My first September bird record was of two tawny owls having a territorial hooting battle, shortly after midnight on the first. Another willow beauty moth turned up in the kitchen. The long period of gloomy weather continued, although Royston did see a few shafts of sunlight on the 2nd, when five house martins were the first seen from my garden this year.
Willow Beauty Moth, my Kitchen, 1 September
Finally, from the 4th, the weather gods relented and, suddenly, we were plunged into a short 'Indian Summer', with temperatures locally reaching 29C. I took the opportunity to spend a lot of time on The Heath, photographing invertebrates including spiders, grasshoppers and hoverflies. One interesting find was the pretty micro-moth pyrausta purpuralis, an insect that I've encountered at other unimproved chalk grassland sites but never locally, as far as I can remember. The warm weather roused ivy bees from their summer slumbers and, by the middle of the month, thousands of these friendly little invaders were on the wing, with a huge colony on The Heath and smaller colonies elsewhere in Royston.
Ivy Bee on Ivy Leaf, Royston, 6 September
Micro-moth Pyrausta Purpuralis, Church Hill, 8 September
Common lizards must have had a good year locally, because I saw several baby lizards on and close to The Heath. I saw more common darters in the area too, but why were they always females when they are well away from water? Common darters are strongly migratory, with occasional influxes from Continental Europe, but I would have expected to see a few males as well. I've consulted text books, but to no avail....
Female Common Darter, Church Hill, 8 September
Baby Common Lizard, Royston, 6 September
I have suffered from a knee problem this summer, which has limited my walking. However, I was well enough on the 7th to do the 8-mile walk round my 'local patch', taking in both Reed village and Therfield. I had a brief view of the front half of an acrocephalus warbler before it disappeared into a bush, close to my home. Presumably this was a reed warbler, which would make it my third local sighting of this species in 2021. Nearby, a spotted flycatcher (probably a bird on passage) was catching insects from the branches of a dead tree. I was pleased to see at least eight yellow wagtails, including juveniles, at Hatchpen Farm - unlike the spotted flycatcher, these were likely to have bred locally this summer. There was a single little grebe at Mardleybury Lake, where I found hordes of male and female common darters engaged in egg-laying activities, as well as the third male banded demoiselle that I have seen locally this year. I took loads of photos of the egg-laying dragonflies in tandem flight. On examining them later at home (the images were pretty awful) I discovered that I had captured an image showing a small red-eyed damselfly resting on some aquatic surface vegetation (image below) - my first local sighting of this species and the 15th dragonfly species that I have seen, in North Hertfordshire, on my walks from home.
Small Red-eyed Damselfly (lower right) with egg-laying Common Darters, Mardleybury Lake, 7 September
Juvenile Yellow Wagtail, Hatchpen Farm, 7 September
Reports (Barry Reed) of a marsh harrier and a common redstart nearby encouraged me to walk up the Icknield Way on the 10th. Sure enough, a marsh harrier (female or juvenile) flew rapidly across the track, heading east towards the A10. I didn't catch up with the redstart, however. Butterfly activity tailed off from the middle of the month, although 30-40 Adonis blues were still on the wing on Church Hill on the 16th. Searching for female wasp spiders to photograph I came across what I at first thought was an unusual colour variant, only to discover that I was photographing its underside! I guess that it's a mistake that is only made once.....
Female Wasp Spider, seen from Underneath, Church Hill, 8 September
Warm, generally sunny weather continued through the month until the 27th, when a cold front coming off the Atlantic heralded the start of autumn proper. The one exception to this settled period came on the 14th, when 46mm (nearly two inches) of rain fell in my garden in eight hours. Bird activity was very limited, with most summer visitors having left by the middle of the month and winter visitors yet to arrive, whilst a lot of our resident birds were moulting. However, a few herring-type gulls were following the plough in Therfield, alongside a single common gull and 50+ lesser black-backed gulls when I did a 'there and back' walk to Reed End on the 21st. I took a few 'record shots' of these gulls and one adult or near-adult displayed primary wing tip markings consistent with those seen on a yellow-legged gull (image below). A pair of ravens was seen nearby.
Adult or Near-adult Yellow-legged Gull (?), Therfield, 21 September
With butterfly numbers declining rapidly in the second half of the month I turned my (photographic) attention to studying crickets and grasshoppers, whose numbers peak at this time of year. In the past I have wilfully neglected these invertebrates, partly because they don't sit up nicely on flower heads but mainly due to lack of time. With a September holiday postponed for a second year, time was on my side now and a visit to the tiny, local wild flower meadow a few hundred yards from my house proved surprisingly productive as I found several Roesel's bush-crickets, two grasshopper species and a single long-winged conehead. A female wasp spider was another surprise find. I have previously found another bush cricket species (dark bush-cricket) on the far side of the adjacent arable field (which, sadly, is ear-marked for development) and a speckled bush-cricket turned up in my front garden recently, so clearly this area is not just a haven for butterflies but also for many other invertebrate species! I thought that I had found a third grasshopper species (mottled grasshopper) on Therfield Heath, alongside the abundant field- and meadow grasshoppers. My images seemed to have similarities with the images shown in 'Brock'. However, when I showed these images to the Herts. recorder, Ian Carle, he confirmed that the images were of field grasshoppers, which must have very variable colours and markings! Apparently only two sites in Hertfordshire contain mottled grasshoppers. Ian gave me helpful advice on what other species to look out for in my local area and recommended a book to purchase, so that I can sort out any future ID issues myself.
Long-winged Conehead, Royston, 23 September
Field Grasshopper (initially identified as a Mottled Grasshopper), Therfield Heath, 21 September
Roesel's Bush-cricket, Royston, 23 September
A few Adonis blues were still on the wing when I visited Church Hill on the 21st and I found a rather attractive female variant (image) amongst some other, faded and battered individuals. A few meadow browns and a lot of whites were on the wing whilst speckled woods, having apparently had a very poor first generation in the spring and early summer, were common and widespread in woodland and along hedgerows in the final days of the month.
Adonis Blue (Female Variant), Church Hill, 21 September
