Updated with new plot showing when migrants are first expected, and, first recorded in 2021 - hit read more below

With spring migration upon us, we thought it a good time to publish analysis showing the earliest, latest and median arrival dates of some of our more common summer visitors and passage migrants: it shows an interesting trend towards earlier median arrival dates for most the species covered.

The analysis covers the period 1983 - 2019, and uses with kind permission Colin Everett's 'A Review of First and Last Dates for Migrant Birds in Hertfordshire' covering the period 1983 - 2002 as included in The Hertfordshire Bird Report 2006.

Go to - First, Last, Median arrival dates 1983 - 2019 - to download the file

New - a plot showing when our some of our most common spring migrants are most likely to be first seen in Hertfordshire.

The plot for 15-Mar-21 is shown below. The live plot will be regularly updated as migrants are first recorded: go to https://github.com/chrisruis/Species-first-records/blob/master/species_distribution.pdf for full and latest version. (note: if clicking on the link does not work, try copying and pasting into your web browser.









We intend to expand this analysis in future, including adding more species so please look out for updates.