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124 THE CONDOR Vol. XXIV 
mediate neighborhood of Rancho La Brea today. Moderate shift of drainage 
lines would readily produce, or as readily destroy, such thickets, 
At McKittrick, quite a different picture presents inself to the imagination. 
Mud fiats of some appreciable extent are the insistent demand which such a 
wader population would make upon our powers of reconstruction. These dab- 
blers call for mud in quantity, spread out, free from thicket, and barely exposed - 
above quiet waters. The anserine population makes a somewhat similar demand. 
To be sure, an occasional duck will drop down into the smallest of pools, but this 
goodly host of paddlers of all sizes certainly indicates open water somewhere in 
the near vicinity. Storks, herons, and cranes in force raise the water birds to a 
two-thirds majority (67%). Surely such a population could have been assem- 
bled only by the lure of open country. Conditions during the Pleistocene might 
well be considered to have been much like those now prevailing at Buena Vista 
Lake a few miles to the eastward of McKittrick. 
The oil seepage which entrapped the birds may well be considered to have 
been located at or somewhat back from the margin of such a lake. The upheaval 
and subsequent erosion that resulted in the present location of the asphalt lens 
upon a hillside could easily have obliterated other evidences of the lake by re- 
moval of typical lacustrine deposits. 
The other alternative to such a reconstruction, a view supported by the 
abundant remains of mud-gathering swallows, is that of an oil seepage accom- 
panied by springs of fresh water discharged through vents of common origin 
with the oil. To such springs, in seasons of increased alkalinity of lake waters, 
many species of birds might repair for drink. Probably the hypothesis most 
nearly approximating the truth, however, is of a marginal seepage connected at 
least by slough or muddy runway with a lagoon of appreciable size. 
The chief objection to this lacustrine reconstruction is the previously men- 
tioned fact that remains of gulls and divers are entirely lacking. But may we 
not find some measure of reason for this discrepancy in the habits of these birds? 
Would not their habits offer a measure of immunity from the dangers of the oil- 
seepage that ducks and waders would not enjoy? They are birds of open water 
or sand bars, rather than dabblers in the mud. Buena Vista Lake is today a not- 
able breeding place for ducks of several species. Their nests are placed in grassy 
and marshy spots in the vicinity of, yet removed from, open water. Runways 
to and from such sites might readily lead the birds into danger from oil seepages 
and deprive them of the immunity accorded to gulis and grebes. 
Can we derive profit in comparing the McKittrick fauna with that of other 
lacustrine deposits such as Fossil Lake, Oregon? At this locality there has been 
worked out one of the most varied faunas thus far recorded from western Amer- 
ica. Shufeldt (Journ. Acad. Nat. Sci. Phila., ser. 2, no. 9, 1892, p. 389) cata- 
logued fifty or more of its species in 1892 and several have been added since 
that time. This interesting fauna includes the following groups: Order Pygo- 
podes, 8 species; Longipennes, 9; Steganopodes, 2; Anseres, 30; Odontoglossae, 
1; Herodiones, 3; Paludicolae, 2; Limicolae, 1; Gallinae, 5; Accipitres, 3; Striges, 
1; Passeres, 2. a. 
This list is notably lacking in storks, in cranes, and in. scavengers, while 
herons and shore birds are but sparingly present. On the other hand, it is rich 
in divers, in gulls, and in ducks. The several students who have studied the as- 
semblage of species agree that an open, shallow, and possibly ephemeral lake 
