8 Cooke, Routes of Bird Migration. [^ a " k 



from northwestern Florida across the Gulf, continuing the south- 

 west direction which most of the birds of the Atlantic coast follow 

 in passing to Florida." 



But it is probable that the case is stronger than so far stated. 

 If one will study the distribution and migration of birds around 

 the Gulf of Mexico, he will come to believe in what I call ' paral- 

 lels of migration.' There is no single fact or series of facts that 

 proves this, but many facts are explained by it that are difficult to 

 explain otherwise. An example will show what I mean by paral- 

 lels of migration. The western edge of the regular range of the 

 Kingbird (Tyrannus tyrannus) extends from Corpus Christi, 

 Texas, to the State of Tabasco in Mexico ; the eastern edge from 

 Florida to Yucatan. The whole path of migration crosses the 

 Gulf of Mexico. It is a fair presumption that the individuals that 

 are farthest west in Texas are the ones that fly to Tabasco, and 

 that the Yucatan Kingbirds come from Florida. Between Florida 

 and Texas, it is practically certain that the Kingbirds in the fall, 

 as they reach the coast of the Gulf of Mexico from the north, 

 launch out across the Gulf from the place where they came to the 

 coast, without migrating either east or west along the north coast 

 before undertaking their water flight. Tims each Kingbird starts 

 across the Gulf in an approximately southerly direction and so 

 their lines of migration across the Gulf are approximately parallel. 



As already stated, this theory is not at present susceptible of 

 proof, but it seems the most reasonable explanation of the known 

 facts. It is not meant that all the individuals of a species follow 

 these parallel lines, because it is known that there are wanderers, 

 from choice or accident, in most species, but that these parallels 

 represent the normal and usual lines of flight of the larger portion 

 of the species. 



If this theory of parallels of migration is correct, then it follows 

 that, in the case of a wide ranging species, like the Black and 

 White Warbler, occurring in the Bahamas, Cuba, Yucatan and 

 most of Mexico, the individuals from eastern Florida probably 

 pass to the Bahamas, from central Florida to Cuba, from north- 

 western Florida to Yucatan, from the mouth of the Mississippi 

 southward across the Gulf, and from central Texas to Mexico by 

 land. 



