BIRDS OF INDIANA. 531 



at the southern edge of the farm, or the almost endless voyage of some 

 shore birds across every one of the earth's zones. It may mean a change 

 of individuals; a moving of those which summer with us a little farther 

 south and a filling of their places by others of the same kind from a lit- 

 tle farther north. It may mean a restlessness which some years impels 

 the Bob White to move southward a few miles, or again to leave the 

 hills and congregate in the valleys, or the reverse. Many times they 

 fly into towns, and becoming confused, enter houses and stores, and 

 are readily caught in the hand. It may mean the slow movement of 

 the short-winged warblers and wrens, or the rapid flight of the swallo\7 

 and Wild Pigeon. Its cause is the instinct which tells them to prepare 

 for winter or return for spring. A call that must be answered, an in- 

 herent demand that comes to each individual through the accumulated 

 experiences of the past which it cannot disobey. 



Birds do not move promiscuously over the country, but are observed 

 to have migratory routes. The Mississippi River is a great artery 

 along which in spring courses a mighty stream of avian life destined 

 to its breeding ground. At the mouth of the Ohio a large stream 

 turns off to ascend that river, sending out branches of considerable 

 size up the Wabash, Whitewater and Miami rivers. The Whitewater 

 Valley forms one channel by which these wandering birds reach the 

 Maumee and the lakes, whence many pass on still farther northward 

 to their summer homes. As the rivers become the channels of migra- 

 tion for certain species, other forms of different habits follow 'the 

 higher lands or the mountain bases, along characteristic topographical 

 features. As the warm air of spring comes, as from the throbbing of 

 a great tropical heart, so the birds come, in pulsating movements, each 

 succeeding one stronger and driving its tide of life farther along its 

 course. Each bird-wave seems to move as though the rear of the mi- 

 grating forms was continually passing over the more advanced and tak- 

 ing the lead. Among the smaller streams, the main ridges, the connect- 

 ing woodland, at the height of the migration may readily be observed 

 the smaller currents of bird life given off by the larger streams, each 

 following its own course, all instinctively going in a definite direction 

 north. The whole movement may be compared to the circulation of 

 sap in a tree. From trunk to limb, from limb to branch, from branch 

 to bough, from bough to twig, from twig to leaf. The entire move- 

 ment over either hemisphere may be likened to numberless trees with 

 their roots at the equator, their topmost branches approaching the 

 poles. In autumn the courses of the bird currents are not so plainly 

 marked, but yet along the borders of our streams may be seen, at 

 favorable times, hordes of little wanderers moving past in almost end- 

 less streams at early morn and eventide. 



