DISTANCES TRAVELLED 117 



penetrate even as far as Ecuador. Part of the yellow 

 warblers travel even farther, as they range south 

 into Brazil. The last species mentioned is one of the 

 earliest to begin its migratory movements south, as 

 it is recorded in southward flight in Florida at the 

 end of July. 



The nighthawk that nests on the upper Yukon 

 may winter in Argentina, while the marsh wren of 

 the upper Mississippi Valley, with wings apparently 

 weak, may fly south in autumn as far as central 

 Mexico. The migration routes of some of the wag- 

 tails, the common swallow, the willow warbler, and 

 the spotted flycatcher, which pass from northern or 

 central Europe to South Africa, may be cited as 

 among the longest journeys for small land birds of 

 which we have knowledge. Some of these long 

 flights must be performed without great delay en 

 route \ for I found the North American barn swallow 

 in western Paraguay shortly after the twentieth of 

 September, when no doubt a part of the species had 

 not yet left the United States. 



A number of birds that have extended breeding 

 ranges withdraw in autumn to the south, to concen- 

 trate in the southern portion of the breeding area, or 

 spread only a short distance farther south. This is 

 true of the rock wren, the black-capped chickadee, 

 the black-headed grosbeak, the field sparrow, and 

 the migrant shrike. In such forms the entire group 



