I have not been able to program Mrs. Mackrackit. Fuzzy logic

Mm, how about sending the PIC back to SLEEP awaiting another Interrupt_On_Change (the birds have started visiting again it was only a cloud) so carry on counting. If after say SLEEP 1800(about half an hour) the LDR is still high then Send_Data it really is dark!
That should work.

the INPUT COUNTER will need some thinking about.
"Debounce" so one count per bird...