The overall abundance is indicated as follows:

-	Not recorded in the two counties
!	Rarely reported (<10 records on database)
O	Occasional (11-100 records on database)
OO	Regular (101-200 records on database)
OOO	Common (201-1000 records on database)
OOOO	Very common (1000 - 5000 records on database)
OOOOO	Abundant (over 5000 records on database)

The abundance in each month is indicated as follows:

No records
Very occasional
Irregular
Uncommon
Off-peak, but not unusual
Outside of main flight time, but not uncommon
Main flight time