ornithological Observatory.” p, 57. 
i“ Bird Migration in the Mississippi Valley.” U. S, Dept. Agri., 
Beon, Ornith., Bull. 2, p. 17. 
