List Basics

List Calculation Rules

• A sighting is summarised into a list when all the list criteria are met by the sighting. Sightings which have a status code of "E" (i.e. escapes) are not summarised unless the list specifically allows sightings with a status of "E".

• When a sighting matches the list criteria the list is updated in the following way:

  • If no entry for the species exists, a new entry is created and all the data in the entry are initialised from the sighting records.

  • If an entry already exists for the species it is updated as follows:

    • The number of sightings is incremented.

    • If the record is not a repeat sighting the number of individuals specified in the sighting record is added to the list entry.

    • If the record is a repeat sighting the number of individuals specified in the sighting record new individuals field is added to the list entry.

    • The status for the list entry is changed if necessary.

    • If any of the dates in the sighting are earlier or later than the list entry the relevant date in the list record will be updated. If the sighting contains a vague date the early and late dates will not be altered in the list entry

    • If the species has not previously been seen in the month or year of the sighting the month and years seen will be updated in the list entry.

• When sighting records are changed or are deleted the count of individuals and count of sightings in the corresponding list entries are amended correctly. Months and years recorded, earliest and latest sighting dates, first and last date recorded cannot be altered as there is no quick way the system can determine the new earliest date etc. These data items are left as they were before the change and may, therefore, be incorrect. If you know that this situation has occurred you can correct it by requesting that the list is repopulated.