DUCKS, GEESE, AND SWANS: MALLARD 
113 
Townsend that during courtship the drake, besides bowing to the duck, 
“rears himself up in the water,” apparently to display his richly colored 
breast (1916, p. 13). He may also display his handsome feet as do some 
of the other drakes. 
At Lake Burford Doctor Wetmore found that while the females were 
at the nest the males remained from a hundred yards to half a mile 
away, standing on shore or swimming in open water. These males were 
alert and called instantly at the approach of danger. “As early as May 
29, drakes that had finished breeding were banding together ... A 
bird that was molting into eclipse was noted on June 4, and from then 
on birds in changing plumage were common. In this molt they first 
become dull in color about the head and at the same time lose the 
recurled upper tail coverts. A male almost entirely in eclipse plumage 
was seen on June 18” (1920a, p. 239). (See Millais, 1902, pp. 18-23— 
eclipse.) 
One of the Mallard drakes taken on Lake Burford on September 28 
was mainly in winter plumage, but both his green head and his mahogany 
breast were still spotty with the dull feathers of his “eclipse.” In the 
region of Albuquerque, by October 16, Mr. Aldo Leopold states, the 
drakes have the chestnut breast patch, the white ring around the neck, 
and the green head well developed. There are still spots and black 
wash on the underparts and rusty feather tips on the head as well as 
undeveloped curly feathers above the tail, but the general effect is 
unmistakable. By November 15, practically full adult plumage is 
attained. The molt of the female Mallard, Bonhote tells us, is post¬ 
poned until the young can fly, and as soon as her quills are grown again, 
“the family moves off to join the flocks which are now rapidly forming.” 
An interesting local example of what Mr. Leopold denominates “differ¬ 
ential sex migration” is given by him in his study of Mallards on the Rio 
Grande near Albuquerque. “When the season opened in October,” 
he says, “there was a notable preponderance of hen Mallards ... by 
the first week in November this preponderance of hens disappeared, and 
until the main flight was over, about December 1, there was a pre¬ 
ponderance of drakes. Among the Mallards wintering here, after the 
main flight was over, the proportion of drakes to hens was normal” 
(1919e, p. 182). 
During the shooting seasons of 1917 and 1918, Mr. Leopold kept an 
interesting plotted record of plumages and weights of ducks taken. He 
says that the curves for all species are flat for the period October 16- 
November 1. The curves for all species show an increase in weight from 
November 1 to November 15. After November 15,the curves aresubject 
to sudden drops, and during the winter period to very gradual drops. 
The sudden drops appear to be coincident with severe general storms. 
The gradual winter drop seems obviously due to cold weather and 
scarcer feed. The fall ducks are very fat, but the heaviest killed by Mr. 
