Has Spring sprung?
Even deciding on the “official” first day of spring is difficult. According to the Met Office spring starts on March 1st, traditionalists go with the date of the spring equinox which falls on March 20th or 21st. I suspect, though, that a lot of us have a personal, natural sign that we look out for each year that reassures us that spring has arrived or is at least well on the way. When I worked at Malham Tarn it was always the first curlew or more specifically the first curlew call that told me that winter was on its way out.
There is a science (phenology) to do with the dates when natural things happen and the UK government has an “official” Spring Index that is based on the occurrence of certain natural phenomena. The index is one of the UK Biodiversity Indicators and is, to quote,
...calculated from the annual mean observation date of the following four biological events: first flowering of hawthorn (Crataegus monogyna), first flowering of horse chestnut (Aesculus hippocastanum), first recorded flight of an orange-tip butterfly (Anthocharis cardamines) and first sighting of a swallow (Hirundo rustica).
This doesn’t tell us when spring has started but gives us a sort of middle date for spring. Now in some years, as we all know, spring is early and some years it’s late, and not surprisingly this is do with the weather
When March and April are warm spring is early and when it is cold spring is late. No real surprise there but phenology is an old science in the UK and scientists have noticed that spring is getting, on average, earlier.
This year FSC is asking all of its centres to monitor the arrival of spring by recording the four natural events that contribute to the Spring Index and we want you to join in as well. Follow the link and complete the form and send it back to firstname.lastname@example.org
If you want to work out your own Spring Index you can type your four sighting dates in this spreadsheet and it will work it out for you.
If you are interested in knowing more about phenology and helping them to record many more aspects of when natural events happen have a look at the Nature’s Calendar website run by the Woodland Trust.
Read our 2015 Spring Index findings.
Published by: Robin Sutton
Tuesday, March 3, 2015