1870.] LETTER FROM MR. W. H. HUDSON. a7 
The following letter, addressed to the Secretary by Mr. William H. 
* oe 
Hudson*, was read : “Buenos Ayres, Dec. 14, 1869. 
** My pear Sir,—Probably I shall not be able to send any more 
birds to the Smithsonian Institution. The specimens I may find 
leisure to collect can be disposed of in Buenos Ayres; but should I 
meet with any thing new I will forwaid it to the Zoological Society 
of London. I was well pleased with your favour of November 9th, 
expressing your desire to see my notes on the birds I have collected ; 
and should this letter and others I shall shortly send contain any 
thing of interest I shall be glad. 
“Though the pampas of this part of the republic are all but en- 
tirely bare of trees, the swampy margins of the Rio de la Plata are 
covered with an almost impenetrable thicket from two to four miles 
in width. In this wood neither the thorny Curumamnel nor the 
gigantic Ambu, that flourish on the open plains, are found; but its 
trees and shrubs and many of its herbs are natives of the northern 
states of La Plata, the Chaco, and Paraguay. The seeds have been 
brought from those countries by the river, or on the Camalote—a 
species of water-lily that grows round the islands of the Parana and 
its tributaries. These plants accumulate on the water year by year 
till they form vast floating islands, and are ultimately torn from their 
moorings by the floods, carried hundreds of miles down the river, 
and stranded on its low shores. These migratory islands bring with 
them not only the seeds of northern vegetation, but colonies of in- 
sects, reptiles, and other animals. I have known the Cierno, Jaguar, 
Aquard, and Carpincho, and other large mammals, also large Ser- 
pents and Alligators, to have been thus brought down and landed 
within a few miles of the city of Buenos Ayres. Such large animals 
soon disappear; but smaller ones remain, so that in this forest 
Snakes and Batrachians are found of different species from those of 
the neighbouring plains—also insects, whose great size and gaudy 
colours prove their northern origin. The reptiles maintain their 
existence apparently within narrow limits; but many of the insects 
(particularly the Lepidoptera) become widely distributed, and show, 
by the dimmer colours and diminished size of many individuals, the 
modifying influences of climate and other physical conditions. The 
strips of vegetation stretching so far into this country from the 
northern wooded regions have also greatly promoted the distribution 
of birds. 
“There are but a very few species of true ‘ Pampas-birds.’ This 
name I apply to Anthus correndera, Centrites niger, the Red-breasted 
Lark (Tenioptera), and all those kinds especially adapted to the 
conditions of the Pampa. These species avoid trees, and find their 
subsistence, roost, and breed on the ground. But the woody fringe 
to the river above mentioned has served as a grand highway by 
which most of our small birds have been introduced into this country. 
* See articles by Messrs. Sclater and Salvin on Mr. Hudson’s collections 
(P. Z. 8. 1868, p. 137, 1869, p. 158 and p. 631), and Mr. Hudson’s letter (P. Z. S. 
1869, p. 432). - 
