Mill Hill (June 2013)
Spring Downland Butterflies (May):
Adonis Blues (Photograph                    by Andy Horton)
Dingy Skipper                    (Photograph by Andy Horton)
Small Heath Butterfly
Grizzled Skipper
Adonis Blue Butterfly
Dingy Skipper
Small Heath Butterfly

Noticeable summer plants of the upper meadows include Greater Knapweed, Hardheads (=Lesser Knapweed), Field Scabious, Meadow Cranesbill, Alexanders, Pyramidal Orchids, Plantains, Melilots, Meadow Vetchling, Yarrow, Eyebrights, Musk Thistles, Hounds-tongue*, Perforate St. John's Wort*, Great Mullein* and many others. Herb Robert is found amongst the scrub.
(*notably on disturbed ground.)

Some Indicator Plants of Ancient Downland

Horseshoe Vetch (Photograph by Andy Horton)
Autumn Gentian
Horseshoe Vetch
Common Milkwort
Dog Violet
Autumn Gentian

Other indicators on the lower slopes include Dropwort, Autumn Ladies Tresses (upper plateau), Hairy Violet, all of which are rarely found on pastures, restored wildlife meadows or agricultural downland. Other downland plants that are more likely on the biodiverse down herbland are Wild Thyme, Carline Thistle, Dwarf Thistle, Squinancywort, Fairy Flax, Small Scabious, Common Centaury and Wild Basil. There are other more widespread wild plants like the Mouse-eared Hawkweed, Rough Hawkbit, Lesser Hawkbit, Bird's Foot Trefoil, Ground Ivy, Germander Speedwell, Field Speedwell, Sweet Violet, Self-heal and Yellow Wort.
Wild Flora and Fauna on Chalk   flickr
Adur Wild Flowers 2009


A large part (724 acres) of the downs including Mill Hill were presented to the people of Shoreham in 1937

Lower Slopes of Mill Hill, May 2006 

Just over 30 acres still remain as public open land and a Local Nature Reserve.  This is divided into about 11 acres of grassland and meadows above the ridge, about 9 acres of scrub, the copse and glades at the northern end, and about half of the prime Chalkhill Blue area of 6.4 acres of herbland remaining. 6 acres has been lost to a Sycamore woodland on the southern slopes. 

This is low fertility chalkland not suitable for grazing. The top area is effectively a wild meadow and the lower slopes a rabbit warren dominated by prostrate (not the upright form) Horseshoe Vetch, Hippocrepis comosa

Link to                            the Mill Hill web page for 2009

Horseshoe Vetch

Chalkhill Blues:

Mill Hill is nationally important because of its population of Chalkhill Blue Butterflies. Estimates of the numbers are notoriously inaccurate. In the 1950s the population was estimated by R. M. Craske to be 50,000. This may be an exceptionally good year. I would estimate the numbers at that time to be nearer 25,000 for Mill Hill only. After the cattle grazing and thorn incursions the numbers plummeted to the most reliable estimate in 1960 of 6,000. The new road and Sycamore woodland further denuded the Horseshoe Vetch, Hippocrepis comosa, and bare chalk downland to a figure I have estimated at a top figure of 3,000 Chalkhill Blue Butterflies at the turn of the millennium (counted in 2003). Almost all these butterflies are now to be found on the six acres of the lower slopes.
Graham Hart in the 1990s estimated the numbers at 6,000. This is not out of the question and this would accord with the R. M. Craske estimate of 50,000. This would be the maximum population density that could be expected on the carpets of Horseshoe Vetch (based on German figures).
Protection of the current population requires man management of the scrub incursions, which means removal of the Privet

Text by Andy Horton Calcareous Grassland Message
"Our family lived at The Mill House, Mill Hill, from around 1933 until about 1967, and every July we saw the "Butterfly Men" walking past onto the Downs. My father used to tell us that they were interested in the blue butterflies."
Heather Clark (née Eager), Ryde, Isle of Wight
Nearest Postcode:  BN43 5FH
Grid Ref:  TQ 21170 07444  (upper car park)
Geographic Link      OS Map
Google Earth Map
Magic Map of Mill Hill NR
Local Nature Reserve Designation
Natural England: Local Nature Reserves
Multi-Map (Bird's Eye View)
Grid Reference Finder

Threats to the Butterfly Downland site at Mill Hill
The butterfly lower slopes at Mill Hill are under serious threat by a natural process known as ecological succession where the woody shrubs like Privet, Brambles and Hawthorn invade the herb-rich slopes gradually turning the downs into woodland and eliminating the butterfly larval food plants especially the Horseshoe Vetch, Hippocrepis comosa, on which the Chalkhill Blue Butterflies rely. The remedy is by expert professional removal of the Privet on a regular basis. This job is now being undertaken by volunteers. 


Mill Hill on

Mill Hill on


OS Map

   Footpaths at Mill Hill

Map Geograph Satellite


22 May 2018
I cycled to the upper car park on Mill Hill (as I missed out the top and gentler middle slopes on my last two visits). The upper plateau was covered in grasses and Bulbous Buttercups and the amount of Horseshoe Vetch was noticeable less than in previous years. Small Heath Butterflies were a frequent sight. An open meadow-like area north-west of the car park hosted a mixed collection of butterflies fluttering occasionally in the sunshine. The first contestants turned out to be the first of a few male Common Blues and his surprising opponent was revealed as my first Green Hairstreak of the year. A single fine condition Dingy Skipper was querulous with other butterflies as well. Hawthorn was blossoming near to the border to Erringham Hill. On close inspection most of the handful of blue butterflies in the meadow were Holly Blues although there was at least one male Adonis Blue.  A Brimstone Butterfly and a Large White fluttered by and two Wall Browns landed briefly where passage had worn a path and revealed bare chalk. Another first of the year was a pretty Mother Shipton Moth.

The meadows of the middle slopes have long grasses and a different flora from the lower slopes

The rough meadow north of the car park lacked anything of interest until another Wall Brown fluttered over. I cycled up to Beeding Hill and the top part of Anchor Bottom. But this was covered in more grasses and buttercups and despite looking, I could not find anything worth a photograph.

Dogwood and longer grasses swamp out the Horseshoe Vetch on the middle slopes

21 May 2018

Lower slopes of Mill Hill

Warm (20.4 °C) and humid, so humid that there a few sports of rain, and slightly overcast conditions in the early afternoon, which might make the butterflies hide but easier to photograph. The lower slopes of Mill Hill were still covered in the glorious carpet of Horseshoe Vetch, Hippocrepis comosa, and the blue butterflies were semi-torpid but easily disturbed and many of them seen resting. I decided to count the Adonis Blues in a slightly altered one acre transect (taking 50 minutes with pauses for photography) and this slowly built up to an unprecedented* 206 males and 10 females. There was a higher density of butterflies on the richer swathes of Horseshoe Vetch at the northern end. After I completed a count I saw over a hundred more males on the steeper slopes, and the female count rose to 25+ including one mating pair. These numbers simply swamped the other species with frequent Common Blues, frequent Small Heaths, just a few Grizzled Skippers and Dingy Skippers, and one Brimstone Butterfly and one Small White. I spotted at least one Treble-bar Moth on the lower slopes. The micro-moths were not seen. (*since my records were compiled from 2003)

Hawthorn, Hound's-tongue, Adonis Blues
Common Blue, Wild Mignonette, Common Daisy

I returned by the ridge route where I spotted a further dozen male Adonis Blues.
Adur Butterfly List 2018

18 May 2018

Common Blues
Cinnabar Moth, Adonis Blues

WIth the yellow carpet of Horseshoe Vetch, Hippocrepis comosa, on the lower slopes of Mill Hill, looking splendid a day or two off its peak, the butterflies were out in force, in numbers, if not variety. In the transect acre there were estimated to be in excess of a hundred butterflies fluttering around in the sunshine. At least sixty were the lively and amorous male Adonis Blues, and the rest were made up of female Adonis Blues, frequent Common Blues, frequent Small Heaths, occasional Grizzled Skippers and Dingy Skippers, and a few Brimstone Butterflies and Small Whites. I spotted at least one Cinnabar Moth on the lower slopes, and one Carpet Moth where the cattle had disturbed the flora and spoilt the habitat by the water trough. There was almost an absence of the micro-moths that are usually so common, no Pancalia and just the one pyralid: a Pyrausta purpuralis. The only surprise of the early afternoon was a very quick male Broad-bodied Chaser (dragonfly) chasing after the skippers. A few Azure Damselflies were seen around the Brambles. There was a brown butterfly over the southern steps which was either a Wall Brown or a Speckled Wood.

Horseshoe Vetch

The Horseshoe Vetch was dominant on the lower slopes except for one Bramble-covered bare patch which I put down to mismanagement. A few diminutive, Milkwort , Germander Speedwell and Scarlet Pimpernel, and taller Salad Burnet interrupted the blaze of yellow. I noted the much larger Hound's-tongue in bud near the scrub.
When the pack of dogs had moved off the hill, the Kestrel hovered over edge of the Hawthorn-flowering scrub. A couple of adult Slow Worms were hiding under a piece of wood at the top. I was satisfied with only visiting the lower slopes.
Adur Butterfly List 2018

17 May 2018

Hawthorn and Horseshoe Vetch on Mill Hill and
Hawthorn on the hedgerows of the Downs Link Cyclepath

14 May 2018

Hawthorn and Horseshoe Vetch

Hawthorn was in blossom all over Mill Hill and most be about 60% of full flowering. Likewise the yellow swathes of  Horseshoe Vetch, Hippocrepis comosa, were more than half in flower, attracting the bees and butterflies.
The annual photographs show large bare patches where Horseshoe Vetch used to be prevalent in 2006.

Brown Argus, Adonis Blue
Dingy Skipper, Common Blue, Grizzled Skipper

It was only on the lower slopes that butterflies and moths were frequent if rather patchily distributed. The first of 9+ Grizzled Skippers were immediately seen from the southern steps. But I was simultaneously distracted by two Cinnabar Moths which I may have disturbed. Small Heaths (15+) were chasing other butterflies around all over the place. They prevailed over at least two surprise clearly seen Brown Argus. All this before I spotted my first dozen or so blue butterflies, mostly quarrelling with other butterflies and skippers and not keeping still. The first recognised were the slightly more numerous (8+) male Common Blues, but at the same time there were at least five male Adonis Blues. They were causing such a commotion with each other that it was difficult to count them. Dingy Skippers were seen all the time, rarely keeping still, but the count was only five as one kept flying to and fro. An Azure Damselfly, Coenagrion puella, avoided the melee. A pale flutter was a Treble-bar Moth. A few Brimstone Butterflies patrolled the thickets/hedge and the larger brown butterfly was seen to be a Wall Brown. I did not note any of the very small moths. A few small white butterflies, on the top of the hill, were not positively identified, but were most likely Green-veined Whites.

A large adult Slow Worm slithered into hiding on the top southern part of Mill Hill. More of a surprise was the skitter of a very small Common Lizard  amongst the vegetation and green grasshopper nymphs of the sheltered lower slopes. In the top copse, gusts of wind blew the Garlic Mustard horizontal and flat at times.
Adur Butterfly List 2018

11 May 2018
I haven't had a chance to get to Mill Hill for awhile so with the prospect of fading sunlight I headed there at lunchtime. What a difference a couple of weeks makes. The place was alive with Dingy Skipper, Grizzled Skipper, Small Heath. A single Green Hairstreak was seen and about 6 male Common Blue and 6 male Adonis Blue and 1 female.

Report by Dave Cook on Butterfly Conservation Sussex Sightings

7 May 2018

Wayfaring Tree was in flower next to the path down to the lower slopes

Hawthorn was starting to flower in the hedges. Butterflies were out in the baking sunshine with my first Large White of the year at the top of Chanctonbury Drive (south-east of the Mill Hill Road Bridge). On the southern part of Mill Hill, I spotted my first of the year Small Heath almost immediately followed a clear sighting of at least two Green-veined White Butterflies. Down the steps on to the lower slopes where it was shimmering warm and the first Horseshoe Vetch, Hippocrepis comosa, was flowering. The flowers attracted occasional (10+) Dingy Skippers which were not allowed to settle by frequent (20+) agonistic Small Heaths. Small moths flitted amongst the intertwined leaves including small Pyrausta moths with a definite Pyrausta nigrata and Pyrausta despicata. Two Brimstone Butterflies fluttered overhead and I disturbed two very fresh Wall Browns.

Grizzled Skipper on Milkwort
Horseshoe Vetch,  Cinnabar Moth

Only after ten minutes did the first of  at least ten fresh, lively and amorous Grizzled Skippers appear. A brightly coloured Cinnabar Moth fluttered around but would not stay still as usual. Crane Flies were frequently seen on the lower slopes. A large clump of Wayfaring Tree was in flower next to the path down to the lower slopes. The small Milkwort flower appeared but mostly blue ones were seen.  But they exceeded in number over the few remaining Dog Violets. There were still patches of Ground Ivy and the new Germander Speedwell. A black and yellow hoverfly Xanthogramma pedissequum flitted amongst Stinging Nettles on the southern steps. It was so warm that I returned by the path without completing the full transect. Cowslips were in flower on the southern top part of Mill Hill.
Adur Butterfly List 2018

20 April 2018
After the recent sunny spell of a few days, the mud on the southern steps down to the lower slopes of Mill Hill has already dried out and the Blackthorn was in blossom everywhere. It was even too warm for diligently spotting butterflies and on the lower slops where on passage I noted a mere one Speckled Wood, 2+ Peacocks, a Brimstone or two, one Small White, and frequent small Pyrausta moths. Too warm for packs of dogs and there were only four butterfly watchers who reported Grizzled Skippers and a Green Hairstreak. It was really too warm for me as well and I did not stay long in the afternoon. Common Bee-flies visited Ground Ivy and Dog Violets. My first adult Slow Worm of the year was seen under a flat piece of wood on the southern top part. A Kestrel flew over but this regular inhabitant of Mill Hill has a tendency not to stay around when there is even one dog, however small. A Wren was making more noise than the buzz of the traffic, the drone of small aircraft and the baaing of the sheep in the field below.

Old Erringham and the  Lower Slopes of  Mill Hill
with Blackthorn in flower

Earlier in the day there was more than one hearsay report of Red Kites over Erringham Hill flying towards New Erringham.

11 April 2018

Mixed Fauna and Flora and Fungi
Zebra Spider, Salticus scenicus, Dog Violet
Unknown small larva, Thimble Morel Verpa conica

A disturbing visit to the lower slopes of Mill Hill, spoilt entirely by 18 dogs and four people all at one time on the lower slopes. The dogs were yapping and running free and leaving their mess over the chalkhill flora. Two dogs were barking repeatedly at me over a distance of 12 metres in separate incidents. I wish I had not bothered as the steps and paths were muddy and nearly treacherous caused by excessive footfall. In the middle of the day I did spot a handful of Brimstone Butterflies and the same number of Peacock Butterflies. Dog Violets had already taken over from Sweet Violets as the dominant violet over the lower slopes. After the rain there was a mushroom I had not seen before on Mill Hill, and a Common Bee-fly visiting violets.  I looked for possible Grizzled Skippers but even the dead remnants of Carline Thistle in which they hide were hardly present. I was so depressed by the state of Mill Hill Nature Reserve and the dogs that I hurried home by the ridge route.  There were a few Blackthorn flowers south of the Reservoir but there were no sign of flowers on the main clump next to the road.
Adur Spiders

NB: The bye-laws for Mill Hill Nature Reserve state that dogs should be on a lead (interpreted to mean under close control, not in packs running around free).

Three Thimble Morel, Verpa conica, mushrooms were the first I have ever seen anywhere amongst some grass below the path on the middle area of the lower slopes of Mill Hill

5 April 2018

Lower Slopes (looking southwards)
Despite the rain and muddy steps, the slopes were looking dry and parched
(in contrast to the standing water on the levels below)

Still a slight chill under the cirrus blue sky as a Buzzard glided over Erringham Hill and a Kestrel hovered over the edge of the ridge on Mill Hill above the steep part of the lower slopes. They did not remain on station for long before they were disturbed by an excessive number of dog walkers.

Sweet Violets (top)
Daffodils, Ground Ivy

Sweet Violets were commonly spread over the lower slopes but not abundant and the flowers were a bit bedraggled after the recent rain which left the steps and paths muddy but passable. Ten Peacock Butterflies flew past me and settled very briefly (not on the violets) and seven of these were on my lower slopes one acre transect. I spotted a pair of Small Tortoiseshells, my first of these butterflies of the year, near some short growths of Stinging Nettles on the edge of the scrub on the middle slopes. Buff-tailed Bumblebees were frequently seen and I noted one Common Bee-fly, Bombylius major, on a path through the scrub. A Cherry Plum was spotted in flower but there was no sign of any Blackthorn flowers.
Lastly, a Red Admiral settled on the Chanctonbury Drive lawn at the south-eastern end of the bridge over the A27.

15 March 2018
In the weak sunshine I spotted my first butterfly of the year; a Red Admiral over Mill Hill Road at the southern end of the bridge over the A27.

A Buzzard glided over Erringham Hill, seen in the photograph from the top meadow of Mill Hill Nature Reserve.

2 February 2018

Mill Hill Road

On a cloudy day with a chill breeze, I would have been lucky to see anything of note. The best I could manage was a one second peek of a rodent scurrying into hiding. It was not even long enough to be sure of what it was?  It qualifies as my second wild mammal of the year. It was very rapid with a short white tail and I think it was a Mouse  (rather than a Shrew). There was evidence of the activity of Moles on the top of the hill, with mounds of grey-brown earth.  The dead remnants of Carline Thistle seemed less than usual. Birds were not showing and the sky was empty apart from a few gulls and a Crow. The thorn was bare and hosted a Robin. A young Song Thrush was seen on the top plateau.


Mill Hill Wildlife Reports 2017 (Link)

Mill Hill Wildlife Reports 2016 (Link)
Mill Hill Wildlife Reports 2015 (Link)
Mill Hill Wildlife Reports 2014 (Link)
Mill Hill Wildlife Reports 2013 (Link)
Mill Hill Wildlife Reports 2012 (Link)
Mill Hill Wildlife Reports 2011 (Link)

Adur Valley & Downs on facebook

Identification of Grasses (Link)
Mill Hill Grasses

A Nature Reserve is defined in Section 15 of the National Parks and Access to the Countryside Act 1949, as land managed for the purpose:

(a) of providing, under suitable conditions and control, special opportunities for the study of, and research into, matters relating to the flora and fauna of Great Britain and the physical conditions in which they live, and for the study of geological and physiographical features of special interest in the area; or
(b) of preserving flora, fauna, or geological or physiographical features of special interest in the area; or for both these purposes.

(Estimated numbers for Mill Hill Nature Reserve only are in brackets)

Chalkhill Blue (3000 +)
Adonis Blue (50 -100)
Dingy Skipper  (75)
Small Heath (250)
Wall Brown  (12)
Meadow Brown  (300)
Marbled White  (50)
Gatekeeper    (200)
Speckled Wood  (>50)
Green-veined White (2+)
Common Blue  (>4000+)
Small Blue       (5)
Brimstone        (8)
Small Skipper   (>50)
Large Skipper   (10+)
Grizzled Skipper  (20)
Brown Argus   (>30)
Green Hairstreak ( a few)

The other species may breed on Mill Hill, but there main breeding area will be adjoining fields or slightly further away. e.g. Small Blue (included above), Small Copper, Small Tortoiseshell,Green-veined White, Peacock, Ringlet, Small White, Large White, Comma, Holly Blue, Orange Tip. (=10). There are huge variances each year for most species.

The following are immigrants &/or hibernators:  Red Admiral, Painted Lady, Clouded Yellow.

The following have not been positively identified (because of ID difficulties):  Essex Skipper. This species is now included for a local field on the Adur Levels within 500 metres of Mill Hill.


The following was confirmed only in 2009: Green Hairstreak.

The following was confirmed only in 2014: Dark Green Fritillary

The next one is no longer found on Mill Hill but were there in the distant (1947) past: Grayling.
The next one has been recorded near Mill Hill in the middle distance past:  White-letter Hairstreak


The Silver-spotted Skipper does not appear to ever have occurred on Mill Hill
The Silver-studded Blue has never been recorded from Mill Hill

The Short-tailed Blue was recorded as a single immigrant in 1956.

17 August 2009
A possible (unconfirmed) Brown Hairstreak Butterfly was spotted. A confirmed one was spotted nearby.

Brown Hairstreak and Silver-spotted Skipper have been confirmed from Mill Hill. The first is notoriously difficult to spot and was probably already there. The skipper may be a new addition, but it is small and not easy to spot, and there have now been numerous sightings

Adur Butterfly Page


History of Mill Hill

Aerial Map
Lower Adur Levels (MultiMap) including Lancing Clump and Mill Hill

Horseshoe Vetch, Hippocrepis comosa
First Draft of the Article for the Shoreham Society Newsletter

Link to the            Adur 2012 Nature Notes pagesLink to the Adur Nature Notes 2011            web pages

Link to            the Adur 2010 Nature Notes pagesLink to the Adur Nature Notes 2009            web pagesLink to the            Adur Nature Notes 2008 web pagesLink to the Adur Nature Notes 2007            web pages
Link to Adur            Valley Nature Notes 2003Link to the Adur Nature Notes            2004 Index pageLink to Adur Nature Notes 2005 Index pageLink to the Adur Nature Notes 2006            web pages