Grizzled skipper butterfly at Holme Fen - Tristan Colaco, Natural England

Tristan Colaco, Natural England Reserve Warden, highlights the special wildlife thriving on our nature reserves as a result of habitat management this spring.

Spring is an incredible time to be on our NNRs. Seeing the reserves start to hum with life after the quiet of winter is amazing. It is particularly special to be able to see wildlife thriving as a result of our habitat management.

This spring we had this privilege with grizzled skippers at Holme Fen. This pretty little butterfly is found across the south of the UK but has declined by more than 50% since the 1970s. It requires relatively sparse, open habitat with plants on which its caterpillars can feed, like tormentil, agrimony and creeping cinquefoil. Maintaining the habitat with just the right mix of bare ground, leaf litter, food plants and nectar sources is quite challenging. However, a few years of careful management seems to be paying off. Numbers of grizzled skippers were very encouraging this year, with a peak count of over 70 butterflies; the highest count we have had for 5 years.

Surveying grizzled skippers is relatively straightforward. The adult butterflies are easy to spot so we can simply count how many individuals we see. Some of the other important species we get on the NNRs are trickier to survey. For example, great crested newts are nocturnal and spend their days hidden away in burrows or under rocks and logs. However, surveying great crested newts is extremely important; they are a highly threatened species, but we can only help protect them if we know where they are.

This spring, we were able to get a number of environmental DNA (eDNA) sampling kits for use at our NNRs. When newts spend time in the water, they will continually shed DNA in the form of skin cells, mucus, faeces and so on. We can then take samples of the water which can be sent off to be tested for the presence of this newt DNA. This sort of eDNA sampling is very unobtrusive, and relatively time effective so we can survey a large number of ponds quickly and with very little disturbance. The sampling is done during the spring as this is when newts are breeding in ponds; spending plenty of time in the water and shedding plenty of DNA.

Although spring has been a busy time for surveying at Holme and Woodwalton Fens, from a habitat management point of view, spring is relatively quiet. The winter scrub and woodland management stops in February prevent disturbance to species using these habitats, and our grassland management doesn’t start until mid to late summer. This break in habitat management work gives us a good opportunity to get on with repairs to infrastructure on site. Of particular importance is repairs to the many kilometres of fencing at Woodwalton Fen. These repairs need to be done to enable livestock return to site in the early summer.

Repairing fencing and replacing a gate at Woodwalton Fen

Repairing fencing and replacing a gate at Woodwalton Fen - Tristan Colaco, Natural England

Grazing livestock are a key part of Woodwalton Fen. They keep on top of scrub and vigorous grasses, thus allowing a more diverse range species to thrive in our grasslands. The cattle in particular graze in a way that creates a real variety of vegetation heights, with some areas being closely cropped and others growing longer; creating a more varied habitat that supports more species.

However, grazing is not the only benefit the livestock bring. As they move around, they can create depressions in soil and even areas of bare ground that provide even more habitat niches for other species to exploit. Later in the summer, this trampling can help the seeds of our grassland plants to make their way into the soil ready to germinate. Furthermore, the dung that livestock produce provides a food source for an array of invertebrates, and the livestock themselves provide a food source for a range of parasites.    

Cattle are now back on Woodwalton Fen doing all of their amazing work. Cattle can be dangerous, especially when there are calves in the herds, as there are at Woodwalton. As a result, we have restricted access to some parts of the site; for your safety and the safety of our livestock, please obey all signage on site. Many thanks!

Cattle at Woodwalton Fen

Some of the cattle working hard at Woodwalton Fen - Katy Smith, Natural England