960). As the bag deepens, additional strands of grass are added
to the wall and woven into place.

The male is extremely attentive during this and the following phase.
He follows the female as she gathers nest-material accompanying both
this activity and her building with rapid song; he may give an average
of seven song phrases per minute. The male brings to the nest a strand
of grass, or some other material, about every twentieth trip. He
frequently inspects the nest and the activities of the female from
perches near the nest. Construction of the bag is ordinarily completed
in the third day.

The third phase, the lining of the interior and the smoothing of the
exterior, involves an additional one and one-half to two days.
Smoothing of the exterior refers to tightening of the grasses woven
into the bag and addition of more animal silk. In lining the nest, the
female stands on one of the branches of the fork and emplaces one end
of a long, thin strand of some relatively stiff piece of grass or
strip of bark. She then jumps into the bag and, while slowly turning
around, pecks it into place, thus coiling the strand neatly around the
interior of the bag.

As previously mentioned, the fourth phase overlaps the periods of
lining, smoothing, egglaying, and incubation. The principal activity
is the addition of white spider egg sacs to the exterior. The trips
are infrequent; but, occasionally, birds will interrupt an hour of
incubation with three or four minutes of active adornment, during
which several trips may be made. Both sexes participate in this phase.

_Gathering of Nesting Material_

Nesting materials were gathered anywhere within the territory.
Occasionally materials were collected from within the nest tree, but
usually they were obtained 20 to 200 feet from the nest-site. On
several occasions I observed birds inspecting stems or branches where
bark was frayed. Loose ends are grasped in the beak and torn free with
an upward jerk of the head. Possibly the notch near the distal end of
the upper mandible aids in grasping these strands. Plant down is first
extracted and then rolled into a ball by means of the beak while held
with the feet before being transported to the nest.

_Length and Hours of Nestbuilding_

As indicated by Nolan (1960:230), accurate determination of the length
of nestbuilding is difficult because of continued adornment and
polishing after the nest is functionally complete. Most of the earl