800 LETTER FROM MR. W. H. HUDSON. [ Dec. 6, 
sometimes of a much greater number. A body of these birds on the 
wing is a most interesting sight—now soaring high in the air, dis- 
playing the deep chestnut hue of their breasts, now descending with 
a graceful curve towards the earth, as if to exhibit the beautiful 
metallic green of their upper plumage. The flock is in the mean 
time continually changing its form or disposition, as if at the com- 
mand of a leader. One moment it spreads out in a long straight 
line; suddenly the birds scatter in disorder, or throw themselves 
together like a cloud of Blackbirds; as suddenly they again re-form 
and proceed in the figure of a phalanx, half-moon, or triangle. The 
fanciful notion will scarcely fail to suggest itself to the beholder’s 
mind, that the birds go through these unnecessary evolutions intel- 
ligently to attain greater proficiency in them by practice, or merely 
to make a display of their aérial accomplishments. The Ibis has 
another remarkable habit while flying; it is not, however, a habit 
exclusively confined to this species. The flock is sometimes seen as 
if seized with sudden frenzy or panic, every bird rushing wildly away 
from its fellows, and descending with a violent zigzag flight; in a 
few moments the mad fit leaves them, they rise again, reassemble in 
the air, and resume their journey. 
‘“‘T should like to know if any thing has been recorded concerning 
the nidification of this bird. Having the four quarters of the globe 
for an habitat, perhaps it is in no country more common than in 
this ; yet its only breeding-place here that I have yet heard of is the 
Gualicho, a marshy district about 170 miles south of Buenos Ayres 
city. I have not visited this place in the breeding-season, but have 
been told by people living in its vicinity that the Ibises breed there 
in great numbers, and make their nests close together. The nest is 
made of dry grass on the ground; the eggs are blue, and three in 
number. Baird, in his ‘Synopsis of North-American Birds,’ says 
nothing is known of its nidification; but this may refer to the bird 
only in North America. I hope from my own observation to find 
out something more of its breeding-habits in this country. The 
Lechuson (Otus brachyotus), though, like the preceding species, 
pretty generally distributed over the pampas, was, until within the 
last three years, rather a scarce bird. It breeds on the ground, 
makes no nest, but merely clears and presses a circular spot on the 
ground among the loose tussocks of long grass, and lays four white 
eggs of a slightly oval form. Near sunset the Lechuson is seen 
quitting its concealment and sitting perched upon a thistle or other 
eminence, or sailing above the ground with a slow Heron-like flight ; 
at intervals while flying it strikes its wings together under its breast 
in a very sudden, quick manner. It is not at all shy, the intrusion 
of a man or dog at evening in the field it frequents appearing greatly 
to excite its indignation. An imitation of its ery will attract num- 
bers of them about a person; the report of a gun has the same 
effect. The language of this species has considerable variety ; when 
alarmed or angry they utter a loud sharp hiss, and at times a sudden 
shrill laugh-like ery. They have also a dismal hollow scream, not 
often heard, and at twilight hoot—this part of their vocal perform- 
