. Bird-life; a guide to the study of our common birds . also of assistance to them on their migrations. Indeed, atnight, young birds, who have never made the journey be-fore, must rely largely upon this sense to direct them. Itis difficult for us to realize that on favorable nights duringthe migratory season myriads of birds are passing throughthe dark and apparently deserted air above us. Oftenthey are so numerous as to form a continuous stream, andif we listen we may hear their voices as they call to oneanother while flying rapidly onward. Some idea may be formed of the multitude of birdswhi
. Bird-life; a guide to the study of our common birds . also of assistance to them on their migrations. Indeed, atnight, young birds, who have never made the journey be-fore, must rely largely upon this sense to direct them. Itis difficult for us to realize that on favorable nights duringthe migratory season myriads of birds are passing throughthe dark and apparently deserted air above us. Oftenthey are so numerous as to form a continuous stream, andif we listen we may hear their voices as they call to oneanother while flying rapidly onward. Some idea may be formed of the multitude of birdswhich throng the upper air on favorable nights duringtheir migration by using a telescope. One having a two-inch object glass will answer the purpose. It should befocused on the moon, when the birds in passing are sil-houetted against the glowing background. At the properfocal distance they appear with startling distinctness. Insome cases each wing-beat can be detected, and with alarge glass it is even possible to occasionally, recognizethe kind of Plate XVII. Page 107. SHARP-SHINNED HAWK. Length of male, 11-25 inches; of female, 13-50 inches. Adult, upper partsslaty gray ; under parts white and rusty brown. Young, upper parts black-ish brown ; under parts white, streaked with rusty brown. MANNER OF MIGRATION. 57 Observations of this kind should be made in Septem-ber, when the fall migration is at its height. On thenight of September 3, 1887, at Tenafly, New Jersey, afriend and myself, using a six-and-a-half-inch equatorialglass, saw no less than two hundred and sixty-two birdscross the narrow angle subtended by the limbs of themoon between the hours of eight and eleven. Observa-tions made several years later, in September, from theobservatory of Columbia University, yielded closely simi-lar results. This nocturnal journey of birds may also be studiedfrom lighthouses. On September 26, 1891, I visited theBartholdi Statue of the Goddess of Liberty, in New YorkBay, for this pu
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