40 BIRDS OF SOUTH DAKOTA 
becoming confused and flying low, often perish by dashing 
themselves against monuments, light houses, telegraph poles 
and wires and even the sides of buildings. It is stated upon the 
best authority that “over 1,500 birds have been found dead at the 
base of the Bartholdi statue in New York harbor in a single 
morning, and 230 birds of one species (Black-poll Warblers) 
were killed in a single night by the Fire Island Light. The 
Washington monument, though not illuminated at night, causes 
the death of hundreds of birds annually.” 
Looking through a telescope focused on the moon during 
migrations, the observer sees many birds cross the moon’s disc. 
In this way the direction is noted, their height calculated, and 
often even the species recognized. The multitude of feathered 
migrants that fill the air at such times may be discovered, at 
least in part, by counting the calls as the birds pass. 
The writer stood one evening in early September on the 
shore of Pickerel Lake, in South Dakota, and watched the pass- 
ing of Franklin’s Gulls. They flew southward in great streams. 
When one stream had passed, and what seemed a few belated 
stragglers were hurrying forward, another stream would appear 
in the distance, then another, and another. For half an hour he 
watched them and wondered if there was to be no end. A year 
later, and within a few days of the former date, he witnessed 
the same beautiful sight a second time. 
So regular are the seasonal conditions, so constant also 
is the habit of most birds, that any one who observes dates can 
tell within a few days when any bird will appear. 
A sudden drop of temperature during spring migration 
will often cause birds which otherwise would pass on, to remain 
about for days. Black Terns have been known to linger even for 
weeks as though settled for the summer. A pleasant autumn 
also will retard the fall migrations of many of the feathered folk, 
especially those that come north early in the spring, and do not 
winter far south. In ordinary seasons and weather, however, 
as stated above, the migration of birds is surprisingly regular. 
The males of most species arrive a few days ahead of the 
females. Male House Wrens will carry sticks into three or four 
