There was a UK heatwave from 9–15 July, with amber warnings issued for the South East, including Oxfordshire, with temperatures peaking at around 33°C. Kev @kev07713 and I talked over our plans for the day - spending hours out in the sun didn’t seem like the smartest idea. That led us to a new thought: maybe today was the day to finally go looking for a purple emperor butterfly - we’d been meaning to for a couple of years but had never quite made the time.
These butterflies favour mature deciduous woodland, especially areas with a mix of sunny glades, ride edges, and closed canopy - with oak and sallow trees - and in this weather just like the kind of habitat we wanted today. Not only would it give us a shot at seeing one, but it would also offer shade and respite from the worst of the heat.
As we talked more, I suggested we make a quick stop at RSPB Otmoor for a couple of hours in the morning, then head over to Bernwood Forest, just a few miles beyond Otmoor and a well-known purple emperor site. These butterflies are only on the wing for a short time each year, with timing dependent on weather and region. In southern England, they usually fly from late June to late July, peaking in the first half of July, but this year’s warmth had triggered an early emergence with some sightings already a couple of weeks old. From what we’d read, we were likely at the tail end of peak activity, that precious window when the emperors descend from the canopy. We were hopeful there might still be one or two about.
We set off and, with only short drives planned, grabbed a meal deal at the petrol station - no café breakfast this time. Arriving at Otmoor, we found the car park holding 10 cars, the sun already making it t-shirt weather. We joined the track leading to the bridleway and were almost immediately greeted by a (family) group of lesser whitethroats - my first of the year, it turned out, though I only realised that later. I tried to get a photo, but they stayed frustratingly active and just out of reach, never quite still in the open.
Further along the bridleway, we picked up both sedge and reed warblers and carried on, eventually spotting a rather scruffy-looking chiffchaff. It was partially hidden at first, buried in the foliage, but soon popped out onto our side of the track for a clearer look.
Along the far hedge line of Greenaways, we spotted cattle egrets - some gathered close to the cattle, others perched in the trees nearby. We paused to scan the group, now mostly lifted off the ground, and managed to count 30 birds in total.
These egrets are a familiar sight on Otmoor’s wet grassland pastures, often seen foraging alongside grazing cattle or sheep, using the animals to stir up insects and other prey. As evening approaches, they tend to gather in willow trees near the hides, where large flocks settle to roost before nightfall.
Otmoor’s transformation began in 1997, when former farmland was restored into diverse marshland, creating ideal conditions for wetland species like these cattle egret. The site became a potential breeding location by 2023, with 2 or 3 birds regularly present through early summer. By 2024, their presence had grown significantly, with regular feeding flocks of 30 to 40 birds, and a record peak of 62 arriving to roost on 24 September.
We worked round until we reached First Screen where we joined a handful of people watching across the water - the glossy ibis was feeding out at the base of the tree. After 15 minutes or so it climbed up into the dead tree branches and started to preen. We talked with some of those present and heard reports of water rail off to the left - distracted we were lucky that someone was still watching forward and called a bittern flying across the water from right to left, and down a channel in the reeds. I wasn't quick enough to get a photo.
A bunch of the regulars dropped in, filling up the remainder of the space at the Screen: Peter Barker, John Reynolds, and others. A single cattle egret dropped into the dead tree with the glossy ibis, and then a further 24 landed in the taller tree beside. I'm not sure how many birds were still left on Greenaways.
We dropped down the steps to check the usual spot for common lizards, hoping to catch a glimpse of them basking. Otmoor is a great place to see them, particularly on warm, sunny mornings, when they often appear on logs and tile piles at the so-called “Lizard Lounge”, tucked just beside the First Screen.
These lizards become active in spring, emerging from winter hibernation, and can be seen basking well into late summer. The common lizard is the UK’s most widespread reptile, and unlike many others, it gives birth to live young in July rather than laying eggs.
They typically grow to 10–15 cm in length, with long tails and a wide range of colour variations - many show striped or patterned backs, and males often have yellow-orange spotted bellies, while females tend to be plainer underneath.
We were lucky enough to see at least two, both stopping long enough for me to squirm around for an angle to get a photo.
The regulars emerged from the Screen and were off down to Second Screen, although reports suggested there were no extra species to be found down there. The temperature and sun had both noticeably risen and we decided not to linger - we have a butterfly to find. Back at the car we jumped in and made for Bernwood Forest, less than 10 minutes away.
Once a vast royal hunting forest spanning over 400 km2 and covering around 50 parishes, including parts of Oxfordshire, Bernwood Forest was established by Anglo‑Saxon kings and was especially favoured by Edward the Confessor - Deforestation began around 1217, accelerating in later centuries and by King James I’s reign, much of the original forest had disappeared. The modern Bernwood Forest comprises Shabbington Wood, Waterperry Wood (Oxon), Oakley Wood, York’s Wood, and Hell’s Coppice, forming part of the Shabbington Woods Complex SSSI. It covers about 465 ha of public access land, with approximately 88% ancient woodland, much of which is being restored to ancient semi-natural woodland (ASNW).
The area is renowned as one of the finest butterfly sites in Britain, with about 40 species recorded, including our purple emperor, silver-washed fritillary, white admiral, purple hairstreak, black hairstreak, Duke of Burgundy, and more. Bernwood Meadows, managed by BBOWT, lie adjacent to the forest and consist of traditional hay meadows rich in wildflowers such as green-winged orchids, lady’s bedstraw, knapweeds, ox-eye daisies, and more, attracting abundant insect life.
Facilities are minimal - no visitor centre - but this contributes to the forest’s quiet, tranquil feel and low footfall - however, access is free and open year-round; there are no parking charges. Bernwood Jubilee Way (61 miles long) and a dedicated butterfly trail with waymarked routes guide walkers through woods, rides, and meadows.
We’d never visited before but had some intel on where to search for the purple emperors, so we headed straight there, occasionally branching off to explore nearby areas when we had no early luck. There were plenty of butterflies, just not the one we’d come for.
What did catch our attention, though, were the numbers of silver-washed fritillaries - the largest and one of the most striking fritillaries in the UK. Once largely confined to southern England, they’ve been steadily expanding their range northward, with recent sightings as far as Yorkshire and the East Midlands.
These butterflies are a vivid orange with black spots, and the males are unmistakable thanks to four bold black scent streaks on their forewings - the greenish-bronze hindwings reveal the distinctive silvery streaks that give the species its name. On a trip away from our spot Kev came across something quite special, a Valesina form of the silver-washed Fritillary. This rare genetic variation occurs in a small percentage of females, mostly in larger colonies in southern England. Instead of the typical orange and black, Valesina females have a dusky olive-green or violet-brown upperwing, with a pinkish flush underneath, while still displaying the trademark silver streaks ... a remarkable find.
We saw a few species we have seen more regularly such as the small, large, and green-veined whites but they were all great company as our wait continued.
Time wore on and we continued to add to the count with large skipper and comma butterflies. We waited, eyes lifted toward the oak canopy, scanning every movement and glint of light - waiting to see a purple emperor appears to not just a matter of chance; it’s a quiet exercise in patience and hope - we know the feeling from some of our birding trips. The woods around us were alive: ringlets danced low over the brambles, silver-washed fritillaries continued to cruise confidently along sunlit rides, and red admirals zipped through in flashes. But still, no emperor - we knew they were up there, gliding high in the canopy, invisible against the leaves.
The ruddy darter is widespread across southern and central England, with its range steadily pushing northward. The woodland ponds and shaded pools found in and around Bernwood Forest provide ideal habitat for this species. As we watched butterflies along one of the rides, several dragonflies drifted through, weaving along the sunlit paths. One (a ruddy darter) paused long enough for me to manage a photograph as it settled briefly on a leaf right in front of us.
You wait, and the waiting becomes part of the experience. Because when the emperor finally appears, it’s special. At first, we thought the butterfly that landed in front of us was a white admiral, but it turned out to be our target - a female - we'd then see another (a female) as a family stood motionless as one landed just to the side of them on the stone path. We followed it up the track and into the car park before we lost it into the trees and lost from view.
Male and female purple emperor butterflies can be distinguished by several physical and behavioural differences, even though they are similar in overall size and shape. Both sexes have beautiful, mottled underwings - browns, greys, and a distinctive orange-ringed eyespot but the male has striking iridescent purple sheen on upper wings when viewed from certain angles, while the female lacks purple sheen on the upper wings - they are mostly dark brown/black with white bands.
We'd get one more chance to see another (another female), this time following it down the path before it again disappeared into the trees.
I spotted one high in the canopy, but it refused to come down, and when it moved, it settled even higher and completely out of sight.
Our final species of the day was a purple hairstreak - most of their flight and interaction happen high in the oak canopies, with occasional descents to lower levels during cooler or later parts of the day. It is a small butterfly with a glossy purple sheen and a narrow black border on the upper wing, then a silvery-grey with a white streak and orange eyespots near the tail.
It was a lovely and slightly different kind of day - I think Kev’s caught the bug, as he headed back for another go midway through the following week.