“After a six months’ vacation the Plovers resume the serious affairs of life and start back toward the Arctic zone, but not by the same course. Their full northward route is a problem still unsolved. They disappear from Argentina and shun the whole Atlantic coast from Brazil to Labrador. In March they appear in Guatemala and Texas; April finds their long lines trailing across the prairies of the Mississippi valleys; the first of May sees them crossing our northern boundary; and by the first week in June they reappear at their breeding-grounds in the frozen North. What a journey! Eight thousand miles of latitude separates the extremes of their course, and 3000 miles of longitude constitutes the shorter diameter, and all for the sake of spending ten weeks on an Arctic coast! Do you realize this endurance when you see birds passing that window? * * * * * “As to the fatigue of the bird from travel, this is now thought to be very slight, as bird flocks that have crossed great bodies of water do not stop to rest, but usually continue many miles inland. It is, undoubtedly, accident or illness that sometimes causes birds to stop for rest on the rigging of vessels or offshore islands. _The Unknown_ “Interest in bird migration goes back to a far distant period. Marvellous tales of the spring and fall movements of birds were spun by early observers, yet hardly less incredible are the ascertained facts. Much remains to be learned, and it may be of interest to note a few of the mysteries which still occupy attention. Even the daily flight of a bird is a wonderful thing apart from the endurance required in the long migrations. Though the wings of birds are built on very much the same plan, few species use them in precisely the same manner; while on a windy day the wings assume a dozen different positions in as many seconds, and to watch the flight of a sea-bird, as it rises and trims itself to the wind and then shapes its course, is to be awe-struck by this mysterious power of flight. “Snap shot pictures of birds on the wing will show you this better than many words. Some birds, like the Hawks and Eagles, can sustain themselves in the air for hours, sailing against the wind without any visible motion of the wings. Others fly both by swift beating and sailing, like the Terns in one of these pictures. “In short, the differences are so great that the Wise Men can often identify a bird by the sharp outline of its shadow in flight. “This power of flight has been a subject of wonder for many thousand years; we think and we speculate, but no one has yet learned the secret in its fulness.