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 foHage 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 



