Consider a 25 pound (10 kg) bird with 10 feet (3 m) of wings passing through the air. Is there a sound to be heard? What is that sound?
This post quotes 8 historical reports of the sound of the flight of the California condor.
The quotations below date from the mid-19th to mid-20th centuries (citations for the quotations are at the end of this post).
[The birds] move directly and rapidly … cutting the wind with their wings and creating a Buzzing sound which may [be] heard at a miles distance …
Otto W. Emerson:
I hardly expected to have the good fortune to see this rare bird, but one day I heard a sound, as of wind coming through the oaks …
William L. Finley:
There was something ominous about the condors and their nest cave. Never a sound came from the birds: they came and went like great black shadows.
Gerald B. Burtnett:
The rush of air through the feathers as the bird soars makes a whistling noise, like that of the taut wires of a biplane in a dive for the airport.
When the Condor swerved to elude the Hawk, his wings made a loud, almost deafening, booming noise.
… a huge blurred shadow swept the ground at the cave entrance…. The wind passing through his wing pinions made a soft echoing thunder in the cave …
Robert Porter Allen:
As they move through the air, their stiff, heavy flight feathers make a loud whistling sound.
Alden Miller, Ian I. McMillan, and Eben McMillan:
The air passing through its wingtips sets up a steady whine as it is pressed into service to keep the great glider aloft.
So, as is usually the case with the California condor, the answer to even simple questions – is there a sound to be heard? what is that sound? – is complicated.
Clyman, James. James Clyman: his diaries and reminiscences. California Historical Society Quarterly. June 1926. [The diary was written in the 1840s]
Emerson, W Otto. Ornithological observations in San Diego County. Bulletin of the California Academy of Sciences. June 1887.
Finley, William L. Life history of the California condor: part III – home life of the condors. Condor. March-April 1908.
Burtnett, Gerald B. Oh, king condor … live forever. Los Angeles Times. 11 August 1935.
Seibert, Milton. A week with the California condor. Field Ornithology. January-February 1941.
Nevins, Ken. Condor of ice age battles to survive. Los Angeles Times. 14 March 1949.
Allen, Robert Porter. The giant golden book of birds. Golden. 1962.
Miller, Alden H, Ian I McMillan, and Eben McMillan. Hope for the California condor. Audubon Magazine. January-February 1965.