i was sitting on my patio eating. it was clear, no clouds, about 70f degrees. i live in a condominium complex with many tall redwoods around, but i also have an unobstructed view of a pretty good sized portion open sky. i was watching birds in the trees around me. i live near the flight path to san jose airport (sjc) and am about 5 miles away, so it is common to see airplanes approaching for landing. during the time i was outside, maybe 20-30 minutes, i'd say i saw 5-7 aircraft approaching, i would guess the aircraft are about 1500-2500 feet high on approach. the bay area has three international airports, so air space is busy. i also saw other aircraft at higher altitude probably coming and going to and from sfo and oak. i was watching a crow high up in a redwood tree when i noticed an object, at what appeared to be high altitude, moving in a east to west direction. i was curious but could not get a good look because it was partially blocked by the tree. based on the objects trajectory and direction of travel i assumed it would reappear from behind the tree at a certain point. i waited but it did not reappear. i searched the sky but could not find it again. several minutes passed and then an object, about the size of a sesame seed, caught my eye high overhead slightly to the east. i assumed it was a bird but could make out no avian features. it appeared round and solid, colored grey and white. it was moving north at what i perceived to be a high rate of speed. at least 200-300 mph when compared to other aircraft in the sky overhead at the same time. i also got the impression for a moment that it might be an escaped party balloon. however, the flight path it took was not straight line but instead a gentle back and forth almost like it was doing a slalom course. it continued north until i lost sight of it behind the roof of my garage. not long after this, maybe 5 minutes at most, i spotted 8-10 objects almost 90 degrees overhead. my impression was that it was a flock of birds. but again, there was no motion of wings flapping, and they appeared to be the same size and color as the first object. they appeared to be following each other in two different circles, about 4-5 in each circle. several of the objects seemed to be interacting playfully with each other. they circled briefly then formed into 2 loose v's and headed north in the same direction as the first object. these objects also seemed to be traveling at a high rate of speed and traveled in a straight line. at this time my impression was they were flying as fast as a jet at 30,000ft. normally i would have written this off as birds. but i couldn't shake what seemed odd to me. the appearance of the objects, their motion, their rate speed.