Royston Wildlife Blog: Local Wildlife Sightings, August 2025

After a changeable first week, in which there was some (but not enough) rain, the weather settled into another spell of very warm or hot weather, with the fourth 'heatwave' of the year arriving from the 11th - at least in the Royston area. On Therfield Heath, Chalkhill Blue numbers peaked at the beginning of the month, before a gradual (or rapid, in the case of Gatekeepers) decline of these and most other species set in. The exceptions were Small Heath, with the appearance of another generation, and Adonis Blues, first reported at the end of July, which were present at both ends of The Heath by the 9th. There was a welcome increase in numbers of these in the second week of August, with a few males being seen away from the colonies on the Old Rifle Range and Church Hill. There has been a small influx of Clouded Yellows from Europe this month. Some were reported on The Heath on the 10th and a single butterfly flew north past me, on the Old Rifle Range, on the 11th.

Male Adonis Blue, Therfield Heath, 11 August

Female Common Blues with varying amounts of blue on the upper wings were seen in the fields near my house. I tried to photograph them all, but unfortunately missed out on the most spectacular one, with wings almost completely covered in a shade of violet. I did a little more photography of blues roosting in the evening light, but by the end of the first week of the month they were becoming increasingly tatty.

Male Common Blue (left) and Chalkhill Blue, Therfield Heath, 7 August

Blue Variant of a Female Common Blue, Royston, 8 August

Whilst butterflies have had a much better year, I have seen very few day flying moths on The Heath or night flying moths coming in to the bathroom this year. Maybe they have been hit harder by last year's poor weather. I can't remember seeing any 'Silver Y' moths (normally the commonest day flying moth hereabouts) at all, although other factors may be at work here, as this species is migratory. Two moths that I have seen regularly are Hummingbird Hawkmoth (one even got into my greenhouse - not too difficult as it has one or two broken panes of glass) and Jersey Tiger Moth, which goes from strength to strength, having only arrived in the Royston area a few years ago.

I start spending more time looking up (for birds) rather than looking down (for insects) in August. Waders are migrating across the country in August and Dernford Farm Reservoir, just across the border in Cambridgeshire, has plenty of mud available for them in the current near drought conditions. I visited on the 11th, looking for Ruddy Shelducks that had been reported there on the previous day. There was no sign of the Shelducks, but I did see six Black-tailed Godwits and a juvenile Spotted Redshank on the mud there. A male Ferruginous Duck (unfortunately an 'escape', so I can't list it) was also present (image)

Male Ferruginous Duck, Dernford Farm Reservoir, 11 August

Spotted Redshank, Dernford Farm Reservoir, 11 August

Closer to home, I flushed three Grey Partridges on The Heath on the 14th. One was much smaller than the others: it must have been a juvenile as juvenile game birds learn to fly well before they are full grown, in order to escape their many ground (and avian?) predators.

High pressure continued to dominate the weather in the third week of August, but, with the wind coming from the north and east, Royston was plagued with lots of low cloud and much cooler temperatures. Insects became much less active under the cloud, although I was lucky to be out on Church Hill when the sun came out for an hour or so in the late afternoon of the 19th, and I was able to photograph male and female Adonis Blues there, as well as a Hummingbird Hawkmoth that seems to have been present in Fox Covert for several weeks. The best photo that I could manage of the hawkmoth is shown below. Around 20-25 Adonis Blues were flying on Church Hill, including 'fresh' females. It may not be true elsewhere, but in this colony many of the females have some blue markings on their backs and upper wings (see example below), which I don't see on the otherwise very similar Chalk Hill Blue females. In addition, the spots on the lower wings are bolder than those on female Chalk Hill Blues. After a very poor 2024, it is good to see numbers of Adonis Blues recovering this summer, even though numbers are still well below where they were in the years after they had first been introduced.

Female Adonis Blue, Church Hill, 19 August. Note the Blue Efflorescence on the Body and Wings

Male Adonis Blue, Church Hill, 19 August

Record Shot of Hummingbird Hawkmoth, Fox Covert, 19 August

The dry weather has resulted in the water levels in lakes and reservoirs falling, resulting in lots of muddy margins - ideal for waders on passage. During the duller days I visited Amwell, the Tring Reservoirs, Dernford Farm Reservoir (which, by the time I visited on the 21st, was almost dry) and Kings Meads, where a juvenile Spotted Redshank had been discovered a couple of days beforehand. Other waders seen at these sites were Ruff (four at Dernford Farm Reservoir on the 21st), Green Sandpipers, Common Sandpipers (lots) and a Common Redshank. At Wilstone Reservoir, where there is very limited access due to long term engineering works, a couple of Hobbies flew over and at Startops End a colourful Mallard (?) hybrid and a Black Swan were seen. Lots of hirundines, including my first (!) Hertfordshire Sand Martin of the year were flying over the water here.