As folk are using e-bird to log their personal sightings, (as well as
contributing to the overall picture), I would say enter what you see + where and
when. I am sure they have a way of turning mass sightings of one bird into a
meaningful statistic. Personally, for me to use e-bird (which I do), it has to
be an all or nothing situation, as I want to build up a complete picture and be
able to compare the current year's sightings with previous years.