22 MICHIGAN BIRD LIFE. 
some of them go and return, and even the approximate time occupied by 
the species in making the trip, but no sane man pretends to say how long 
it takes any individual bird to travel from the Gulf of Mexico to Lake Winni- 
peg,—or even from the Ohio River to the Saginaw Valley. ; 
Formerly well-known scientific men spoke rather confidently of certain 
birds as migrating only by day and of others which journeyed only at night; 
possibly there may be a few species which can still be placed in one or the other 
category, but the number is dwindling every year. The old argument—that 
because a peculiarly marked robin had nested for three consecutive summers 
in the same tree, therefore all robins regularly return to the places of their 
birth; or that because certain sparrows and warblers were killed by flying 
against light-houses, therefore these kinds migrated only at night; such 
reasoning—if it can be so called—has given place largely to better logic 
and the student of today is beginning to demand absolute proof of many of 
the statements which were accepted as established facts fifty years ago. 
A good example of the summer resident is found in the Purple Martin 
which usually arrives in southern Michigan from the Ist to the 20th of April, 
nests during May and June, and again moves out of the state before the 
middle of September, thus spending only five of the twelve months with us. 
In 1884 the northward movement of these birds was noted from the time they 
entered the Mississippi Valley, the last of February, until a few arrived at 
Oak Point, Manitoba, on May 23. The distance from New Orleans to Oak 
Point is about 1,440 miles and apparently about ninety days were consumed 
in making the trip, an average of but sixteen miles a day. However, Prof. 
W. W. Cooke, who collected the data, was convinced that the forward move- 
ment was confined to twelve days (he says nights), which would make the 
average about 120 miles per day for the twelve days of travel.* 
This is a bird of such swift and powerful flight that it is perfectly possible 
for it to speed northward 150 to 200 mjles with a warm southerly wind and yet 
retrace its course the next day in case the weather becomes inhospitable. 
It seems reluctant to retreat, however, and too frequently the early Martins 
which are caught by severe cold weather die from starvation. Their food 
consists almost entirely of insects caught on the wing, and when the temper- 
ature drops anywhere near the freezing point very few insects continue to 
fly. A few benumbed stone-flies may be picked from twigs and grass-tips, 
but not enough to supply heat and strength for these muscular and active 
birds. The Martin spends the winter entirely south of the United States, 
some lingering in Mexico and the West Indies, but more pushing far south 
into Central or even South America. 
Again we have birds like the Longspurs, the Pipits, Rusty Grackles, and 
White-crowned Sparrows, Yellowlegs and Ring-neck Plover, Canada Geese, 
and many ducks, which are strictly birds of passage, or what we prefer to call 
transients, seen only for a few days or weeks in spring as they pass from their 
winter quarters in the south to their nesting grounds beyond our northern 
confines, and again for a few days in fall on their return journey accompanied 
by the young just reared. Yet another group of transients, better called 
winter visitors, should be mentioned which come to us in autumn or winter 
from the north and after spending a longer or shorter time with us again 
withdraw polewards; such are the Snowy Owl, Great Northern Shrike, the 
Pine Grosbeak and two kinds of Crossbills, together with Redpolls, Snow 
* Bird Migration in the Mississippi Valley, Bul. 2, Div. Econ. Ornith., U.S. Dept. Agr. 1888, pp. 
224-225, 
