PREFACE. IX 



leagues from any land, saw a Brown Owl gliding over the 

 ocean with as much apparent ease as when seeking for a 

 mouse over its own native fields. 



The late William Thompson of Belfast, in his Natural 

 History of Ireland, records, vol. i. p. 102, from the log- 

 book kept on board the John and Robert of 500 tons, 

 Captain M'Kechnie, from Quebec to the port of Belfast, 

 that from thirty to forty Snowy Owls on the 16th of 

 November, 1838, were seen when the vessel was 250 

 miles from the straits of Belleisle. Several followed the 

 ship ; from fifty to sixty were seen on the 18th, some 

 alighting on the rigging and yards; three were caught 

 and taken to Belfast alive. The last of those seen at sea 

 was on the 20th November, the vessel then near 700 miles 

 from Belleisle, and sailing along in latitude 54, or nearly 

 so. The ship arrived at Belfast early in December, but 

 had been driven out of her course in the commencement 

 of the voyage by contrary winds. 



Mr. Swainson has remarked that " it is among the in- 

 sectivorous or soft-billed birds that the principal ornitho- 

 logical features of any extensive region will be traced." 



That the obtaining an equalization of temperature 

 has its influence in migration, as well as a search for food, 

 may, I think, be inferred from the circumstance that the 

 summer visitors to this country, coming as they do from 

 the south, leave the winter temperature of North Africa, 

 averaging 55, for England, where the summer heat 

 averages 63, only eight degrees higher than that of the 

 countries they leave, rather than remain where the summer 

 temperature reaches an average of 79, making a differ- 



