Have you seen the first signs of spring in Norfolk?

Norfolk Wildlife Trust (NWT) is asking people to share their first sightings of the iconic bird, along with other species that herald the end of winter in a citizen science survey it's launching on Monday, March 1.

Phenology - the recording and study of the timings of natural events - was pioneered by the 18th century Norfolk naturalist Robert Marsham, who recorded 27 signs of spring around his home in Stratton Strawless, near Norwich.

Almost three centuries later, it is now seen as an important way of knowing how our seasons are changing, especially in relation to climate change.

NWT is asking people to report their first sightings of swallows, orange-tip butterflies and common frogs to map sightings and build a picture of where and when they appear.

Swallows usually arrive around March 20, with spring migration continuing until the middle of May. The UK swallow population is estimated in the region of 705,000 birds, but their numbers are in decline.

Orange tips are often seen on roadside verges, in woodland glades and damp meadows but it also visits gardens. The orange tip is an early spring butterfly with first emerging insects on the wing from mid-April. Scientists say it is emerging earlier because of higher spring temperatures.

Frogs usually emerge from their hibernation sites in February and March, where they then set off to their breeding grounds. The average date for clumps of frogspawn to be seen in Norfolk is March 10.

Frogs will soon be emerging from hibernation to begin spawning (Image: Archant)

Gemma Walker, senior community officer with NWT, said: “We have picked three fantastic indicator of spring for our survey that we hope people in Norfolk will spot in their gardens and on their local patch, and are asking all sightings to be added to our wildlife spotter map."

The spring phenology survey runs throughout March, April and May. Add sightings online at www.norfolkwildlifetrust.org.uk/spotter.