Signs of a British spring including spawning frogs, the arrival of migrating swallows and the first leaves on oak trees took a week longer to spread across the UK this year than in the last two decades, according to nature watchers.
A mild winter saw spring flowers out earlier than usual, and signs of spring such as hawthorn leafing and red admiral butterflies on the wing on Christmas Day.
Lower than average temperatures in April, however, meant that the ecological heralds of spring travelled from south to north more slowly than in recent years. They took four weeks to travel the length of the UK, compared with three weeks last year.
The onset of spring spread north at an average speed of 1.2mph, compared with 1.9mph in 2015, according to analysis by the Woodland Trust.
The slow spring was more in line with Victorian times, when Royal Meteorology Society records from 1891 to 1947 show spring moved northwards at an average of 1.2mph.
December was the warmest on record, according to the Met Office, which also said March had been about average – 0.2C below the long-term average, to be precise. April was a “little bit cool” at 0.9C lower than average.
The Woodland Trust’s nature calendar project has been running since 2000 and receives as many as 70,000 fauna and flora records a year from between 2,000 and 3,000 recorders. The miles-per-hour measurement is based on records of frogspawn, swallows, orange tip butterflies, the first leaf on oak and first flowers on hawthorn.
“There’s no clear reason why we’ve seen this,” said Kate Lewthwaite, the Woodland Trust’s citizen science manager. “It creates more questions than it answers.”
Climate change has been blamed for increasingly early starts to spring in the UK, bringing forward the season’s arrival in the natural world by several days.
