thereafter as this grosbeak crosses the Gulf of Mexico and enters the 

 northern part of its winter quarters in southern Mexico the lines do 

 not further converge. However, the pathway of those individuals that 

 continue on to South America is considerably constricted by the 

 narrowing of the land through Central America to Panama (Fig. 16). 



Although the cases cited represent extremes of convergence, a 

 narrowing of the migratory path is the rule to a greater or lesser 

 degree for the majority of North American birds. Both the shape of 

 the continent and major habitat belts tend to constrict southward 

 movement so that the width of the migration route in the latitude of 

 the Gulf of Mexico is usually much less than in the breeding territory. 



The American redstart represents a case of a wide migration route, 

 but even in the southern United States, this is still much narrower 

 than the breeding range (Fig. 17). These birds, however, cross all of 

 the Gulf of Mexico and pass from Florida to Cuba and Haiti by way of 

 the Bahamas, so here their route is about 2,500 miles wide. 



Figure 1 7. Distribution and migration of the redstart. An example of a wide migration 

 route, birds of this species cross all parts of the Gulf of Mexico, or may travel from 

 Florida to Cuba and through the Bahamas. Their route has an east-and-west width of 

 more than 2,000 miles. 



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