THE MIGRATION OF NORTH AMERICAN BIRDS 13 
son’s hawks (B. swainsonz), and rough-legged hawks (B. lagopus and 
B. regalis) might be seen wheeling majestically across the sky in the 
Plains States, and in the East the flights of broad-winged hawks 
(B. platypterus), Cooper’s hawks (Accipiter cooperr), and sharp- 
shinned hawks (A. velor) are still occasionally seen, although these 
birds do not actually travel in flocks. To the birds of prey and 
possibly to the gulls also, a day’s fasting now and then is no hard- 
ship, particularly since they frequently gorge themselves to repletion 
when opportunity is afforded. 
The spring migrations of the blackpoll warbler (Dendroica striata) 
and the cliff swallow (Petrochelidon albifrons) afford an interesting 
comparison of the fights of day and night migrants. Both spend the 
winter in South America, at which season they are neighbors. But 
when the impulse comes to start northward toward their respective 
breeding grounds, the warblers strike straight across the Caribbean 
Sea to Florida, while the swallows begin their journey by a westward 
fight of several hundred miles to Panama (fig. 5). Thence they 
move leisurely along the western shore of the Caribbean Sea to 
Mexico, and continuing to avoid a long trip over water, they go 
completely around the western end of the Gulf of Mexico. This 
circuitous route adds more than 2,000 miles to the journey of the 
swallows that nest in Nova Scotia. The question may be asked, 
Why should the swallow select a route so much longer and more 
roundabout than that taken by the blackpoll warbler? The simple 
explanation is that the swallow is a day migrant while the warbler 
travels at night. The migration of the warbler is made up of a 
series of long, nocturnal flights, alternated with days of rest and feeding 
in favorable localities. The swallow, on the other hand, starts its 
migration several weeks earlier and catches each day’s ration of 
flying insects during a few hours of aerial evolutions, which at the 
same time carry it slowly in the proper direction. Flying along the 
insect-teeming shores of the Gulf of Mexico, the 2,000 extra miles 
that are added to the migration route are but a fraction of the dis- 
tance that these birds cover in pursuit of their food. 
Although most of our smaller birds make their longest flights at 
night, close observation shows that travel is continued to some 
extent by day. This is particularly the case during the latter half of 
a migratory season, when the birds manifest a desire to hasten to 
their breeding grounds. At this time flocks of birds while feeding 
maintain a movement in the general direction of the seasonal journey. 
Sometimes they travel hurriedly, and while their flights may be 
short, they cover considerable distances in the course of a day. 
HOW BIRDS MIGRATE 
SPEED OF FLIGHT AND SPEED OF MIGRATION 
There is wide-spread misconception concerning the speed at which 
birds normally fly, and even regarding the speed they can attain 
when occasion demands, as when closely pursued by an enemy. It 
is not unusual to hear accounts of birds flying ‘‘a mile a minute.” 
While undoubtedly some birds can and do attain a speed even greater 
than this, such cases are exceptional, and it is safe to say that even 
when pressed, few can develop an air speed of 60 miles an hour. 
They do, however, have two speeds, one being the normal rate for 
