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


2 August 2021

Melilot, Greater Knapweed
Fleabane, Wild Parsnip, Dwarf Thistle
Lower Slopes of Mill Hill

After a rain sodden and cloudy week, moderate rain curtailed my visit to Mill Hill before any resting butterflies were disturbed on the lower slopes. Dwarf Thistle was common. The first shoots of Carline Thistle were seen.

23 July 2021
At last, a handful of male Chalkhill Blue Butterflies fluttered restlessly over the lower slopes of Mill Hill.

Large White on Bristly Ox-tongue, Lesser Centaury with Eyebright. Chalkhill Blue on Ragwort
Dwarf Thistle

19 July 2021

Gatekeeper on Perforate St. John's Wort, Wild Basil
Round-headed Rampion, Dwarf Thistle

I visited the lower slopes in the sunshine where there were frequent butterflies: Gatekeepers, Meadow Browns,  Marbled Whites. Large Whites, Small Skippers, a Red Admiral, a Small Heath, but no Chalkhill Blues.
Notable flowers were hundreds of Wild Basil, frequent Round-headed Rampion, frequent Small Scabious, Common Centaury, Dwarf Thistle and Perforate St. John's Wort, Lesser Hawkbit.

18 July 2021
On a virtually cloudless day the sun (25º C) burned anybody who ventured out of the shade. I still visited the upper part of Mill Hill in the mid-afternoon where two dozen butterflies fluttered around the attractive selection of chalkhill flowers amongst the long grasses south and west of the top car park. Marbled Whites. Large Whites, and Meadow Browns were all restless. There was at least one Small Heath, a probable Wall Brown and my first Painted Lady of the year on the middle slopes south of the copse,

Round-headed Rampion, Small Scabious, Pyramidal Orchid

Notable flowers were frequent and more than usual Round-headed Rampion, frequent Small Scabious, and Greater Knapweed on the exposed top of the hill. On the sheltered middle slopes the notables were Melilot, Lady's Bedstraw, Marjoram, and Field Scabious.

14 July 2021

Marjoram, Centaury. Squinancywort, Dwarf Thistle

A couple of Gatekeepers on the southern steps to the lower slopes were the first of the year, Other butterflies were occasional Marbled Whites. Large Whites, Meadow Browns, Red Admirals, a few Small Skippers, Small Heaths and one Wall Brown.

28 June 2021
Marbled White Butterflies were very lively over the lower slopes of Mill Hill where I also spotted my first Small Skipper of the year. New flowers appeared on a cloudy humid afternoon. Small Heath Butterflies, pristine Red Admirals, large Meadow Browns, a Silver Y Moth and a 6-spotted Burnet Moth were noted as the first spots of rain were felt.
A Great Green Bush Cricket, Tettigonia viridissima, was spotted on the southern top part of Mill Hill for the first time.
Adur Crickets and Grasshoppers

Knapweed (white) and Knapweed Broomrape
Southern top part of Mill Hill

8 June 2021

A Buzzard soared over a sunny (19°C) Mill Hill in the early afternoon. Butterflies were lively and frequent: Common Blues, Dingy Skippers, Small Heath Butterflies, Brimstones and Silver Y Moths over the lower slopes. A Holly Blue fluttered by the hedge by the southern car park to Mill Hill.

Dropwort, Dog Rose

The first flowers of Dropwort and the dimunitive Thyme appeared.

31 May 2021
Butterflies fluttered over the sun-drenched (21°C) lower slopes of Mill Hill: 30+ male Common Blues, 4+ male Adonis Blues, frequent Dingy Skippers and Grizzled Skippers, my first Brown Argus and Cinnabar Moth of the year, frequent Brimstones, a few Small Heath Butterflies and a probable Wall Brown. By the flowering Hawthorn-lined road there was a Holly Blue. All the butterflies were restless.

On the southern top of the hill, the first Greater Bird's Foot Trefoil was seen in flower.
Common Bird's-foot Trefoil Lotus corniculatus is shorter and grows in dry grassland. Its stems are solid whereas the stems of Lotus pedunculatus are hollow.

27 May 2021

Grizzled Skipper, Round-leaved Cranesbill, Milkwort
Horseshoe Vetch, Adonis Blue Butterfly, Common Blue

The sun shined in the afternoon for the first time in over a week, I was able to confirm my first male Adonis Blue Butterfly of the year with frequent Brimstones but not many other butterflies on the lower slopes of Mill Hill. There were occasional amorous Wall Browns. a few Small Heath Butterflies, a few Dingy Skippers, Grizzled Skippers, and Common Blues (including a dark blue female). At the top of Chanctonbury Drive, there was the flutter of a Holly Blue and some Large Whites. Early Elderflower appeared.

19 May 2021

May Gallery on facebook

Swathes of Horseshoe Vetch, Hippocrepis comosa, covered the lower slopes of Mill Hill on a cloudy afternoon inimical for watching butterflies. In an hour I spotted to my first of the year Small Heath Butterfly and a few first of the year Dingy Skippers, at least three male Common Blues, a Brimstone Butterfly, a few Large Whites and Red Admirals. At the top of Chanctonbury Drive, the flutter of blue was a Holly Blue.

Hawthorn was beginning to flower in the hedgerows. Patches of Crosswort, Cowslips and Germander Speedwell decorated the area south of the Reservoir.

A Buzzard soared overhead  mobbed by the frequent Crows. And a rather scruffy Jay put in two appearances.

12 May 2021
Five o'clock in the afternoon is a bit late in the day for seeing active butterflies on the lower slopes of Mill Hill as most of them will have gone to roost. I managed to spot my first male Adonis Blue (not confirmed -subsequently thought to be a Common Blue), and my first of the year Small Copper visiting the abundant Horseshoe Vetch, Hippocrepis comosa. A flock of up to a dozen corvids, mostly Jackdaws. were persistently feeding on something amongst the short vegetation on the steeper slopes. A Peacock Butterfly flew down and I disturbed a handful of Grizzled Skippers.  Hawthorn was beginning to flower. Cowslips were seen south of the Reservoir.

Hawthorn, Wayfaring Tree
Cowslips, Dog Violets

7 May 2021
Tripping over butterflies at Mill Hill today with a grand total of 14 species recorded. Dozens of Dingy Skipper & Grizzled Skipper, Green-veined White, Small White, Brimstone and a singleton Orange-tip doing the rounds. Wall are coming along nicely with at least half a dozen bobbing around, a female already ovipositing. A handful of Small Copper seeing off all-comers which included my first Common Blue of the year, around 6 males seen. Green Hairstreak also doing well, regularly getting stuck in with the multi species aerial brawls, again about half a dozen active. The afternoon brought out 4 or 5 fresh looking Peacock and like Abbots Wood on Wednesday, there were good numbers of fresh immigrant Red Admirals, a female was seen egg laying (from the state of some they must have come via Jersey!). A single Comma made a very brief appearance (unable to tell if it were an early hutchinsoni or a late hibernator). The day started off with a rare Sussex sight of a female Small Tortoiseshell avidly investigating some nettle on the edge of the horse paddocks on the south side of the Shoreham Bypass.

Report by Paul Atkin on Sussex Butterflies

Horseshoe Vetch, Hippocrepis comosa

I only managed to spot eleven species of butterfly, the last seven on the lower slopes of Mill Hill: Red Admiral, Speckled Wood, Small White, Large White, Green-veined White, Brimstone, Wall Brown, Peacock, Grizzled Skipper, Dingy Skipper, Common Blue. I also noted a few pyralid mothsPyrausta nigrata. Blackthorn had ceased to flower.

Mill Hill Nature Reserve on facebook

22 April 2021


A few Peacock Butterflies visited the battered and frequent Sweet Violets and Dog Violets scattered thinly over the lower slopes of Mill Hill. A bright yellow Brimstone Butterfly fluttered by the Holly Tree, where the Wayfaring Tree had been hacked down by the conservation workers.

19 April 2021

by Tegan Newman

15 April 2021

Mill Hill (south)

Mill Hill Wildlife Reports 2020 (Link)




Mill Hill Wildlife Reports 2018 (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

Mill Hill Nature Reserve 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