THE CONDOR 
A Bi-Monthly Magazine of 
Western Ornithology 
Volume XXIV November-December, 1922 Number 6 
[Issued December 19, 1922] 
THE DEVELOPMENT OF YOUNG COSTA HUMMINGBIRDS 
By ROBERT S. WOODS 
WITH FOUR PHOTOS BY THE AUTHOR 
HILE following the progress of a pair of young Costa Hummingbirds 
(Calypte costae) at Azusa, California, in May, 1921, I was impressed 
with their slow growth as compared with that of the smaller passerine 
birds; so, on finding another nest, on May 18, 1922, I kept as accurate a record 
as possible of their development. 
This latter nest (figure 46) was located about four feet from the ground 
on a lower limb of an avocado tree some ten feet in height. It contained the 
usual two eggs when discovered and for two weeks thereafter. On the morn- 
ing of June 1 there appeared one black, grub-like young hummer, with stubby, 
triangular bill and a double row of yellowish down along the back, the body 
being otherwise bare. The afternoon of the following day the second egg was 
hatched. The egg shells were not removed from the nest. The bill of the newly 
hatched hummingbird is a little longer than the width at the base, light in color, 
and abruptly differentiated from the head, which is comparatively broad and 
straight across the front. The abdomen is reddish brown, and the sides as well 
as the upper parts are black. 
On the morning of June 7 pin-feathers had Soneared on the older bird and 
by the afternoon of June 8 on the younger also. The bills were longer by this 
time and more tapering from the head and were mainly dark colored. On the 
10th the older one had assumed the peculiar position shown in figure 47, with 
bill pointing straight up. This attitude is apparently made necessary by the 
fact that the young hummer is too long for the nest, but not yet large enough to 
hold its head above the edge. On the 13th the feathers were becoming soft and 
fluffy-looking and the older bird could open its eyes, at least partly. By the 
15th both birds were able to sit up and stretch their wines and view the sur- 
roundings, 
When inspected on June 17 the older hummer appeared fullv feathered 
except for the shortness of tail and wing feathers. The bill was about the leneth 
of the head and was still straight and conical in outline. On the ev ening of the 
21st the older bird seemed alert and ready to leave the nest. Upon moving the 
limb on which the nest was placed both birds suddenly flew to neighboring 
trees thirty feet away. The younger, though it could fly from one tree to another, 
