There's a couple of reasons for this. Firstly, species that over winter in adult form are free to emerge early in the year and secondly, milder winters and warm warmth soaked stonework in our cities make them the ideal habitat for early emerging butterflies.
If you spend some time in nature, see if you can spot all of the special six before spring is out and when the clocks go forward. Look out for them on warmer days as they all like a bit of sun on their back.
The Brimstone
One of our earliest butterflies on the wing, often fairly solitary but also very obvious with the males being sulphur yellow and the females white with a yellow tinge - a bit like the colour of old fashioned sherbet.
The Comma
So called due to a small white comma shaped mark on their. Look for them in flight with their burnished orange wings flecked with sooty black and their most obvious characteristic of tatty edges to their wings.
The Peacock
The beauty queen of the bunch with obvious eye spots on both wings. If you can get close to one they make for a great photograph with the subtle pastel hues that make up the complex patterns on their wings.
The Red Admiral
So called not because its striking velvet black with scarlet flashes deemed it an "admirable" butterfly. Most of our UK sightings are migrants which join us from the continent later in the year so any you see in spring will be members of a select bunch of resident Red Admirals.
Small Tortoiseshell
Numbers have dropped significantly in recent years, believed to be due to a parasitic fly infecting them. Look out for the orange, black and white patterns on the wing and the distinctive the blue flashes along the wing edges.
Speckled Wood
The only one of our special six that doesn't overwinter as an adult. Some Speckled woods can however, emerge from their larval form as early as March in the right conditions. They're a brown butterfly with creamy markings and some obvious eye spots on their lower wing and often seen flitting around woodland edges.