makes the longest
flight, according to the late Wells W. Cooke, America's greatest
authority on bird migration, is the Arctic Tern. Professor Cooke, to
{73} whom we owe so much of our knowledge of the subject, says of this
bird:

"It deserves its title of 'arctic' for it nests as far North as land
has been discovered; that is, as far North as the bird can find
anything stable on which to construct its nest. Indeed, so arctic are
the conditions under which it breeds that the first nest found by man
in this region, only seven and one-half degrees from the pole,
contained a downy chick surrounded by a wall of newly fallen snow that
had been scooped out of the nest by the parent. When the young are
full grown the entire family leaves the Arctic, and several months
later they are found skirting the edge of the Antarctic continent.

"What their track is over that eleven thousand miles of intervening
space no one knows. A few scattered individuals have been noted along
the United States coast south to Long Island, but the great flocks of
thousands and thousands of these Terns which range from pole to pole
have never been noted by ornithologists competent to indicate their
{74} preferred route and their time schedule. The Arctic Terns arrive
in the Far North about June fifteenth and leave about August
twenty-fifth, thus staying fourteen weeks at the nesting site. They
probably spend a few weeks longer in the winter than in the summer
home, and this would leave them scarcely twenty weeks for the round
trip of twenty-two thousand miles. Not less than one hundred and fifty
miles in a straight line must be their daily task, and this is
undoubtedly multiplied several times by their zigzag twistings and
turnings in pursuit of food.

"The Arctic Tern has more hours of daylight and sunlight than any other
animal on the globe. At the most northern nesting site the midnight
sun has already appeared before the birds' arrival, and it never sets
during their entire stay at the breeding grounds. During two months of
their sojourn in the Antarctic the birds do not see a sunset, and for
the rest of the time the sun dips only a little way below the horizon
and broad daylight is continuous. The birds, therefore, have
twenty-four hours of daylight for at least {75} eight months in the
year, and during the other four months have considerably more daylight
than darkness."

_Perils of Migration._--The periods of migration are fraught