BIRD LIFE Ilsr THE URUBAMBA VALLEY OF PERU. 23 



lower hills and ridges just within the front range are relatively dry. The deep val- 

 leys are much drier. Each broad expansion of a deep valley is therefore a dry 

 pocket. Into it the sun pours even when all the surrounding hills are wrapped in 

 cloud. The gi'eater number of hours of sunshine hastens the rate of evaporation and 

 still further increases the dryness. 



The influence of the local climate upon tree-growth is striking. Every few days, 

 even in the relatively dry winter season, clouds gather about the hills and there are 

 local showers. The lower limit of the zone of clouds is sharply marked and both at 

 Santa Ana and Echarati it is strikingly constant in elevation — about five thousand 

 feet above sea level. From the upper mountains the forest descends, with only small 

 patches of glade and prairie. At the lower edge of the cloud zone it stops abruptly 

 on the warmer and drier slopes that face the afternoon sun and continues on the 

 moister slopes that face the forenoon sun or that slope away from the sun. 



It may be added that this cloud forest, which so strongly charac- 

 terizes the Subtropical Zone, descends in drainage areas considerably 

 below the o,000-foot level — a condition clearly illustrated by a pho- 

 tograph of the western slope of the Central Andes of Colombia pub- 

 lished in my Distribution of Bird Life in Colombia.^" The climate 

 of the Cauca Valley, it may further be said, is due in a large measure 

 to the causes which create semi-aridity at Santa Ana. 



Santa Ana is historic in the annals of Urubamba ornithology. 

 Formerly the site of a Jesuit Mission it is now a hacienda devoted 

 to the production of sugar cane and coca where the unbounded hos- 

 pitality of the proprietor, Senor Duque, the delightful climate, the 

 ease with which adjoining areas may be reached have induced prac- 

 tically all the naturalists and explorers who have visited this region 

 to make it, for a time, their headquarters. 



Kalinowski collected here at intervals from June to December, 

 1894, securing, according to Berlepsch and Stolzmann", examples 

 of 56 species. Various members of the Yale University-National 

 Geographic Society Expedition also stopped at Santa Ana, including 

 Heller, whose notes on the region are here appended: 



The valley at Santa Ana is particularly wide, fully a league, and the confining slopes 

 are gentle, although they rise to considerable heights and give the valley a deep effect. 

 Owing to the great width of the valley, and the distant position of the summit ridges, 

 the rain clouds do not collect at this point but pass on and hang themselves to the 

 higher slopes beyond. While we were at Santa Ana in October, the days were bright 

 and clear, but not far distant could be seen the rain clouds and storms in progress and 

 occasionally the thunder reached our ears. The valley floor is covered by a black 

 humus soil, and devoted largely to coca culture, but cane fields are numerous, and, 

 at certain seasons, maize also. The valley slopes show a red soil where they are not 

 grass-covered. Bordering the river are groves of the graceful algaroba trees, the timber 

 of which has been used in the construction of the hacienda buildings which were 

 originally designed for the purpose of a mission station. Cecropia and Erythrina trees 

 border the creeks and fields, but the landscape generally has a highly artificial and 

 denuded aspect. The altitude is 3,480 feet, but owing to the dryness at this particular 

 point, the climate is cooler than usual at so low an elevation, corresponding to that of 

 San Miguel Bridge, which has an altitude almost twice as great. The manager of the 



10 Bull. Amer. Mus. Nat. Hist., vol. 36, 1017, pi. 27. " Ornis, 1906, pp. 73-102. 



