FLYING NORTH 199 



away by the increasing wind. It was perhaps a better 

 simile or comparison which occurred to me later 

 I think it was when riding through the bush on the 

 Patagonian table-land in a strong wind, and noting 

 how the trees and bushes of various kinds were acted 

 on by the current. Some with slender boles, pliant 

 branches and a loose feathery foliage would be swayed 

 about and bent almost to the ground at every gust, 

 others would bend a little, and still others not at all, 

 although their whole foliage trembled violently, and 

 finally some with stiff holly-like leaves would scarcely 

 show a tremor. Migration once started, the line of flight 

 was almost invariably due north in all species, although 

 they travelled at different heights. The very large 

 birds wood ibis, swan, spoonbill, etc. journeyed at 

 so great a height they were scarcely visible in the sky. 

 Plover and shore birds generally, inland-breeding 

 gulls, duck and pigeon and the glossy ibis, travelled 

 at a moderate height; swallows lower still, and 

 lowest of all were the small short-winged birds 

 all the kinds whose only refuge when a hawk appears 

 is on the ground. 



The most notable exception as to the route in all 

 these birds was the rock-swallow in its passage from 

 South Patagonia to Arizona in North America. The 

 manner of this bird when migrating and the direction 

 of its flight was a continual puzzle to me. Its move- 

 ment northwards began in January, and continued 

 for about a month, sometimes longer. But its appear- 

 ance was irregular; in some seasons very few birds 

 appeared, in others they were passing in numbers 



