S.R. Wilbur — Page 3 | Geology Reports

USGS1973

California condor survey, 1972

Explore the source record for details and available documents.

California Fish and Game↗

USGS1972

Copulation by California condors

Koford (Res. Rept. No. 3, Natl. Audubon Soc., 1953) observed sexual display among California Condors ( Gymnogyps californianus ) on more than 30 occasions, yet only once did he see what he thought was copulation. Some of the displays he watched were quite intricate, with considerable posturing and "male" aggression, but no such activity preceded this copulation. The birds sat several feet apart for over 1 hour, then one climbed onto the other's back, staying there 1/2 minute and flapping gently at the apparent moment of coition. Afterward they sat quietly 1/2 hour before flying away. This led Koford to state (p. 79) that "possibly in Gymnogyps copulation is not immediately preceded by display." We have records of 8 California Condor copulations, 5 of which are similar to that described above. The three other occasions began similarly, with the birds sitting quietly, but then the "male" displayed briefly before the "female" with wings half spread and head drooping forward. This elicited no apparent response, but the male immediately walked behind and mounted the female. The apparent moment of coition was accompanied by gentle wing flapping in all instances.

The Auk↗

USGS1972

Food resources of the California condor

Conclusions and Recommendations: Although much of the above information is imprecise and inconclusive, it is evident that the condors foraging habitat is diminishing. Food supply probably is still adequate for free-ranging nonbreeding birds, but could become limited if current land use trends continue. Congregating condors on fewer and fewer acres could be detrimental in other ways. It seems the needs of condors can best be met by maintaining a continuous band of :foraging country throughout the species' horseshoe-shaped range. Public needs for open space and livestock agriculture can also be served by land use zoning, cooperative agreements, easements or other land controls implemented with consideration :for the condors' welfare. Of immediate concern is the declining food situation in the general vicinity of the active condor nests in the Sespe-Piru region. Reproduction is definitely depressed, and the reduced local food supply is the only apparent cause. Predicted future developments can only worsen the situation. A concerted effort should be made immediately to slow the loss of food and foraging area closest to the Sespe Condor Sanctuary including: (1) the Big Mountain-Newhall Ranch regions of southern Ventura County; (2) the arc of grassland around the southern and eastern boundaries of the Sespe Sanctuary; and (3) the Tejon Ranch. Within these areas efforts should be made to increase the amount of condor food by: (1) increasing the amount of livestock, if compatible with proper land use; (2) modifying procedures for disposal of dead livestock, so that more are available to condors; (3) encouraging (subsidizing) ranchers to sacrifice livestock for condor food at certain times o:f the year; and (4) developing a state or Federal supplemental feeding program utilizing cattle, deer or other carrion regularly distributed at close, protected feeding sites. If a convenient food supply is as important to reproduction as it appears, those nest sites closest to the best food source may become most productive and significant in the preservation of this species. These sites, which are in the Piru Creek area, are outside the boundaries o:f the Sespe Condor Sanctuary, but are recognized by the U.S. Forest Service (1971) as extremely important to condor survival. Protective measures recommended in the Forest Service plan should be implemented as soon as possible to preserve this area's usefulness as condor nesting habitat. Food may not be the factor currently limiting condor reproduction. However, the reproductive rate is inadequate to sustain the condor population for long. As food shortage has been shown to limit breeding in many species (Lack 1954, 1966), and as it is something which can be manipulated, it is a logical factor for further study and experimentation.

Administrative Report.↗

USGS1972