I cannot recall ever having observed Slavonian Grebe in their very striking summer plumage, and definitely have no past pictorial record of one. So when at 8:30 this morning the Oxon WhatsApp scarcities alert announced an early Farmoor regular had found a pair in their full breeding finery, it was a “get out the door” moment. It takes something a bit special to draw me out birding locally now, but the buzz and sudden sense of motivation that at once seized me was just the same as it had ever been.

Not quite so when an hour later I arrived at the cited corner of F2 to find neither birds nor birders, just two boats manned by fee-paying anglers. My quest had clearly been flushed elsewhere and another alert at once revealed the new location, which was as far from the former as it could possibly be. Cue a stomp that doubled as a respiratory health check, until I met up with a small group that included both Ewan and Badger. They were watching the two drifting Slavonian Grebe as distantly as another birder who had shown them to me in his scope on my way, and I picked them up in my own bins. That proved to be the scenario for the ensuing five hours that I spent here today.

This initial gathering dispersed, while Ewan and I repaired to the sailing club café to await developments. Suitably revived we decided to tramp the opposite way around F2’s breezy two-mile perimeter, in the hope that now active wind surfers or other recreational activity might displace the birds into a safer and more sheltered corner. Eventually, with the help of another birder, we tracked them back almost to where they had first been reported. Then, after offering some quite reasonable views, they drifted back out to the middle of the reservoir.

These birds were noticeably fast swimmers, and at intervals would take flight from speedily approaching wind surfers and relocate even further away. But for a second time they did move closer inshore, though never near enough for the quality of pictures I or others were seeking. We managed to persuade passing less-experienced bird watchers and general public agreeably to keep back from the wave wall, but still the wary Slavs would only get so close before drifting quickly away again.

The pair would have been moving north, probably to breeding grounds in Scotland, Scandinavia or possibly beyond. The small and now declining British breeding population of Slavonian Grebe is restricted to a few lochs in the eastern highlands of Scotland. They winter either in more sheltered Scottish waters or around the English coast mainly from East Anglia to Cornwall. Further afield, the Eurasian sub-species is distributed over most of northern Europe and northern Asia. Range losses have occurred across much of Europe and this item is consequently listed as vulnerable on the Global IUCN Red List.

We must have walked over five, even six miles pursuing today’s birds, and the longer it went on the more mobile they seemed to become. I was surprised by how few of Oxon’s finest were present in the morning, but as we left in mid-afternoon a steady stream of birders was moving in the opposite direction. The above record shots are my own first of this plumage, to realize that ambition in kind. In the prevailing light conditions nobody seemed to be getting anything really good, but this post’s images do show how these scarce Grebes were actually seen. It was an enjoyable day doing something new and different in Oxfordshire, and overnight the birds went on their way.

This is a “migrant addition” to my almost complete (bar one) British butterfly list. Large Tortoiseshell is one of a select group to have made inroads, with global warming into southern and south-east England and East Anglia over the last 15 years or so. Hence when I was invited by Ewan to observe a cluster of emerged hibernators from a small breeding colony in a Kent woodland, the opportunity was sufficiently evolved to arouse my interest.

Large Tortoiseshell occurs across continental Europe, being common in some regions though erratic in others. The species was once widespread nationally, mostly in central and southern English woodland habitat, particularly such containing the historic food plant Elm and where blooming Sallows and Cherries provided nectar sources in spring. But its numbers were always known to fluctuate and the butterfly became extinct here by the 1960s. There were various suggested causes for the decline including climate change, parasitism and the impact of Dutch Elm disease. As the species was disappearing in the UK, its numbers also decreased dramatically elsewhere in north-western Europe. 

My pre-trip research revealed that since then there have been sporadic national records annually, mostly in high summer from the south coast and Isle of Wight. It was always open to question whether those might be released by breeders from reared stock rather than genuine migrants. The spring of 2020 brought a marked influx by modern standards when sightings in Norfolk and Suffolk exceeded national totals over the previous 10 years. At the same time other European countries including Holland experienced their best emergences in 40 years. There have also been a few sightings of what are considered to be hibernators each spring since 2018 on the Isle of Portland in Dorset, and breeding has been confirmed there and at Sheringham in Norfolk.

I myself had recorded this butterfly pictorially, just once previously in Sardinia in 2018. Today the weather forecast that prompted our visit was for temperatures as high as 19 degrees, to match conditions earlier this month when my companion had first been alerted to our potential experience. That was certainly warm enough for Brimstones, my first for this season having been on 2nd March locally, and hibernators to be showing themselves. In the event this spring equinox was actually the warmest day of the year so far in southern England.

We arrived on site at 1pm to find a full car park, with butterfly people’s vehicles most likely outnumbering those of dog walkers. It wasn’t until meeting and listening to other observers here that I realised Forestry England Orlestone Forest (TQ 985347) is a further well-known (in informed circles) and established breeding location of some four-years’ standing. But there are thought to be around 12 individuals flying here at present, which to me suggested the colony is quite fragile. The first warm days of spring when hibernators emerge are said to be the most likely time to connect with Large Tortoiseshell, since the single-brooded insects in high summer are only on the wing for a couple of weeks and generally more elusive.

From near the parking area a long ride leads downward and into the woods. When we found and made our way along this we met a group walking up that contained some clearly very seasoned butterfly people, and a high-profile figure who was known to us. Soon someone located a Large Tortoiseshell on the ground and everyone got pictures of it (lead picture, above). We learned that our quest might be encountered anywhere along this ride, but the main concentration of observers was some way further along in a low-lying area that due to its warmth is especially attractive to the butterflies. Several specimens had been present there during the previous day.

Fortunately the gathering today was of genuine butterfly enthusiasts and not peripheral “butterfly tourists” as I term them, suggesting this site is not yet well known to that social-media generated underclass that always creates a circus around scarce species locations. When we reached the spot in question we further learned that as the sun begins to lower from around 2:30pm the LTs would settle open-winged against tree trunks. So this proved twice while we were there, the image below being the best I could manage in the circumstances, given the competition for camera angles. Ewan, through a combination of better position and equipment, fared a little better at this point (see here).

These butterflies were quite like Purple Emperor in their behaviour, starting their day in the tree-tops then coming down to ground level as conditions warm up. They were at all times fast-moving and elusive. But their graceful, gliding flight set them apart from the numbers of Comma and Peacock that were on the wing here, while even more new-season Brimstone were nectaring on scattered forest floor carpets of Primrose and Wood Anenome.

In around three hours here today we encountered possibly five Large Tortoiseshell, while there are reputed to be more in other parts of Orlestone Forest. This is not of course my preferred mode of butterflying, which is alone when it is then possible to gain the confidence of and enjoy communion with individual subjects. I was unlikely to attain pictures that then arise of the standard I seek today, given the constraints of being in a jostling group; ie lack of free movement and not wanting to be the one who puts subjects up. Whenever they did go, LT would always fly high and a long way before settling again. But I would not have gained this conversion had I been alone, so that is the trade-off.

The end of February and first week of March offered at first a cold sunny, then exceptionally mild weather windows, and so my attention turned to re-experiencing the annual Common Frog spawning event at north-east Oxford’s Lye Valley LNR (SP547058). But the unseasonal conditions seemed to have caught the amphibians themselves unprepared.

The Friends of Lye Valley volunteer group that maintains this SSSI so excellently (pictured above) first reported frogs on 21st February. The site is just up the road from the supermarket where I shop most regularly, and so ensued four fair-weather visits that yielded just one frog first time around, then nothing further. I became disheartened. Where had they gone and what was happening? Then on 10th I received a call from Ewan saying the frogs had returned en masse over my prior working weekend. Game on!

We met on site next morning. Weather conditions were now much colder again but no matter. There must have been 100 or more Common Frog in the usual ponds, all singing their intent upon propagating the species. The soft chorus of croaking that filled the air was somehow very soothing in what is always a tranquil setting. What a transformation! Last year things were all over when I visited at around this time, and I found only spawn. My previous post herein (see here), containing the complete guide, was rather earlier in the last week of February 2022.

I believe the top right picture is of a male Common Frog and the one below it a female

The above (click to enlarge) are my favourite pictures from today. All are edited, some with creative intent. There were large quantities of spawn in two of the ponds and the juxtaposition of frogs with it in some of the images was something I found quite engaging. Very soon all this will be over for another season. The frogs will disperse again to whence they came across suburban Oxford, while the spawn will remain and hatch. Visitors to Lye Valley are asked not to enter the ponds or allow their dogs to do so, and not to disturb or remove spawn.