Last recorded

In a location that you monitor regularly (at least once a week), record the date on which you last see a swift before it migrates from July.

As the departure time gets closer keep a note of the dates when you do see the birds. Do this until you no longer see them and then you have your ‘last recorded’ date.

Available historic data: we have good records from 1907-1914, and from 1923-1999