MORTALITY AMONG MIGRANT BIRDS 127 



have been reported recently from eastern Colorado 

 and Nebraska, so that the destruction of individuals 

 in this one species has been almost inconceivable, 

 running to many hundreds of thousands in these 

 known instances. It is of interest to observe that 

 among these longspurs and in the instance noted for 

 other birds on Lake Huron, destruction took place 

 during a fall of snow. It may be suggested that the 

 snow was the active factor rather than the cold, and 

 that the steady fall of flakes, more or less visible, 

 brought such confusion and uncertainty that the 

 birds flew downward rather than directly ahead and 

 so came to their death. 



Ducks in various places in the west have perished 

 in multitudes from poisonous alkalis concentrated in 

 or about lakes or ponds in which on other years the 

 birds have fed with impunity. In part this has been 

 due to the agency of man in withdrawing water from 

 streams for irrigation thus lessening the supply of 

 fresh water that had formerly washed alkaline flats. 

 Such has been the case around Great Salt Lake in 

 Utah, where ducks and waders have died in tens of 

 thousands since 1910. Similar conditions occur reg- 

 ularly from the natural desiccation of alkaline 

 lakes at scattered points throughout the Great 

 Basin, a condition that has probably continued 

 since long before the advent of civilized man. Al- 

 though these conditions operate against resident 



