known as a fast-flying duck and quite a few of these banded on 

 Canadian breeding grounds have covered 2,300 to 3,000 miles in a 

 30day period. Nevertheless, the majority of those that have traveled 

 to South America were not recovered in that region until 2 or 3 

 months after they were banded. Probably the fastest flight over a 

 long distance for one of these little ducks was one made by a young 

 male that traveled 3,800 miles from the delta of the Athabaska River, 

 northern Alberta, Canada, to Maracaibo, Venezuela, in exactly 1 

 month. This flight was at an average speed of 125 miles per day. A 

 very rapid migration speed was maintained by a lesser yellowlegs 

 banded at North Eastham, Cape Cod, Massachusetts, on 28 August 

 1935 and killed 6 days later, 1,900 miles away, at Lamentin, 

 Martinique, French West Indies. This bird traveled an average daily 

 distance of more than 316 miles. 



It seems probable that most migratory journeys are performed at 

 little more than the normal, unforced rate of flight, as this would best 

 conserve the strength of the birds. Migrating birds passing 

 lightships and lighthouses or crossing the face of the moon have been 

 observed to fly without hurry or evidence of straining to attain high 

 speed. The speed or rate of migration would therefore depend chiefly 

 on the duration of flights and tail wind velocity. 



The speed of migration is demonstrated by the dates of arrival, 

 particularly during the spring movement. The Canada goose affords 

 a typical example of regular but slow migration. Its advance 

 northward is at the same rate as the advance of the season (Fig. 5). In 

 fact, the isotherm of 35 F appears to be a governing factor in the 

 speed at which these geese move north. (An isotherm is a line that 

 connects points that have the same temperature at the same time.) 

 From an evolutionary viewpoint we might expect this. If the geese 

 continually advanced ahead of the 32 F isotherm, they would always 

 find food and water frozen and unavailable. By migrating north just 

 behind the advance of this isotherm, birds that breed in the far north 

 will find food and open water available and have as long a breeding 

 season as the climate will allow. 



Few species perform such leisurely migrations; many wait in their 

 winter homes until spring is well advanced, then move rapidly to 

 their breeding grounds. Sometimes this advance is so rapid, late 

 migrants actually catch up with species that may have been pressing 

 slowly but steadily northward for a month or more. The following 

 several examples of well-known migrants illustrate this. 



The grey-cheeked thrush, which winters in the Colombia- 

 Ecuador-Peru-Venezuela-British Guiana area, does not start its 

 northward journey until many other species are well on their way. It 

 does not appear in the United States until the last of April 25 April 

 near the mouth of the Mississippi and 30 April in northern Florida 

 (Fig. 6). A month later, or by the last week in May, the bird is seen in 

 northwestern Alaska. Therefore, the 4,000-mile trip from Louisiana 

 was made at an average distance of about 130 miles per day. 



Another example of rapid migration is furnished by the yellow 



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