1870. | LETTER FROM MR. W. H. HUDSON. 333 
the effects it had had on the migration of our summer and winter 
birds. All the species of Plover had disappeared, with the exception 
of a few individuals ; and these were so bruised by the wind that they 
could hardly raise themselves from the ground. Most of the small 
birds had also disappeared before their usual time of departure ; but 
of some species the young remained. 
* Storms and other sudden changes in the temperature are probably 
the immediate causes of migration in most of the birds that visit the 
Pampas. Those that are very regular in their coming and going— 
such as the Currincha (Pyrocephalus rubineus), the Summer Red- 
breast (Letstes superciliaris), the Tijereta (Milvulus violentus), one 
of our Swallows, the Humming-birds, and a few others—are the latest 
to appear, and the earliest to depart. 
‘In the others, the irregularity in the time of migration is the 
greater the longer the species remains with us—it being, perhaps, 
greatest in the common Blackbird (Molothrus bonariensis), which 
sometimes remains all winter and sometimes leaves us early in 
autumn. The Asquita (Centrites niger) and the Cinclodes fuscus 
are almost the first winter birds to appear ; but I have not yet seen 
one individual of either of these species, while some usually late 
comers, such as Thinocorus rumicivorus and Tenioptera variegata, 
are plentiful since the storm. The last species has appeared in such 
numbers that I saw more individuals during an hour’s ride a few 
days ago than I usually see in the course of an entire winter. 
“ Tenioptera variegata is one of the most interesting of the Pata- 
gonian birds that visit us in this season, or, indeed, of all the trne 
Pampas birds. ‘The other species of the genus or subgenus to which 
this bird belongs, the Tenioptere irrupero, coronata, and dominicana, 
in every thing closely resemble each other. But J. variegata, 
although, in structure, it has a general resemblance to these, and also 
possesses their melancholy, whistling note and rapid, graceful flight, 
in some respects differs from them very materially. It.is somewhat 
larger, has a straighter bill, more pointed wings ; and its prevailing 
colour is chocolate, instead of white. It does not quietly watch for 
its food nor hop on the ground like the 7’. dominicana, but, like the 
Plover, runs rapidly along the ground in search of insects. Unlike 
the others, this T’nioptera is also sociable, quarrelsome, and sportive 
in its habits, frequently chasing its fellows and pursuing Hawks and 
other large birds, sometimes with an appearance of great animosity, 
and often wheeling about them as if in play. I have watched it 
associating with birds so different in walk and flight that it ap- 
parently cost it much trouble to keep their company. It has, when 
flying, a very pretty appearance, even if it is not what Dr. Burmeister 
calls it, ‘the prettiest bird in this country.’ But naturalists, like 
kings, have their favourites, and this species is evidently his. It is 
rapid and easy in all its motions and exceedingly active ; it takes to 
flight very frequently, and occasionally alights for a moment on a 
thistle-top, but never on reeds and shrubs, the favourite resting- 
place of the white Tenioptera. 
“It is remarkable that its note, which always sounds as if pro- 
Proc. Zoou. Soc.—1870, No. XXIII. 
