6 ECONOMIC OltNlTllULOG Y.

then, mounting high in the air, pursue their journey under cover of the night. Birds direct their flight by coast lines and river valleys which are easilydistinguishable in clear weather. Un l'avorable nights these natural highw: s of migration are throngcd by a continuous stream of a'érial Voyager's passing from dusk until dawn.

Looking through a telescope at the moon, one may see numbers of birds cross its glowing surface. From such observations it is coni- puted that migrating birds fly at a height of from one to three miles.

The eyesight of birds is so far superior to ours that we do not realize its value to them while migrating. The height at which they fly gives them command of a wide ‘ange of country. and on clear nights they can undoubtedly distinguish its prominent features with case. But when fogs or clouds obscure these landmarks. they lose their way. It is then that lighthouses prove beacons luring them to destruction. The Bartholdi Statue, at the mouth of the lludson River, is directly in the path of the great; streams of migrants which flow up and down this natural highway of migration. and for this reason is particularly destructive to birds which t ‘avel at night. On one occasion after a storm no less than fourteen hundred birds were picked up at its base, having been killed by striking the statue or pedestal upon which it rests.

But while sight is of the first importance to the older and more experienced birds who know the way, young birds, who are making the journey for the first time. doubtless rely on their hearing to guide them. Birds" ears are exceedingly acute. They readily detect sounds which to us would be inaudible. Almost invariably they respond to an imitation of their notes. and. when under way. frequentlychirp and call. When we consider their power of h luring and thei ' abundance in routes of migration, it seems probable that at no time during the night is a bird beyond the h xaring of his fellow—travelers. The line of flight once established. therefore, by the older birds, who leave first, it becomes a compa‘atively easy matter for the younger birds to join the throng.

Ewmmmt'c 0mz'Hmln'r/j/.—This branch of the study of ornithology treats of the relationships of bird to man from the standpoint of dollars and cents. (‘ivilized man is Nature's worst enemy. 110 is a disturbing element whose presence is a constant menace to the balance of life. It is of the utmost importance. therefore. that we should acquaint ourselves with the conditions which make a true equilibrium and endeavor to sustain them when it proves to our advantage to do so.

The disastrous results which have. followed man's introduction of the English or House Sparrow in America. the mongoose in the West