Back in January a few of us involved in Curracag and the Outer Hebrides Biological Recording group decided to launch a phenology survey we ended up calling Signs of Spring. Phenology is the study of when things happen and for centuries people have systematically recorded when certain natural events...
As if to tease us, indications of better things to come arrived just as daylight hours reached their minimum. The first tentative daffodil shoots appeared amongst the rapidly dwindling Calendulas in the garden and deep in the hedge a Song Thrush started to sing.
Knowing that the worst of winter is still to come I grasp these early stirrings as evidence that it won’t last for ever and, at some point, better times will arrive.
I suspect that every naturalist has their own seasonal markers of spring, the first sighting of Snowdrop, Daffodil, Swallow, Bumble Bee or Butterfly. The first time a Cuckoo is heard calling or the first Arctic Tern is sighted on the coast. When I used to live on the moors of Northern England it was the first time I heard the bubbling display call of returning Curlew. Here in the Hebrides it’s the drumming of Snipe, the tumbling territorial display flights of Lapwing or the rollercoaster rides of male Redshank both accompanied by exaggerated versions of their normal calls. Spring here is an aural as well as visual event.
The UK government has an official index of spring. It’s not about when spring starts but is more to do with when we know spring is here. An average of the first dates of four spring events is taken to produce the index;
- the first flight of an Orange-tip Butterfly,
- first date when Hawthorn flowers,
- and Horse Chestnut flowers are fully out,
- the date when the first Swallow is seen.
The government uses this index to “highlight a biological response to climate change and a potential pressure on biological systems”. Because of that pressure, “since 1999, the annual mean observation dates have been around 6 days in advance of the average dates in the first part of the 20th century” https://jncc.gov.uk/our-work/ukbi-b4-spring-index/. It might seem as if early springs are to be welcomed. The risk is that it could lead to all sorts of synchronicity problems though. Migrant birds arriving after the peak of spring caterpillars is often quoted as such a risk.
Using the UK governments indicators, spring would never arrive in the Outer Hebrides outside of a few specialised locations. Apart from Swallows none of the other species are likely to be spotted here. But there are things we could record that would give us our own indicator of spring. So why not keep your own record of events that mean spring to you?
It would be nice to agree a list of events that all of us could try and record so we can start to look at how climate change is changing the date when spring arrives up here. Some springs will always be early whilst others will be late but on average will springs in five, ten or fifteen years hence be more likely to be early, and if so by how many days? Or will our strongly oceanic climate level things out and result in no great change at all?
To start the ball rolling I’m going to suggest we record the first dates for:
- Green-veined White butterfly
- Common Blue butterfly
- Queen White-tailed Bumblebee emerging after hibernation
- Arctic Tern
- Sedge Warbler (singing)
- Cuckoo (calling)
- Frog spawn
- Dune Pansy in flower
- Goat Willow catkin
I deliberately didn’t include some things on my list. Events such as the first Dandelion or Snowdrop are complicated because of the wide range of different varieties that are planted in our gardens. Dandelions and Daisies are in flower almost throughout the year, so they’re no good. Also ignored were things like the first sightings of Red Admiral or Small Tortoiseshell butterflies. These overwinter as adult butterflies and just a couple of warm days at any point in late winter can induce them to break hibernation – that doesn’t indicate spring but just that we’ve had a couple of odd warm days.
My list is a bit light in terms of plant events. We probably need a couple of extras so please post your suggested plant event or other event ideas here. They need to be events that typically happen between late March and early June, and ideally we want things that most people can identify and are likely to be spotted almost anywhere in the Outer Hebrides. I look forward to hearing from you.
Song Thrush singing
Sedge Warbler singing