Expected date ranges explained: early sightings in spring 2019

Judith Garforth, 31/05/2019

Our recorders have been sending in their wildlife timings for many years now. This means we have a pretty good idea when to expect certain species to do certain things. Sometimes though, unusual weather means that we receive records earlier or later than expected. This was the case this spring, so I’ve delved into the data to find out more.

Expected date ranges

In 2017, we calculated an 'expected date range' for each species and event by looking back at the previous 10 years of records. We used these expected date ranges to make a helpful calendar poster to show what you can look out for each month of the year.

If you add a record to our website with a date that falls outside of the expected date range, you’ll see a warning message in red:

It’s nothing to worry about! It’s just a double check that you’re absolutely sure this is the correct date. It helps us keep the Nature’s Calendar data as accurate as possible which is very important because it’s often used by scientists for research.

It asks you to check that your date is correct, because it’s possible you may have clicked the wrong day, month or year on the calendar by accident. If the date is correct then you’ll be asked to add a comment about your record before you can continue. You can include any extra details that you think might be interesting and helpful, for example what the weather has been like in your area recently, or if the species is in a sheltered location.  If you can add a photo that’s even better, but it’s optional.

Once you’ve saved your record, it goes into the Nature’s Calendar database, but the Nature’s Calendar team will also be alerted to it. This allows us to understand how unusual weather is affecting wildlife immediately and helps us to respond to media and research enquiries. Very occasionally we spot an identification or recording error in which case we’ll be in touch to help, so that we can get the data corrected. A record that falls outside of the expected date range won’t appear on the live map until it has been checked by our team.

Early records in spring 2019

February this year was warm, dry and sunny, and we noticed that many of your records fell earlier than the expected date ranges. We received 441 records of brimstone butterfly, first recorded earlier than the expected date range.

Brimstone butterfly, first recorded records, spring 2019

Brimstone butterfly (Libby Owen/WTML)

We received 69 records of red-tailed bumblebee (queen), first recorded earlier than the expected date range.

Red-tailed bumblebee (Pete Holmes/WTML)

Red-tailed bumblebee (queen), first recorded records, spring 2019

We received 152 records of small tortoiseshell, first recorded earlier than the expected date range.

Small tortoiseshell butterfly, first recorded records, spring 2019

Small tortoiseshell (Christine Martine/WTML)

Regional Differences in Timing

The expected date ranges are calculated using records from all over the UK. Spring species and events tend to be spotted first in the south west of the UK because of the warmer weather. So if you live in Cornwall or Devon you’re more likely to see things right at the start of the expected date range.

Always early

Some individual plants seem to leaf or flower early compared to the others around them. For example, you might have noticed a hedgerow in spring where one hawthorn shrub has it's leaves before all the rest. It’s important to record the same plant year on year, so that you can see the effect of the weather on the individual plant rather than trying to spot the earliest plant in your area.

Don't be put off

Please don’t be put off by the ‘This date fall outside of the expected range’ warning message. It’s just there to keep the data as accurate as possible. We are recalculating the expected date ranges later this year using the most recent data, ready for spring 2020. So hopefully you’ll see the warning message less often, once our expected ranges have been expanded.

Join thousands of other people and let us know what's happening to wildlife near you.

Join thousands of other people and let us know what's happening to wildlife near you.

Have you seen your first butterfly or swallow of the spring? Is it a good year for wild autumn fruits? Take part in Nature's Calendar and help scientists to monitor the effects of climate change on wildlife.

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