While going through a box of old family pictures I happened on some Kodachrome slides which I made in 1976 on San Bruno Mountain south of San Francisco.
The Great Horned Owl nest was in a hole in the side of a gully near the mountain's east end. I believe I found it during a walk with my dogs right about when the eggs were hatching.
The pictures were made with my Pentax Spotmatic, which I still have and use.
To get some pictures of the adults I made a small portable blind which I carried up near the nest before daylight.
Owls are sometimes aggressive around their nests. They never came after me, but they would not tolerate my dogs in the vicinity. After they gave one of my Salukis a good whack I left the dogs at home when I was going to visit the owls.
There was a good prey supply on the mountain and the owlettes flourished on a steady diet of rabbits, mice and voles.
About the time they start growing real feathers the young owls learn to make threat displays which look pretty intimidating.
The young are ready to leave the nest about six weeks after hatching, though the parents will continue to bring them food for some time beyond that.