Sept., 1903 j 
THE CONDOR 
117 
Some Observations on the Nesting Habits of the Prairie Falcon 
BY DONALD A. COHEN 
Read before the A. O. U. — Cooper Club Convention, May i6, 1903 
T his falcon, Falco mexicamis, is very rare in the San Francisco Bay region 
and in a radius of a day’s journey about the adjacent territory. Nowhere 
does it appear to locate its eyry upon the rocky sea coast after the manner 
of the duck hawk {Falco peregrhms anatuni), but prefers the low mountain ranges 
interspersed with plenty of canyons and rolling valleys. It is hardly necessary 
to mention that it is less plentiful than in bygone years, having fallen into line 
with many others of our fauna in their retreat from the encroachments of civiliza- 
tion. In June 1884 while visiting friends in the foothills of Mt. Diablo, Contra 
Costa county, I was one of a small party in quest of birds’ eggs among the cliffs 
and rocks on the sage-covered slope of the mountain, and incidentally flushed a 
family of prairie falcons from one of the loftiest cliffs. There were five of them, 
the family of that year, that circled overhead at no great distance during our 
presence near the cliff. My host, w’ho was present, said they were prairie falcons 
and said that Walter Bryant had gone over these rocky cliffs by means of ropes 
and taken their eggs, from time to time. In later years when I made Mr. Bryant’s 
acquaintance he corroborated this. I first noticed the birds here in 1881 and have 
wondered for how many centuries the species nested in that spot. About the last 
set of eggs taken in this locahtj^ was, from memory, in 1889. If was of four eggs 
taken by a boy living near by and procured for me by my friend and exchanged 
to the late Chester Barlow. The nest was described as being placed on a ledge 
and lined with a few sticks and I believe, some grass, while all the prairie falcons 
and duck hawk sets I have ever taken, about twenty-five sets, were all in small 
caves or potholes, with a bed of sand or fine gravel and .sand with a few bones of 
small mammals and birds. The birds were either killed off by the numerous 
campers that infest the region or worried into leaving for more secure quarters. 
The boulders and cliffs and even the top of the ridge is not so high but that rifle 
balls will go over from the road in the narrow valley below. Among one of my 
curios is a partly flattened bullet from a large calibre rifle that I picked up at the 
base of a boulder near the top of the ridge. 
In this latitude, I may assume, the birds are constantly resident except for 
excursions during fall and winter when the young are probably in search of a 
home, as the old ones will not suffer their presence any longer, so I am told by a 
mountaineer. On two occasions I have noted single birds in Alameda. One 
attacked a band of half grown turkeys early in the fall and the other flew from an 
oak at some pigeons inside their enclosures and struck the wire netting with con- 
siderable force. Being w'ell acquainted with the duck hawk in adult and juvenile 
plumages there is no mistaking a prairie falcon at close range. 
The complement to a set of eggs is five and it is hardly possible to confound 
them with eggs of the duck hawk. As a rule those of the former are plainer and 
lighter colored, and in exceptional cases some are exquisitely blotched or mot- 
tled, being gems among gems. In the general run they lack the generous rich 
coloring of some of our duck hawk eggs but some of the best sets possess such a 
different style of beauty as to hold their own with any set of duck hawk I have 
ever seen. They average a trifle smaller although the superior size of the duck 
hawk over the prairie falcon is greater in proportion. 
