Todd-Carriker: Birds of Santa Marta Region, Colombia. 77 



element was probably the first to enter, and came in from the east, 

 followed in due course by the Colombian element from the south, while 

 the Humid Tropical forms are a later infusion, and all came in from 

 the south, extending their range from the middle Magdalena to reach 



Fig. 3. Range of Thamnophilus nigriceps, a species of the Humid Cauca- 

 Magdalena Fauna which reaches the Santa Marta Region from the south. 



the forest country which was gradually being formed as the land 

 raised to the east of the Cienaga Grande. From here some of them 

 have crossed over to the humid forest area on the north coast. 



