336 
ANAS SPINI CAUDA 
in March, the sex organs were small in seven, “large” in one, and in “breeding 
condition” in one. Of eight females taken at the same time in the same place, one 
was just through nesting in late March, two were actually nesting, one had the 
organs apparently ready to breed, two had the ovaries “swelling,” and the remain- 
ing two had the sex glands “small.” 
Not only is the season irregular, but the locality chosen varies from year to year. 
At Cape San Antonio, E. Gibson (1920) never saw a nest in twenty-five years; and 
then in 1898 the species suddenly became an abundant breeder, and after that there 
followed another gap till 1904, when nests again became very numerous. The mere 
presence of much water and rank herbage does not necessarily result in nesting. 
The nest is always on the ground in various situations, some in long grass in pam- 
pas bottoms, others on higher ground, often among thistles and sometimes on islands 
in swamps. Nests within a few yards of each other have been found by E. Gibson 
(1920). The clutch seems to be the same as in the Common Pintail, although some 
writers give the impression that clutches of from four to six are common. In north- 
western Patagonia eleven clutches taken by Peters averaged eight each, and E. 
Gibson (1920) says clutches generally consist of eight or nine, and that he has seen 
ten or eleven and even twelve. The eggs are cream-colored, somewhat variable in 
shape and average 52 by 40 mm. The incubation period is not known, but it is 
probably the same as in Anas acuta. In confinement clutches hatched in twenty-four 
days (Wormald, in litt.). 
The exact time when the males leave the females is not certain, but that they do 
leave about the time the clutch is completed, is now beyond question from the ob- 
servations of Mr. Peters (MS.) on the breeding grounds and of Dr. Wetmore (MS.), 
who on November 6-8 witnessed an astonishing flight consisting almost entirely of 
old males. It is clear that these males, still in fresh plumage and sexually active, 
had left the breeding grounds, probably farther south, and were seeking a summering 
ground or a moulting ground, in exactly the same manner as their northern cousins. 
This summer excursion began on November 6, on the coast fifteen miles south of 
Cape San Antonio, following a severe storm which flooded large areas and killed 
many thousands of sheep. On the evening of the 7th the flight greatly increased, the 
larger flocks traveling abreast as if on true migration. On the following morning the 
movement lasted until ten o’clock, and between five o’clock and noon the total 
number seen was estimated by Dr. Wetmore at from 15,000 to 20,000! 
The female on the nest or when leading young behaves in exactly the same way as 
any of the northern ducks, employing various ruses to divert the attention of the 
intruder and lead him from the concealed treasures. 
Status. The extraordinary numbers of these ducks have aroused the interest 
of naturalists and the enthusiasm of sportsmen. Of the eleven kinds of ducks 
