It’s time to look for Black Hairstreaks!
The Black Hairstreak season certainly seems to have started in earnest here in Northamptonshire. They were first recorded on the 29th of May at Glapthorn Cow Pastures, and by the time of writing (2nd of June), 236 Black Hairstreaks have already been recorded in the county, with 91 recorded in a single day at Glapthorn Cow Pastures during a full survey on the 1st of June!
Black Hairstreak, Salcey Forest, 31st May
The Black Hairstreak has expanded its range over the last few years, and now is an ideal time to look for them and hopefully find new colonies. When I first became the Northamptonshire county butterfly recorder, the known populations of Black Hairstreaks hadn’t changed much for many years. Below is a distribution map showing their locations.
Black Hairstreak Distribution Before 2016
However, since then, and particularly in recent years, they have been seen in quite a few new locations. In fact, 6 new locations were discovered just last year! Here is a map showing the changes in their distribution since 2016.
Black Hairstreak Distribution After 2016
I’m sure there has been some range expansion, but this is a secretive butterfly, and one which can remain undetected as it spends the majority of its time in the canopies of stands of Blackthorn. Today, on the 2nd of June, I received a very exciting record of a Black Hairstreak at Twywell Hills and Dales, recorded by the transect walker Fiona Barclay. Amazingly, she spotted this Black Hairstreak on a blade of grass, pumping up its wings, after a very recent emergence! This is an incredible record, and one which adds Twywell Hills and Dales to the list of new locations for this special species of butterfly.
Black Hairstreak, Twywell Hills and Dales, 2nd June 2025.
Photo credit, Fiona Barclay.
Now we know that there are populations out there that haven’t been discovered, it is a great time to go out and look for new colonies. The method is quite simple. It is best to choose a day with quite a lot of sun, and preferably with not much wind. If the conditions are suitable, whenever you pass any suitable areas of blackthorn, stop for a while and keep a close eye on the canopy for any butterflies that may be flying around the top of it. Binoculars can be a great help here, as the butterflies can often spend most of their time high up and out of range of the naked eye. If you do see any, please let me know, either by submitting the record on iRecord or by contacting me using the contact form on this website.
Let’s hope we can make some more exciting discoveries and add some more locations to the map in 2025!