Last recorded

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

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 very good records from 1891-1999 (7384 records) 

Last recorded image
Swallow (Jerome Murray/Alamy)