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most interested, who have ever seen a flock of m',g;rants in their north- 

 ward or southward flight is remarkably small. With the exception of 

 some of the larger waterfowl and hawks, nearly all birds of passage 

 pursue their journey at night, and generally at a great height in the air. 

 From observations made a few years ago at an astronomical observatory 

 near New York, upon migrants seen with a telescope passing across the 

 face of the moon, it was calculated that these birds were flying at a 

 height of from i to 4 miles above the earth. The theory now pretty 

 generally accepted by those who have made these movements a study, 

 is that the birds are guided in their course by rivers and the sea coast, 

 the line of water being easily traceable by moonlight cr starlight on a 

 clear ni^^ht, even at these great altitudes. When the weather is dull or 

 stormy, h>>wcver, and especially when a haze hangs low down, obscu- 

 ring the landmarks, the travellers are forced to fly low. At these times, 

 although it is not often possible to see them, their rallying calls may 

 frequently be heard with great distinctness. 



Oi;e of the best points about Ottawa for such, observations is the 

 Maria Street bridge over the Rideau Canal. 'I'he Gatineau River to 

 the northward with the first stretch of the Rideau on this side, form an 

 almost due north-and-south line for about 250 miles, and no doubt 

 compose one link in the chain of landmarks followed by the birds in 

 passing between the Hudson Bay region and the Atlantic c 'ast of the 

 Southern States, On almost any dull night durmg the season of migra- 

 tion — April and May for the northward movement and September and 

 October f t the southward — at an hour when the noises of the streets 

 have somewhat quieted, the cries of the passing birds can be clearly 

 heard. Very often too, the direction of the flight of certain mdividuals 

 or small groups may be traced with reasonable certainty, showing the 

 course at the former season to be "down" the canal, i.e. north-westerly 

 at this point, and in the autumn months in the contrary direction. The 

 identification of species in the darkness is a more difficult matter. The 

 rallying cries of most birds differ considerably from the songs and calls 

 which we know so well in the d lylight. Still there are a few species 

 whose voices are familiar enou,;j;h to be recognized at any time. The 

 cry of the Greater Yellow-leg Plover ( T. melanoleucus) is at once striking 

 and easy to imitate, as every sport >m.in knows. Oae night last fall this 



