Randy:
Yes 1963 was the earliest (or at least the earliest that was recorded).
All the data from all years can be seen here:
https://drive.google.com/file/d/19EWVe-v5fKI3s93ciNoNwy2Wpp-GpNg6/view.
There were 61 species observed in 1963. Of those, two have not shown up
on the count since:
When was the first Ithaca Christmas Bird Count? It may have been 1/1/63, as
that is the earliest NYIT CBC that I could find in the National Audubon
Society web archive. Perhaps I could find it somewhere in my old files, as
I recall working
with Dorothy McIlroy to establish the first circle,