Air carrier Captain reported a bird strike into engine which was detected/confirmed by maintenance after landing.

Narrative

A bird was ingested in the number one engine at Vr while departing runway 1L. We had been sitting at the runway on the east side of 1R waiting on a wheels up time to LAX for approximately 20 minutes. During that time; there was discussion on tower frequency about bird activity near the departure end of the runway; which is not at all unusual for SFO. We did not observe any birds in our immediate vicinity or over the runway prior to our departure clearance. Just as I called 'rotate'; the FO said 'bird'. I saw it go past the left window and immediately looked at the engine indications to ensure proper engine operation. Both engines appeared to be operating completely normally; with no abnormal indications and no exceedances. We continued the departure uneventfully and commented that 'that was close'. We fully believed that we had missed impacting the bird. We continued on to LAX without further incident. During our two-hour sit in LAX; maintenance initiated contact with me via phone to inquire about whether or not we had a bird strike. I was very surprised and told them what I just outlined. Maintenance indicated that during their post arrival walk around; they saw evidence of a bird strike in the number one engine. They apparently then removed the aircraft from service and did a boroscope inspection which revealed core damage.Also; the UTC time for this report appears to be off. We departed at XA:44 local time or (17:44Z).