120 
THE CONDOR 
VOL. V 
ing a loud noise for a few moments. The female remained on duty until we were 
directly over the nest. They made but little fuss this time, probably owing to the 
fog. Upon lying down and looking well over the edge of the ledge, the eggs 
were seen on the sandy floor of a small pothole. They were five in number and 
so far advanced that the embryos were covered with down. Incubation must 
have been at least two weeks, causing this set to be the earliest laid of any in the 
latitude. Bendire’s “Life Histories of North American Birds’’ records a set taken 
by Mr. W. E. Bryant on March 25, incubation fresh, some years ago at the place 
hereinbefore mentioned, at the foot of Mt. Diablo. 
In 1900, March 31, we arrived at the ranch house and were told the birds had 
left the locality because one of the party had passed up the canyon last week and 
failed to see the birds. This was far from encouraging news after our long trip 
and it seemed our informant knew what he said, but I surmised he failed to see 
any birds because the female was a close sitter and the male might have been off 
on a hunting excursion, and we therefore decided to labor over the steep and 
winding route once more and not return without investigating more closely than a 
hunter would. When on the opposite hill, before the ledge appeared to view, we 
breathed a sigh of relief, for wasn’t that the music we were anxious to hear, the 
notes of a prairie falcon? In a short time we saw the female reconnoitre from the 
nest-hole and after crossing the canyon and adjusting the rope, soon had five eggs 
in our possession; incubation fully one week. The male had alighted on a dead 
snag across the canyon and now and then uttered his “chug” notes, described 
where he allowed his mate to fly to and fro along the canyon, and once as she flew 
rather close to him he joined her for a short flight, then resumed his perch and 
uttered a sort of cackle unlike any I ever heard, neither can I _emember it nor de- 
scribe it after hearing it, except that it varied considerably from the usual sounds. 
An advanced or retarded spring apparently cuts no figure with these birds. 
This year spring was well advanced while nidification was later. 
In 1901, March 30, the site was tenanted by a pair of duck hawks, but no eggs 
were found although we worked the length of the ridge very thoroughly, nor did 
the birds raise any disturbance, as is the rule. One of them was sitting in the 
nest-hole when seen across the canyon, and the pair allowed us to approach sur- 
prisingly close before taking wing for a resting place further along the ridge, 
instead of making any sort of demonstration or flying about overhead. They 
were flushed again but only made a half-hearted fuss. From its superior size and 
fiercer habits I judged they had driven the prairie falcons into a new precinct, for 
we were not able to obtain a glimpse of them. It is probable that no pair of duck 
hawks or even prairie falcons dwell within a few miles of each other’s domain 
owing to mutual antagonism. Once while robbing a duck hawk’s nest in a dizzy 
cliff over a canyon the male had settled on a dead tree half a mile along the ridge 
leaving the angry female to swoop at us and do all the screeching. She took but 
little intere.st in abusing a couple of turkey vultures that came too close, but all at 
once a prairie falcon chanced across the zone of her short flights and she imme- 
diately attacked him, about 250 feet over the side hill. Both birds clinched with 
their talons, and in each others grip fell straight down like dead weights. Seem- 
ingly in an inextricable position they were about to meet with injury or death by 
contact with the ground below, but when within a few feet of the hill they simul- 
taneously and deftly parted, swinging gracefully aside, the prairie falcon continu- 
ing its original course and the duck hawk resuming her swoops and invectives at 
us, with increased energy. 
In 1902 we did not arrive at the prairie falcon nest until April 15, so as to 
